syscall.c

/*
 * Copyright (c) 1991, 1992 Paul Kranenburg <pk@cs.few.eur.nl>
 * Copyright (c) 1993 Branko Lankester <branko@hacktic.nl>
 * Copyright (c) 1993, 1994, 1995, 1996 Rick Sladkey <jrs@world.std.com>
 * Copyright (c) 1996-1999 Wichert Akkerman <wichert@cistron.nl>
 * Copyright (c) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *                     Linux for s390 port by D.J. Barrow
 *                    <barrow_dj@mail.yahoo.com,djbarrow@de.ibm.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *	$Id$
 */

#include "defs.h"

#include <signal.h>
#include <time.h>
#include <errno.h>
#include <sys/user.h>
#include <sys/syscall.h>
#include <sys/param.h>

#ifdef HAVE_SYS_REG_H
#include <sys/reg.h>
#ifndef PTRACE_PEEKUSR
# define PTRACE_PEEKUSR PTRACE_PEEKUSER
#endif
#elif defined(HAVE_LINUX_PTRACE_H)
#undef PTRACE_SYSCALL
# ifdef HAVE_STRUCT_IA64_FPREG
#  define ia64_fpreg XXX_ia64_fpreg
# endif
# ifdef HAVE_STRUCT_PT_ALL_USER_REGS
#  define pt_all_user_regs XXX_pt_all_user_regs
# endif
#include <linux/ptrace.h>
# undef ia64_fpreg
# undef pt_all_user_regs
#endif

#if defined (LINUX) && defined (SPARC64)
# undef PTRACE_GETREGS
# define PTRACE_GETREGS PTRACE_GETREGS64
# undef PTRACE_SETREGS
# define PTRACE_SETREGS PTRACE_SETREGS64
#endif /* LINUX && SPARC64 */

#if defined(LINUX) && defined(IA64)
# include <asm/ptrace_offsets.h>
# include <asm/rse.h>
#endif

#define NR_SYSCALL_BASE 0
#ifdef LINUX
#ifndef ERESTARTSYS
#define ERESTARTSYS	512
#endif
#ifndef ERESTARTNOINTR
#define ERESTARTNOINTR	513
#endif
#ifndef ERESTARTNOHAND
#define ERESTARTNOHAND	514	/* restart if no handler.. */
#endif
#ifndef ENOIOCTLCMD
#define ENOIOCTLCMD	515	/* No ioctl command */
#endif
#ifndef ERESTART_RESTARTBLOCK
#define ERESTART_RESTARTBLOCK 516	/* restart by calling sys_restart_syscall */
#endif
#ifndef NSIG
#define NSIG 32
#endif
#ifdef ARM
#undef NSIG
#define NSIG 32
#undef NR_SYSCALL_BASE
#define NR_SYSCALL_BASE __NR_SYSCALL_BASE
#endif
#endif /* LINUX */

#include "syscall.h"

/* Define these shorthand notations to simplify the syscallent files. */
#define TD TRACE_DESC
#define TF TRACE_FILE
#define TI TRACE_IPC
#define TN TRACE_NETWORK
#define TP TRACE_PROCESS
#define TS TRACE_SIGNAL
#define NF SYSCALL_NEVER_FAILS

static const struct sysent sysent0[] = {
#include "syscallent.h"
};
static const int nsyscalls0 = sizeof sysent0 / sizeof sysent0[0];
int qual_flags0[MAX_QUALS];

#if SUPPORTED_PERSONALITIES >= 2
static const struct sysent sysent1[] = {
#include "syscallent1.h"
};
static const int nsyscalls1 = sizeof sysent1 / sizeof sysent1[0];
int qual_flags1[MAX_QUALS];
#endif /* SUPPORTED_PERSONALITIES >= 2 */

#if SUPPORTED_PERSONALITIES >= 3
static const struct sysent sysent2[] = {
#include "syscallent2.h"
};
static const int nsyscalls2 = sizeof sysent2 / sizeof sysent2[0];
int qual_flags2[MAX_QUALS];
#endif /* SUPPORTED_PERSONALITIES >= 3 */

const struct sysent *sysent;
int *qual_flags;
int nsyscalls;

/* Now undef them since short defines cause wicked namespace pollution. */
#undef TD
#undef TF
#undef TI
#undef TN
#undef TP
#undef TS
#undef NF

static const char *const errnoent0[] = {
#include "errnoent.h"
};
static const int nerrnos0 = sizeof errnoent0 / sizeof errnoent0[0];

#if SUPPORTED_PERSONALITIES >= 2
static const char *const errnoent1[] = {
#include "errnoent1.h"
};
static const int nerrnos1 = sizeof errnoent1 / sizeof errnoent1[0];
#endif /* SUPPORTED_PERSONALITIES >= 2 */

#if SUPPORTED_PERSONALITIES >= 3
static const char *const errnoent2[] = {
#include "errnoent2.h"
};
static const int nerrnos2 = sizeof errnoent2 / sizeof errnoent2[0];
#endif /* SUPPORTED_PERSONALITIES >= 3 */

const char *const *errnoent;
int nerrnos;

int current_personality;

#ifndef PERSONALITY0_WORDSIZE
# define PERSONALITY0_WORDSIZE sizeof(long)
#endif
const int personality_wordsize[SUPPORTED_PERSONALITIES] = {
	PERSONALITY0_WORDSIZE,
#if SUPPORTED_PERSONALITIES > 1
	PERSONALITY1_WORDSIZE,
#endif
#if SUPPORTED_PERSONALITIES > 2
	PERSONALITY2_WORDSIZE,
#endif
};;

int
set_personality(int personality)
{
	switch (personality) {
	case 0:
		errnoent = errnoent0;
		nerrnos = nerrnos0;
		sysent = sysent0;
		nsyscalls = nsyscalls0;
		ioctlent = ioctlent0;
		nioctlents = nioctlents0;
		signalent = signalent0;
		nsignals = nsignals0;
		qual_flags = qual_flags0;
		break;

#if SUPPORTED_PERSONALITIES >= 2
	case 1:
		errnoent = errnoent1;
		nerrnos = nerrnos1;
		sysent = sysent1;
		nsyscalls = nsyscalls1;
		ioctlent = ioctlent1;
		nioctlents = nioctlents1;
		signalent = signalent1;
		nsignals = nsignals1;
		qual_flags = qual_flags1;
		break;
#endif /* SUPPORTED_PERSONALITIES >= 2 */

#if SUPPORTED_PERSONALITIES >= 3
	case 2:
		errnoent = errnoent2;
		nerrnos = nerrnos2;
		sysent = sysent2;
		nsyscalls = nsyscalls2;
		ioctlent = ioctlent2;
		nioctlents = nioctlents2;
		signalent = signalent2;
		nsignals = nsignals2;
		qual_flags = qual_flags2;
		break;
#endif /* SUPPORTED_PERSONALITIES >= 3 */

	default:
		return -1;
	}

	current_personality = personality;
	return 0;
}


static int qual_syscall(), qual_signal(), qual_fault(), qual_desc();

static const struct qual_options {
	int bitflag;
	const char *option_name;
	int (*qualify)(const char *, int, int);
	const char *argument_name;
} qual_options[] = {
	{ QUAL_TRACE,	"trace",	qual_syscall,	"system call"	},
	{ QUAL_TRACE,	"t",		qual_syscall,	"system call"	},
	{ QUAL_ABBREV,	"abbrev",	qual_syscall,	"system call"	},
	{ QUAL_ABBREV,	"a",		qual_syscall,	"system call"	},
	{ QUAL_VERBOSE,	"verbose",	qual_syscall,	"system call"	},
	{ QUAL_VERBOSE,	"v",		qual_syscall,	"system call"	},
	{ QUAL_RAW,	"raw",		qual_syscall,	"system call"	},
	{ QUAL_RAW,	"x",		qual_syscall,	"system call"	},
	{ QUAL_SIGNAL,	"signal",	qual_signal,	"signal"	},
	{ QUAL_SIGNAL,	"signals",	qual_signal,	"signal"	},
	{ QUAL_SIGNAL,	"s",		qual_signal,	"signal"	},
	{ QUAL_FAULT,	"fault",	qual_fault,	"fault"		},
	{ QUAL_FAULT,	"faults",	qual_fault,	"fault"		},
	{ QUAL_FAULT,	"m",		qual_fault,	"fault"		},
	{ QUAL_READ,	"read",		qual_desc,	"descriptor"	},
	{ QUAL_READ,	"reads",	qual_desc,	"descriptor"	},
	{ QUAL_READ,	"r",		qual_desc,	"descriptor"	},
	{ QUAL_WRITE,	"write",	qual_desc,	"descriptor"	},
	{ QUAL_WRITE,	"writes",	qual_desc,	"descriptor"	},
	{ QUAL_WRITE,	"w",		qual_desc,	"descriptor"	},
	{ 0,		NULL,		NULL,		NULL		},
};

static void
qualify_one(int n, int bitflag, int not, int pers)
{
	if (pers == 0 || pers < 0) {
		if (not)
			qual_flags0[n] &= ~bitflag;
		else
			qual_flags0[n] |= bitflag;
	}

#if SUPPORTED_PERSONALITIES >= 2
	if (pers == 1 || pers < 0) {
		if (not)
			qual_flags1[n] &= ~bitflag;
		else
			qual_flags1[n] |= bitflag;
	}
#endif /* SUPPORTED_PERSONALITIES >= 2 */

#if SUPPORTED_PERSONALITIES >= 3
	if (pers == 2 || pers < 0) {
		if (not)
			qual_flags2[n] &= ~bitflag;
		else
			qual_flags2[n] |= bitflag;
	}
#endif /* SUPPORTED_PERSONALITIES >= 3 */
}

static int
qual_syscall(const char *s, int bitflag, int not)
{
	int i;
	int rc = -1;

	if (isdigit((unsigned char)*s)) {
		int i = atoi(s);
		if (i < 0 || i >= MAX_QUALS)
			return -1;
		qualify_one(i, bitflag, not, -1);
		return 0;
	}
	for (i = 0; i < nsyscalls0; i++)
		if (strcmp(s, sysent0[i].sys_name) == 0) {
			qualify_one(i, bitflag, not, 0);
			rc = 0;
		}

#if SUPPORTED_PERSONALITIES >= 2
	for (i = 0; i < nsyscalls1; i++)
		if (strcmp(s, sysent1[i].sys_name) == 0) {
			qualify_one(i, bitflag, not, 1);
			rc = 0;
		}
#endif /* SUPPORTED_PERSONALITIES >= 2 */

