diff mbox series

[bpf] s390/bpf: Use bcr 0,%0 as tail call nop filler

Message ID 20200602174555.2501389-1-iii@linux.ibm.com
State Accepted
Delegated to: BPF Maintainers
Headers show
Series [bpf] s390/bpf: Use bcr 0,%0 as tail call nop filler | expand

Commit Message

Ilya Leoshkevich June 2, 2020, 5:45 p.m. UTC 
Currently used 0x0000 filler confuses bfd disassembler, making bpftool
prog dump xlated output nearly useless. Fix by using a real instruction.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 arch/s390/net/bpf_jit_comp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Daniel Borkmann June 2, 2020, 8:36 p.m. UTC | #1 
On 6/2/20 7:45 PM, Ilya Leoshkevich wrote:
> Currently used 0x0000 filler confuses bfd disassembler, making bpftool
> prog dump xlated output nearly useless. Fix by using a real instruction.
> 
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>

Applied, thanks!
diff mbox series

Patch

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 0f37a1b635f8..f4242b894cf2 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -503,7 +503,8 @@  static void bpf_jit_prologue(struct bpf_jit *jit, u32 stack_depth)
 	} else {
 		/* j tail_call_start: NOP if no tail calls are used */
 		EMIT4_PCREL(0xa7f40000, 6);
-		_EMIT2(0);
+		/* bcr 0,%0 */
+		EMIT2(0x0700, 0, REG_0);
 	}
 	/* Tail calls have to skip above initialization */
 	jit->tail_call_start = jit->prg;