arch/um/os-Linux/start_up.c - fp2-dev/kernel/msm - Gitiles

 /*
  * Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
  * Licensed under the GPL
  */

 #include <stdio.h>
 #include <stddef.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <signal.h>
 #include <sched.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <setjmp.h>
 #include <sys/time.h>
 #include <sys/wait.h>
 #include <sys/mman.h>
 #include <asm/unistd.h>
 #include <asm/page.h>
 #include <sys/types.h>
 #include "user_util.h"
 #include "kern_util.h"
 #include "user.h"
 #include "signal_kern.h"
 #include "sysdep/ptrace.h"
 #include "sysdep/sigcontext.h"
 #include "irq_user.h"
 #include "ptrace_user.h"
 #include "mem_user.h"
 #include "time_user.h"
 #include "init.h"
 #include "os.h"
 #include "uml-config.h"
 #include "choose-mode.h"
 #include "mode.h"
 #include "tempfile.h"
 #include "kern_constants.h"

 #ifdef UML_CONFIG_MODE_SKAS
 #include "skas.h"
 #include "skas_ptrace.h"
 #include "registers.h"
 #endif

 static int ptrace_child(void *arg)
 {
 	int ret;
 	int pid = os_getpid(), ppid = getppid();
 	int sc_result;

 	if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
 		perror("ptrace");
 		os_kill_process(pid, 0);
 	}
 	os_stop_process(pid);

 	/*This syscall will be intercepted by the parent. Don't call more than
 	 * once, please.*/
 	sc_result = os_getpid();

 	if (sc_result == pid)
 		ret = 1; /*Nothing modified by the parent, we are running
 			   normally.*/
 	else if (sc_result == ppid)
 		ret = 0; /*Expected in check_ptrace and check_sysemu when they
 			   succeed in modifying the stack frame*/
 	else
 		ret = 2; /*Serious trouble! This could be caused by a bug in
 			   host 2.6 SKAS3/2.6 patch before release -V6, together
 			   with a bug in the UML code itself.*/
 	_exit(ret);
 }

 static int start_ptraced_child(void **stack_out)
 {
 	void *stack;
 	unsigned long sp;
 	int pid, n, status;

 	stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
 		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 	if(stack == MAP_FAILED)
 		panic("check_ptrace : mmap failed, errno = %d", errno);
 	sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
 	pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
 	if(pid < 0)
 		panic("start_ptraced_child : clone failed, errno = %d", errno);
 	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 	if(n < 0)
 		panic("check_ptrace : clone failed, errno = %d", errno);
 	if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
 		panic("check_ptrace : expected SIGSTOP, got status = %d",
 		      status);

 	*stack_out = stack;
 	return(pid);
 }

 /* When testing for SYSEMU support, if it is one of the broken versions, we
  * must just avoid using sysemu, not panic, but only if SYSEMU features are
  * broken.
  * So only for SYSEMU features we test mustpanic, while normal host features
  * must work anyway!
  */
 static int stop_ptraced_child(int pid, void *stack, int exitcode,
 			      int mustpanic)
 {
 	int status, n, ret = 0;

 	if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
 		panic("check_ptrace : ptrace failed, errno = %d", errno);
 	CATCH_EINTR(n = waitpid(pid, &status, 0));
 	if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
 		int exit_with = WEXITSTATUS(status);
 		if (exit_with == 2)
 			printf("check_ptrace : child exited with status 2. "
 			       "Serious trouble happening! Try updating your "
 			       "host skas patch!\nDisabling SYSEMU support.");
 		printf("check_ptrace : child exited with exitcode %d, while "
 		      "expecting %d; status 0x%x", exit_with,
 		      exitcode, status);
 		if (mustpanic)
 			panic("\n");
 		else
 			printf("\n");
 		ret = -1;
 	}

 	if(munmap(stack, PAGE_SIZE) < 0)
 		panic("check_ptrace : munmap failed, errno = %d", errno);
 	return ret;
 }

 int ptrace_faultinfo = 1;
 int ptrace_ldt = 1;
 int proc_mm = 1;
 int skas_needs_stub = 0;

 static int __init skas0_cmd_param(char *str, int* add)
 {
 	ptrace_faultinfo = proc_mm = 0;
 	return 0;
 }

 /* The two __uml_setup would conflict, without this stupid alias. */

 static int __init mode_skas0_cmd_param(char *str, int* add)
 	__attribute__((alias("skas0_cmd_param")));

