On Mon, 27 Oct 2025 17:04:39 +0530 Ankit Khushwaha ankitkhushwaha.linux@gmail.com wrote:
Accessing 'reg.write_index' directly triggers a -Waddress-of-packed-member warning due to potential unaligned pointer access:
perf_test.c:239:38: warning: taking address of packed member 'write_index' of class or structure 'user_reg' may result in an unaligned pointer value [-Waddress-of-packed-member] 239 | ASSERT_NE(-1, write(self->data_fd, ®.write_index, | ^~~~~~~~~~~~~~~
Use memcpy() instead to safely copy the value and avoid unaligned pointer access across architectures.
...
--- a/tools/testing/selftests/user_events/perf_test.c +++ b/tools/testing/selftests/user_events/perf_test.c @@ -201,6 +201,7 @@ TEST_F(user, perf_empty_events) { struct perf_event_mmap_page *perf_page; int page_size = sysconf(_SC_PAGESIZE); int id, fd;
- __u32 write_index; __u32 *val;
reg.size = sizeof(reg); @@ -236,7 +237,8 @@ TEST_F(user, perf_empty_events) { ASSERT_EQ(1 << reg.enable_bit, self->check); /* Ensure write shows up at correct offset */
- ASSERT_NE(-1, write(self->data_fd, ®.write_index,
- memcpy(&write_index, ®.write_index, sizeof(reg.write_index));
- ASSERT_NE(-1, write(self->data_fd, &write_index, sizeof(reg.write_index)));
Simply casting &write_index to void* would fix this?
val = (void *)(((char *)perf_page) + perf_page->data_offset); ASSERT_EQ(PERF_RECORD_SAMPLE, *val);