#if SUPPORTED_PERSONALITIES >= 3
	for (i = 0; i < nsyscalls2; i++)
		if (strcmp(s, sysent2[i].sys_name) == 0) {
			qualify_one(i, bitflag, not, 2);
			rc = 0;
		}
#endif /* SUPPORTED_PERSONALITIES >= 3 */

	return rc;
}

static int
qual_signal(const char *s, int bitflag, int not)
{
	int i;
	char buf[32];

	if (isdigit((unsigned char)*s)) {
		int signo = atoi(s);
		if (signo < 0 || signo >= MAX_QUALS)
			return -1;
		qualify_one(signo, bitflag, not, -1);
		return 0;
	}
	if (strlen(s) >= sizeof buf)
		return -1;
	strcpy(buf, s);
	s = buf;
	if (strncasecmp(s, "SIG", 3) == 0)
		s += 3;
	for (i = 0; i <= NSIG; i++)
		if (strcasecmp(s, signame(i) + 3) == 0) {
			qualify_one(i, bitflag, not, -1);
			return 0;
		}
	return -1;
}

static int
qual_fault(const char *s, int bitflag, int not)
{
	return -1;
}

static int
qual_desc(const char *s, int bitflag, int not)
{
	if (isdigit((unsigned char)*s)) {
		int desc = atoi(s);
		if (desc < 0 || desc >= MAX_QUALS)
			return -1;
		qualify_one(desc, bitflag, not, -1);
		return 0;
	}
	return -1;
}

static int
lookup_class(const char *s)
{
	if (strcmp(s, "file") == 0)
		return TRACE_FILE;
	if (strcmp(s, "ipc") == 0)
		return TRACE_IPC;
	if (strcmp(s, "network") == 0)
		return TRACE_NETWORK;
	if (strcmp(s, "process") == 0)
		return TRACE_PROCESS;
	if (strcmp(s, "signal") == 0)
		return TRACE_SIGNAL;
	if (strcmp(s, "desc") == 0)
		return TRACE_DESC;
	return -1;
}

void
qualify(const char *s)
{
	const struct qual_options *opt;
	int not;
	char *copy;
	const char *p;
	int i, n;

	opt = &qual_options[0];
	for (i = 0; (p = qual_options[i].option_name); i++) {
		n = strlen(p);
		if (strncmp(s, p, n) == 0 && s[n] == '=') {
			opt = &qual_options[i];
			s += n + 1;
			break;
		}
	}
	not = 0;
	if (*s == '!') {
		not = 1;
		s++;
	}
	if (strcmp(s, "none") == 0) {
		not = 1 - not;
		s = "all";
	}
	if (strcmp(s, "all") == 0) {
		for (i = 0; i < MAX_QUALS; i++) {
			qualify_one(i, opt->bitflag, not, -1);
		}
		return;
	}
	for (i = 0; i < MAX_QUALS; i++) {
		qualify_one(i, opt->bitflag, !not, -1);
	}
	if (!(copy = strdup(s))) {
		fprintf(stderr, "out of memory\n");
		exit(1);
	}
	for (p = strtok(copy, ","); p; p = strtok(NULL, ",")) {
		if (opt->bitflag == QUAL_TRACE && (n = lookup_class(p)) > 0) {
			for (i = 0; i < nsyscalls0; i++)
				if (sysent0[i].sys_flags & n)
					qualify_one(i, opt->bitflag, not, 0);

#if SUPPORTED_PERSONALITIES >= 2
			for (i = 0; i < nsyscalls1; i++)
				if (sysent1[i].sys_flags & n)
					qualify_one(i, opt->bitflag, not, 1);
#endif /* SUPPORTED_PERSONALITIES >= 2 */

#if SUPPORTED_PERSONALITIES >= 3
			for (i = 0; i < nsyscalls2; i++)
				if (sysent2[i].sys_flags & n)
					qualify_one(i, opt->bitflag, not, 2);
#endif /* SUPPORTED_PERSONALITIES >= 3 */

			continue;
		}
		if (opt->qualify(p, opt->bitflag, not)) {
			fprintf(stderr, "strace: invalid %s `%s'\n",
				opt->argument_name, p);
			exit(1);
		}
	}
	free(copy);
	return;
}

static void
dumpio(struct tcb *tcp)
{
	if (syserror(tcp))
		return;
	if (tcp->u_arg[0] < 0 || tcp->u_arg[0] >= MAX_QUALS)
		return;
	if (tcp->scno < 0 || tcp->scno >= nsyscalls)
		return;
	if (sysent[tcp->scno].sys_func == printargs)
		return;
	if (qual_flags[tcp->u_arg[0]] & QUAL_READ) {
		if (sysent[tcp->scno].sys_func == sys_read ||
		    sysent[tcp->scno].sys_func == sys_pread ||
		    sysent[tcp->scno].sys_func == sys_pread64 ||
		    sysent[tcp->scno].sys_func == sys_recv ||
		    sysent[tcp->scno].sys_func == sys_recvfrom)
			dumpstr(tcp, tcp->u_arg[1], tcp->u_rval);
		else if (sysent[tcp->scno].sys_func == sys_readv)
			dumpiov(tcp, tcp->u_arg[2], tcp->u_arg[1]);
		return;
	}
	if (qual_flags[tcp->u_arg[0]] & QUAL_WRITE) {
		if (sysent[tcp->scno].sys_func == sys_write ||
		    sysent[tcp->scno].sys_func == sys_pwrite ||
		    sysent[tcp->scno].sys_func == sys_pwrite64 ||
		    sysent[tcp->scno].sys_func == sys_send ||
		    sysent[tcp->scno].sys_func == sys_sendto)
			dumpstr(tcp, tcp->u_arg[1], tcp->u_arg[2]);
		else if (sysent[tcp->scno].sys_func == sys_writev)
			dumpiov(tcp, tcp->u_arg[2], tcp->u_arg[1]);
		return;
	}
}

#ifndef FREEBSD
enum subcall_style { shift_style, deref_style, mask_style, door_style };
#else /* FREEBSD */
enum subcall_style { shift_style, deref_style, mask_style, door_style, table_style };

struct subcall {
  int call;
  int nsubcalls;
  int subcalls[5];
};

static const struct subcall subcalls_table[] = {
  { SYS_shmsys, 5, { SYS_shmat, SYS_shmctl, SYS_shmdt, SYS_shmget, SYS_shmctl } },
#ifdef SYS_semconfig
  { SYS_semsys, 4, { SYS___semctl, SYS_semget, SYS_semop, SYS_semconfig } },
#else
  { SYS_semsys, 3, { SYS___semctl, SYS_semget, SYS_semop } },
#endif
  { SYS_msgsys, 4, { SYS_msgctl, SYS_msgget, SYS_msgsnd, SYS_msgrcv } },
};
#endif /* FREEBSD */

#if !(defined(LINUX) && ( defined(ALPHA) || defined(MIPS) || defined(__ARM_EABI__) ))

static void
decode_subcall(tcp, subcall, nsubcalls, style)
struct tcb *tcp;
int subcall;
int nsubcalls;
enum subcall_style style;
{
	unsigned long addr, mask;
	int i;
	int size = personality_wordsize[current_personality];

	switch (style) {
	case shift_style:
		if (tcp->u_arg[0] < 0 || tcp->u_arg[0] >= nsubcalls)
			return;
		tcp->scno = subcall + tcp->u_arg[0];
		if (sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs--;
		for (i = 0; i < tcp->u_nargs; i++)
			tcp->u_arg[i] = tcp->u_arg[i + 1];
		break;
	case deref_style:
		if (tcp->u_arg[0] < 0 || tcp->u_arg[0] >= nsubcalls)
			return;
		tcp->scno = subcall + tcp->u_arg[0];
		addr = tcp->u_arg[1];
		for (i = 0; i < sysent[tcp->scno].nargs; i++) {
			if (size == sizeof(int)) {
				unsigned int arg;
				if (umove(tcp, addr, &arg) < 0)
					arg = 0;
				tcp->u_arg[i] = arg;
			}
			else if (size == sizeof(long)) {
				unsigned long arg;
				if (umove(tcp, addr, &arg) < 0)
					arg = 0;
				tcp->u_arg[i] = arg;
			}
			else
				abort();
			addr += size;
		}
		tcp->u_nargs = sysent[tcp->scno].nargs;
		break;
	case mask_style:
		mask = (tcp->u_arg[0] >> 8) & 0xff;
		for (i = 0; mask; i++)
			mask >>= 1;
		if (i >= nsubcalls)
			return;
		tcp->u_arg[0] &= 0xff;
		tcp->scno = subcall + i;
		if (sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		break;
	case door_style:
		/*
		 * Oh, yuck.  The call code is the *sixth* argument.
		 * (don't you mean the *last* argument? - JH)
		 */
		if (tcp->u_arg[5] < 0 || tcp->u_arg[5] >= nsubcalls)
			return;
		tcp->scno = subcall + tcp->u_arg[5];
		if (sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs--;
		break;
#ifdef FREEBSD
	case table_style:
		for (i = 0; i < sizeof(subcalls_table) / sizeof(struct subcall); i++)
			if (subcalls_table[i].call == tcp->scno) break;
		if (i < sizeof(subcalls_table) / sizeof(struct subcall) &&
		    tcp->u_arg[0] >= 0 && tcp->u_arg[0] < subcalls_table[i].nsubcalls) {
			tcp->scno = subcalls_table[i].subcalls[tcp->u_arg[0]];
			for (i = 0; i < tcp->u_nargs; i++)
				tcp->u_arg[i] = tcp->u_arg[i + 1];
		}
		break;
#endif /* FREEBSD */
	}
}
#endif

struct tcb *tcp_last = NULL;

static int
internal_syscall(struct tcb *tcp)
{
	/*
	 * We must always trace a few critical system calls in order to
	 * correctly support following forks in the presence of tracing
	 * qualifiers.
	 */
	int	(*func)();

	if (tcp->scno < 0 || tcp->scno >= nsyscalls)
		return 0;

	func = sysent[tcp->scno].sys_func;

	if (sys_exit == func)
		return internal_exit(tcp);

	if (   sys_fork == func
#if defined(FREEBSD) || defined(LINUX) || defined(SUNOS4)
	    || sys_vfork == func
#endif
#ifdef LINUX
	    || sys_clone == func
#endif
#if UNIXWARE > 2
	    || sys_rfork == func
#endif
	   )
		return internal_fork(tcp);

	if (   sys_execve == func
#if defined(SPARC) || defined(SPARC64) || defined(SUNOS4)
	    || sys_execv == func
#endif
#if UNIXWARE > 2
	    || sys_rexecve == func
#endif
	   )
		return internal_exec(tcp);

	if (   sys_waitpid == func
	    || sys_wait4 == func
#if defined(SVR4) || defined(FREEBSD) || defined(SUNOS4)
	    || sys_wait == func
#endif
#ifdef ALPHA
	    || sys_osf_wait4 == func
#endif
	   )
		return internal_wait(tcp, 2);