 __uml_setup("skas0", skas0_cmd_param,
 		"skas0\n"
 		"    Disables SKAS3 usage, so that SKAS0 is used, unless \n"
 	        "    you specify mode=tt.\n\n");

 __uml_setup("mode=skas0", mode_skas0_cmd_param,
 		"mode=skas0\n"
 		"    Disables SKAS3 usage, so that SKAS0 is used, unless you \n"
 		"    specify mode=tt. Note that this was recently added - on \n"
 		"    older kernels you must use simply \"skas0\".\n\n");

 static int force_sysemu_disabled = 0;

 static int __init nosysemu_cmd_param(char *str, int* add)
 {
 	force_sysemu_disabled = 1;
 	return 0;
 }

 __uml_setup("nosysemu", nosysemu_cmd_param,
 "nosysemu\n"
 "    Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
 "    SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
 "    behaviour of ptrace() and helps reducing host context switch rate.\n"
 "    To make it working, you need a kernel patch for your host, too.\n"
 "    See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n"
 "    information.\n\n");

 static void __init check_sysemu(void)
 {
 	void *stack;
  	int pid, n, status, count=0;

 	printf("Checking syscall emulation patch for ptrace...");
 	sysemu_supported = 0;
 	pid = start_ptraced_child(&stack);

 	if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
 		goto fail;

 	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 	if (n < 0)
 		panic("check_sysemu : wait failed, errno = %d", errno);
 	if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
 		panic("check_sysemu : expected SIGTRAP, "
 		      "got status = %d", status);

 	n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 		   os_getpid());
 	if(n < 0)
 		panic("check_sysemu : failed to modify system "
 		      "call return, errno = %d", errno);

 	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 		goto fail_stopped;

 	sysemu_supported = 1;
 	printf("OK\n");
 	set_using_sysemu(!force_sysemu_disabled);

 	printf("Checking advanced syscall emulation patch for ptrace...");
 	pid = start_ptraced_child(&stack);

 	if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
 		  (void *) PTRACE_O_TRACESYSGOOD) < 0)
 		panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d",
 		      errno);

 	while(1){
 		count++;
 		if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
 			goto fail;
 		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 		if(n < 0)
 			panic("check_ptrace : wait failed, errno = %d", errno);
 		if(WIFSTOPPED(status) && (WSTOPSIG(status) == (SIGTRAP|0x80))){
 			if (!count)
 				panic("check_ptrace : SYSEMU_SINGLESTEP "
 				      "doesn't singlestep");
 			n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 				   os_getpid());
 			if(n < 0)
 				panic("check_sysemu : failed to modify system "
 				      "call return, errno = %d", errno);
 			break;
 		}
 		else if(WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP))
 			count++;
 		else
 			panic("check_ptrace : expected SIGTRAP or "
 			      "(SIGTRAP|0x80), got status = %d", status);
 	}
 	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 		goto fail_stopped;

 	sysemu_supported = 2;
 	printf("OK\n");

 	if ( !force_sysemu_disabled )
 		set_using_sysemu(sysemu_supported);
 	return;

 fail:
 	stop_ptraced_child(pid, stack, 1, 0);
 fail_stopped:
 	printf("missing\n");
 }

 static void __init check_ptrace(void)
 {
 	void *stack;
 	int pid, syscall, n, status;

 	printf("Checking that ptrace can change system call numbers...");
 	pid = start_ptraced_child(&stack);

 	if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 		panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d", errno);

 	while(1){
 		if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
 			panic("check_ptrace : ptrace failed, errno = %d",
 			      errno);
 		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 		if(n < 0)
 			panic("check_ptrace : wait failed, errno = %d", errno);
 		if(!WIFSTOPPED(status) || (WSTOPSIG(status) != (SIGTRAP|0x80)))
 			panic("check_ptrace : expected (SIGTRAP|0x80), "
 			      "got status = %d", status);

 		syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
 				 0);
 		if(syscall == __NR_getpid){
 			n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
 				   __NR_getppid);
 			if(n < 0)
 				panic("check_ptrace : failed to modify system "
 				      "call, errno = %d", errno);
 			break;
 		}
 	}
 	stop_ptraced_child(pid, stack, 0, 1);
 	printf("OK\n");
 	check_sysemu();
 }

