linux-kernel - [PATCH bpf-next] bpf, arm64: Fix compile error in dummy

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Date:   Thu, 21 Jul 2022 08:13:19 -0400
From:   Xu Kuohai <xukuohai@...weicloud.com>
To:     bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Hao Luo <haoluo@...gle.com>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Jiri Olsa <jolsa@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Jon Hunter <jonathanh@...dia.com>,
        KP Singh <kpsingh@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Will Deacon <will@...nel.org>, Yonghong Song <yhs@...com>,
        Zi Shen Lim <zlim.lnx@...il.com>
Subject: [PATCH bpf-next] bpf, arm64: Fix compile error in dummy_tramp()

From: Xu Kuohai <xukuohai@...wei.com>

dummy_tramp() uses "lr" to refer to the x30 register, but some assembler
does not recognize "lr" and reports a build failure:

/tmp/cc52xO0c.s: Assembler messages:
/tmp/cc52xO0c.s:8: Error: operand 1 should be an integer register -- `mov lr,x9'
/tmp/cc52xO0c.s:7: Error: undefined symbol lr used as an immediate value
make[2]: *** [scripts/Makefile.build:250: arch/arm64/net/bpf_jit_comp.o] Error 1
make[1]: *** [scripts/Makefile.build:525: arch/arm64/net] Error 2

So replace "lr" with "x30" to fix it.

Fixes: b2ad54e1533e ("bpf, arm64: Implement bpf_arch_text_poke() for arm64")
Reported-by: Jon Hunter <jonathanh@...dia.com>
Tested-by: Jon Hunter <jonathanh@...dia.com>
Signed-off-by: Xu Kuohai <xukuohai@...wei.com>
---
 arch/arm64/net/bpf_jit_comp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index dcc572b7d4da..7ca8779ae34f 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -610,8 +610,8 @@ asm (
 #if IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)
 "	bti j\n" /* dummy_tramp is called via "br x10" */
 #endif
-"	mov x10, lr\n"
-"	mov lr, x9\n"
+"	mov x10, x30\n"
+"	mov x30, x9\n"
 "	ret x10\n"
 "	.size dummy_tramp, .-dummy_tramp\n"
 "	.popsection\n"
-- 
2.30.2