#if defined(LINUX) || defined(SVR4)
	if (sys_waitid == func)
		return internal_wait(tcp, 3);
#endif

	return 0;
}


#ifdef LINUX
#if defined (I386)
	static long eax;
#elif defined (IA64)
	long r8, r10, psr;
	long ia32 = 0;
#elif defined (POWERPC)
	static long result,flags;
#elif defined (M68K)
	static long d0;
#elif defined(BFIN)
	static long r0;
#elif defined (ARM)
	static struct pt_regs regs;
#elif defined (ALPHA)
	static long r0;
	static long a3;
#elif defined(AVR32)
	static struct pt_regs regs;
#elif defined (SPARC) || defined (SPARC64)
	static struct pt_regs regs;
	static unsigned long trap;
#elif defined(LINUX_MIPSN32)
	static long long a3;
	static long long r2;
#elif defined(MIPS)
	static long a3;
	static long r2;
#elif defined(S390) || defined(S390X)
	static long gpr2;
	static long pc;
	static long syscall_mode;
#elif defined(HPPA)
	static long r28;
#elif defined(SH)
	static long r0;
#elif defined(SH64)
	static long r9;
#elif defined(X86_64)
	static long rax;
#elif defined(CRISV10) || defined(CRISV32)
	static long r10;
#elif defined(MICROBLAZE)
	static long r3;
#endif
#endif /* LINUX */
#ifdef FREEBSD
	struct reg regs;
#endif /* FREEBSD */

int
get_scno(struct tcb *tcp)
{
	long scno = 0;

#ifdef LINUX
# if defined(S390) || defined(S390X)
	if (tcp->flags & TCB_WAITEXECVE) {
		/*
		 * When the execve system call completes successfully, the
		 * new process still has -ENOSYS (old style) or __NR_execve
		 * (new style) in gpr2.  We cannot recover the scno again
		 * by disassembly, because the image that executed the
		 * syscall is gone now.  Fortunately, we don't want it.  We
		 * leave the flag set so that syscall_fixup can fake the
		 * result.
		 */
		if (tcp->flags & TCB_INSYSCALL)
			return 1;
		/*
		 * This is the SIGTRAP after execve.  We cannot try to read
		 * the system call here either.
		 */
		tcp->flags &= ~TCB_WAITEXECVE;
		return 0;
	}

	if (upeek(tcp, PT_GPR2, &syscall_mode) < 0)
			return -1;

	if (syscall_mode != -ENOSYS) {
		/*
		 * Since kernel version 2.5.44 the scno gets passed in gpr2.
		 */
		scno = syscall_mode;
	} else {
		/*
		 * Old style of "passing" the scno via the SVC instruction.
		 */

		long opcode, offset_reg, tmp;
		void * svc_addr;
		int gpr_offset[16] = {PT_GPR0,  PT_GPR1,  PT_ORIGGPR2, PT_GPR3,
				      PT_GPR4,  PT_GPR5,  PT_GPR6,     PT_GPR7,
				      PT_GPR8,  PT_GPR9,  PT_GPR10,    PT_GPR11,
				      PT_GPR12, PT_GPR13, PT_GPR14,    PT_GPR15};

		if (upeek(tcp, PT_PSWADDR, &pc) < 0)
			return -1;
		errno = 0;
		opcode = ptrace(PTRACE_PEEKTEXT, tcp->pid, (char *)(pc-sizeof(long)), 0);
		if (errno) {
			perror("peektext(pc-oneword)");
			return -1;
		}

		/*
		 *  We have to check if the SVC got executed directly or via an
		 *  EXECUTE instruction. In case of EXECUTE it is necessary to do
		 *  instruction decoding to derive the system call number.
		 *  Unfortunately the opcode sizes of EXECUTE and SVC are differently,
		 *  so that this doesn't work if a SVC opcode is part of an EXECUTE
		 *  opcode. Since there is no way to find out the opcode size this
		 *  is the best we can do...
		 */

		if ((opcode & 0xff00) == 0x0a00) {
			/* SVC opcode */
			scno = opcode & 0xff;
		}
		else {
			/* SVC got executed by EXECUTE instruction */

			/*
			 *  Do instruction decoding of EXECUTE. If you really want to
			 *  understand this, read the Principles of Operations.
			 */
			svc_addr = (void *) (opcode & 0xfff);

			tmp = 0;
			offset_reg = (opcode & 0x000f0000) >> 16;
			if (offset_reg && (upeek(tcp, gpr_offset[offset_reg], &tmp) < 0))
				return -1;
			svc_addr += tmp;

			tmp = 0;
			offset_reg = (opcode & 0x0000f000) >> 12;
			if (offset_reg && (upeek(tcp, gpr_offset[offset_reg], &tmp) < 0))
				return -1;
			svc_addr += tmp;

			scno = ptrace(PTRACE_PEEKTEXT, tcp->pid, svc_addr, 0);
			if (errno)
				return -1;
#  if defined(S390X)
			scno >>= 48;
#  else
			scno >>= 16;
#  endif
			tmp = 0;
			offset_reg = (opcode & 0x00f00000) >> 20;
			if (offset_reg && (upeek(tcp, gpr_offset[offset_reg], &tmp) < 0))
				return -1;

			scno = (scno | tmp) & 0xff;
		}
	}
# elif defined (POWERPC)
	if (upeek(tcp, sizeof(unsigned long)*PT_R0, &scno) < 0)
		return -1;
	if (!(tcp->flags & TCB_INSYSCALL)) {
		/* Check if we return from execve. */
		if (scno == 0 && (tcp->flags & TCB_WAITEXECVE)) {
			tcp->flags &= ~TCB_WAITEXECVE;
			return 0;
		}
	}

#  ifdef POWERPC64
	if (!(tcp->flags & TCB_INSYSCALL)) {
		static int currpers = -1;
		long val;
		int pid = tcp->pid;

		/* Check for 64/32 bit mode. */
		if (upeek(tcp, sizeof (unsigned long)*PT_MSR, &val) < 0)
			return -1;
		/* SF is bit 0 of MSR */
		if (val < 0)
			currpers = 0;
		else
			currpers = 1;
		if (currpers != current_personality) {
			static const char *const names[] = {"64 bit", "32 bit"};
			set_personality(currpers);
			fprintf(stderr, "[ Process PID=%d runs in %s mode. ]\n",
					pid, names[current_personality]);
		}
	}
#  endif
# elif defined(AVR32)
	/*
	 * Read complete register set in one go.
	 */
	if (ptrace(PTRACE_GETREGS, tcp->pid, NULL, &regs) < 0)
		return -1;

	/*
	 * We only need to grab the syscall number on syscall entry.
	 */
	if (!(tcp->flags & TCB_INSYSCALL)) {
		scno = regs.r8;

		/* Check if we return from execve. */
		if (tcp->flags & TCB_WAITEXECVE) {
			tcp->flags &= ~TCB_WAITEXECVE;
			return 0;
		}
	}
# elif defined(BFIN)
	if (upeek(tcp, PT_ORIG_P0, &scno))
		return -1;
# elif defined (I386)
	if (upeek(tcp, 4*ORIG_EAX, &scno) < 0)
		return -1;
# elif defined (X86_64)
	if (upeek(tcp, 8*ORIG_RAX, &scno) < 0)
		return -1;

	if (!(tcp->flags & TCB_INSYSCALL)) {
		static int currpers = -1;
		long val;
		int pid = tcp->pid;

		/* Check CS register value. On x86-64 linux it is:
		 * 	0x33	for long mode (64 bit)
		 * 	0x23	for compatibility mode (32 bit)
		 * It takes only one ptrace and thus doesn't need
		 * to be cached.
		 */
		if (upeek(tcp, 8*CS, &val) < 0)
			return -1;
		switch (val) {
			case 0x23: currpers = 1; break;
			case 0x33: currpers = 0; break;
			default:
				fprintf(stderr, "Unknown value CS=0x%02X while "
					 "detecting personality of process "
					 "PID=%d\n", (int)val, pid);
				currpers = current_personality;
				break;
		}
#  if 0
		/* This version analyzes the opcode of a syscall instruction.
		 * (int 0x80 on i386 vs. syscall on x86-64)
		 * It works, but is too complicated.
		 */
		unsigned long val, rip, i;

		if (upeek(tcp, 8*RIP, &rip) < 0)
			perror("upeek(RIP)");

		/* sizeof(syscall) == sizeof(int 0x80) == 2 */
		rip -= 2;
		errno = 0;

		call = ptrace(PTRACE_PEEKTEXT, pid, (char *)rip, (char *)0);
		if (errno)
			fprintf(stderr, "ptrace_peektext failed: %s\n",
					strerror(errno));
		switch (call & 0xffff) {
			/* x86-64: syscall = 0x0f 0x05 */
			case 0x050f: currpers = 0; break;
			/* i386: int 0x80 = 0xcd 0x80 */
			case 0x80cd: currpers = 1; break;
			default:
				currpers = current_personality;
				fprintf(stderr,
					"Unknown syscall opcode (0x%04X) while "
					"detecting personality of process "
					"PID=%d\n", (int)call, pid);
				break;
		}
#  endif
		if (currpers != current_personality) {
			static const char *const names[] = {"64 bit", "32 bit"};
			set_personality(currpers);
			fprintf(stderr, "[ Process PID=%d runs in %s mode. ]\n",
					pid, names[current_personality]);
		}
	}
# elif defined(IA64)
#	define IA64_PSR_IS	((long)1 << 34)
	if (upeek (tcp, PT_CR_IPSR, &psr) >= 0)
		ia32 = (psr & IA64_PSR_IS) != 0;
	if (!(tcp->flags & TCB_INSYSCALL)) {
		if (ia32) {
			if (upeek(tcp, PT_R1, &scno) < 0)	/* orig eax */
				return -1;
		} else {
			if (upeek (tcp, PT_R15, &scno) < 0)
				return -1;
		}
		/* Check if we return from execve. */
		if (tcp->flags & TCB_WAITEXECVE) {
			tcp->flags &= ~TCB_WAITEXECVE;
			return 0;
		}
	} else {
		/* syscall in progress */
		if (upeek (tcp, PT_R8, &r8) < 0)
			return -1;
		if (upeek (tcp, PT_R10, &r10) < 0)
			return -1;
	}
# elif defined (ARM)
	/*
	 * Read complete register set in one go.
	 */
	if (ptrace(PTRACE_GETREGS, tcp->pid, NULL, (void *)&regs) == -1)
		return -1;

	/*
	 * We only need to grab the syscall number on syscall entry.
	 */
	if (regs.ARM_ip == 0) {
		if (!(tcp->flags & TCB_INSYSCALL)) {
			/* Check if we return from execve. */
			if (tcp->flags & TCB_WAITEXECVE) {
				tcp->flags &= ~TCB_WAITEXECVE;
				return 0;
			}
		}

		/*
		 * Note: we only deal with only 32-bit CPUs here.
		 */
		if (regs.ARM_cpsr & 0x20) {
			/*
			 * Get the Thumb-mode system call number
			 */
			scno = regs.ARM_r7;
		} else {
			/*
			 * Get the ARM-mode system call number
			 */
			errno = 0;
			scno = ptrace(PTRACE_PEEKTEXT, tcp->pid, (void *)(regs.ARM_pc - 4), NULL);
			if (errno)
				return -1;

			if (scno == 0 && (tcp->flags & TCB_WAITEXECVE)) {
				tcp->flags &= ~TCB_WAITEXECVE;
				return 0;
			}

			/* Handle the EABI syscall convention.  We do not
			   bother converting structures between the two
			   ABIs, but basic functionality should work even
			   if strace and the traced program have different
			   ABIs.  */
			if (scno == 0xef000000) {
				scno = regs.ARM_r7;
			} else {
				if ((scno & 0x0ff00000) != 0x0f900000) {
					fprintf(stderr, "syscall: unknown syscall trap 0x%08lx\n",
						scno);
					return -1;
				}

