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libbpf: Fix libbpf build on compilers missing __builtin_mul_overflow

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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 <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
This commit is contained in:
Andrii Nakryiko
2020-08-19 23:14:09 -07:00
committed by Andrii Nakryiko
parent a8a3089b5e
commit 4a2f7ac55f
1 changed files with 10 additions and 0 deletions
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10
src/libbpf_internal.h
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@@ -10,6 +10,7 @@
#define __LIBBPF_LIBBPF_INTERNAL_H #define __LIBBPF_LIBBPF_INTERNAL_H
#include <stdlib.h> #include <stdlib.h>
#include <limits.h>
/* make sure libbpf doesn't use kernel-only integer typedefs */ /* make sure libbpf doesn't use kernel-only integer typedefs */
#pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64 #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_info(fmt, ...) __pr(LIBBPF_INFO, fmt, ##__VA_ARGS__)
#define pr_debug(fmt, ...) __pr(LIBBPF_DEBUG, 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. * Re-implement glibc's reallocarray() for libbpf internal-only use.
* reallocarray(), unfortunately, is not available in all versions of glibc, * 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; size_t total;
#if __has_builtin(__builtin_mul_overflow)
if (unlikely(__builtin_mul_overflow(nmemb, size, &total))) if (unlikely(__builtin_mul_overflow(nmemb, size, &total)))
return NULL; return NULL;
#else
if (size == 0 || nmemb > ULONG_MAX / size)
return NULL;
total = nmemb * size;
#endif
return realloc(ptr, total); return realloc(ptr, total);
} }