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s390/bpf: Store backchain even for leaf progs

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[ Upstream commit 5f55f21684 ]

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: 0546231057 ("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>
This commit is contained in:
Ilya Leoshkevich 2025-05-12 14:26:15 +02:00 committed by Greg Kroah-Hartman
parent 5f8a599afa
commit ba3d5b12f7
1 changed files with 5 additions and 7 deletions
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12
arch/s390/net/bpf_jit_comp.c
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@ -543,17 +543,15 @@ static void bpf_jit_prologue(struct bpf_jit *jit, u32 stack_depth)
}
/* 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);
}
}