				/*
				 * Fixup the syscall number
				 */
				scno &= 0x000fffff;
			}
		}
		if (scno & 0x0f0000) {
			/*
			 * Handle ARM specific syscall
			 */
			set_personality(1);
			scno &= 0x0000ffff;
		} else
			set_personality(0);

		if (tcp->flags & TCB_INSYSCALL) {
			fprintf(stderr, "pid %d stray syscall entry\n", tcp->pid);
			tcp->flags &= ~TCB_INSYSCALL;
		}
	} else {
		if (!(tcp->flags & TCB_INSYSCALL)) {
			fprintf(stderr, "pid %d stray syscall exit\n", tcp->pid);
			tcp->flags |= TCB_INSYSCALL;
		}
	}
# elif defined (M68K)
	if (upeek(tcp, 4*PT_ORIG_D0, &scno) < 0)
		return -1;
# elif defined (LINUX_MIPSN32)
	unsigned long long regs[38];

	if (ptrace (PTRACE_GETREGS, tcp->pid, NULL, (long) &regs) < 0)
		return -1;
	a3 = regs[REG_A3];
	r2 = regs[REG_V0];

	if(!(tcp->flags & TCB_INSYSCALL)) {
		scno = r2;

		/* Check if we return from execve. */
		if (scno == 0 && tcp->flags & TCB_WAITEXECVE) {
			tcp->flags &= ~TCB_WAITEXECVE;
			return 0;
		}

		if (scno < 0 || scno > nsyscalls) {
			if(a3 == 0 || a3 == -1) {
				if(debug)
					fprintf (stderr, "stray syscall exit: v0 = %ld\n", scno);
				return 0;
			}
		}
	}
# elif defined (MIPS)
	if (upeek(tcp, REG_A3, &a3) < 0)
		return -1;
	if(!(tcp->flags & TCB_INSYSCALL)) {
		if (upeek(tcp, REG_V0, &scno) < 0)
			return -1;

		/* Check if we return from execve. */
		if (scno == 0 && tcp->flags & TCB_WAITEXECVE) {
			tcp->flags &= ~TCB_WAITEXECVE;
			return 0;
		}

		if (scno < 0 || scno > nsyscalls) {
			if(a3 == 0 || a3 == -1) {
				if(debug)
					fprintf (stderr, "stray syscall exit: v0 = %ld\n", scno);
				return 0;
			}
		}
	} else {
		if (upeek(tcp, REG_V0, &r2) < 0)
			return -1;
	}
# elif defined (ALPHA)
	if (upeek(tcp, REG_A3, &a3) < 0)
		return -1;

	if (!(tcp->flags & TCB_INSYSCALL)) {
		if (upeek(tcp, REG_R0, &scno) < 0)
			return -1;

		/* Check if we return from execve. */
		if (scno == 0 && tcp->flags & TCB_WAITEXECVE) {
			tcp->flags &= ~TCB_WAITEXECVE;
			return 0;
		}

		/*
		 * Do some sanity checks to figure out if it's
		 * really a syscall entry
		 */
		if (scno < 0 || scno > nsyscalls) {
			if (a3 == 0 || a3 == -1) {
				if (debug)
					fprintf (stderr, "stray syscall exit: r0 = %ld\n", scno);
				return 0;
			}
		}
	}
	else {
		if (upeek(tcp, REG_R0, &r0) < 0)
			return -1;
	}
# elif defined (SPARC) || defined (SPARC64)
	/* Everything we need is in the current register set. */
	if (ptrace(PTRACE_GETREGS, tcp->pid, (char *)&regs, 0) < 0)
		return -1;

	/* If we are entering, then disassemble the syscall trap. */
	if (!(tcp->flags & TCB_INSYSCALL)) {
		/* Retrieve the syscall trap instruction. */
		errno = 0;
#  if defined(SPARC64)
		trap = ptrace(PTRACE_PEEKTEXT, tcp->pid, (char *)regs.tpc, 0);
		trap >>= 32;
#  else
		trap = ptrace(PTRACE_PEEKTEXT, tcp->pid, (char *)regs.pc, 0);
#  endif
		if (errno)
			return -1;

		/* Disassemble the trap to see what personality to use. */
		switch (trap) {
		case 0x91d02010:
			/* Linux/SPARC syscall trap. */
			set_personality(0);
			break;
		case 0x91d0206d:
			/* Linux/SPARC64 syscall trap. */
			set_personality(2);
			break;
		case 0x91d02000:
			/* SunOS syscall trap. (pers 1) */
			fprintf(stderr,"syscall: SunOS no support\n");
			return -1;
		case 0x91d02008:
			/* Solaris 2.x syscall trap. (per 2) */
			set_personality(1);
			break;
		case 0x91d02009:
			/* NetBSD/FreeBSD syscall trap. */
			fprintf(stderr,"syscall: NetBSD/FreeBSD not supported\n");
			return -1;
		case 0x91d02027:
			/* Solaris 2.x gettimeofday */
			set_personality(1);
			break;
		default:
			/* Unknown syscall trap. */
			if(tcp->flags & TCB_WAITEXECVE) {
				tcp->flags &= ~TCB_WAITEXECVE;
				return 0;
			}
#  if defined (SPARC64)
			fprintf(stderr,"syscall: unknown syscall trap %08lx %016lx\n", trap, regs.tpc);
#  else
			fprintf(stderr,"syscall: unknown syscall trap %08lx %08lx\n", trap, regs.pc);
#  endif
			return -1;
		}

		/* Extract the system call number from the registers. */
		if (trap == 0x91d02027)
			scno = 156;
		else
			scno = regs.u_regs[U_REG_G1];
		if (scno == 0) {
			scno = regs.u_regs[U_REG_O0];
			memmove (&regs.u_regs[U_REG_O0], &regs.u_regs[U_REG_O1], 7*sizeof(regs.u_regs[0]));
		}
	}
# elif defined(HPPA)
	if (upeek(tcp, PT_GR20, &scno) < 0)
		return -1;
	if (!(tcp->flags & TCB_INSYSCALL)) {
		/* Check if we return from execve. */
		if ((tcp->flags & TCB_WAITEXECVE)) {
			tcp->flags &= ~TCB_WAITEXECVE;
			return 0;
		}
	}
# elif defined(SH)
	/*
	 * In the new syscall ABI, the system call number is in R3.
	 */
	if (upeek(tcp, 4*(REG_REG0+3), &scno) < 0)
		return -1;

	if (scno < 0) {
		/* Odd as it may seem, a glibc bug has been known to cause
		   glibc to issue bogus negative syscall numbers.  So for
		   our purposes, make strace print what it *should* have been */
		long correct_scno = (scno & 0xff);
		if (debug)
			fprintf(stderr,
				"Detected glibc bug: bogus system call"
				" number = %ld, correcting to %ld\n",
				scno,
				correct_scno);
		scno = correct_scno;
	}

	if (!(tcp->flags & TCB_INSYSCALL)) {
		/* Check if we return from execve. */
		if (scno == 0 && tcp->flags & TCB_WAITEXECVE) {
			tcp->flags &= ~TCB_WAITEXECVE;
			return 0;
		}
	}
# elif defined(SH64)
	if (upeek(tcp, REG_SYSCALL, &scno) < 0)
		return -1;
	scno &= 0xFFFF;

	if (!(tcp->flags & TCB_INSYSCALL)) {
		/* Check if we return from execve. */
		if (tcp->flags & TCB_WAITEXECVE) {
			tcp->flags &= ~TCB_WAITEXECVE;
			return 0;
		}
	}
# elif defined(CRISV10) || defined(CRISV32)
	if (upeek(tcp, 4*PT_R9, &scno) < 0)
		return -1;
# elif defined(TILE)
	if (upeek(tcp, PTREGS_OFFSET_REG(10), &scno) < 0)
		return -1;

	if (!(tcp->flags & TCB_INSYSCALL)) {
		/* Check if we return from execve. */
		if (tcp->flags & TCB_WAITEXECVE) {
			tcp->flags &= ~TCB_WAITEXECVE;
			return 0;
		}
	}
# elif defined(MICROBLAZE)
	if (upeek(tcp, 0, &scno) < 0)
		return -1;
# endif
#endif /* LINUX */

#ifdef SUNOS4
	if (upeek(tcp, uoff(u_arg[7]), &scno) < 0)
		return -1;
#elif defined(SH)
	/* new syscall ABI returns result in R0 */
	if (upeek(tcp, 4*REG_REG0, (long *)&r0) < 0)
		return -1;
#elif defined(SH64)
	/* ABI defines result returned in r9 */
	if (upeek(tcp, REG_GENERAL(9), (long *)&r9) < 0)
		return -1;
#endif

#ifdef USE_PROCFS
# ifdef HAVE_PR_SYSCALL
	scno = tcp->status.PR_SYSCALL;
# else
#  ifndef FREEBSD
	scno = tcp->status.PR_WHAT;
#  else
	if (pread(tcp->pfd_reg, &regs, sizeof(regs), 0) < 0) {
		perror("pread");
		return -1;
	}
	switch (regs.r_eax) {
	case SYS_syscall:
	case SYS___syscall:
		pread(tcp->pfd, &scno, sizeof(scno), regs.r_esp + sizeof(int));
		break;
	default:
		scno = regs.r_eax;
		break;
	}
#  endif /* FREEBSD */
# endif /* !HAVE_PR_SYSCALL */
#endif /* USE_PROCFS */

	if (!(tcp->flags & TCB_INSYSCALL))
		tcp->scno = scno;
	return 1;
}


long
known_scno(struct tcb *tcp)
{
	long scno = tcp->scno;
#if SUPPORTED_PERSONALITIES > 1
	if (scno >= 0 && scno < nsyscalls && sysent[scno].native_scno != 0)
		scno = sysent[scno].native_scno;
	else
#endif
		scno += NR_SYSCALL_BASE;
	return scno;
}

