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| author | James Hilliard <james.hilliard1@gmail.com> | 2022-08-29 15:05:46 -0600 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2022-08-31 20:54:23 +0200 |
| commit | 14e5ce79943a72b9bf0fff8a5867320a9fa3e40d (patch) | |
| tree | 366c1cec405f7e3a454d85de08de45e2042b10b0 | |
| parent | 6f95de6d713130c953af0a40b13c1da519f91c4e (diff) | |
| download | linux-stable-14e5ce79943a72b9bf0fff8a5867320a9fa3e40d.tar.gz linux-stable-14e5ce79943a72b9bf0fff8a5867320a9fa3e40d.tar.bz2 linux-stable-14e5ce79943a72b9bf0fff8a5867320a9fa3e40d.zip | |
libbpf: Add GCC support for bpf_tail_call_static
The bpf_tail_call_static function is currently not defined unless
using clang >= 8.
To support bpf_tail_call_static on GCC we can check if __clang__ is
not defined to enable bpf_tail_call_static.
We need to use GCC assembly syntax when the compiler does not define
__clang__ as LLVM inline assembly is not fully compatible with GCC.
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220829210546.755377-1-james.hilliard1@gmail.com
| -rw-r--r-- | tools/lib/bpf/bpf_helpers.h | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index 7349b16b8e2f..867b734839dd 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -131,7 +131,7 @@ /* * Helper function to perform a tail call with a constant/immediate map slot. */ -#if __clang_major__ >= 8 && defined(__bpf__) +#if (!defined(__clang__) || __clang_major__ >= 8) && defined(__bpf__) static __always_inline void bpf_tail_call_static(void *ctx, const void *map, const __u32 slot) { @@ -139,8 +139,8 @@ bpf_tail_call_static(void *ctx, const void *map, const __u32 slot) __bpf_unreachable(); /* - * Provide a hard guarantee that LLVM won't optimize setting r2 (map - * pointer) and r3 (constant map index) from _different paths_ ending + * Provide a hard guarantee that the compiler won't optimize setting r2 + * (map pointer) and r3 (constant map index) from _different paths_ ending * up at the _same_ call insn as otherwise we won't be able to use the * jmpq/nopl retpoline-free patching by the x86-64 JIT in the kernel * given they mismatch. See also d2e4c1e6c294 ("bpf: Constant map key @@ -148,12 +148,19 @@ bpf_tail_call_static(void *ctx, const void *map, const __u32 slot) * * Note on clobber list: we need to stay in-line with BPF calling * convention, so even if we don't end up using r0, r4, r5, we need - * to mark them as clobber so that LLVM doesn't end up using them - * before / after the call. + * to mark them as clobber so that the compiler doesn't end up using + * them before / after the call. */ - asm volatile("r1 = %[ctx]\n\t" + asm volatile( +#ifdef __clang__ + "r1 = %[ctx]\n\t" "r2 = %[map]\n\t" "r3 = %[slot]\n\t" +#else + "mov %%r1,%[ctx]\n\t" + "mov %%r2,%[map]\n\t" + "mov %%r3,%[slot]\n\t" +#endif "call 12" :: [ctx]"r"(ctx), [map]"r"(map), [slot]"i"(slot) : "r0", "r1", "r2", "r3", "r4", "r5"); |