tools/testing/selftests/x86/nx_stack.c

Source file repositories/reference/linux-study-clean/tools/testing/selftests/x86/nx_stack.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/x86/nx_stack.c
Extension
.c
Size
5482 bytes
Lines
213
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

if (1) {
			printf("stack min %lx\n", stack_min_addr);
		}
		uc->uc_mcontext.gregs[RIP] = (uintptr_t)&make_stack2;
		test_state = 1;
	} else if (test_state == 1) {
		/* Stack has been cleared from top to bottom. */
		unsigned long stack_max_addr = uc->uc_mcontext.gregs[RDI];
		if (1) {
			printf("stack max %lx\n", stack_max_addr);
		}
		/* Start faulting pages on stack and see what happens. */
		uc->uc_mcontext.gregs[RIP] = stack_max_addr - PAGE_SIZE;
		test_state = 2;
	} else if (test_state == 2) {
		/* Stack page is NX -- good, test next page. */
		uc->uc_mcontext.gregs[RIP] -= PAGE_SIZE;
		if (uc->uc_mcontext.gregs[RIP] == stack_min_addr) {
			/* One more SIGSEGV and test ends. */
			test_state = 3;
		}
	} else {
		printf("PASS\tAll stack pages are NX\n");
		_exit(EXIT_SUCCESS);
	}
}

static void sigtrap(int _, siginfo_t *__, void *uc_)
{
	const ucontext_t *uc = uc_;
	unsigned long rip = uc->uc_mcontext.gregs[RIP];
	printf("FAIL\texecutable page on the stack: " RIP_STRING " %lx\n", rip);
	_exit(EXIT_FAILURE);
}

int main(void)
{
	{
		struct sigaction act = {};
		sigemptyset(&act.sa_mask);
		act.sa_flags = SA_SIGINFO;
		act.sa_sigaction = &sigsegv;
		int rv = sigaction(SIGSEGV, &act, NULL);
		assert(rv == 0);
	}
	{
		struct sigaction act = {};
		sigemptyset(&act.sa_mask);
		act.sa_flags = SA_SIGINFO;
		act.sa_sigaction = &sigtrap;
		int rv = sigaction(SIGTRAP, &act, NULL);
		assert(rv == 0);
	}
	{
		struct rlimit rlim;
		int rv = getrlimit(RLIMIT_STACK, &rlim);
		assert(rv == 0);
		/* Cap stack at time-honored 8 MiB value. */
		rlim.rlim_max = rlim.rlim_cur;
		if (rlim.rlim_max > 8 * 1024 * 1024) {
			rlim.rlim_max = 8 * 1024 * 1024;
		}
		rv = setrlimit(RLIMIT_STACK, &rlim);
		assert(rv == 0);
	}
	{
		/*
		 * We don't know now much stack SIGSEGV handler uses.
		 * Bump this by 1 page every time someone complains,
		 * or rewrite it in assembly.
		 */
		const size_t len = SIGSTKSZ;
		void *p = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
		assert(p != MAP_FAILED);
		stack_t ss = {};
		ss.ss_sp = p;
		ss.ss_size = len;
		int rv = sigaltstack(&ss, NULL);
		assert(rv == 0);
	}
	make_stack1();
	/*
	 * Unreachable, but if _this_ INT3 is ever reached, it's a bug somewhere.
	 * Fold it into main SIGTRAP pathway.
	 */
	__builtin_trap();
}

Annotation

Implementation Notes