linux-stable.git/tools/testing/selftests/bpf/prog_tests/stack_arg_precision.c, branch master Linux kernel stable tree selftests/bpf: Add precision backtracking test for stack arguments 2026-05-13T16:27:32+00:00 Yonghong Song yonghong.song@linux.dev 2026-05-13T04:51:48+00:00 6e277efbb19dd1a536cbffd9ea5c049a427dc7cb Add a test that verifies precision backtracking works correctly across BPF-to-BPF calls when stack arguments are involved. The test passes a size value as incoming stack arg (arg6) to a subprog, which forwards it as the mem__sz parameter (outgoing arg7) to bpf_kfunc_call_stack_arg_mem. The expected __msg annotations verify that precision propagates from the kfunc's mem__sz argument back through the subprog frame to the caller's outgoing stack arg store. A companion BTF file (btf__stack_arg_precision.c) provides named parameter BTF for the __naked subprog via __btf_func_path. Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20260513045148.2400087-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
Add a test that verifies precision backtracking works correctly
across BPF-to-BPF calls when stack arguments are involved.

The test passes a size value as incoming stack arg (arg6) to a
subprog, which forwards it as the mem__sz parameter (outgoing arg7)
to bpf_kfunc_call_stack_arg_mem. The expected __msg annotations
verify that precision propagates from the kfunc's mem__sz argument
back through the subprog frame to the caller's outgoing stack arg
store.

A companion BTF file (btf__stack_arg_precision.c) provides named
parameter BTF for the __naked subprog via __btf_func_path.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260513045148.2400087-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>