From dda1ec9fc7f8383cb469a82614dbce61f357f3f8 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Wed, 19 Aug 2020 23:14:09 -0700 Subject: [PATCH] libbpf: Fix libbpf build on compilers missing __builtin_mul_overflow GCC compilers older than version 5 don't support __builtin_mul_overflow yet. Given GCC 4.9 is the minimal supported compiler for building kernel and the fact that libbpf is a dependency of resolve_btfids, which is dependency of CONFIG_DEBUG_INFO_BTF=y, this needs to be handled. This patch fixes the issue by falling back to slower detection of integer overflow in such cases. Fixes: 029258d7b228 ("libbpf: Remove any use of reallocarray() in libbpf") Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20200820061411.1755905-2-andriin@fb.com --- tools/lib/bpf/libbpf_internal.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index 61dff515a2f0..4d1c366fca2c 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -10,6 +10,7 @@ #define __LIBBPF_LIBBPF_INTERNAL_H #include +#include /* make sure libbpf doesn't use kernel-only integer typedefs */ #pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64 @@ -77,6 +78,9 @@ do { \ #define pr_info(fmt, ...) __pr(LIBBPF_INFO, fmt, ##__VA_ARGS__) #define pr_debug(fmt, ...) __pr(LIBBPF_DEBUG, fmt, ##__VA_ARGS__) +#ifndef __has_builtin +#define __has_builtin(x) 0 +#endif /* * Re-implement glibc's reallocarray() for libbpf internal-only use. * reallocarray(), unfortunately, is not available in all versions of glibc, @@ -90,8 +94,14 @@ static inline void *libbpf_reallocarray(void *ptr, size_t nmemb, size_t size) { size_t total; +#if __has_builtin(__builtin_mul_overflow) if (unlikely(__builtin_mul_overflow(nmemb, size, &total))) return NULL; +#else + if (size == 0 || nmemb > ULONG_MAX / size) + return NULL; + total = nmemb * size; +#endif return realloc(ptr, total); }