sysdeps/linux-gnu/trace.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include "ptrace.h"
#include <asm/unistd.h>

#include "ltrace.h"
#include "options.h"
#include "sysdep.h"
#include "debug.h"

/* If the system headers did not provide the constants, hard-code the normal
   values.  */
#ifndef PTRACE_EVENT_FORK

#define PTRACE_OLDSETOPTIONS    21
#define PTRACE_SETOPTIONS       0x4200
#define PTRACE_GETEVENTMSG      0x4201

/* options set using PTRACE_SETOPTIONS */
#define PTRACE_O_TRACESYSGOOD   0x00000001
#define PTRACE_O_TRACEFORK      0x00000002
#define PTRACE_O_TRACEVFORK     0x00000004
#define PTRACE_O_TRACECLONE     0x00000008
#define PTRACE_O_TRACEEXEC      0x00000010
#define PTRACE_O_TRACEVFORKDONE 0x00000020
#define PTRACE_O_TRACEEXIT      0x00000040

/* Wait extended result codes for the above trace options.  */
#define PTRACE_EVENT_FORK       1
#define PTRACE_EVENT_VFORK      2
#define PTRACE_EVENT_CLONE      3
#define PTRACE_EVENT_EXEC       4
#define PTRACE_EVENT_VFORK_DONE 5
#define PTRACE_EVENT_EXIT       6

#endif /* PTRACE_EVENT_FORK */

static int fork_exec_syscalls[][5] = {
	{
#ifdef __NR_fork
	 __NR_fork,
#else
	 -1,
#endif
#ifdef __NR_clone
	 __NR_clone,
#else
	 -1,
#endif
#ifdef __NR_clone2
	 __NR_clone2,
#else
	 -1,
#endif
#ifdef __NR_vfork
	 __NR_vfork,
#else
	 -1,
#endif
#ifdef __NR_execve
	 __NR_execve,
#else
	 -1,
#endif
	 }
#ifdef FORK_EXEC_SYSCALLS
	FORK_EXEC_SYSCALLS
#endif
};

#ifdef ARCH_HAVE_UMOVELONG
extern int arch_umovelong (Process *, void *, long *, arg_type_info *);
int
umovelong (Process *proc, void *addr, long *result, arg_type_info *info) {
	return arch_umovelong (proc, addr, result, info);
}
#else
/* Read a single long from the process's memory address 'addr' */
int
umovelong (Process *proc, void *addr, long *result, arg_type_info *info) {
	long pointed_to;

	errno = 0;
	pointed_to = ptrace (PTRACE_PEEKTEXT, proc->pid, addr, 0);
	if (pointed_to == -1 && errno)
		return -errno;

	*result = pointed_to;
	return 0;
}
#endif


/* Returns 1 if the sysnum may make a new child to be created
 * (ie, with fork() or clone())
 * Returns 0 otherwise.
 */
int
fork_p(Process *proc, int sysnum) {
	unsigned int i;
	if (proc->personality
	    >= sizeof fork_exec_syscalls / sizeof(fork_exec_syscalls[0]))
		return 0;
	for (i = 0; i < sizeof(fork_exec_syscalls[0]) / sizeof(int) - 1; ++i)
		if (sysnum == fork_exec_syscalls[proc->personality][i])
			return 1;
	return 0;
}

/* Returns 1 if the sysnum may make the process exec other program
 */
int
exec_p(Process *proc, int sysnum) {
	int i;
	if (proc->personality
	    >= sizeof fork_exec_syscalls / sizeof(fork_exec_syscalls[0]))
		return 0;
	i = sizeof(fork_exec_syscalls[0]) / sizeof(int) - 1;
	if (sysnum == fork_exec_syscalls[proc->personality][i])
		return 1;
	return 0;
}

