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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <signal.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <asm/unistd.h>
#include <init.h>
#include <os.h>
#include <mem_user.h>
#include <ptrace_user.h>
#include <registers.h>
#include <skas.h>
static void ptrace_child(void)
{
int ret;
/* Calling os_getpid because some libcs cached getpid incorrectly */
int pid = os_getpid(), ppid = getppid();
int sc_result;
if (change_sig(SIGWINCH, 0) < 0 ||
ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) {
perror("ptrace");
kill(pid, SIGKILL);
}
kill(pid, SIGSTOP);
/*
* This syscall will be intercepted by the parent. Don't call more than
* once, please.
*/
sc_result = os_getpid();
if (sc_result == pid)
/* Nothing modified by the parent, we are running normally. */
ret = 1;
else if (sc_result == ppid)
/*
* Expected in check_ptrace and check_sysemu when they succeed
* in modifying the stack frame
*/
ret = 0;
else
/* 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.
*/
ret = 2;
exit(ret);
}
static void fatal_perror(const char *str)
{
perror(str);
exit(1);
}
static void fatal(char *fmt, ...)
{
va_list list;
va_start(list, fmt);
vfprintf(stderr, fmt, list);
va_end(list);
exit(1);
}
static void non_fatal(char *fmt, ...)
{
va_list list;
va_start(list, fmt);
vfprintf(stderr, fmt, list);
va_end(list);
}
static int start_ptraced_child(void)
{
int pid, n, status;
fflush(stdout);
pid = fork();
if (pid == 0)
ptrace_child();
else if (pid < 0)
fatal_perror("start_ptraced_child : fork failed");
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
if (n < 0)
fatal_perror("check_ptrace : waitpid failed");
if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
fatal("check_ptrace : expected SIGSTOP, got status = %d",
status);
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, int exitcode, int mustexit)
{
int status, n, ret = 0;
if (ptrace(PTRACE_CONT, pid, 0, 0) < 0) {
perror("stop_ptraced_child : ptrace failed");
return -1;
}
CATCH_EINTR(n = waitpid(pid, &status, 0));
if (!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
int exit_with = WEXITSTATUS(status);
if (exit_with == 2)
non_fatal("check_ptrace : child exited with status 2. "
"\nDisabling SYSEMU support.\n");
non_fatal("check_ptrace : child exited with exitcode %d, while "
"expecting %d; status 0x%x\n", exit_with,
exitcode, status);
if (mustexit)
exit(1);
ret = -1;
}
return ret;
}
/* Changed only during early boot */
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).\n"
" SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
" behaviour of ptrace() and helps reduce host context switch rates.\n"
" To make it work, 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)
{
unsigned long regs[MAX_REG_NR];
int pid, n, status, count=0;
os_info("Checking syscall emulation patch for ptrace...");
sysemu_supported = 0;
pid = start_ptraced_child();
if (ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
goto fail;
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
if (n < 0)
fatal_perror("check_sysemu : wait failed");
if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
fatal("check_sysemu : expected SIGTRAP, got status = %d\n",
status);
if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
fatal_perror("check_sysemu : PTRACE_GETREGS failed");
if (PT_SYSCALL_NR(regs) != __NR_getpid) {
non_fatal("check_sysemu got system call number %d, "
"expected %d...", PT_SYSCALL_NR(regs), __NR_getpid);
goto fail;
}
n = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_RET_OFFSET, os_getpid());
if (n < 0) {
non_fatal("check_sysemu : failed to modify system call "
"return");
goto fail;
}
if (stop_ptraced_child(pid, 0, 0) < 0)
goto fail_stopped;
sysemu_supported = 1;
os_info("OK\n");
set_using_sysemu(!force_sysemu_disabled);
os_info("Checking advanced syscall emulation patch for ptrace...");
pid = start_ptraced_child();
if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
(void *) PTRACE_O_TRACESYSGOOD) < 0))
fatal_perror("check_sysemu: PTRACE_OLDSETOPTIONS failed");
while (1) {
count++;
if (ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
goto fail;
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
if (n < 0)
fatal_perror("check_sysemu: wait failed");
if (WIFSTOPPED(status) &&
(WSTOPSIG(status) == (SIGTRAP|0x80))) {
if (!count) {
non_fatal("check_sysemu: SYSEMU_SINGLESTEP "
"doesn't singlestep");
goto fail;
}
n = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_RET_OFFSET,
os_getpid());
if (n < 0)
fatal_perror("check_sysemu : failed to modify "
"system call return");
break;
}
else if (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP))
count++;
else {
non_fatal("check_sysemu: expected SIGTRAP or "
"(SIGTRAP | 0x80), got status = %d\n",
status);
goto fail;
}
}
if (stop_ptraced_child(pid, 0, 0) < 0)
goto fail_stopped;
sysemu_supported = 2;
os_info("OK\n");
if (!force_sysemu_disabled)
set_using_sysemu(sysemu_supported);
return;
fail:
stop_ptraced_child(pid, 1, 0);
fail_stopped:
non_fatal("missing\n");
}
static void __init check_ptrace(void)
{
int pid, syscall, n, status;
os_info("Checking that ptrace can change system call numbers...");
pid = start_ptraced_child();
if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
(void *) PTRACE_O_TRACESYSGOOD) < 0))
fatal_perror("check_ptrace: PTRACE_OLDSETOPTIONS failed");
while (1) {
if (ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
fatal_perror("check_ptrace : ptrace failed");
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
if (n < 0)
fatal_perror("check_ptrace : wait failed");
if (!WIFSTOPPED(status) ||
(WSTOPSIG(status) != (SIGTRAP | 0x80)))
fatal("check_ptrace : expected (SIGTRAP|0x80), &qu
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