From: Ilya Leoshkevich Date: Mon, 12 May 2025 12:26:15 +0000 (+0200) Subject: s390/bpf: Store backchain even for leaf progs X-Git-Tag: v6.16-rc1~131^2~22 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=5f55f2168432298f5a55294831ab6a76a10cb3c3;p=linux-2.6-block.git s390/bpf: Store backchain even for leaf progs 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 Link: https://lore.kernel.org/r/20250512122717.54878-1-iii@linux.ibm.com Signed-off-by: Alexei Starovoitov --- 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); } }