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@xxxxxx>
---
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 <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);
}
--
2.24.1
