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selftests/x86/single_step_syscall: Check SYSENTER directly 

We used to test SYSENTER only through the vDSO.  Test it directly
too, just in case.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2019-11-20 12:22:46 -08:00 committed by Ingo Molnar
parent 9a62d20027
commit 3300c4f3af
1 changed files with 86 additions and 10 deletions
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96
tools/testing/selftests/x86/single_step_syscall.c
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@ -43,7 +43,19 @@ static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
err(1, "sigaction");
}
static volatile sig_atomic_t sig_traps;
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");
}
static volatile sig_atomic_t sig_traps, sig_eflags;
sigjmp_buf jmpbuf;
static unsigned char altstack_data[SIGSTKSZ];
#ifdef __x86_64__
# define REG_IP REG_RIP
@ -90,6 +102,25 @@ static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
}
}
static char const * const signames[] = {
[SIGSEGV] = "SIGSEGV",
[SIGBUS] = "SIBGUS",
[SIGTRAP] = "SIGTRAP",
[SIGILL] = "SIGILL",
};
static void print_and_longjmp(int sig, siginfo_t *si, void *ctx_void)
{
ucontext_t *ctx = ctx_void;
printf("\tGot %s with RIP=%lx, TF=%ld\n", signames[sig],
(unsigned long)ctx->uc_mcontext.gregs[REG_IP],
(unsigned long)ctx->uc_mcontext.gregs[REG_EFL] & X86_EFLAGS_TF);
sig_eflags = (unsigned long)ctx->uc_mcontext.gregs[REG_EFL];
siglongjmp(jmpbuf, 1);
}
static void check_result(void)
{
unsigned long new_eflags = get_eflags();
@ -109,6 +140,22 @@ static void check_result(void)
sig_traps = 0;
}
static void fast_syscall_no_tf(void)
{
sig_traps = 0;
printf("[RUN]\tFast syscall with TF cleared\n");
fflush(stdout); /* Force a syscall */
if (get_eflags() & X86_EFLAGS_TF) {
printf("[FAIL]\tTF is now set\n");
exit(1);
}
if (sig_traps) {
printf("[FAIL]\tGot SIGTRAP\n");
exit(1);
}
printf("[OK]\tNothing unexpected happened\n");
}
int main()
{
#ifdef CAN_BUILD_32
@ -163,17 +210,46 @@ int main()
check_result();
/* Now make sure that another fast syscall doesn't set TF again. */
printf("[RUN]\tFast syscall with TF cleared\n");
fflush(stdout); /* Force a syscall */
if (get_eflags() & X86_EFLAGS_TF) {
printf("[FAIL]\tTF is now set\n");
fast_syscall_no_tf();
/*
* And do a forced SYSENTER to make sure that this works even if
* fast syscalls don't use SYSENTER.
*
* Invoking SYSENTER directly breaks all the rules. Just handle
* the SIGSEGV.
*/
if (sigsetjmp(jmpbuf, 1) == 0) {
unsigned long nr = SYS_getpid;
printf("[RUN]\tSet TF and check SYSENTER\n");
stack_t stack = {
.ss_sp = altstack_data,
.ss_size = SIGSTKSZ,
};
if (sigaltstack(&stack, NULL) != 0)
err(1, "sigaltstack");
sethandler(SIGSEGV, print_and_longjmp,
SA_RESETHAND | SA_ONSTACK);
sethandler(SIGILL, print_and_longjmp, SA_RESETHAND);
set_eflags(get_eflags() | X86_EFLAGS_TF);
/* Clear EBP first to make sure we segfault cleanly. */
asm volatile ("xorl %%ebp, %%ebp; SYSENTER" : "+a" (nr) :: "flags", "rcx"
#ifdef __x86_64__
, "r11"
#endif
);
/* We're unreachable here. SYSENTER forgets RIP. */
}
clearhandler(SIGSEGV);
clearhandler(SIGILL);
if (!(sig_eflags & X86_EFLAGS_TF)) {
printf("[FAIL]\tTF was cleared\n");
exit(1);
}
if (sig_traps) {
printf("[FAIL]\tGot SIGTRAP\n");
exit(1);
}
printf("[OK]\tNothing unexpected happened\n");
/* Now make sure that another fast syscall doesn't set TF again. */
fast_syscall_no_tf();
return 0;
}