[mirror_ubuntu-bionic-kernel.git] / arch / um / os-Linux / start_up.c

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

#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <sched.h>
#include <errno.h>
#include <stdarg.h>
#include <stdlib.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 "user_util.h"
#include "kern_util.h"
#include "user.h"
#include "signal_kern.h"
#include "signal_user.h"
#include "sysdep/ptrace.h"
#include "sysdep/sigcontext.h"
#include "irq_user.h"
#include "ptrace_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"
#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)
			printk("check_ptrace : child exited with status 2. "
			       "Serious trouble happening! Try updating your "
			       "host skas patch!\nDisabling SYSEMU support.");
		printk("check_ptrace : child exited with exitcode %d, while "
		      "expecting %d; status 0x%x", exit_with,
		      exitcode, status);
		if (mustpanic)
			panic("\n");
		else
			printk("\n");
		ret = -1;
	}

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

int ptrace_faultinfo = 1;
int proc_mm = 1;

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

__uml_setup("skas0", skas0_cmd_param,
		"skas0\n"
		"    Disables SKAS3 usage, so that SKAS0 is used, unless \n"
	        "    you specify mode=tt.\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, syscall, n, status, count=0;

	printk("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;
	printk("OK\n");
	set_using_sysemu(!force_sysemu_disabled);

	printk("Checking advanced syscall emulation patch for ptrace...");
	pid = start_ptraced_child(&stack);
	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))
			panic("check_ptrace : expected (SIGTRAP|SYSCALL_TRAP), "
			      "got status = %d", status);

		syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
				 0);
		if(syscall == __NR_getpid){
			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;
		}
	}
	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
		goto fail_stopped;

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

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

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

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

	printk("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);
	printk("OK\n");
	check_sysemu();
}

void os_early_checks(void)
{
	check_ptrace();
}

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");

#ifdef UML_CONFIG_MODE_SKAS
static inline void check_skas3_ptrace_support(void)
{
	struct ptrace_faultinfo fi;
	void *stack;
	int pid, n;

	printf("Checking for the skas3 patch in the host...");
	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);
}

int can_do_skas(void)
{
	printf("Checking for /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");
	}

