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

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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: Ackerley Tng <ackerleytng@google.com>
Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Tested-by: Ackerley Tng <ackerleytng@google.com>
Reviewed-by: Lisa Wang <wyihan@google.com>
Tested-by: Lisa Wang <wyihan@google.com>
Link: https://lore.kernel.org/r/20251003232606.4070510-12-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2025-10-03 16:26:04 -07:00
parent 505c953009
commit f91187c0ec
3 changed files with 27 additions and 17 deletions
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18
tools/testing/selftests/kvm/guest_memfd_test.c
View File

@ -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);

19
tools/testing/selftests/kvm/include/test_util.h
View File

@ -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);

7
tools/testing/selftests/kvm/lib/test_util.c
View File

@ -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.