/* Called in trace_syscall() at each syscall entry and exit.
 * Returns:
 * 0: "ignore this syscall", bail out of trace_syscall() silently.
 * 1: ok, continue in trace_syscall().
 * other: error, trace_syscall() should print error indicator
 *    ("????" etc) and bail out.
 */
static int
syscall_fixup(struct tcb *tcp)
{
#ifdef USE_PROCFS
	int scno = known_scno(tcp);

	if (!(tcp->flags & TCB_INSYSCALL)) {
		if (tcp->status.PR_WHY != PR_SYSENTRY) {
			if (
			    scno == SYS_fork
#ifdef SYS_vfork
			    || scno == SYS_vfork
#endif /* SYS_vfork */
#ifdef SYS_fork1
			    || scno == SYS_fork1
#endif /* SYS_fork1 */
#ifdef SYS_forkall
			    || scno == SYS_forkall
#endif /* SYS_forkall */
#ifdef SYS_rfork1
			    || scno == SYS_rfork1
#endif /* SYS_fork1 */
#ifdef SYS_rforkall
			    || scno == SYS_rforkall
#endif /* SYS_rforkall */
			    ) {
				/* We are returning in the child, fake it. */
				tcp->status.PR_WHY = PR_SYSENTRY;
				trace_syscall(tcp);
				tcp->status.PR_WHY = PR_SYSEXIT;
			}
			else {
				fprintf(stderr, "syscall: missing entry\n");
				tcp->flags |= TCB_INSYSCALL;
			}
		}
	}
	else {
		if (tcp->status.PR_WHY != PR_SYSEXIT) {
			fprintf(stderr, "syscall: missing exit\n");
			tcp->flags &= ~TCB_INSYSCALL;
		}
	}
#endif /* USE_PROCFS */
#ifdef SUNOS4
	if (!(tcp->flags & TCB_INSYSCALL)) {
		if (scno == 0) {
			fprintf(stderr, "syscall: missing entry\n");
			tcp->flags |= TCB_INSYSCALL;
		}
	}
	else {
		if (scno != 0) {
			if (debug) {
				/*
				 * This happens when a signal handler
				 * for a signal which interrupted a
				 * a system call makes another system call.
				 */
				fprintf(stderr, "syscall: missing exit\n");
			}
			tcp->flags &= ~TCB_INSYSCALL;
		}
	}
#endif /* SUNOS4 */
#ifdef LINUX
#if defined (I386)
	if (upeek(tcp, 4*EAX, &eax) < 0)
		return -1;
	if (eax != -ENOSYS && !(tcp->flags & TCB_INSYSCALL)) {
		if (debug)
			fprintf(stderr, "stray syscall exit: eax = %ld\n", eax);
		return 0;
	}
#elif defined (X86_64)
	if (upeek(tcp, 8*RAX, &rax) < 0)
		return -1;
	if (current_personality == 1)
		rax = (long int)(int)rax; /* sign extend from 32 bits */
	if (rax != -ENOSYS && !(tcp->flags & TCB_INSYSCALL)) {
		if (debug)
			fprintf(stderr, "stray syscall exit: rax = %ld\n", rax);
		return 0;
	}
#elif defined (S390) || defined (S390X)
	if (upeek(tcp, PT_GPR2, &gpr2) < 0)
		return -1;
	if (syscall_mode != -ENOSYS)
		syscall_mode = tcp->scno;
	if (gpr2 != syscall_mode && !(tcp->flags & TCB_INSYSCALL)) {
		if (debug)
			fprintf(stderr, "stray syscall exit: gpr2 = %ld\n", gpr2);
		return 0;
	}
	else if (((tcp->flags & (TCB_INSYSCALL|TCB_WAITEXECVE))
		  == (TCB_INSYSCALL|TCB_WAITEXECVE))
		 && (gpr2 == -ENOSYS || gpr2 == tcp->scno)) {
		/*
		 * Fake a return value of zero.  We leave the TCB_WAITEXECVE
		 * flag set for the post-execve SIGTRAP to see and reset.
		 */
		gpr2 = 0;
	}
#elif defined (POWERPC)
# define SO_MASK 0x10000000
	if (upeek(tcp, sizeof(unsigned long)*PT_CCR, &flags) < 0)
		return -1;
	if (upeek(tcp, sizeof(unsigned long)*PT_R3, &result) < 0)
		return -1;
	if (flags & SO_MASK)
		result = -result;
#elif defined (M68K)
	if (upeek(tcp, 4*PT_D0, &d0) < 0)
		return -1;
	if (d0 != -ENOSYS && !(tcp->flags & TCB_INSYSCALL)) {
		if (debug)
			fprintf(stderr, "stray syscall exit: d0 = %ld\n", d0);
		return 0;
	}
#elif defined (ARM)
	/*
	 * Nothing required
	 */
#elif defined(BFIN)
	if (upeek(tcp, PT_R0, &r0) < 0)
		return -1;
#elif defined (HPPA)
	if (upeek(tcp, PT_GR28, &r28) < 0)
		return -1;
#elif defined(IA64)
	if (upeek(tcp, PT_R10, &r10) < 0)
		return -1;
	if (upeek(tcp, PT_R8, &r8) < 0)
		return -1;
	if (ia32 && r8 != -ENOSYS && !(tcp->flags & TCB_INSYSCALL)) {
		if (debug)
			fprintf(stderr, "stray syscall exit: r8 = %ld\n", r8);
		return 0;
	}
#elif defined(CRISV10) || defined(CRISV32)
	if (upeek(tcp, 4*PT_R10, &r10) < 0)
		return -1;
	if (r10 != -ENOSYS && !(tcp->flags & TCB_INSYSCALL)) {
		if (debug)
			fprintf(stderr, "stray syscall exit: r10 = %ld\n", r10);
		return 0;
	}
#elif defined(MICROBLAZE)
	if (upeek(tcp, 3 * 4, &r3) < 0)
		return -1;
	if (r3 != -ENOSYS && !(tcp->flags & TCB_INSYSCALL)) {
		if (debug)
			fprintf(stderr, "stray syscall exit: r3 = %ld\n", r3);
		return 0;
	}
#endif
#endif /* LINUX */
	return 1;
}

#ifdef LINUX
/*
 * Check the syscall return value register value for whether it is
 * a negated errno code indicating an error, or a success return value.
 */
static inline int
is_negated_errno(unsigned long int val)
{
	unsigned long int max = -(long int) nerrnos;
	if (personality_wordsize[current_personality] < sizeof(val)) {
		val = (unsigned int) val;
		max = (unsigned int) max;
	}
	return val > max;
}
#endif

static int
get_error(struct tcb *tcp)
{
	int u_error = 0;
#ifdef LINUX
	int check_errno = 1;
	if (tcp->scno >= 0 && tcp->scno < nsyscalls &&
	    sysent[tcp->scno].sys_flags & SYSCALL_NEVER_FAILS) {
		check_errno = 0;
	}
# if defined(S390) || defined(S390X)
	if (check_errno && is_negated_errno(gpr2)) {
		tcp->u_rval = -1;
		u_error = -gpr2;
	}
	else {
		tcp->u_rval = gpr2;
		u_error = 0;
	}
# elif defined(I386)
	if (check_errno && is_negated_errno(eax)) {
		tcp->u_rval = -1;
		u_error = -eax;
	}
	else {
		tcp->u_rval = eax;
		u_error = 0;
	}
# elif defined(X86_64)
	if (check_errno && is_negated_errno(rax)) {
		tcp->u_rval = -1;
		u_error = -rax;
	}
	else {
		tcp->u_rval = rax;
		u_error = 0;
	}
# elif defined(IA64)
	if (ia32) {
		int err;

		err = (int)r8;
		if (check_errno && is_negated_errno(err)) {
			tcp->u_rval = -1;
			u_error = -err;
		}
		else {
			tcp->u_rval = err;
			u_error = 0;
		}
	} else {
		if (check_errno && r10) {
			tcp->u_rval = -1;
			u_error = r8;
		} else {
			tcp->u_rval = r8;
			u_error = 0;
		}
	}
# elif defined(MIPS)
		if (check_errno && a3) {
			tcp->u_rval = -1;
			u_error = r2;
		} else {
			tcp->u_rval = r2;
			u_error = 0;
		}
# elif defined(POWERPC)
		if (check_errno && is_negated_errno(result)) {
			tcp->u_rval = -1;
			u_error = -result;
		}
		else {
			tcp->u_rval = result;
			u_error = 0;
		}
# elif defined(M68K)
		if (check_errno && is_negated_errno(d0)) {
			tcp->u_rval = -1;
			u_error = -d0;
		}
		else {
			tcp->u_rval = d0;
			u_error = 0;
		}
# elif defined(ARM)
		if (check_errno && is_negated_errno(regs.ARM_r0)) {
			tcp->u_rval = -1;
			u_error = -regs.ARM_r0;
		}
		else {
			tcp->u_rval = regs.ARM_r0;
			u_error = 0;
		}
# elif defined(AVR32)
		if (check_errno && regs.r12 && (unsigned) -regs.r12 < nerrnos) {
			tcp->u_rval = -1;
			u_error = -regs.r12;
		}
		else {
			tcp->u_rval = regs.r12;
			u_error = 0;
		}
# elif defined(BFIN)
		if (check_errno && is_negated_errno(r0)) {
			tcp->u_rval = -1;
			u_error = -r0;
		} else {
			tcp->u_rval = r0;
			u_error = 0;
		}
# elif defined(ALPHA)
		if (check_errno && a3) {
			tcp->u_rval = -1;
			u_error = r0;
		}
		else {
			tcp->u_rval = r0;
			u_error = 0;
		}
# elif defined(SPARC)
		if (check_errno && regs.psr & PSR_C) {
			tcp->u_rval = -1;
			u_error = regs.u_regs[U_REG_O0];
		}
		else {
			tcp->u_rval = regs.u_regs[U_REG_O0];
			u_error = 0;
		}
# elif defined(SPARC64)
		if (check_errno && regs.tstate & 0x1100000000UL) {
			tcp->u_rval = -1;
			u_error = regs.u_regs[U_REG_O0];
		}
		else {
			tcp->u_rval = regs.u_regs[U_REG_O0];
			u_error = 0;
		}
# elif defined(HPPA)
		if (check_errno && is_negated_errno(r28)) {
			tcp->u_rval = -1;
			u_error = -r28;
		}
		else {
			tcp->u_rval = r28;
			u_error = 0;
		}
# elif defined(SH)
		/* interpret R0 as return value or error number */
		if (check_errno && is_negated_errno(r0)) {
			tcp->u_rval = -1;
			u_error = -r0;
		}
		else {
			tcp->u_rval = r0;
			u_error = 0;
		}
# elif defined(SH64)
		/* interpret result as return value or error number */
		if (check_errno && is_negated_errno(r9)) {
			tcp->u_rval = -1;
			u_error = -r9;
		}
		else {
			tcp->u_rval = r9;
			u_error = 0;
		}
# elif defined(CRISV10) || defined(CRISV32)
		if (check_errno && r10 && (unsigned) -r10 < nerrnos) {
			tcp->u_rval = -1;
			u_error = -r10;
		}
		else {
			tcp->u_rval = r10;
			u_error = 0;
		}
# elif defined(TILE)
		long rval;
		/* interpret result as return value or error number */
		if (upeek(tcp, PTREGS_OFFSET_REG(0), &rval) < 0)
			return -1;
		if (check_errno && rval < 0 && rval > -nerrnos) {
			tcp->u_rval = -1;
			u_error = -rval;
		}
		else {
			tcp->u_rval = rval;
			u_error = 0;
		}
# elif defined(MICROBLAZE)
		/* interpret result as return value or error number */
		if (check_errno && is_negated_errno(r3)) {
			tcp->u_rval = -1;
			u_error = -r3;
		}
		else {
			tcp->u_rval = r3;
			u_error = 0;
		}
# endif
#endif /* LINUX */
#ifdef SUNOS4
		/* get error code from user struct */
		if (upeek(tcp, uoff(u_error), &u_error) < 0)
			return -1;
		u_error >>= 24; /* u_error is a char */

