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| author | Ilya Leoshkevich <iii@linux.ibm.com> | 2025-08-13 14:06:28 +0200 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2025-08-18 15:08:29 +0200 |
| commit | eada40e057fc1842358d9daca3abe5cacb21e8a1 (patch) | |
| tree | 99877796c0fc0078da667415b1b260114e03d155 | |
| parent | Merge branch 'libbpf-fix-reuse-of-devmap' (diff) | |
| download | linux-eada40e057fc1842358d9daca3abe5cacb21e8a1.tar.gz linux-eada40e057fc1842358d9daca3abe5cacb21e8a1.zip | |
s390/bpf: Do not write tail call counter into helper and kfunc frames
Only BPF functions make use of the tail call counter; helpers and
kfuncs ignore and most likely also clobber it. Writing it into these
functions' frames is pointless and misleading, so do not do it.
Fixes: dd691e847d28 ("s390/bpf: Implement bpf_jit_supports_subprog_tailcalls()")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20250813121016.163375-2-iii@linux.ibm.com
| -rw-r--r-- | arch/s390/net/bpf_jit_comp.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index bb17efe29d65..bfac1ddf3447 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -1790,6 +1790,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, REG_SET_SEEN(BPF_REG_5); jit->seen |= SEEN_FUNC; + /* * Copy the tail call counter to where the callee expects it. * @@ -1800,10 +1801,17 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, * Note 2: We assume that the verifier does not let us call the * main program, which clears the tail call counter on entry. */ - /* mvc tail_call_cnt(4,%r15),frame_off+tail_call_cnt(%r15) */ - _EMIT6(0xd203f000 | offsetof(struct prog_frame, tail_call_cnt), - 0xf000 | (jit->frame_off + - offsetof(struct prog_frame, tail_call_cnt))); + + if (insn->src_reg == BPF_PSEUDO_CALL) + /* + * mvc tail_call_cnt(4,%r15), + * frame_off+tail_call_cnt(%r15) + */ + _EMIT6(0xd203f000 | offsetof(struct prog_frame, + tail_call_cnt), + 0xf000 | (jit->frame_off + + offsetof(struct prog_frame, + tail_call_cnt))); /* Sign-extend the kfunc arguments. */ if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) { |