Re: [PATCH bpf v2] bpf: Fix jited line info off by the CFI preamble

[sashiko-bot@kernel.org]

> With CONFIG_CFI=y, every jited line info entry after a function's
> first is cfi_get_offset() bytes too high on x86-64, riscv64 and arm64,
> so tools that use it show the wrong source line.
> 
> The JITs count the insn_to_jit_off[] offsets from the start of the
> image. Since the CFI commits below, prog->bpf_func starts
> cfi_get_offset() bytes into the image, and bpf_prog_fill_jited_linfo()
> adds the offsets to prog->bpf_func. s390 corrects its offsets before
> the call, the other three JITs do not.
> 
> Subtract cfi_get_offset() once in bpf_prog_fill_jited_linfo() and drop
> the s390 correction. jited_linfo[0] stays prog->bpf_func, the
> function's ksym address. Without CONFIG_CFI, cfi_get_offset() is 0 and
> nothing changes.
> 
> Fixes: 4f9087f16651 ("x86/cfi,bpf: Fix BPF JIT call")
> Fixes: e63985ecd226 ("bpf, riscv64/cfi: Support kCFI + BPF on riscv64")
> Fixes: 710618c760c0 ("arm64/cfi,bpf: Support kCFI + BPF on arm64")
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Closes: https://lore.kernel.org/all/20260904014748.C04AA1F000E9@smtp.kernel.org/
> Reported-by: Alexei Starovoitov <ast@kernel.org>
> Closes: https://lore.kernel.org/all/DLNXZ2WK7TPD.2RZBUNRS4FA4L@gmail.com/
> Signed-off-by: Jose Fernandez (Anthropic) <jose.fernandez@linux.dev>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261030-b4-arm64-bpf-linfo-cfi-v2-1-4eac83435d4b@linux.dev?part=1