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From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org,
	luto@kernel.org, x86@kernel.org
Cc: len.brown@intel.com, dave.hansen@intel.com, hjl.tools@gmail.com,
	Dave.Martin@arm.com, jannh@google.com, mpe@ellerman.id.au,
	carlos@redhat.com, tony.luck@intel.com, ravi.v.shankar@intel.com,
	libc-alpha@sourceware.org, linux-arch@vger.kernel.org,
	linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
	chang.seok.bae@intel.com, linux-kselftest@vger.kernel.org
Subject: [PATCH v6 4/6] selftest/sigaltstack: Use the AT_MINSIGSTKSZ aux vector if available
Date: Sat, 27 Feb 2021 08:59:09 -0800	[thread overview]
Message-ID: <20210227165911.32757-5-chang.seok.bae@intel.com> (raw)
In-Reply-To: <20210227165911.32757-1-chang.seok.bae@intel.com>

The SIGSTKSZ constant may not represent enough stack size in some
architectures as the hardware state size grows.

Use getauxval(AT_MINSIGSTKSZ) to increase the stack size.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Len Brown <len.brown@intel.com>
Cc: linux-kselftest@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
Changes from v5:
* Added as a new patch.
---
 tools/testing/selftests/sigaltstack/sas.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/sigaltstack/sas.c b/tools/testing/selftests/sigaltstack/sas.c
index 8934a3766d20..c53b070755b6 100644
--- a/tools/testing/selftests/sigaltstack/sas.c
+++ b/tools/testing/selftests/sigaltstack/sas.c
@@ -17,6 +17,7 @@
 #include <string.h>
 #include <assert.h>
 #include <errno.h>
+#include <sys/auxv.h>
 
 #include "../kselftest.h"
 
@@ -24,6 +25,11 @@
 #define SS_AUTODISARM  (1U << 31)
 #endif
 
+#ifndef AT_MINSIGSTKSZ
+#define AT_MINSIGSTKSZ	51
+#endif
+
+static unsigned int stack_size;
 static void *sstack, *ustack;
 static ucontext_t uc, sc;
 static const char *msg = "[OK]\tStack preserved";
@@ -47,7 +53,7 @@ void my_usr1(int sig, siginfo_t *si, void *u)
 #endif
 
 	if (sp < (unsigned long)sstack ||
-			sp >= (unsigned long)sstack + SIGSTKSZ) {
+			sp >= (unsigned long)sstack + stack_size) {
 		ksft_exit_fail_msg("SP is not on sigaltstack\n");
 	}
 	/* put some data on stack. other sighandler will try to overwrite it */
@@ -108,6 +114,10 @@ int main(void)
 	stack_t stk;
 	int err;
 
+	/* Make sure more than the required minimum. */
+	stack_size = getauxval(AT_MINSIGSTKSZ) + SIGSTKSZ;
+	ksft_print_msg("[NOTE]\tthe stack size is %lu\n", stack_size);
+
 	ksft_print_header();
 	ksft_set_plan(3);
 
@@ -117,7 +127,7 @@ int main(void)
 	sigaction(SIGUSR1, &act, NULL);
 	act.sa_sigaction = my_usr2;
 	sigaction(SIGUSR2, &act, NULL);
-	sstack = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,
+	sstack = mmap(NULL, stack_size, PROT_READ | PROT_WRITE,
 		      MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
 	if (sstack == MAP_FAILED) {
 		ksft_exit_fail_msg("mmap() - %s\n", strerror(errno));
@@ -139,7 +149,7 @@ int main(void)
 	}
 
 	stk.ss_sp = sstack;
-	stk.ss_size = SIGSTKSZ;
+	stk.ss_size = stack_size;
 	stk.ss_flags = SS_ONSTACK | SS_AUTODISARM;
 	err = sigaltstack(&stk, NULL);
 	if (err) {
@@ -161,7 +171,7 @@ int main(void)
 		}
 	}
 
-	ustack = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,
+	ustack = mmap(NULL, stack_size, PROT_READ | PROT_WRITE,
 		      MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
 	if (ustack == MAP_FAILED) {
 		ksft_exit_fail_msg("mmap() - %s\n", strerror(errno));
@@ -170,7 +180,7 @@ int main(void)
 	getcontext(&uc);
 	uc.uc_link = NULL;
 	uc.uc_stack.ss_sp = ustack;
-	uc.uc_stack.ss_size = SIGSTKSZ;
+	uc.uc_stack.ss_size = stack_size;
 	makecontext(&uc, switch_fn, 0);
 	raise(SIGUSR1);
 
-- 
2.17.1


  parent reply	other threads:[~2021-02-27 17:23 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-27 16:59 [PATCH v6 0/6] x86: Improve Minimum Alternate Stack Size Chang S. Bae
2021-02-27 16:59 ` [PATCH v6 1/6] uapi: Define the aux vector AT_MINSIGSTKSZ Chang S. Bae
2021-03-01 19:09   ` Borislav Petkov
2021-03-10 16:31     ` Bae, Chang Seok
2021-02-27 16:59 ` [PATCH v6 2/6] x86/signal: Introduce helpers to get the maximum signal frame size Chang S. Bae
2021-02-27 16:59 ` [PATCH v6 3/6] x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ Chang S. Bae
2021-03-05 10:43   ` Borislav Petkov
2021-03-10 16:34     ` Bae, Chang Seok
2021-03-10 17:43       ` Borislav Petkov
2021-03-10 18:01         ` Bae, Chang Seok
2021-02-27 16:59 ` Chang S. Bae [this message]
2021-02-27 16:59 ` [PATCH v6 5/6] x86/signal: Detect and prevent an alternate signal stack overflow Chang S. Bae
2021-02-27 16:59 ` [PATCH v6 6/6] selftest/x86/signal: Include test cases for validating sigaltstack Chang S. Bae

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