From b0a0c2566f28e71e5e32121992ac8060cec75510 Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <daniel@iogearbox.net>
Date: Fri, 4 Aug 2017 14:20:54 +0200
Subject: [PATCH 1/2] bpf, s390: fix jit branch offset related to ldimm64
While testing some other work that required JIT modifications, I
run into test_bpf causing a hang when JIT enabled on s390. The
problematic test case was the one from ddc665a4bb4b (bpf, arm64:
fix jit branch offset related to ldimm64), and turns out that we
do have a similar issue on s390 as well. In bpf_jit_prog() we
update next instruction address after returning from bpf_jit_insn()
with an insn_count. bpf_jit_insn() returns either -1 in case of
error (e.g. unsupported insn), 1 or 2. The latter is only the
case for ldimm64 due to spanning 2 insns, however, next address
is only set to i + 1 not taking actual insn_count into account,
thus fix is to use insn_count instead of 1. bpf_jit_enable in
mode 2 provides also disasm on s390:
Before fix:
000003ff800349b6: a7f40003 brc 15,3ff800349bc ; target
000003ff800349ba: 0000 unknown
000003ff800349bc: e3b0f0700024 stg %r11,112(%r15)
000003ff800349c2: e3e0f0880024 stg %r14,136(%r15)
000003ff800349c8: 0db0 basr %r11,%r0
000003ff800349ca: c0ef00000000 llilf %r14,0
000003ff800349d0: e320b0360004 lg %r2,54(%r11)
000003ff800349d6: e330b03e0004 lg %r3,62(%r11)
000003ff800349dc: ec23ffeda065 clgrj %r2,%r3,10,3ff800349b6 ; jmp
000003ff800349e2: e3e0b0460004 lg %r14,70(%r11)
000003ff800349e8: e3e0b04e0004 lg %r14,78(%r11)
000003ff800349ee: b904002e lgr %r2,%r14
000003ff800349f2: e3b0f0700004 lg %r11,112(%r15)
000003ff800349f8: e3e0f0880004 lg %r14,136(%r15)
000003ff800349fe: 07fe bcr 15,%r14
After fix:
000003ff80ef3db4: a7f40003 brc 15,3ff80ef3dba
000003ff80ef3db8: 0000 unknown
000003ff80ef3dba: e3b0f0700024 stg %r11,112(%r15)
000003ff80ef3dc0: e3e0f0880024 stg %r14,136(%r15)
000003ff80ef3dc6: 0db0 basr %r11,%r0
000003ff80ef3dc8: c0ef00000000 llilf %r14,0
000003ff80ef3dce: e320b0360004 lg %r2,54(%r11)
000003ff80ef3dd4: e330b03e0004 lg %r3,62(%r11)
000003ff80ef3dda: ec230006a065 clgrj %r2,%r3,10,3ff80ef3de6 ; jmp
000003ff80ef3de0: e3e0b0460004 lg %r14,70(%r11)
000003ff80ef3de6: e3e0b04e0004 lg %r14,78(%r11) ; target
000003ff80ef3dec: b904002e lgr %r2,%r14
000003ff80ef3df0: e3b0f0700004 lg %r11,112(%r15)
000003ff80ef3df6: e3e0f0880004 lg %r14,136(%r15)
000003ff80ef3dfc: 07fe bcr 15,%r14
test_bpf.ko suite runs fine after the fix.
Fixes: 054623105728 ("s390/bpf: Add s390x eBPF JIT compiler backend")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
arch/s390/net/bpf_jit_comp.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 01c6fbc3e85b6..1803797fc885c 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -1253,7 +1253,8 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp)
insn_count = bpf_jit_insn(jit, fp, i);
if (insn_count < 0)
return -1;
- jit->addrs[i + 1] = jit->prg; /* Next instruction address */
+ /* Next instruction address */
+ jit->addrs[i + insn_count] = jit->prg;
}
bpf_jit_epilogue(jit);
From bad1926dd2f60bbb4af5223ace3a7b34a0219a66 Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <daniel@iogearbox.net>
Date: Fri, 4 Aug 2017 14:20:55 +0200
Subject: [PATCH 2/2] bpf, s390: fix build for libbpf and selftest suite
The BPF feature test as well as libbpf is missing the __NR_bpf
define for s390 and currently refuses to compile (selftest suite
depends on libbpf as well). Similar issue was fixed some time
ago via b0c47807d31d ("bpf: Add sparc support to tools and
samples."), just do the same and add definitions.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
tools/build/feature/test-bpf.c | 2 ++
tools/lib/bpf/bpf.c | 2 ++
2 files changed, 4 insertions(+)
diff --git a/tools/build/feature/test-bpf.c b/tools/build/feature/test-bpf.c
index 7598361ef1f10..da2172ff9662d 100644
--- a/tools/build/feature/test-bpf.c
+++ b/tools/build/feature/test-bpf.c
@@ -11,6 +11,8 @@
# define __NR_bpf 280
# elif defined(__sparc__)
# define __NR_bpf 349
+# elif defined(__s390__)
+# define __NR_bpf 351
# else
# error __NR_bpf not defined. libbpf does not support your arch.
# endif
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 256f571f2ab52..e5bbb090bf885 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -39,6 +39,8 @@
# define __NR_bpf 280
# elif defined(__sparc__)
# define __NR_bpf 349
+# elif defined(__s390__)
+# define __NR_bpf 351
# else
# error __NR_bpf not defined. libbpf does not support your arch.
# endif