 extern int create_tmp_file(unsigned long long len);

 static void check_tmpexec(void)
 {
 	void *addr;
 	int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);

 	addr = mmap(NULL, UM_KERN_PAGE_SIZE,
 		    PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
 	printf("Checking PROT_EXEC mmap in /tmp...");
 	fflush(stdout);
 	if(addr == MAP_FAILED){
 		err = errno;
 		perror("failed");
 		if(err == EPERM)
 			printf("/tmp must be not mounted noexec\n");
 		exit(1);
 	}
 	printf("OK\n");
 	munmap(addr, UM_KERN_PAGE_SIZE);

 	close(fd);
 }

 void os_early_checks(void)
 {
 	check_ptrace();

 	/* Need to check this early because mmapping happens before the
 	 * kernel is running.
 	 */
 	check_tmpexec();
 }

 static int __init noprocmm_cmd_param(char *str, int* add)
 {
 	proc_mm = 0;
 	return 0;
 }

 __uml_setup("noprocmm", noprocmm_cmd_param,
 "noprocmm\n"
 "    Turns off usage of /proc/mm, even if host supports it.\n"
 "    To support /proc/mm, the host needs to be patched using\n"
 "    the current skas3 patch.\n\n");

 static int __init noptracefaultinfo_cmd_param(char *str, int* add)
 {
 	ptrace_faultinfo = 0;
 	return 0;
 }

 __uml_setup("noptracefaultinfo", noptracefaultinfo_cmd_param,
 "noptracefaultinfo\n"
 "    Turns off usage of PTRACE_FAULTINFO, even if host supports\n"
 "    it. To support PTRACE_FAULTINFO, the host needs to be patched\n"
 "    using the current skas3 patch.\n\n");

 static int __init noptraceldt_cmd_param(char *str, int* add)
 {
 	ptrace_ldt = 0;
 	return 0;
 }

 __uml_setup("noptraceldt", noptraceldt_cmd_param,
 "noptraceldt\n"
 "    Turns off usage of PTRACE_LDT, even if host supports it.\n"
 "    To support PTRACE_LDT, the host needs to be patched using\n"
 "    the current skas3 patch.\n\n");

 #ifdef UML_CONFIG_MODE_SKAS
 static inline void check_skas3_ptrace_faultinfo(void)
 {
 	struct ptrace_faultinfo fi;
 	void *stack;
 	int pid, n;

 	printf("  - PTRACE_FAULTINFO...");
 	pid = start_ptraced_child(&stack);

 	n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
 	if (n < 0) {
 		ptrace_faultinfo = 0;
 		if(errno == EIO)
 			printf("not found\n");
 		else
 			perror("not found");
 	}
 	else {
 		if (!ptrace_faultinfo)
 			printf("found but disabled on command line\n");
 		else
 			printf("found\n");
 	}

 	init_registers(pid);
 	stop_ptraced_child(pid, stack, 1, 1);
 }

 static inline void check_skas3_ptrace_ldt(void)
 {
 #ifdef PTRACE_LDT
 	void *stack;
 	int pid, n;
 	unsigned char ldtbuf[40];
 	struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
 		.func = 2, /* read default ldt */
 		.ptr = ldtbuf,
 		.bytecount = sizeof(ldtbuf)};

 	printf("  - PTRACE_LDT...");
 	pid = start_ptraced_child(&stack);

 	n = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
 	if (n < 0) {
 		if(errno == EIO)
 			printf("not found\n");
 		else {
 			perror("not found");
 		}
 		ptrace_ldt = 0;
 	}
 	else {
 		if(ptrace_ldt)
 			printf("found\n");
 		else
 			printf("found, but use is disabled\n");
 	}

 	stop_ptraced_child(pid, stack, 1, 1);
 #else
 	/* PTRACE_LDT might be disabled via cmdline option.
 	 * We want to override this, else we might use the stub
 	 * without real need
 	 */
 	ptrace_ldt = 1;
 #endif
 }

 static inline void check_skas3_proc_mm(void)
 {
 	printf("  - /proc/mm...");
 	if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
  		proc_mm = 0;
 		printf("not found\n");
 	}
 	else {
 		if (!proc_mm)
 			printf("found but disabled on command line\n");
 		else
 			printf("found\n");
 	}
 }

 int can_do_skas(void)
 {
 	printf("Checking for the skas3 patch in the host:\n");

 	check_skas3_proc_mm();
 	check_skas3_ptrace_faultinfo();
 	check_skas3_ptrace_ldt();

 	if(!proc_mm || !ptrace_faultinfo || !ptrace_ldt)
 		skas_needs_stub = 1;

 	return 1;
 }
 #else
 int can_do_skas(void)
 {
 	return(0);
 }
 #endif

 int have_devanon = 0;