		/* get system call return value */
		if (upeek(tcp, uoff(u_rval1), &tcp->u_rval) < 0)
			return -1;
#endif /* SUNOS4 */
#ifdef SVR4
#ifdef SPARC
		/* Judicious guessing goes a long way. */
		if (tcp->status.pr_reg[R_PSR] & 0x100000) {
			tcp->u_rval = -1;
			u_error = tcp->status.pr_reg[R_O0];
		}
		else {
			tcp->u_rval = tcp->status.pr_reg[R_O0];
			u_error = 0;
		}
#endif /* SPARC */
#ifdef I386
		/* Wanna know how to kill an hour single-stepping? */
		if (tcp->status.PR_REG[EFL] & 0x1) {
			tcp->u_rval = -1;
			u_error = tcp->status.PR_REG[EAX];
		}
		else {
			tcp->u_rval = tcp->status.PR_REG[EAX];
#ifdef HAVE_LONG_LONG
			tcp->u_lrval =
				((unsigned long long) tcp->status.PR_REG[EDX] << 32) +
				tcp->status.PR_REG[EAX];
#endif
			u_error = 0;
		}
#endif /* I386 */
#ifdef X86_64
		/* Wanna know how to kill an hour single-stepping? */
		if (tcp->status.PR_REG[EFLAGS] & 0x1) {
			tcp->u_rval = -1;
			u_error = tcp->status.PR_REG[RAX];
		}
		else {
			tcp->u_rval = tcp->status.PR_REG[RAX];
			u_error = 0;
		}
#endif /* X86_64 */
#ifdef MIPS
		if (tcp->status.pr_reg[CTX_A3]) {
			tcp->u_rval = -1;
			u_error = tcp->status.pr_reg[CTX_V0];
		}
		else {
			tcp->u_rval = tcp->status.pr_reg[CTX_V0];
			u_error = 0;
		}
#endif /* MIPS */
#endif /* SVR4 */
#ifdef FREEBSD
		if (regs.r_eflags & PSL_C) {
			tcp->u_rval = -1;
		        u_error = regs.r_eax;
		} else {
			tcp->u_rval = regs.r_eax;
			tcp->u_lrval =
			  ((unsigned long long) regs.r_edx << 32) +  regs.r_eax;
		        u_error = 0;
		}
#endif /* FREEBSD */
	tcp->u_error = u_error;
	return 1;
}

int
force_result(tcp, error, rval)
	struct tcb *tcp;
	int error;
	long rval;
{
#ifdef LINUX
# if defined(S390) || defined(S390X)
	gpr2 = error ? -error : rval;
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)PT_GPR2, gpr2) < 0)
		return -1;
# elif defined(I386)
	eax = error ? -error : rval;
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(EAX * 4), eax) < 0)
		return -1;
# elif defined(X86_64)
	rax = error ? -error : rval;
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(RAX * 8), rax) < 0)
		return -1;
# elif defined(IA64)
	if (ia32) {
		r8 = error ? -error : rval;
		if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(PT_R8), r8) < 0)
			return -1;
	}
	else {
		if (error) {
			r8 = error;
			r10 = -1;
		}
		else {
			r8 = rval;
			r10 = 0;
		}
		if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(PT_R8), r8) < 0 ||
		    ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(PT_R10), r10) < 0)
			return -1;
	}
# elif defined(BFIN)
	r0 = error ? -error : rval;
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)PT_R0, r0) < 0)
		return -1;
# elif defined(MIPS)
	if (error) {
		r2 = error;
		a3 = -1;
	}
	else {
		r2 = rval;
		a3 = 0;
	}
	/* PTRACE_POKEUSER is OK even for n32 since rval is only a long.  */
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(REG_A3), a3) < 0 ||
	    ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(REG_V0), r2) < 0)
		return -1;
# elif defined(POWERPC)
	if (upeek(tcp, sizeof(unsigned long)*PT_CCR, &flags) < 0)
		return -1;
	if (error) {
		flags |= SO_MASK;
		result = error;
	}
	else {
		flags &= ~SO_MASK;
		result = rval;
	}
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(sizeof(unsigned long)*PT_CCR), flags) < 0 ||
	    ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(sizeof(unsigned long)*PT_R3), result) < 0)
		return -1;
# elif defined(M68K)
	d0 = error ? -error : rval;
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(4*PT_D0), d0) < 0)
		return -1;
# elif defined(ARM)
	regs.ARM_r0 = error ? -error : rval;
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(4*0), regs.ARM_r0) < 0)
		return -1;
# elif defined(AVR32)
	regs.r12 = error ? -error : rval;
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)REG_R12, regs.r12) < 0)
		return -1;
# elif defined(ALPHA)
	if (error) {
		a3 = -1;
		r0 = error;
	}
	else {
		a3 = 0;
		r0 = rval;
	}
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(REG_A3), a3) < 0 ||
	    ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(REG_R0), r0) < 0)
		return -1;
# elif defined(SPARC)
	if (ptrace(PTRACE_GETREGS, tcp->pid, (char *)&regs, 0) < 0)
		return -1;
	if (error) {
		regs.psr |= PSR_C;
		regs.u_regs[U_REG_O0] = error;
	}
	else {
		regs.psr &= ~PSR_C;
		regs.u_regs[U_REG_O0] = rval;
	}
	if (ptrace(PTRACE_SETREGS, tcp->pid, (char *)&regs, 0) < 0)
		return -1;
# elif defined(SPARC64)
	if (ptrace(PTRACE_GETREGS, tcp->pid, (char *)&regs, 0) < 0)
		return -1;
	if (error) {
		regs.tstate |= 0x1100000000UL;
		regs.u_regs[U_REG_O0] = error;
	}
	else {
		regs.tstate &= ~0x1100000000UL;
		regs.u_regs[U_REG_O0] = rval;
	}
	if (ptrace(PTRACE_SETREGS, tcp->pid, (char *)&regs, 0) < 0)
		return -1;
# elif defined(HPPA)
	r28 = error ? -error : rval;
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(PT_GR28), r28) < 0)
		return -1;
# elif defined(SH)
	r0 = error ? -error : rval;
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)(4*REG_REG0), r0) < 0)
		return -1;
# elif defined(SH64)
	r9 = error ? -error : rval;
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)REG_GENERAL(9), r9) < 0)
		return -1;
# endif
#endif /* LINUX */

#ifdef SUNOS4
	if (ptrace(PTRACE_POKEUSER, tcp->pid, (char*)uoff(u_error),
		   error << 24) < 0 ||
	    ptrace(PTRACE_POKEUSER, tcp->pid, (char*)uoff(u_rval1), rval) < 0)
		return -1;
#endif /* SUNOS4 */

#ifdef SVR4
	/* XXX no clue */
	return -1;
#endif /* SVR4 */

#ifdef FREEBSD
	if (pread(tcp->pfd_reg, &regs, sizeof(regs), 0) < 0) {
		perror("pread");
		return -1;
	}
	if (error) {
		regs.r_eflags |= PSL_C;
		regs.r_eax = error;
	}
	else {
		regs.r_eflags &= ~PSL_C;
		regs.r_eax = rval;
	}
	if (pwrite(tcp->pfd_reg, &regs, sizeof(regs), 0) < 0) {
		perror("pwrite");
		return -1;
	}
#endif /* FREEBSD */

	/* All branches reach here on success (only).  */
	tcp->u_error = error;
	tcp->u_rval = rval;
	return 0;
}

static int
syscall_enter(struct tcb *tcp)
{
#ifdef LINUX
#if defined(S390) || defined(S390X)
	{
		int i;
		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; i++) {
			if (upeek(tcp,i==0 ? PT_ORIGGPR2:PT_GPR2+i*sizeof(long), &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#elif defined (ALPHA)
	{
		int i;
		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; i++) {
			/* WTA: if scno is out-of-bounds this will bomb. Add range-check
			 * for scno somewhere above here!
			 */
			if (upeek(tcp, REG_A0+i, &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#elif defined (IA64)
	{
		if (!ia32) {
			unsigned long *out0, cfm, sof, sol, i;
			long rbs_end;
			/* be backwards compatible with kernel < 2.4.4... */
#			ifndef PT_RBS_END
#			  define PT_RBS_END	PT_AR_BSP
#			endif

			if (upeek(tcp, PT_RBS_END, &rbs_end) < 0)
				return -1;
			if (upeek(tcp, PT_CFM, (long *) &cfm) < 0)
				return -1;

			sof = (cfm >> 0) & 0x7f;
			sol = (cfm >> 7) & 0x7f;
			out0 = ia64_rse_skip_regs((unsigned long *) rbs_end, -sof + sol);

			if (tcp->scno >= 0 && tcp->scno < nsyscalls
			    && sysent[tcp->scno].nargs != -1)
				tcp->u_nargs = sysent[tcp->scno].nargs;
			else
				tcp->u_nargs = MAX_ARGS;
			for (i = 0; i < tcp->u_nargs; ++i) {
				if (umoven(tcp, (unsigned long) ia64_rse_skip_regs(out0, i),
					   sizeof(long), (char *) &tcp->u_arg[i]) < 0)
					return -1;
			}
		} else {
			int i;

			if (/* EBX = out0 */
			    upeek(tcp, PT_R11, (long *) &tcp->u_arg[0]) < 0
			    /* ECX = out1 */
			    || upeek(tcp, PT_R9,  (long *) &tcp->u_arg[1]) < 0
			    /* EDX = out2 */
			    || upeek(tcp, PT_R10, (long *) &tcp->u_arg[2]) < 0
			    /* ESI = out3 */
			    || upeek(tcp, PT_R14, (long *) &tcp->u_arg[3]) < 0
			    /* EDI = out4 */
			    || upeek(tcp, PT_R15, (long *) &tcp->u_arg[4]) < 0
			    /* EBP = out5 */
			    || upeek(tcp, PT_R13, (long *) &tcp->u_arg[5]) < 0)
				return -1;

			for (i = 0; i < 6; ++i)
				/* truncate away IVE sign-extension */
				tcp->u_arg[i] &= 0xffffffff;

			if (tcp->scno >= 0 && tcp->scno < nsyscalls
			    && sysent[tcp->scno].nargs != -1)
				tcp->u_nargs = sysent[tcp->scno].nargs;
			else
				tcp->u_nargs = 5;
		}
	}
#elif defined (LINUX_MIPSN32) || defined (LINUX_MIPSN64)
	/* N32 and N64 both use up to six registers.  */
	{
		unsigned long long regs[38];
		int i, nargs;

		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			nargs = tcp->u_nargs = MAX_ARGS;

		if (ptrace (PTRACE_GETREGS, tcp->pid, NULL, (long) &regs) < 0)
			return -1;

		for(i = 0; i < nargs; i++) {
			tcp->u_arg[i] = regs[REG_A0 + i];
# if defined (LINUX_MIPSN32)
			tcp->ext_arg[i] = regs[REG_A0 + i];
# endif
		}
	}
#elif defined (MIPS)
	{
		long sp;
		int i, nargs;