	check_skas3_ptrace_support();
	return 1;
}
#else
int can_do_skas(void)
{
	return(0);
}
#endif
Commit	Line	Data
60d339f6	1	/*
1da177e4 LT	2	* Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
	3	* Licensed under the GPL
	4	*/
	5
	6	#include <stdio.h>
	7	#include <unistd.h>
	8	#include <signal.h>
	9	#include <sched.h>
	10	#include <errno.h>
	11	#include <stdarg.h>
	12	#include <stdlib.h>
	13	#include <setjmp.h>
	14	#include <sys/time.h>
	15	#include <sys/wait.h>
	16	#include <sys/mman.h>
	17	#include <asm/unistd.h>
	18	#include <asm/page.h>
	19	#include "user_util.h"
	20	#include "kern_util.h"
	21	#include "user.h"
1da177e4 LT	22	#include "signal_kern.h"
	23	#include "signal_user.h"
	24	#include "sysdep/ptrace.h"
	25	#include "sysdep/sigcontext.h"
	26	#include "irq_user.h"
	27	#include "ptrace_user.h"
	28	#include "time_user.h"
	29	#include "init.h"
	30	#include "os.h"
	31	#include "uml-config.h"
1da177e4 LT	32	#include "choose-mode.h"
1da177e4 LT	33	#include "mode.h"
d67b569f	34	#include "tempfile.h"
1da177e4 LT	35	#ifdef UML_CONFIG_MODE_SKAS
	36	#include "skas.h"
	37	#include "skas_ptrace.h"
	38	#include "registers.h"
	39	#endif
	40
b85e9680	41	static int ptrace_child(void *arg)
1da177e4 LT	42	{
	43	int ret;
	44	int pid = os_getpid(), ppid = getppid();
	45	int sc_result;
	46
	47	if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
	48	perror("ptrace");
	49	os_kill_process(pid, 0);
	50	}
	51	os_stop_process(pid);
	52
	53	/*This syscall will be intercepted by the parent. Don't call more than
	54	* once, please.*/
	55	sc_result = os_getpid();
	56
	57	if (sc_result == pid)
	58	ret = 1; /*Nothing modified by the parent, we are running
	59	normally.*/
	60	else if (sc_result == ppid)
	61	ret = 0; /*Expected in check_ptrace and check_sysemu when they
	62	succeed in modifying the stack frame*/
	63	else
	64	ret = 2; /*Serious trouble! This could be caused by a bug in
	65	host 2.6 SKAS3/2.6 patch before release -V6, together
	66	with a bug in the UML code itself.*/
	67	_exit(ret);
	68	}
	69
b85e9680	70	static int start_ptraced_child(void **stack_out)
1da177e4	71	{
b85e9680 JD	72	void *stack;
b85e9680 JD	73	unsigned long sp;
1da177e4	74	int pid, n, status;
60d339f6	75
b85e9680 JD	76	stack = mmap(NULL, PAGE_SIZE, PROT_READ \| PROT_WRITE \| PROT_EXEC,
	77	MAP_PRIVATE \| MAP_ANONYMOUS, -1, 0);
	78	if(stack == MAP_FAILED)
	79	panic("check_ptrace : mmap failed, errno = %d", errno);
	80	sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
	81	pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
1da177e4	82	if(pid < 0)
60d339f6	83	panic("start_ptraced_child : clone failed, errno = %d", errno);
1da177e4 LT	84	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
1da177e4 LT	85	if(n < 0)
60d339f6	86	panic("check_ptrace : clone failed, errno = %d", errno);
1da177e4 LT	87	if(!WIFSTOPPED(status) \|\| (WSTOPSIG(status) != SIGSTOP))
	88	panic("check_ptrace : expected SIGSTOP, got status = %d",
	89	status);
	90
b85e9680	91	*stack_out = stack;
1da177e4 LT	92	return(pid);
	93	}
	94
60d339f6 GS	95	/* When testing for SYSEMU support, if it is one of the broken versions, we
	96	* must just avoid using sysemu, not panic, but only if SYSEMU features are
	97	* broken.
1da177e4	98	* So only for SYSEMU features we test mustpanic, while normal host features
60d339f6 GS	99	* must work anyway!
	100	*/
	101	static int stop_ptraced_child(int pid, void *stack, int exitcode,
	102	int mustpanic)
1da177e4 LT	103	{
	104	int status, n, ret = 0;
	105
	106	if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
b85e9680	107	panic("check_ptrace : ptrace failed, errno = %d", errno);
1da177e4 LT	108	CATCH_EINTR(n = waitpid(pid, &status, 0));
	109	if(!WIFEXITED(status) \|\| (WEXITSTATUS(status) != exitcode)) {
	110	int exit_with = WEXITSTATUS(status);
	111	if (exit_with == 2)
	112	printk("check_ptrace : child exited with status 2. "
