Commit f91187c0 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: selftests: Add wrapper macro to handle and assert on expected SIGBUS 



Extract the guest_memfd test's SIGBUS handling functionality into a common
TEST_EXPECT_SIGBUS() macro in anticipation of adding more SIGBUS testcases.
Eating a SIGBUS isn't terrible difficult, but it requires a non-trivial
amount of boilerplate code, and using a macro allows selftests to print
out the exact action that failed to generate a SIGBUS without the developer
needing to remember to add a useful error message.

Explicitly mark the SIGBUS handler as "used", as gcc-14 at least likes to
discard the function before linking.

Opportunistically use TEST_FAIL(...) instead of TEST_ASSERT(false, ...),
and fix the write path of the guest_memfd test to use the local "val"
instead of hardcoding the literal value a second time.

Suggested-by: default avatarAckerley Tng <ackerleytng@google.com>
Reviewed-by: default avatarAckerley Tng <ackerleytng@google.com>
Tested-by: default avatarAckerley Tng <ackerleytng@google.com>
Reviewed-by: default avatarLisa Wang <wyihan@google.com>
Tested-by: default avatarLisa Wang <wyihan@google.com>
Link: https://lore.kernel.org/r/20251003232606.4070510-12-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 505c9530

tools/testing/selftests/kvm/guest_memfd_test.c

+1 −17
Original line number Diff line number Diff line
@@ -14,8 +14,6 @@ 
#include <linux/bitmap.h>

#include <linux/falloc.h>

#include <linux/sizes.h>

#include <setjmp.h>

#include <signal.h>

#include <sys/mman.h>

#include <sys/types.h>

#include <sys/stat.h>
@@ -77,17 +75,8 @@ static void test_mmap_supported(int fd, size_t total_size) 
	kvm_munmap(mem, total_size);

}



static sigjmp_buf jmpbuf;

void fault_sigbus_handler(int signum)

{

	siglongjmp(jmpbuf, 1);

}



static void test_fault_overflow(int fd, size_t total_size)

{

	struct sigaction sa_old, sa_new = {

		.sa_handler = fault_sigbus_handler,

	};

	size_t map_size = total_size * 4;

	const char val = 0xaa;

	char *mem;
@@ -95,12 +84,7 @@ static void test_fault_overflow(int fd, size_t total_size) 


	mem = kvm_mmap(map_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd);



	sigaction(SIGBUS, &sa_new, &sa_old);

	if (sigsetjmp(jmpbuf, 1) == 0) {

		memset(mem, 0xaa, map_size);

		TEST_ASSERT(false, "memset() should have triggered SIGBUS.");

	}

	sigaction(SIGBUS, &sa_old, NULL);

	TEST_EXPECT_SIGBUS(memset(mem, val, map_size));



	for (i = 0; i < total_size; i++)

		TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);

tools/testing/selftests/kvm/include/test_util.h

+19 −0
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 
#ifndef SELFTEST_KVM_TEST_UTIL_H

#define SELFTEST_KVM_TEST_UTIL_H



#include <setjmp.h>

#include <signal.h>

#include <stdlib.h>

#include <stdarg.h>

#include <stdbool.h>
@@ -78,6 +80,23 @@ do { \ 
	__builtin_unreachable(); \

} while (0)



extern sigjmp_buf expect_sigbus_jmpbuf;

void expect_sigbus_handler(int signum);



#define TEST_EXPECT_SIGBUS(action)						\

do {										\

	struct sigaction sa_old, sa_new = {					\

		.sa_handler = expect_sigbus_handler,				\

	};									\

										\

	sigaction(SIGBUS, &sa_new, &sa_old);					\

	if (sigsetjmp(expect_sigbus_jmpbuf, 1) == 0) {				\

		action;								\

		TEST_FAIL("'%s' should have triggered SIGBUS", #action);	\

	}									\

	sigaction(SIGBUS, &sa_old, NULL);					\

} while (0)



size_t parse_size(const char *size);



int64_t timespec_to_ns(struct timespec ts);

tools/testing/selftests/kvm/lib/test_util.c

+7 −0
Original line number Diff line number Diff line
@@ -18,6 +18,13 @@ 


#include "test_util.h"



sigjmp_buf expect_sigbus_jmpbuf;



void __attribute__((used)) expect_sigbus_handler(int signum)

{

	siglongjmp(expect_sigbus_jmpbuf, 1);

}



/*

 * Random number generator that is usable from guest code. This is the

 * Park-Miller LCG using standard constants.