 /* Runs on boot kernel stack - already safe to use printk. */

 void check_devanon(void)
 {
 	int fd;

 	printk("Checking for /dev/anon on the host...");
 	fd = open("/dev/anon", O_RDWR);
 	if(fd < 0){
 		printk("Not available (open failed with errno %d)\n", errno);
 		return;
 	}

 	printk("OK\n");
 	have_devanon = 1;
 }

 int __init parse_iomem(char *str, int *add)
 {
 	struct iomem_region *new;
 	struct uml_stat buf;
 	char *file, *driver;
 	int fd, err, size;

 	driver = str;
 	file = strchr(str,',');
 	if(file == NULL){
 		printf("parse_iomem : failed to parse iomem\n");
 		goto out;
 	}
 	*file = '\0';
 	file++;
 	fd = os_open_file(file, of_rdwr(OPENFLAGS()), 0);
 	if(fd < 0){
 		os_print_error(fd, "parse_iomem - Couldn't open io file");
 		goto out;
 	}

 	err = os_stat_fd(fd, &buf);
 	if(err < 0){
 		os_print_error(err, "parse_iomem - cannot stat_fd file");
 		goto out_close;
 	}

 	new = malloc(sizeof(*new));
 	if(new == NULL){
 		perror("Couldn't allocate iomem_region struct");
 		goto out_close;
 	}

 	size = (buf.ust_size + UM_KERN_PAGE_SIZE) & ~(UM_KERN_PAGE_SIZE - 1);

 	*new = ((struct iomem_region) { .next		= iomem_regions,
 					.driver		= driver,
 					.fd		= fd,
 					.size		= size,
 					.phys		= 0,
 					.virt		= 0 });
 	iomem_regions = new;
 	iomem_size += new->size + UM_KERN_PAGE_SIZE;

 	return(0);
  out_close:
 	os_close_file(fd);
  out:
 	return(1);
 }
	/*
	* Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
	* Licensed under the GPL
	*/

	#include <stdio.h>
	#include <stddef.h>
	#include <stdarg.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>
	#include <signal.h>
	#include <sched.h>
	#include <fcntl.h>
	#include <errno.h>
	#include <setjmp.h>
	#include <sys/time.h>
	#include <sys/wait.h>
	#include <sys/mman.h>
	#include <asm/unistd.h>
	#include <asm/page.h>
	#include <sys/types.h>
	#include "user_util.h"
	#include "kern_util.h"
	#include "user.h"
	#include "signal_kern.h"
	#include "sysdep/ptrace.h"
	#include "sysdep/sigcontext.h"
	#include "irq_user.h"
	#include "ptrace_user.h"
	#include "mem_user.h"
	#include "time_user.h"
	#include "init.h"
	#include "os.h"
	#include "uml-config.h"
	#include "choose-mode.h"
	#include "mode.h"
	#include "tempfile.h"
	#include "kern_constants.h"

	#ifdef UML_CONFIG_MODE_SKAS
	#include "skas.h"
	#include "skas_ptrace.h"
	#include "registers.h"
	#endif

	static int ptrace_child(void *arg)
	{
	int ret;
	int pid = os_getpid(), ppid = getppid();
	int sc_result;

	if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
	perror("ptrace");
	os_kill_process(pid, 0);
	}
	os_stop_process(pid);

