bpf, arm64: fix stack_depth tracking in combination with tail calls

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Using dynamic stack_depth tracking in arm64 JIT is currently broken in
combination with tail calls. In prologue, we cache ctx->stack_size and
adjust SP reg for setting up function call stack, and tearing it down
again in epilogue. Problem is that when doing a tail call, the cached
ctx->stack_size might not be the same.

One way to fix the problem with minimal overhead is to re-adjust SP in
emit_bpf_tail_call() and properly adjust it to the current program's
ctx->stack_size. Tested on Cavium ThunderX ARMv8.

Fixes: f1c9eed7f4 ("bpf, arm64: take advantage of stack_depth tracking")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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Daniel Borkmann 2018-01-16 03:46:08 +01:00 • committed by Alexei Starovoitov

parent 68fda450a7

commit a2284d912b

1 changed files with 11 additions and 9 deletions

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arch/arm64/net/bpf_jit_comp.c

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