		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			nargs = tcp->u_nargs = MAX_ARGS;
		if(nargs > 4) {
			if(upeek(tcp, REG_SP, &sp) < 0)
				return -1;
			for(i = 0; i < 4; i++) {
				if (upeek(tcp, REG_A0 + i, &tcp->u_arg[i])<0)
					return -1;
			}
			umoven(tcp, sp+16, (nargs-4) * sizeof(tcp->u_arg[0]),
			       (char *)(tcp->u_arg + 4));
		} else {
			for(i = 0; i < nargs; i++) {
				if (upeek(tcp, REG_A0 + i, &tcp->u_arg[i]) < 0)
					return -1;
			}
		}
	}
#elif defined (POWERPC)
# ifndef PT_ORIG_R3
#  define PT_ORIG_R3 34
# endif
	{
		int i;
		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; i++) {
			if (upeek(tcp, (i==0) ?
				(sizeof(unsigned long)*PT_ORIG_R3) :
				((i+PT_R3)*sizeof(unsigned long)),
					&tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#elif defined (SPARC) || defined (SPARC64)
	{
		int i;

		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; i++)
			tcp->u_arg[i] = regs.u_regs[U_REG_O0 + i];
	}
#elif defined (HPPA)
	{
		int i;

		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; i++) {
			if (upeek(tcp, PT_GR26-4*i, &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#elif defined(ARM)
	{
		int i;

		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; i++)
			tcp->u_arg[i] = regs.uregs[i];
	}
#elif defined(AVR32)
	tcp->u_nargs = sysent[tcp->scno].nargs;
	tcp->u_arg[0] = regs.r12;
	tcp->u_arg[1] = regs.r11;
	tcp->u_arg[2] = regs.r10;
	tcp->u_arg[3] = regs.r9;
	tcp->u_arg[4] = regs.r5;
	tcp->u_arg[5] = regs.r3;
#elif defined(BFIN)
	{
		int i;
		int argreg[] = {PT_R0, PT_R1, PT_R2, PT_R3, PT_R4, PT_R5};

		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = sizeof(argreg) / sizeof(argreg[0]);

		for (i = 0; i < tcp->u_nargs; ++i)
			if (upeek(tcp, argreg[i], &tcp->u_arg[i]) < 0)
				return -1;
	}
#elif defined(SH)
	{
		int i;
		static int syscall_regs[] = {
			REG_REG0+4, REG_REG0+5, REG_REG0+6, REG_REG0+7,
			REG_REG0, REG_REG0+1, REG_REG0+2
		};

		tcp->u_nargs = sysent[tcp->scno].nargs;
		for (i = 0; i < tcp->u_nargs; i++) {
			if (upeek(tcp, 4*syscall_regs[i], &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#elif defined(SH64)
	{
		int i;
		/* Registers used by SH5 Linux system calls for parameters */
		static int syscall_regs[] = { 2, 3, 4, 5, 6, 7 };

		/*
		 * TODO: should also check that the number of arguments encoded
		 *       in the trap number matches the number strace expects.
		 */
		/*
		assert(sysent[tcp->scno].nargs <
		       sizeof(syscall_regs)/sizeof(syscall_regs[0]));
		 */

		tcp->u_nargs = sysent[tcp->scno].nargs;
		for (i = 0; i < tcp->u_nargs; i++) {
			if (upeek(tcp, REG_GENERAL(syscall_regs[i]), &tcp->u_arg[i]) < 0)
				return -1;
		}
	}

#elif defined(X86_64)
	{
		int i;
		static int argreg[SUPPORTED_PERSONALITIES][MAX_ARGS] = {
			{RDI,RSI,RDX,R10,R8,R9},	/* x86-64 ABI */
			{RBX,RCX,RDX,RSI,RDI,RBP}	/* i386 ABI */
		};

		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; i++) {
			if (upeek(tcp, argreg[current_personality][i]*8, &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#elif defined(MICROBLAZE)
	{
		int i;
		if (tcp->scno >= 0 && tcp->scno < nsyscalls)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = 0;
		for (i = 0; i < tcp->u_nargs; i++) {
			if (upeek(tcp, (5 + i) * 4, &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#elif defined(CRISV10) || defined(CRISV32)
	{
		int i;
		static const int crisregs[] = {
			4*PT_ORIG_R10, 4*PT_R11, 4*PT_R12,
			4*PT_R13, 4*PT_MOF, 4*PT_SRP
		};

		if (tcp->scno >= 0 && tcp->scno < nsyscalls)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = 0;
		for (i = 0; i < tcp->u_nargs; i++) {
			if (upeek(tcp, crisregs[i], &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#elif defined(TILE)
	{
		int i;
		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; ++i) {
			if (upeek(tcp, PTREGS_OFFSET_REG(i), &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#elif defined (M68K)
	{
		int i;
		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; i++) {
			if (upeek(tcp, (i < 5 ? i : i + 2)*4, &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#else /* Other architecture (like i386) (32bits specific) */
	{
		int i;
		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; i++) {
			if (upeek(tcp, i*4, &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#endif
#endif /* LINUX */
#ifdef SUNOS4
	{
		int i;
		if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
			tcp->u_nargs = sysent[tcp->scno].nargs;
		else
			tcp->u_nargs = MAX_ARGS;
		for (i = 0; i < tcp->u_nargs; i++) {
			struct user *u;

			if (upeek(tcp, uoff(u_arg[0]) +
			    (i*sizeof(u->u_arg[0])), &tcp->u_arg[i]) < 0)
				return -1;
		}
	}
#endif /* SUNOS4 */
#ifdef SVR4
#ifdef MIPS
	/*
	 * SGI is broken: even though it has pr_sysarg, it doesn't
	 * set them on system call entry.  Get a clue.
	 */
	if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
		tcp->u_nargs = sysent[tcp->scno].nargs;
	else
		tcp->u_nargs = tcp->status.pr_nsysarg;
	if (tcp->u_nargs > 4) {
		memcpy(tcp->u_arg, &tcp->status.pr_reg[CTX_A0],
			4*sizeof(tcp->u_arg[0]));
		umoven(tcp, tcp->status.pr_reg[CTX_SP] + 16,
			(tcp->u_nargs - 4)*sizeof(tcp->u_arg[0]), (char *) (tcp->u_arg + 4));
	}
	else {
		memcpy(tcp->u_arg, &tcp->status.pr_reg[CTX_A0],
			tcp->u_nargs*sizeof(tcp->u_arg[0]));
	}
#elif UNIXWARE >= 2
	/*
	 * Like SGI, UnixWare doesn't set pr_sysarg until system call exit
	 */
	if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
		tcp->u_nargs = sysent[tcp->scno].nargs;
	else
		tcp->u_nargs = tcp->status.pr_lwp.pr_nsysarg;
	umoven(tcp, tcp->status.PR_REG[UESP] + 4,
		tcp->u_nargs*sizeof(tcp->u_arg[0]), (char *) tcp->u_arg);
#elif defined (HAVE_PR_SYSCALL)
	if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
		tcp->u_nargs = sysent[tcp->scno].nargs;
	else
		tcp->u_nargs = tcp->status.pr_nsysarg;
	{
		int i;
		for (i = 0; i < tcp->u_nargs; i++)
			tcp->u_arg[i] = tcp->status.pr_sysarg[i];
	}
#elif defined (I386)
	if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs != -1)
		tcp->u_nargs = sysent[tcp->scno].nargs;
	else
		tcp->u_nargs = 5;
	umoven(tcp, tcp->status.PR_REG[UESP] + 4,
		tcp->u_nargs*sizeof(tcp->u_arg[0]), (char *) tcp->u_arg);
#else
	I DONT KNOW WHAT TO DO
#endif /* !HAVE_PR_SYSCALL */
#endif /* SVR4 */
#ifdef FREEBSD
	if (tcp->scno >= 0 && tcp->scno < nsyscalls &&
	    sysent[tcp->scno].nargs > tcp->status.val)
		tcp->u_nargs = sysent[tcp->scno].nargs;
	else
		tcp->u_nargs = tcp->status.val;
	if (tcp->u_nargs < 0)
		tcp->u_nargs = 0;
	if (tcp->u_nargs > MAX_ARGS)
		tcp->u_nargs = MAX_ARGS;
	switch(regs.r_eax) {
	case SYS___syscall:
		pread(tcp->pfd, &tcp->u_arg, tcp->u_nargs * sizeof(unsigned long),
		      regs.r_esp + sizeof(int) + sizeof(quad_t));
		break;
	case SYS_syscall:
		pread(tcp->pfd, &tcp->u_arg, tcp->u_nargs * sizeof(unsigned long),
		      regs.r_esp + 2 * sizeof(int));
		break;
	default:
		pread(tcp->pfd, &tcp->u_arg, tcp->u_nargs * sizeof(unsigned long),
		      regs.r_esp + sizeof(int));
		break;
	}
#endif /* FREEBSD */
	return 1;
}

static int
trace_syscall_exiting(struct tcb *tcp)
{
	int sys_res;
	struct timeval tv;
	int res, scno_good;
	long u_error;

	/* Measure the exit time as early as possible to avoid errors. */
	if (dtime || cflag)
		gettimeofday(&tv, NULL);

	/* BTW, why we don't just memorize syscall no. on entry
	 * in tcp->something?
	 */
	scno_good = res = get_scno(tcp);
	if (res == 0)
		return res;
	if (res == 1)
		res = syscall_fixup(tcp);
	if (res == 0)
		return res;
	if (res == 1)
		res = get_error(tcp);
	if (res == 0)
		return res;
	if (res == 1)
		internal_syscall(tcp);

	if (res == 1 && tcp->scno >= 0 && tcp->scno < nsyscalls &&
	    !(qual_flags[tcp->scno] & QUAL_TRACE)) {
		tcp->flags &= ~TCB_INSYSCALL;
		return 0;
	}

	if (tcp->flags & TCB_REPRINT) {
		printleader(tcp);
		tprintf("<... ");
		if (scno_good != 1)
			tprintf("????");
		else if (tcp->scno >= nsyscalls || tcp->scno < 0)
			tprintf("syscall_%lu", tcp->scno);
		else
			tprintf("%s", sysent[tcp->scno].sys_name);
		tprintf(" resumed> ");
	}

	if (cflag) {
		struct timeval t = tv;
		int rc = count_syscall(tcp, &t);
		if (cflag == CFLAG_ONLY_STATS)
		{
			tcp->flags &= ~TCB_INSYSCALL;
			return rc;
		}
	}

	if (res != 1) {
		tprintf(") ");
		tabto(acolumn);
		tprintf("= ? <unavailable>");
		printtrailer();
		tcp->flags &= ~TCB_INSYSCALL;
		return res;
	}

	if (tcp->scno >= nsyscalls || tcp->scno < 0
	    || (qual_flags[tcp->scno] & QUAL_RAW))
		sys_res = printargs(tcp);
	else {
		if (not_failing_only && tcp->u_error)
			return 0;	/* ignore failed syscalls */
		sys_res = (*sysent[tcp->scno].sys_func)(tcp);
	}