	/*This syscall will be intercepted by the parent. Don't call more than
	* once, please.*/
	sc_result = os_getpid();

	if (sc_result == pid)
	ret = 1; /*Nothing modified by the parent, we are running
	normally.*/
	else if (sc_result == ppid)
	ret = 0; /*Expected in check_ptrace and check_sysemu when they
	succeed in modifying the stack frame*/
	else
	ret = 2; /*Serious trouble! This could be caused by a bug in
	host 2.6 SKAS3/2.6 patch before release -V6, together
	with a bug in the UML code itself.*/
	_exit(ret);
	}

	static int start_ptraced_child(void **stack_out)
	{
	void *stack;
	unsigned long sp;
	int pid, n, status;

	stack = mmap(NULL, PAGE_SIZE, PROT_READ \| PROT_WRITE \| PROT_EXEC,
	MAP_PRIVATE \| MAP_ANONYMOUS, -1, 0);
	if(stack == MAP_FAILED)
	panic("check_ptrace : mmap failed, errno = %d", errno);
	sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
	pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
	if(pid < 0)
	panic("start_ptraced_child : clone failed, errno = %d", errno);
	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
	if(n < 0)
	panic("check_ptrace : clone failed, errno = %d", errno);
	if(!WIFSTOPPED(status) \|\| (WSTOPSIG(status) != SIGSTOP))
	panic("check_ptrace : expected SIGSTOP, got status = %d",
	status);

	*stack_out = stack;
	return(pid);
	}

	/* When testing for SYSEMU support, if it is one of the broken versions, we
	* must just avoid using sysemu, not panic, but only if SYSEMU features are
	* broken.
	* So only for SYSEMU features we test mustpanic, while normal host features
	* must work anyway!
	*/
	static int stop_ptraced_child(int pid, void *stack, int exitcode,
	int mustpanic)
	{
	int status, n, ret = 0;

	if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
	panic("check_ptrace : ptrace failed, errno = %d", errno);
	CATCH_EINTR(n = waitpid(pid, &status, 0));
	if(!WIFEXITED(status) \|\| (WEXITSTATUS(status) != exitcode)) {
	int exit_with = WEXITSTATUS(status);
	if (exit_with == 2)
	printf("check_ptrace : child exited with status 2. "
	"Serious trouble happening! Try updating your "
	"host skas patch!\nDisabling SYSEMU support.");
	printf("check_ptrace : child exited with exitcode %d, while "
	"expecting %d; status 0x%x", exit_with,
	exitcode, status);
	if (mustpanic)
	panic("\n");
	else
	printf("\n");
	ret = -1;
	}

	if(munmap(stack, PAGE_SIZE) < 0)
	panic("check_ptrace : munmap failed, errno = %d", errno);
	return ret;
	}

	int ptrace_faultinfo = 1;
	int ptrace_ldt = 1;
	int proc_mm = 1;
	int skas_needs_stub = 0;

	static int __init skas0_cmd_param(char str, int add)
	{
	ptrace_faultinfo = proc_mm = 0;
	return 0;
	}

	/* The two __uml_setup would conflict, without this stupid alias. */

	static int __init mode_skas0_cmd_param(char str, int add)
	__attribute__((alias("skas0_cmd_param")));

	__uml_setup("skas0", skas0_cmd_param,
	"skas0\n"
	" Disables SKAS3 usage, so that SKAS0 is used, unless \n"
	" you specify mode=tt.\n\n");

	__uml_setup("mode=skas0", mode_skas0_cmd_param,
	"mode=skas0\n"
	" Disables SKAS3 usage, so that SKAS0 is used, unless you \n"
	" specify mode=tt. Note that this was recently added - on \n"
	" older kernels you must use simply \"skas0\".\n\n");

	static int force_sysemu_disabled = 0;

	static int __init nosysemu_cmd_param(char str, int add)
	{
	force_sysemu_disabled = 1;
	return 0;
	}

	__uml_setup("nosysemu", nosysemu_cmd_param,
	"nosysemu\n"
	" Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
	" SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
	" behaviour of ptrace() and helps reducing host context switch rate.\n"
	" To make it working, you need a kernel patch for your host, too.\n"
	" See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n"
	" information.\n\n");

	static void __init check_sysemu(void)
	{
	void *stack;
	int pid, n, status, count=0;

	printf("Checking syscall emulation patch for ptrace...");
	sysemu_supported = 0;
	pid = start_ptraced_child(&stack);

	if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
	goto fail;

	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
	if (n < 0)
	panic("check_sysemu : wait failed, errno = %d", errno);
	if(!WIFSTOPPED(status) \|\| (WSTOPSIG(status) != SIGTRAP))
	panic("check_sysemu : expected SIGTRAP, "
	"got status = %d", status);

	n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
	os_getpid());
	if(n < 0)
	panic("check_sysemu : failed to modify system "
	"call return, errno = %d", errno);

