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kernel-ark/tools/testing/selftests/x86/ptrace_syscall.c
Andy Lutomirski 04235c00b6 selftests/x86: Add a test for ptrace syscall restart and arg modification 
This tests assumptions about how fast syscall works wrt pt_regs
and, in particular, what happens if IP is decremented by 2
during a syscall.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1c44dbfe59000ba135bbf35ccc5d2433a0b31618.1444091584.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-07 11:34:07 +02:00

295 lines
7.9 KiB
C
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#define _GNU_SOURCE
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/syscall.h>
#include <sys/user.h>
#include <unistd.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <err.h>
#include <string.h>
#include <asm/ptrace-abi.h>
#include <sys/auxv.h>
/* Bitness-agnostic defines for user_regs_struct fields. */
#ifdef __x86_64__
# define user_syscall_nr orig_rax
# define user_arg0 rdi
# define user_arg1 rsi
# define user_arg2 rdx
# define user_arg3 r10
# define user_arg4 r8
# define user_arg5 r9
# define user_ip rip
# define user_ax rax
#else
# define user_syscall_nr orig_eax
# define user_arg0 ebx
# define user_arg1 ecx
# define user_arg2 edx
# define user_arg3 esi
# define user_arg4 edi
# define user_arg5 ebp
# define user_ip eip
# define user_ax eax
#endif
static int nerrs = 0;
struct syscall_args32 {
uint32_t nr, arg0, arg1, arg2, arg3, arg4, arg5;
};
#ifdef __i386__
extern void sys32_helper(struct syscall_args32 *, void *);
extern void int80_and_ret(void);
#endif
/*
* Helper to invoke int80 with controlled regs and capture the final regs.
*/
static void do_full_int80(struct syscall_args32 *args)
{
#ifdef __x86_64__
register unsigned long bp asm("bp") = args->arg5;
asm volatile ("int $0x80"
: "+a" (args->nr),
"+b" (args->arg0), "+c" (args->arg1), "+d" (args->arg2),
"+S" (args->arg3), "+D" (args->arg4), "+r" (bp));
args->arg5 = bp;
#else
sys32_helper(args, int80_and_ret);
#endif
}
#ifdef __i386__
static void (*vsyscall32)(void);
/*
* Nasty helper to invoke AT_SYSINFO (i.e. __kernel_vsyscall) with
* controlled regs and capture the final regs. This is so nasty that it
* crashes my copy of gdb :)
*/
static void do_full_vsyscall32(struct syscall_args32 *args)
{
sys32_helper(args, vsyscall32);
}
#endif
static siginfo_t wait_trap(pid_t chld)
{
siginfo_t si;
if (waitid(P_PID, chld, &si, WEXITED|WSTOPPED) != 0)
err(1, "waitid");
if (si.si_pid != chld)
errx(1, "got unexpected pid in event\n");
if (si.si_code != CLD_TRAPPED)
errx(1, "got unexpected event type %d\n", si.si_code);
return si;
}
static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
int flags)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = handler;
sa.sa_flags = SA_SIGINFO | flags;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
}
static void clearhandler(int sig)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = SIG_DFL;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
}
#ifdef __x86_64__
# define REG_BP REG_RBP
#else
# define REG_BP REG_EBP
#endif
static void empty_handler(int sig, siginfo_t *si, void *ctx_void)
{
}
static void test_sys32_regs(void (*do_syscall)(struct syscall_args32 *))
{
struct syscall_args32 args = {
.nr = 224, /* gettid */
.arg0 = 10, .arg1 = 11, .arg2 = 12,
.arg3 = 13, .arg4 = 14, .arg5 = 15,
};
do_syscall(&args);
if (args.nr != getpid() ||
args.arg0 != 10 || args.arg1 != 11 || args.arg2 != 12 ||
args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
printf("[FAIL]\tgetpid() failed to preseve regs\n");
nerrs++;
} else {
printf("[OK]\tgetpid() preserves regs\n");
}
sethandler(SIGUSR1, empty_handler, 0);
args.nr = 37; /* kill */
args.arg0 = getpid();
args.arg1 = SIGUSR1;
do_syscall(&args);
if (args.nr != 0 ||
