selftests/x86/single_step_syscall: Check SYSENTER directly (3300c4f3) · Commits · 戴 / test

tools/testing/selftests/x86/single_step_syscall.c

+85 −9

Original line number	Diff line number	Diff line
		@@ -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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