/* Check that we just hit an exec.
 */
int
was_exec(Process *proc, int status) {
	if (!WIFSTOPPED (status))
		return 0;

	if (WSTOPSIG (status) == SIGTRAP
	    && (status >> 16) == PTRACE_EVENT_EXEC) {
		debug (1, "detected exec (PTRACE_EVENT_EXEC)");
		return 1;
	}

	if (WSTOPSIG (status) == SIGTRAP
	    && proc->callstack_depth > 0) {
		/* Check whether this SIGTRAP is received just after
		   execve is called for this process.  Ideally we'd
		   like to check that the exec succeeded, but e.g. on
		   s390 we have no way of knowing, because return
		   value is not set to -1 (as it should).  Never mind,
		   reseting breakpoints for current process doesn't
		   hurt. */
		struct callstack_element *elem;
		elem = &proc->callstack[proc->callstack_depth - 1];
		if (elem && elem->is_syscall &&  exec_p(proc, elem->c_un.syscall)) {
			debug (1, "detected exec (callstack)");
			return 1;
		}
	}

	return 0;
}

void
trace_me(void) {
	if (ptrace(PTRACE_TRACEME, 0, 1, 0) < 0) {
		perror("PTRACE_TRACEME");
		exit(1);
	}
}

int
trace_pid(pid_t pid) {
	if (ptrace(PTRACE_ATTACH, pid, 1, 0) < 0) {
		return -1;
	}

	/* man ptrace: PTRACE_ATTACH attaches to the process specified
	   in pid.  The child is sent a SIGSTOP, but will not
	   necessarily have stopped by the completion of this call;
	   use wait() to wait for the child to stop. */
	if (waitpid (pid, NULL, 0) != pid) {
		perror ("trace_pid: waitpid");
		exit (1);
	}

	return 0;
}

void
trace_set_options(Process *proc, pid_t pid) {
	if (proc->tracesysgood & 0x80)
		return;

	long options = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEFORK |
		PTRACE_O_TRACEVFORK | PTRACE_O_TRACECLONE |
		PTRACE_O_TRACEEXEC;
	if (ptrace(PTRACE_SETOPTIONS, pid, 0, options) < 0 &&
	    ptrace(PTRACE_OLDSETOPTIONS, pid, 0, options) < 0) {
		perror("PTRACE_SETOPTIONS");
		return;
	}
	proc->tracesysgood |= 0x80;
}

void
untrace_pid(pid_t pid) {
	ptrace(PTRACE_DETACH, pid, 1, 0);
}

void
continue_after_signal(pid_t pid, int signum) {
	Process *proc;

	proc = pid2proc(pid);
	if (proc && proc->breakpoint_being_enabled) {
#if defined __sparc__  || defined __ia64___
		ptrace(PTRACE_SYSCALL, pid, 0, signum);
#else
		ptrace(PTRACE_SINGLESTEP, pid, 0, signum);
#endif
	} else {
		ptrace(PTRACE_SYSCALL, pid, 0, signum);
	}
}

void
continue_process(pid_t pid) {
	/* We always trace syscalls to control fork(), clone(), execve()... */

	ptrace(PTRACE_SYSCALL, pid, 0, 0);
}

void
continue_enabling_breakpoint(pid_t pid, struct breakpoint *sbp) {
	enable_breakpoint(pid, sbp);
	continue_process(pid);
}

void
continue_after_breakpoint(Process *proc, struct breakpoint *sbp) {
	if (sbp->enabled)
		disable_breakpoint(proc->pid, sbp);
	set_instruction_pointer(proc, sbp->addr);
	if (sbp->enabled == 0) {
		continue_process(proc->pid);
	} else {
		proc->breakpoint_being_enabled = sbp;
#if defined __sparc__  || defined __ia64___
		/* we don't want to singlestep here */
		continue_process(proc->pid);
#else
		ptrace(PTRACE_SINGLESTEP, proc->pid, 0, 0);
#endif
	}
}

/* Read a series of bytes starting at the process's memory address
   'addr' and continuing until a NUL ('\0') is seen or 'len' bytes
   have been read.
*/
int
umovestr(Process *proc, void *addr, int len, void *laddr) {
	union {
		long a;
		char c[sizeof(long)];
	} a;
	int i;
	int offset = 0;

	while (offset < len) {
		a.a = ptrace(PTRACE_PEEKTEXT, proc->pid, addr + offset, 0);
		for (i = 0; i < sizeof(long); i++) {
			if (a.c[i] && offset + (signed)i < len) {
				*(char *)(laddr + offset + i) = a.c[i];
			} else {
				*(char *)(laddr + offset + i) = '\0';
				return 0;
			}
		}
		offset += sizeof(long);
	}
	*(char *)(laddr + offset) = '\0';
	return 0;
}