[PATCH] bpf, arm64: Mark dummy_tramp as global

Nathan Chancellor
2022-07-13T17:35:23Z

When building with clang + CONFIG_CFI_CLANG=y, the following error
occurs at link time:

ld.lld: error: undefined symbol: dummy_tramp

dummy_tramp is declared globally in C but its definition in inline
assembly does not use .global, which prevents clang from properly
resolving the references to it when creating the CFI jump tables.

Mark dummy_tramp as global so that the reference can be properly
resolved.

Fixes: b2ad54e1533e ("bpf, arm64: Implement bpf_arch_text_poke() for arm64")
Link: https://github.com/ClangBuiltLinux/linux/issues/1661
Suggested-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
arch/arm64/net/bpf_jit_comp.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index fd1cb0d2aaa6..dcc572b7d4da 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -604,6 +604,7 @@ void dummy_tramp(void);

asm (
" .pushsection .text, \"ax\", @progbits\n"
+" .global dummy_tramp\n"
" .type dummy_tramp, %function\n"
"dummy_tramp:"
#if IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)

base-commit: ace2bee839e08df324cb320763258dfd72e6120e
--
2.37.1