	113	"Serious trouble happening! Try updating your "
	114	"host skas patch!\nDisabling SYSEMU support.");
	115	printk("check_ptrace : child exited with exitcode %d, while "
	116	"expecting %d; status 0x%x", exit_with,
	117	exitcode, status);
b85e9680	118	if (mustpanic)
1da177e4 LT	119	panic("\n");
	120	else
	121	printk("\n");
	122	ret = -1;
	123	}
	124
b85e9680 JD	125	if(munmap(stack, PAGE_SIZE) < 0)
b85e9680 JD	126	panic("check_ptrace : munmap failed, errno = %d", errno);
1da177e4 LT	127	return ret;
	128	}
	129
cb66504d PBG	130	int ptrace_faultinfo = 1;
	131	int proc_mm = 1;
	132
	133	static int __init skas0_cmd_param(char str, int add)
	134	{
	135	ptrace_faultinfo = proc_mm = 0;
	136	return 0;
	137	}
	138
60d339f6 GS	139	__uml_setup("skas0", skas0_cmd_param,
	140	"skas0\n"
	141	" Disables SKAS3 usage, so that SKAS0 is used, unless \n"
	142	" you specify mode=tt.\n\n");
	143
	144	static int force_sysemu_disabled = 0;
	145
1da177e4 LT	146	static int __init nosysemu_cmd_param(char str, int add)
	147	{
	148	force_sysemu_disabled = 1;
	149	return 0;
	150	}
	151
	152	__uml_setup("nosysemu", nosysemu_cmd_param,
60d339f6 GS	153	"nosysemu\n"
	154	" Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
	155	" SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
	156	" behaviour of ptrace() and helps reducing host context switch rate.\n"
	157	" To make it working, you need a kernel patch for your host, too.\n"
	158	" See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n"
	159	" information.\n\n");
1da177e4 LT	160
	161	static void __init check_sysemu(void)
	162	{
b85e9680	163	void *stack;
1da177e4 LT	164	int pid, syscall, n, status, count=0;
	165
	166	printk("Checking syscall emulation patch for ptrace...");
	167	sysemu_supported = 0;
b85e9680	168	pid = start_ptraced_child(&stack);
1da177e4 LT	169
	170	if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
	171	goto fail;
	172
	173	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
	174	if (n < 0)
	175	panic("check_sysemu : wait failed, errno = %d", errno);
	176	if(!WIFSTOPPED(status) \|\| (WSTOPSIG(status) != SIGTRAP))
	177	panic("check_sysemu : expected SIGTRAP, "
	178	"got status = %d", status);
	179
	180	n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
	181	os_getpid());
	182	if(n < 0)
	183	panic("check_sysemu : failed to modify system "
	184	"call return, errno = %d", errno);
	185
b85e9680	186	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
1da177e4 LT	187	goto fail_stopped;
	188
	189	sysemu_supported = 1;
	190	printk("OK\n");
	191	set_using_sysemu(!force_sysemu_disabled);
	192
	193	printk("Checking advanced syscall emulation patch for ptrace...");
b85e9680	194	pid = start_ptraced_child(&stack);
1da177e4 LT	195	while(1){
	196	count++;
	197	if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
	198	goto fail;
	199	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
	200	if(n < 0)
	201	panic("check_ptrace : wait failed, errno = %d", errno);
	202	if(!WIFSTOPPED(status) \|\| (WSTOPSIG(status) != SIGTRAP))
	203	panic("check_ptrace : expected (SIGTRAP\|SYSCALL_TRAP), "
	204	"got status = %d", status);
	205
	206	syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
	207	0);
	208	if(syscall == __NR_getpid){
	209	if (!count)
	210	panic("check_ptrace : SYSEMU_SINGLESTEP doesn't singlestep");
	211	n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
	212	os_getpid());
	213	if(n < 0)
	214	panic("check_sysemu : failed to modify system "
	215	"call return, errno = %d", errno);
	216	break;
	217	}
	218	}
b85e9680	219	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
1da177e4 LT	220	goto fail_stopped;
	221
	222	sysemu_supported = 2;
	223	printk("OK\n");
	224
	225	if ( !force_sysemu_disabled )
	226	set_using_sysemu(sysemu_supported);
	227	return;
	228
	229	fail:
