diff options
| -rw-r--r-- | tools/testing/selftests/x86/single_step_syscall.c | 94 |
1 files changed, 85 insertions, 9 deletions
diff --git a/tools/testing/selftests/x86/single_step_syscall.c b/tools/testing/selftests/x86/single_step_syscall.c index 50ce6c3dd904..1063328e275c 100644 --- a/tools/testing/selftests/x86/single_step_syscall.c +++ b/tools/testing/selftests/x86/single_step_syscall.c @@ -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"); - exit(1); + 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. */ } - if (sig_traps) { - printf("[FAIL]\tGot SIGTRAP\n"); + clearhandler(SIGSEGV); + clearhandler(SIGILL); + if (!(sig_eflags & X86_EFLAGS_TF)) { + printf("[FAIL]\tTF was cleared\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; } |