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Message-ID: <157484277024.21853.2643521750694270592.tip-bot2@tip-bot2>
Date: Wed, 27 Nov 2019 08:19:30 -0000
From: "tip-bot2 for Andy Lutomirski" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...en8.de>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Ingo Molnar <mingo@...nel.org>, x86 <x86@...nel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/urgent] selftests/x86/single_step_syscall: Check SYSENTER directly
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 3300c4f3afbb59a1f4bfdbe0f0b6c91e241541b1
Gitweb: https://git.kernel.org/tip/3300c4f3afbb59a1f4bfdbe0f0b6c91e241541b1
Author: Andy Lutomirski <luto@...nel.org>
AuthorDate: Wed, 20 Nov 2019 12:22:46 -08:00
Committer: Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 26 Nov 2019 21:53:34 +01:00
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@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
tools/testing/selftests/x86/single_step_syscall.c | 94 ++++++++++++--
1 file 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 50ce6c3..1063328 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;
}
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