Some architectures require mappings to be aligned to the system page size.
The build_id selftest currently uses a smaller alignment, which can result
in madvise operations executing on a different page than intended.
Increase the mapping alignment to 64K so the buffer is page-aligned on
all supported architectures.
Signed-off-by: Gregory Bell <grbell@redhat.com>
Link: https://lore.kernel.org/r/93543253b32d1cb178ab6e31e4291e387ba1c372.1771338492.git.grbell@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add a new set of tests validating behavior of capturing stack traces
with build ID. We extend uprobe_multi target binary with ability to
trigger uprobe (so that we can capture stack traces from it), but also
we allow to force build ID data to be either resident or non-resident in
memory (see also a comment about quirks of MADV_PAGEOUT).
That way we can validate that in non-sleepable context we won't get
build ID (as expected), but with sleepable uprobes we will get that
build ID regardless of it being physically present in memory.
Also, we add a small add-on linker script which reorders
.note.gnu.build-id section and puts it after (big) .text section,
putting build ID data outside of the very first page of ELF file. This
will test all the relaxations we did in build ID parsing logic in kernel
thanks to freader abstraction.
Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240829174232.3133883-11-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
