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

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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>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200602174555.2501389-1-iii@linux.ibm.com
This commit is contained in:
Ilya Leoshkevich 2020-06-02 19:45:55 +02:00 committed by Daniel Borkmann
parent effe5be177
commit 33d21f1820
1 changed files with 2 additions and 1 deletions
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arch/s390/net/bpf_jit_comp.c
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@ -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;