[PATCH net-next 2/3] s390/bpf: fix bpf frame pointer setup
From: Alexei Starovoitov <hidden>
Date: 2015-05-30 17:42:23
Subsystem:
bpf jit for s390, bpf [general] (safe dynamic programs and tools), s390 architecture, the rest · Maintainers:
Ilya Leoshkevich, Heiko Carstens, Vasily Gorbik, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Alexander Gordeev, Linus Torvalds
From: Michael Holzheu <redacted> Currently the bpf frame pointer is set to the old r15. This is wrong because of packed stack. Fix this and adjust the frame pointer to respect packed stack. This now generates a prolog like the following: 3ff8001c3fa: eb67f0480024 stmg %r6,%r7,72(%r15) 3ff8001c400: ebcff0780024 stmg %r12,%r15,120(%r15) 3ff8001c406: b904001f lgr %r1,%r15 <- load backchain 3ff8001c40a: 41d0f048 la %r13,72(%r15) <- load adjusted bfp 3ff8001c40e: a7fbfd98 aghi %r15,-616 3ff8001c412: e310f0980024 stg %r1,152(%r15) <- save backchain Cc: stable@vger.kernel.org # 4.0+ Signed-off-by: Michael Holzheu <redacted> Acked-by: Heiko Carstens <redacted> Signed-off-by: Alexei Starovoitov <redacted> --- arch/s390/net/bpf_jit_comp.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 20c146d1251a..55423d8be580 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c@@ -384,13 +384,16 @@ static void bpf_jit_prologue(struct bpf_jit *jit) } /* Setup stack and backchain */ if (jit->seen & SEEN_STACK) { - /* lgr %bfp,%r15 (BPF frame pointer) */ - EMIT4(0xb9040000, BPF_REG_FP, REG_15); + if (jit->seen & SEEN_FUNC) + /* 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); if (jit->seen & SEEN_FUNC) - /* stg %bfp,152(%r15) (backchain) */ - EMIT6_DISP_LH(0xe3000000, 0x0024, BPF_REG_FP, REG_0, + /* stg %w1,152(%r15) (backchain) */ + EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0, REG_15, 152); } /*
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1.7.9.5