	u_error = tcp->u_error;
	tprintf(") ");
	tabto(acolumn);
	if (tcp->scno >= nsyscalls || tcp->scno < 0 ||
	    qual_flags[tcp->scno] & QUAL_RAW) {
		if (u_error)
			tprintf("= -1 (errno %ld)", u_error);
		else
			tprintf("= %#lx", tcp->u_rval);
	}
	else if (!(sys_res & RVAL_NONE) && u_error) {
		switch (u_error) {
#ifdef LINUX
		case ERESTARTSYS:
			tprintf("= ? ERESTARTSYS (To be restarted)");
			break;
		case ERESTARTNOINTR:
			tprintf("= ? ERESTARTNOINTR (To be restarted)");
			break;
		case ERESTARTNOHAND:
			tprintf("= ? ERESTARTNOHAND (To be restarted)");
			break;
		case ERESTART_RESTARTBLOCK:
			tprintf("= ? ERESTART_RESTARTBLOCK (To be restarted)");
			break;
#endif /* LINUX */
		default:
			tprintf("= -1 ");
			if (u_error < 0)
				tprintf("E??? (errno %ld)", u_error);
			else if (u_error < nerrnos)
				tprintf("%s (%s)", errnoent[u_error],
					strerror(u_error));
			else
				tprintf("ERRNO_%ld (%s)", u_error,
					strerror(u_error));
			break;
		}
		if ((sys_res & RVAL_STR) && tcp->auxstr)
			tprintf(" (%s)", tcp->auxstr);
	}
	else {
		if (sys_res & RVAL_NONE)
			tprintf("= ?");
		else {
			switch (sys_res & RVAL_MASK) {
			case RVAL_HEX:
				tprintf("= %#lx", tcp->u_rval);
				break;
			case RVAL_OCTAL:
				tprintf("= %#lo", tcp->u_rval);
				break;
			case RVAL_UDECIMAL:
				tprintf("= %lu", tcp->u_rval);
				break;
			case RVAL_DECIMAL:
				tprintf("= %ld", tcp->u_rval);
				break;
#ifdef HAVE_LONG_LONG
			case RVAL_LHEX:
				tprintf("= %#llx", tcp->u_lrval);
				break;
			case RVAL_LOCTAL:
				tprintf("= %#llo", tcp->u_lrval);
				break;
			case RVAL_LUDECIMAL:
				tprintf("= %llu", tcp->u_lrval);
				break;
			case RVAL_LDECIMAL:
				tprintf("= %lld", tcp->u_lrval);
				break;
#endif
			default:
				fprintf(stderr,
					"invalid rval format\n");
				break;
			}
		}
		if ((sys_res & RVAL_STR) && tcp->auxstr)
			tprintf(" (%s)", tcp->auxstr);
	}
	if (dtime) {
		tv_sub(&tv, &tv, &tcp->etime);
		tprintf(" <%ld.%06ld>",
			(long) tv.tv_sec, (long) tv.tv_usec);
	}
	printtrailer();

	dumpio(tcp);
	if (fflush(tcp->outf) == EOF)
		return -1;
	tcp->flags &= ~TCB_INSYSCALL;
	return 0;
}

static int
trace_syscall_entering(struct tcb *tcp)
{
	int sys_res;
	int res, scno_good;

	scno_good = res = get_scno(tcp);
	if (res == 0)
		return res;
	if (res == 1)
		res = syscall_fixup(tcp);
	if (res == 0)
		return res;
	if (res == 1)
		res = syscall_enter(tcp);
	if (res == 0)
		return res;

	if (res != 1) {
		printleader(tcp);
		tcp->flags &= ~TCB_REPRINT;
		tcp_last = tcp;
		if (scno_good != 1)
			tprintf("????" /* anti-trigraph gap */ "(");
		else if (tcp->scno >= nsyscalls || tcp->scno < 0)
			tprintf("syscall_%lu(", tcp->scno);
		else
			tprintf("%s(", sysent[tcp->scno].sys_name);
		/*
		 * " <unavailable>" will be added later by the code which
		 * detects ptrace errors.
		 */
		tcp->flags |= TCB_INSYSCALL;
		return res;
	}

	switch (known_scno(tcp)) {
#ifdef SYS_socket_subcall
	case SYS_socketcall:
		decode_subcall(tcp, SYS_socket_subcall,
			SYS_socket_nsubcalls, deref_style);
		break;
#endif
#ifdef SYS_ipc_subcall
	case SYS_ipc:
		decode_subcall(tcp, SYS_ipc_subcall,
			SYS_ipc_nsubcalls, shift_style);
		break;
#endif
#ifdef SVR4
#ifdef SYS_pgrpsys_subcall
	case SYS_pgrpsys:
		decode_subcall(tcp, SYS_pgrpsys_subcall,
			SYS_pgrpsys_nsubcalls, shift_style);
		break;
#endif /* SYS_pgrpsys_subcall */
#ifdef SYS_sigcall_subcall
	case SYS_sigcall:
		decode_subcall(tcp, SYS_sigcall_subcall,
			SYS_sigcall_nsubcalls, mask_style);
		break;
#endif /* SYS_sigcall_subcall */
	case SYS_msgsys:
		decode_subcall(tcp, SYS_msgsys_subcall,
			SYS_msgsys_nsubcalls, shift_style);
		break;
	case SYS_shmsys:
		decode_subcall(tcp, SYS_shmsys_subcall,
			SYS_shmsys_nsubcalls, shift_style);
		break;
	case SYS_semsys:
		decode_subcall(tcp, SYS_semsys_subcall,
			SYS_semsys_nsubcalls, shift_style);
		break;
	case SYS_sysfs:
		decode_subcall(tcp, SYS_sysfs_subcall,
			SYS_sysfs_nsubcalls, shift_style);
		break;
	case SYS_spcall:
		decode_subcall(tcp, SYS_spcall_subcall,
			SYS_spcall_nsubcalls, shift_style);
		break;
#ifdef SYS_context_subcall
	case SYS_context:
		decode_subcall(tcp, SYS_context_subcall,
			SYS_context_nsubcalls, shift_style);
		break;
#endif /* SYS_context_subcall */
#ifdef SYS_door_subcall
	case SYS_door:
		decode_subcall(tcp, SYS_door_subcall,
			SYS_door_nsubcalls, door_style);
		break;
#endif /* SYS_door_subcall */
#ifdef SYS_kaio_subcall
	case SYS_kaio:
		decode_subcall(tcp, SYS_kaio_subcall,
			SYS_kaio_nsubcalls, shift_style);
		break;
#endif
#endif /* SVR4 */
#ifdef FREEBSD
	case SYS_msgsys:
	case SYS_shmsys:
	case SYS_semsys:
		decode_subcall(tcp, 0, 0, table_style);
		break;
#endif
#ifdef SUNOS4
	case SYS_semsys:
		decode_subcall(tcp, SYS_semsys_subcall,
			SYS_semsys_nsubcalls, shift_style);
		break;
	case SYS_msgsys:
		decode_subcall(tcp, SYS_msgsys_subcall,
			SYS_msgsys_nsubcalls, shift_style);
		break;
	case SYS_shmsys:
		decode_subcall(tcp, SYS_shmsys_subcall,
			SYS_shmsys_nsubcalls, shift_style);
		break;
#endif
	}

	internal_syscall(tcp);
	if (tcp->scno >=0 && tcp->scno < nsyscalls && !(qual_flags[tcp->scno] & QUAL_TRACE)) {
		tcp->flags |= TCB_INSYSCALL;
		return 0;
	}

	if (cflag == CFLAG_ONLY_STATS) {
		tcp->flags |= TCB_INSYSCALL;
		gettimeofday(&tcp->etime, NULL);
		return 0;
	}

	printleader(tcp);
	tcp->flags &= ~TCB_REPRINT;
	tcp_last = tcp;
	if (tcp->scno >= nsyscalls || tcp->scno < 0)
		tprintf("syscall_%lu(", tcp->scno);
	else
		tprintf("%s(", sysent[tcp->scno].sys_name);
	if (tcp->scno >= nsyscalls || tcp->scno < 0 ||
	    ((qual_flags[tcp->scno] & QUAL_RAW) &&
	     sysent[tcp->scno].sys_func != sys_exit))
		sys_res = printargs(tcp);
	else
		sys_res = (*sysent[tcp->scno].sys_func)(tcp);
	if (fflush(tcp->outf) == EOF)
		return -1;
	tcp->flags |= TCB_INSYSCALL;
	/* Measure the entrance time as late as possible to avoid errors. */
	if (dtime || cflag)
		gettimeofday(&tcp->etime, NULL);
	return sys_res;
}

int
trace_syscall(struct tcb *tcp)
{
	return exiting(tcp) ?
		trace_syscall_exiting(tcp) : trace_syscall_entering(tcp);
}

int
printargs(tcp)
struct tcb *tcp;
{
	if (entering(tcp)) {
		int i;

		for (i = 0; i < tcp->u_nargs; i++)
			tprintf("%s%#lx", i ? ", " : "", tcp->u_arg[i]);
	}
	return 0;
}

long
getrval2(tcp)
struct tcb *tcp;
{
	long val = -1;

#ifdef LINUX
#if defined (SPARC) || defined (SPARC64)
	struct pt_regs regs;
	if (ptrace(PTRACE_GETREGS,tcp->pid,(char *)&regs,0) < 0)
		return -1;
	val = regs.u_regs[U_REG_O1];
#elif defined(SH)
	if (upeek(tcp, 4*(REG_REG0+1), &val) < 0)
		return -1;
#elif defined(IA64)
	if (upeek(tcp, PT_R9, &val) < 0)
		return -1;
#endif
#endif /* LINUX */

#ifdef SUNOS4
	if (upeek(tcp, uoff(u_rval2), &val) < 0)
		return -1;
#endif /* SUNOS4 */

#ifdef SVR4
#ifdef SPARC
	val = tcp->status.PR_REG[R_O1];
#endif /* SPARC */
#ifdef I386
	val = tcp->status.PR_REG[EDX];
#endif /* I386 */
#ifdef X86_64
	val = tcp->status.PR_REG[RDX];
#endif /* X86_64 */
#ifdef MIPS
	val = tcp->status.PR_REG[CTX_V1];
#endif /* MIPS */
#endif /* SVR4 */

#ifdef FREEBSD
	struct reg regs;
	pread(tcp->pfd_reg, &regs, sizeof(regs), 0);
	val = regs.r_edx;
#endif
	return val;
}

#ifdef SUNOS4
/*
 * Apparently, indirect system calls have already be converted by ptrace(2),
 * so if you see "indir" this program has gone astray.
 */
int
sys_indir(tcp)
struct tcb *tcp;
{
	int i, scno, nargs;

	if (entering(tcp)) {
		if ((scno = tcp->u_arg[0]) > nsyscalls) {
			fprintf(stderr, "Bogus syscall: %u\n", scno);
			return 0;
		}
		nargs = sysent[scno].nargs;
		tprintf("%s", sysent[scno].sys_name);
		for (i = 0; i < nargs; i++)
			tprintf(", %#lx", tcp->u_arg[i+1]);
	}
	return 0;
}
#endif /* SUNOS4 */

int
is_restart_error(struct tcb *tcp)
{
#ifdef LINUX
	if (!syserror(tcp))
		return 0;
	switch (tcp->u_error) {
		case ERESTARTSYS:
		case ERESTARTNOINTR:
		case ERESTARTNOHAND:
		case ERESTART_RESTARTBLOCK:
			return 1;
		default:
			break;
	}
#endif /* LINUX */
	return 0;
}