libbpf: Fix libbpf build on compilers missing __builtin_mul_overflow (dda1ec9f) · Commits · 戴 / test

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: ("libbpf: Remove any use of reallocarray() in libbpf") Signed-off-by:

Andrii Nakryiko <andriin@fb.com> Signed-off-by:

Daniel Borkmann <daniel@iogearbox.net> Acked-by:

Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20200820061411.1755905-2-andriin@fb.com

tools/lib/bpf/libbpf_internal.h

+10 −0

Original line number	Diff line number	Diff line
		@@ -10,6 +10,7 @@
		#define __LIBBPF_LIBBPF_INTERNAL_H

		#include <stdlib.h>
		#include <limits.h>

		/* 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);
		}

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