selftests/bpf: Add precision backtracking test for stack arguments

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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>

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Yonghong Song 2026-05-12 21:51:48 -07:00 • committed by Alexei Starovoitov

parent 00c3ac4292

commit 6e277efbb1

3 changed files with 167 additions and 0 deletions

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10

tools/testing/selftests/bpf/prog_tests/stack_arg_precision.c

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tools/testing/selftests/bpf/progs/btf__stack_arg_precision.c

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134

tools/testing/selftests/bpf/progs/stack_arg_precision.c

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