Currently a crash in a leaf prog (caused by a bug) produces the
following call trace:
[<000003ff600ebf00>] bpf_prog_6df0139e1fbf2789_fentry+0x20/0x78
[<0000000000000000>] 0x0
This is because leaf progs do not store backchain. Fix by making all
progs do it. This is what GCC and Clang-generated code does as well.
Now the call trace looks like this:
[<000003ff600eb0f2>] bpf_prog_6df0139e1fbf2789_fentry+0x2a/0x80
[<000003ff600ed096>] bpf_trampoline_201863462940+0x96/0xf4
[<000003ff600e3a40>] bpf_prog_05f379658fdd72f2_classifier_0+0x58/0xc0
[<000003ffe0aef070>] bpf_test_run+0x210/0x390
[<000003ffe0af0dc2>] bpf_prog_test_run_skb+0x25a/0x668
[<000003ffe038a90e>] __sys_bpf+0xa46/0xdb0
[<000003ffe038ad0c>] __s390x_sys_bpf+0x44/0x50
[<000003ffe0defea8>] __do_syscall+0x150/0x280
[<000003ffe0e01d5c>] system_call+0x74/0x98
Fixes: 054623105728 ("s390/bpf: Add s390x eBPF JIT compiler backend")
Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
---
arch/s390/net/bpf_jit_comp.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 0776dfde2dba..945106b5562d 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -605,17 +605,15 @@ static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp,
}
/* Setup stack and backchain */
if (is_first_pass(jit) || (jit->seen & SEEN_STACK)) {
- if (is_first_pass(jit) || (jit->seen & SEEN_FUNC))
- /* lgr %w1,%r15 (backchain) */
- EMIT4(0xb9040000, REG_W1, REG_15);
+ /* lgr %w1,%r15 (backchain) */
+ EMIT4(0xb9040000, REG_W1, REG_15);
/* la %bfp,STK_160_UNUSED(%r15) (BPF frame pointer) */
EMIT4_DISP(0x41000000, BPF_REG_FP, REG_15, STK_160_UNUSED);
/* aghi %r15,-STK_OFF */
EMIT4_IMM(0xa70b0000, REG_15, -(STK_OFF + stack_depth));
- if (is_first_pass(jit) || (jit->seen & SEEN_FUNC))
- /* stg %w1,152(%r15) (backchain) */
- EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0,
- REG_15, 152);
+ /* stg %w1,152(%r15) (backchain) */
+ EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0,
+ REG_15, 152);
}
}
--
2.49.0