args.arg0 != getpid() || args.arg1 != SIGUSR1 || args.arg2 != 12 ||
args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
printf("[FAIL]\tkill(getpid(), SIGUSR1) failed to preseve regs\n");
nerrs++;
} else {
printf("[OK]\tkill(getpid(), SIGUSR1) preserves regs\n");
}
clearhandler(SIGUSR1);
}
static void test_ptrace_syscall_restart(void)
{
printf("[RUN]\tptrace-induced syscall restart\n");
pid_t chld = fork();
if (chld < 0)
err(1, "fork");
if (chld == 0) {
if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
err(1, "PTRACE_TRACEME");
printf("\tChild will make one syscall\n");
raise(SIGSTOP);
syscall(SYS_gettid, 10, 11, 12, 13, 14, 15);
_exit(0);
}
int status;
/* Wait for SIGSTOP. */
if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
err(1, "waitpid");
struct user_regs_struct regs;
printf("[RUN]\tSYSEMU\n");
if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
err(1, "PTRACE_SYSCALL");
wait_trap(chld);
if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
err(1, "PTRACE_GETREGS");
if (regs.user_syscall_nr != SYS_gettid ||
regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
regs.user_arg4 != 14 || regs.user_arg5 != 15) {
printf("[FAIL]\tInitial args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
nerrs++;
} else {
printf("[OK]\tInitial nr and args are correct\n");
}
printf("[RUN]\tRestart the syscall (ip = 0x%lx)\n",
(unsigned long)regs.user_ip);
/*
* This does exactly what it appears to do if syscall is int80 or
* SYSCALL64. For SYSCALL32 or SYSENTER, though, this is highly
* magical. It needs to work so that ptrace and syscall restart
* work as expected.
*/
regs.user_ax = regs.user_syscall_nr;
regs.user_ip -= 2;
if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
err(1, "PTRACE_SETREGS");
if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
err(1, "PTRACE_SYSCALL");
wait_trap(chld);
if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
err(1, "PTRACE_GETREGS");
if (regs.user_syscall_nr != SYS_gettid ||
regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
regs.user_arg4 != 14 || regs.user_arg5 != 15) {
printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
nerrs++;
} else {
printf("[OK]\tRestarted nr and args are correct\n");
}
printf("[RUN]\tChange nr and args and restart the syscall (ip = 0x%lx)\n",
(unsigned long)regs.user_ip);
regs.user_ax = SYS_getpid;
regs.user_arg0 = 20;
regs.user_arg1 = 21;
regs.user_arg2 = 22;
regs.user_arg3 = 23;
regs.user_arg4 = 24;
regs.user_arg5 = 25;
regs.user_ip -= 2;
if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
err(1, "PTRACE_SETREGS");
if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
err(1, "PTRACE_SYSCALL");
wait_trap(chld);
if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
err(1, "PTRACE_GETREGS");
if (regs.user_syscall_nr != SYS_getpid ||
regs.user_arg0 != 20 || regs.user_arg1 != 21 || regs.user_arg2 != 22 ||
regs.user_arg3 != 23 || regs.user_arg4 != 24 || regs.user_arg5 != 25) {
printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
nerrs++;
} else {
printf("[OK]\tReplacement nr and args are correct\n");
}
if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
err(1, "PTRACE_CONT");
if (waitpid(chld, &status, 0) != chld)
err(1, "waitpid");
if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
printf("[FAIL]\tChild failed\n");
nerrs++;
} else {
printf("[OK]\tChild exited cleanly\n");
}
}
int main()
{
printf("[RUN]\tCheck int80 return regs\n");
test_sys32_regs(do_full_int80);
#if defined(__i386__) && (!defined(__GLIBC__) || __GLIBC__ > 2 || __GLIBC_MINOR__ >= 16)
vsyscall32 = (void *)getauxval(AT_SYSINFO);
printf("[RUN]\tCheck AT_SYSINFO return regs\n");
test_sys32_regs(do_full_vsyscall32);
#endif
test_ptrace_syscall_restart();
return 0;
}
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