	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
	goto fail_stopped;

	sysemu_supported = 1;
	printf("OK\n");
	set_using_sysemu(!force_sysemu_disabled);

	printf("Checking advanced syscall emulation patch for ptrace...");
	pid = start_ptraced_child(&stack);

	if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
	(void *) PTRACE_O_TRACESYSGOOD) < 0)
	panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d",
	errno);

	while(1){
	count++;
	if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
	goto fail;
	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
	if(n < 0)
	panic("check_ptrace : wait failed, errno = %d", errno);
	if(WIFSTOPPED(status) && (WSTOPSIG(status) == (SIGTRAP\|0x80))){
	if (!count)
	panic("check_ptrace : SYSEMU_SINGLESTEP "
	"doesn't singlestep");
	n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
	os_getpid());
	if(n < 0)
	panic("check_sysemu : failed to modify system "
	"call return, errno = %d", errno);
	break;
	}
	else if(WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP))
	count++;
	else
	panic("check_ptrace : expected SIGTRAP or "
	"(SIGTRAP\|0x80), got status = %d", status);
	}
	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
	goto fail_stopped;

	sysemu_supported = 2;
	printf("OK\n");

	if ( !force_sysemu_disabled )
	set_using_sysemu(sysemu_supported);
	return;

	fail:
	stop_ptraced_child(pid, stack, 1, 0);
	fail_stopped:
	printf("missing\n");
	}

	static void __init check_ptrace(void)
	{
	void *stack;
	int pid, syscall, n, status;

	printf("Checking that ptrace can change system call numbers...");
	pid = start_ptraced_child(&stack);

	if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
	panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d", errno);

	while(1){
	if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
	panic("check_ptrace : ptrace failed, errno = %d",
	errno);
	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
	if(n < 0)
	panic("check_ptrace : wait failed, errno = %d", errno);
	if(!WIFSTOPPED(status) \|\| (WSTOPSIG(status) != (SIGTRAP\|0x80)))
	panic("check_ptrace : expected (SIGTRAP\|0x80), "
	"got status = %d", status);

	syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
	0);
	if(syscall == __NR_getpid){
	n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
	__NR_getppid);
	if(n < 0)
	panic("check_ptrace : failed to modify system "
	"call, errno = %d", errno);
	break;
	}
	}
	stop_ptraced_child(pid, stack, 0, 1);
	printf("OK\n");
	check_sysemu();
	}

	extern int create_tmp_file(unsigned long long len);

	static void check_tmpexec(void)
	{
	void *addr;
	int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);

	addr = mmap(NULL, UM_KERN_PAGE_SIZE,
	PROT_READ \| PROT_WRITE \| PROT_EXEC, MAP_PRIVATE, fd, 0);
	printf("Checking PROT_EXEC mmap in /tmp...");
	fflush(stdout);
	if(addr == MAP_FAILED){
	err = errno;
	perror("failed");
	if(err == EPERM)
	printf("/tmp must be not mounted noexec\n");
	exit(1);
	}
	printf("OK\n");
	munmap(addr, UM_KERN_PAGE_SIZE);

	close(fd);
	}

	void os_early_checks(void)
	{
	check_ptrace();

	/* Need to check this early because mmapping happens before the
	* kernel is running.
	*/
	check_tmpexec();
	}

	static int __init noprocmm_cmd_param(char str, int add)
	{
	proc_mm = 0;
	return 0;
	}

	__uml_setup("noprocmm", noprocmm_cmd_param,
	"noprocmm\n"
	" Turns off usage of /proc/mm, even if host supports it.\n"
	" To support /proc/mm, the host needs to be patched using\n"
	" the current skas3 patch.\n\n");

	static int __init noptracefaultinfo_cmd_param(char str, int add)
	{
	ptrace_faultinfo = 0;
	return 0;
	}

	__uml_setup("noptracefaultinfo", noptracefaultinfo_cmd_param,
	"noptracefaultinfo\n"
	" Turns off usage of PTRACE_FAULTINFO, even if host supports\n"
	" it. To support PTRACE_FAULTINFO, the host needs to be patched\n"
	" using the current skas3 patch.\n\n");

	static int __init noptraceldt_cmd_param(char str, int add)
	{
	ptrace_ldt = 0;
	return 0;
	}

