2022-07-21 12:54:31

by Xu Kuohai

[permalink] [raw]
Subject: [PATCH bpf-next] bpf, arm64: Fix compile error in dummy_tramp()

From: Xu Kuohai <[email protected]>

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 <[email protected]>
Tested-by: Jon Hunter <[email protected]>
Signed-off-by: Xu Kuohai <[email protected]>
---
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


2022-07-21 13:00:56

by Jiri Olsa

[permalink] [raw]
Subject: Re: [PATCH bpf-next] bpf, arm64: Fix compile error in dummy_tramp()

On Thu, Jul 21, 2022 at 08:13:19AM -0400, Xu Kuohai wrote:
> From: Xu Kuohai <[email protected]>
>
> 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 <[email protected]>
> Tested-by: Jon Hunter <[email protected]>
> Signed-off-by: Xu Kuohai <[email protected]>

Jean-Philippe, could you please take a look?

thanks,
jirka

> ---
> 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
>

2022-07-21 14:10:13

by Jean-Philippe Brucker

[permalink] [raw]
Subject: Re: [PATCH bpf-next] bpf, arm64: Fix compile error in dummy_tramp()

On Thu, Jul 21, 2022 at 08:13:19AM -0400, Xu Kuohai wrote:
> From: Xu Kuohai <[email protected]>
>
> 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 <[email protected]>
> Tested-by: Jon Hunter <[email protected]>
> Signed-off-by: Xu Kuohai <[email protected]>

Right, it looks like the lr alias was only added to binutils 2.30, and
Linux supports 2.23+

Reviewed-by: Jean-Philippe Brucker <[email protected]>

> ---
> 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
>

2022-07-21 22:56:13

by patchwork-bot+netdevbpf

[permalink] [raw]
Subject: Re: [PATCH bpf-next] bpf, arm64: Fix compile error in dummy_tramp()

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <[email protected]>:

On Thu, 21 Jul 2022 08:13:19 -0400 you wrote:
> From: Xu Kuohai <[email protected]>
>
> 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
>
> [...]

Here is the summary with links:
- [bpf-next] bpf, arm64: Fix compile error in dummy_tramp()
https://git.kernel.org/bpf/bpf-next/c/339ed900b307

You are awesome, thank you!
--
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