6.12-stable review patch. If anyone has any objections, please let me know.
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From: Ilya Leoshkevich iii@linux.ibm.com
[ Upstream commit 5f55f2168432298f5a55294831ab6a76a10cb3c3 ]
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@linux.ibm.com Link: https://lore.kernel.org/r/20250512122717.54878-1-iii@linux.ibm.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 9d440a0b729eb..64bb8b71013ae 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); } }