	__uml_setup("noptraceldt", noptraceldt_cmd_param,
	"noptraceldt\n"
	" Turns off usage of PTRACE_LDT, even if host supports it.\n"
	" To support PTRACE_LDT, the host needs to be patched using\n"
	" the current skas3 patch.\n\n");

	#ifdef UML_CONFIG_MODE_SKAS
	static inline void check_skas3_ptrace_faultinfo(void)
	{
	struct ptrace_faultinfo fi;
	void *stack;
	int pid, n;

	printf(" - PTRACE_FAULTINFO...");
	pid = start_ptraced_child(&stack);

	n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
	if (n < 0) {
	ptrace_faultinfo = 0;
	if(errno == EIO)
	printf("not found\n");
	else
	perror("not found");
	}
	else {
	if (!ptrace_faultinfo)
	printf("found but disabled on command line\n");
	else
	printf("found\n");
	}

	init_registers(pid);
	stop_ptraced_child(pid, stack, 1, 1);
	}

	static inline void check_skas3_ptrace_ldt(void)
	{
	#ifdef PTRACE_LDT
	void *stack;
	int pid, n;
	unsigned char ldtbuf[40];
	struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
	.func = 2, /* read default ldt */
	.ptr = ldtbuf,
	.bytecount = sizeof(ldtbuf)};

	printf(" - PTRACE_LDT...");
	pid = start_ptraced_child(&stack);

	n = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
	if (n < 0) {
	if(errno == EIO)
	printf("not found\n");
	else {
	perror("not found");
	}
	ptrace_ldt = 0;
	}
	else {
	if(ptrace_ldt)
	printf("found\n");
	else
	printf("found, but use is disabled\n");
	}

	stop_ptraced_child(pid, stack, 1, 1);
	#else
	/* PTRACE_LDT might be disabled via cmdline option.
	* We want to override this, else we might use the stub
	* without real need
	*/
	ptrace_ldt = 1;
	#endif
	}

	static inline void check_skas3_proc_mm(void)
	{
	printf(" - /proc/mm...");
	if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
	proc_mm = 0;
	printf("not found\n");
	}
	else {
	if (!proc_mm)
	printf("found but disabled on command line\n");
	else
	printf("found\n");
	}
	}

	int can_do_skas(void)
	{
	printf("Checking for the skas3 patch in the host:\n");

	check_skas3_proc_mm();
	check_skas3_ptrace_faultinfo();
	check_skas3_ptrace_ldt();

	if(!proc_mm \|\| !ptrace_faultinfo \|\| !ptrace_ldt)
	skas_needs_stub = 1;

	return 1;
	}
	#else
	int can_do_skas(void)
	{
	return(0);
	}
	#endif

	int have_devanon = 0;

	/* Runs on boot kernel stack - already safe to use printk. */

	void check_devanon(void)
	{
	int fd;

	printk("Checking for /dev/anon on the host...");
	fd = open("/dev/anon", O_RDWR);
	if(fd < 0){
	printk("Not available (open failed with errno %d)\n", errno);
	return;
	}

	printk("OK\n");
	have_devanon = 1;
	}

	int __init parse_iomem(char str, int add)
	{
	struct iomem_region *new;
	struct uml_stat buf;
	char file, driver;
	int fd, err, size;

	driver = str;
	file = strchr(str,',');
	if(file == NULL){
	printf("parse_iomem : failed to parse iomem\n");
	goto out;
	}
	*file = '\0';
	file++;
	fd = os_open_file(file, of_rdwr(OPENFLAGS()), 0);
	if(fd < 0){
	os_print_error(fd, "parse_iomem - Couldn't open io file");
	goto out;
	}

	err = os_stat_fd(fd, &buf);
	if(err < 0){
	os_print_error(err, "parse_iomem - cannot stat_fd file");
	goto out_close;
	}

	new = malloc(sizeof(*new));
	if(new == NULL){
	perror("Couldn't allocate iomem_region struct");
	goto out_close;
	}

	size = (buf.ust_size + UM_KERN_PAGE_SIZE) & ~(UM_KERN_PAGE_SIZE - 1);

	*new = ((struct iomem_region) { .next = iomem_regions,
	.driver = driver,
	.fd = fd,
	.size = size,
	.phys = 0,
	.virt = 0 });
	iomem_regions = new;
	iomem_size += new->size + UM_KERN_PAGE_SIZE;

	return(0);
	out_close:
	os_close_file(fd);
	out:
	return(1);
	}