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bpf: Fix jited line info off by the CFI preamble

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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: 4f9087f166 ("x86/cfi,bpf: Fix BPF JIT call")
Fixes: e63985ecd2 ("bpf, riscv64/cfi: Support kCFI + BPF on riscv64")
Fixes: 710618c760 ("arm64/cfi,bpf: Support kCFI + BPF on arm64")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jose Fernandez (Anthropic) <jose.fernandez@linux.dev>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20261030-b4-arm64-bpf-linfo-cfi-v2-1-4eac83435d4b@linux.dev
Closes: https://lore.kernel.org/all/20260904014748.C04AA1F000E9@smtp.kernel.org/
Closes: https://lore.kernel.org/all/DLNXZ2WK7TPD.2RZBUNRS4FA4L@gmail.com/
This commit is contained in:
Jose Fernandez (Anthropic) 2026-10-30 18:14:22 +00:00 committed by Alexei Starovoitov
parent 99681d9a38
commit 3e4279dc51
No known key found for this signature in database
2 changed files with 5 additions and 5 deletions
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2
arch/s390/net/bpf_jit_comp.c
View File

@ -2428,8 +2428,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr
fp->jited_len = jit.size - cfi_get_offset();
if (!fp->is_func || extra_pass) {
for (int i = 0; i < fp->len; i++)
jit.addrs[i] -= cfi_get_offset();
bpf_prog_fill_jited_linfo(fp, jit.addrs + 1);
free_addrs:
kvfree(jit.addrs);

8
kernel/bpf/core.c
View File

@ -206,7 +206,9 @@ void bpf_prog_jit_attempt_done(struct bpf_prog *prog)
* here is relative to the prog itself instead of the main prog.
* This array has one entry for each xlated bpf insn.
*
* jited_off is the byte off to the end of the jited insn.
* jited_off is the byte off to the end of the jited insn, counted from
* the start of the jited image, which is cfi_get_offset() bytes before
* prog->bpf_func.
*
* Hence, with
* insn_start:
@ -220,7 +222,7 @@ void bpf_prog_jit_attempt_done(struct bpf_prog *prog)
*
* For i > linfo_idx,
*
* jited_linfo[i] = prog->bpf_func +
* jited_linfo[i] = prog->bpf_func - cfi_get_offset() +
* insn_to_jit_off[linfo[i].insn_off - insn_start - 1]
*/
void bpf_prog_fill_jited_linfo(struct bpf_prog *prog,
@ -248,7 +250,7 @@ void bpf_prog_fill_jited_linfo(struct bpf_prog *prog,
/* The verifier ensures that linfo[i].insn_off is
* strictly increasing
*/
jited_linfo[i] = prog->bpf_func +
jited_linfo[i] = prog->bpf_func - cfi_get_offset() +
insn_to_jit_off[linfo[i].insn_off - insn_start - 1];
}