b85e9680	230	stop_ptraced_child(pid, stack, 1, 0);
1da177e4 LT	231	fail_stopped:
	232	printk("missing\n");
	233	}
	234
60d339f6	235	static void __init check_ptrace(void)
1da177e4	236	{
b85e9680	237	void *stack;
1da177e4 LT	238	int pid, syscall, n, status;
	239
	240	printk("Checking that ptrace can change system call numbers...");
b85e9680	241	pid = start_ptraced_child(&stack);
1da177e4	242
60d339f6 GS	243	if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
60d339f6 GS	244	panic("check_ptrace: PTRACE_OLDSETOPTIONS failed, errno = %d", errno);
1da177e4 LT	245
	246	while(1){
	247	if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
60d339f6	248	panic("check_ptrace : ptrace failed, errno = %d",
1da177e4 LT	249	errno);
	250	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
	251	if(n < 0)
	252	panic("check_ptrace : wait failed, errno = %d", errno);
	253	if(!WIFSTOPPED(status) \|\| (WSTOPSIG(status) != SIGTRAP + 0x80))
	254	panic("check_ptrace : expected SIGTRAP + 0x80, "
	255	"got status = %d", status);
60d339f6	256
1da177e4 LT	257	syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
	258	0);
	259	if(syscall == __NR_getpid){
	260	n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
	261	__NR_getppid);
	262	if(n < 0)
	263	panic("check_ptrace : failed to modify system "
	264	"call, errno = %d", errno);
	265	break;
	266	}
	267	}
b85e9680	268	stop_ptraced_child(pid, stack, 0, 1);
1da177e4 LT	269	printk("OK\n");
	270	check_sysemu();
	271	}
	272
60d339f6	273	void os_early_checks(void)
1da177e4	274	{
60d339f6	275	check_ptrace();
1da177e4 LT	276	}
1da177e4 LT	277
d9838d86 BS	278	static int __init noprocmm_cmd_param(char str, int add)
	279	{
	280	proc_mm = 0;
	281	return 0;
	282	}
	283
	284	__uml_setup("noprocmm", noprocmm_cmd_param,
	285	"noprocmm\n"
	286	" Turns off usage of /proc/mm, even if host supports it.\n"
	287	" To support /proc/mm, the host needs to be patched using\n"
	288	" the current skas3 patch.\n\n");
	289
	290	static int __init noptracefaultinfo_cmd_param(char str, int add)
	291	{
	292	ptrace_faultinfo = 0;
	293	return 0;
	294	}
	295
	296	__uml_setup("noptracefaultinfo", noptracefaultinfo_cmd_param,
	297	"noptracefaultinfo\n"
	298	" Turns off usage of PTRACE_FAULTINFO, even if host supports\n"
	299	" it. To support PTRACE_FAULTINFO, the host needs to be patched\n"
	300	" using the current skas3 patch.\n\n");
	301
1da177e4	302	#ifdef UML_CONFIG_MODE_SKAS
d67b569f	303	static inline void check_skas3_ptrace_support(void)
1da177e4 LT	304	{
1da177e4 LT	305	struct ptrace_faultinfo fi;
b85e9680	306	void *stack;
d67b569f	307	int pid, n;
1da177e4 LT	308
1da177e4 LT	309	printf("Checking for the skas3 patch in the host...");
b85e9680	310	pid = start_ptraced_child(&stack);
1da177e4 LT	311
	312	n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
	313	if (n < 0) {
cb66504d	314	ptrace_faultinfo = 0;
1da177e4 LT	315	if(errno == EIO)
1da177e4 LT	316	printf("not found\n");
60d339f6	317	else
1da177e4	318	perror("not found");
d67b569f JD	319	}
d67b569f JD	320	else {
cb66504d PBG	321	if (!ptrace_faultinfo)
	322	printf("found but disabled on command line\n");
	323	else
	324	printf("found\n");
1da177e4 LT	325	}
	326
	327	init_registers(pid);
b85e9680	328	stop_ptraced_child(pid, stack, 1, 1);
1da177e4 LT	329	}
	330
	331	int can_do_skas(void)
	332	{
1da177e4 LT	333	printf("Checking for /proc/mm...");
1da177e4 LT	334	if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
60d339f6	335	proc_mm = 0;
1da177e4	336	printf("not found\n");
60d339f6 GS	337	}
60d339f6 GS	338	else {
cb66504d PBG	339	if (!proc_mm)
	340	printf("found but disabled on command line\n");
	341	else
	342	printf("found\n");
1da177e4 LT	343	}
1da177e4 LT	344
d67b569f JD	345	check_skas3_ptrace_support();
d67b569f JD	346	return 1;
1da177e4 LT	347	}
	348	#else
	349	int can_do_skas(void)
	350	{
	351	return(0);
	352	}
	353	#endif