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Don't define default implementations for weak symbols.

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See d72b38e4aa/folly/memory/Malloc.h (L89-L97)

This should work as well and be more robust to the pattern used in
Folly. The branch-predictor in modern CPUs probably makes it equally
fast.

Change-Id: I65b115c16d103b8a5492354411b55f3ef906b097
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/40405
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
This commit is contained in:
Adam Langley 2020-03-30 09:24:45 -07:00 committed by CQ bot account: commit-bot@chromium.org
parent 732b70ee20
commit 0cf14d3ec8
1 changed files with 19 additions and 21 deletions
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40
crypto/mem.c
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@ -84,38 +84,28 @@ static void __asan_unpoison_memory_region(const void *addr, size_t size) {}
// Windows doesn't really support weak symbols as of May 2019, and Clang on
// Windows will emit strong symbols instead. See
// https://bugs.llvm.org/show_bug.cgi?id=37598
#if defined(__GNUC__) || (defined(__clang__) && !defined(_MSC_VER))
#define WEAK_SYMBOL_DECL
#define WEAK_SYMBOL_DEFAULT_IMPL __attribute((weak, noinline))
#if defined(__ELF__) && defined(__GNUC__)
#define WEAK_SYMBOL_FUNC(rettype, name, args) \
rettype name args __attribute__((weak));
#else
#define WEAK_SYMBOL_DECL static
#define WEAK_SYMBOL_DEFAULT_IMPL static
#define WEAK_SYMBOL_FUNC(rettype, name, args) static rettype(*name) args = NULL;
#endif
// sdallocx is a sized |free| function. By passing the size (which we happen to
// always know in BoringSSL), the malloc implementation can save work. We cannot
// depend on |sdallocx| being available so we declare a wrapper that falls back
// to |free| as a weak symbol.
// depend on |sdallocx| being available, however, so it's a weak symbol.
//
// This will always be safe, but will only be overridden if the malloc
// implementation is statically linked with BoringSSL. So, if |sdallocx| is
// provided in, say, libc.so, we still won't use it because that's dynamically
// linked. This isn't an ideal result, but its helps in some cases.
WEAK_SYMBOL_DECL void sdallocx(void *ptr, size_t size, int flags);
WEAK_SYMBOL_DEFAULT_IMPL void sdallocx(void *ptr, size_t size, int flags) {
free(ptr);
}
WEAK_SYMBOL_FUNC(void, sdallocx, (void *ptr, size_t size, int flags));
// The following two functions are for memory tracking. They are no-ops by
// default but can be overridden at link time if the application needs to
// observe heap operations.
WEAK_SYMBOL_DECL void OPENSSL_track_memory_alloc(void *ptr, size_t size);
WEAK_SYMBOL_DEFAULT_IMPL void OPENSSL_track_memory_alloc(void *ptr,
size_t size) {}
WEAK_SYMBOL_DECL void OPENSSL_track_memory_free(void *ptr, size_t size);
WEAK_SYMBOL_DEFAULT_IMPL void OPENSSL_track_memory_free(void *ptr,
size_t size) {}
WEAK_SYMBOL_FUNC(void, OPENSSL_track_memory_alloc, (void *ptr, size_t size));
WEAK_SYMBOL_FUNC(void, OPENSSL_track_memory_free, (void *ptr, size_t size));
void *OPENSSL_malloc(size_t size) {
if (size + OPENSSL_MALLOC_PREFIX < size) {
@ -130,7 +120,9 @@ void *OPENSSL_malloc(size_t size) {
*(size_t *)ptr = size;
__asan_poison_memory_region(ptr, OPENSSL_MALLOC_PREFIX);
OPENSSL_track_memory_alloc(ptr, size + OPENSSL_MALLOC_PREFIX);
if (OPENSSL_track_memory_alloc) {
OPENSSL_track_memory_alloc(ptr, size + OPENSSL_MALLOC_PREFIX);
}
return ((uint8_t *)ptr) + OPENSSL_MALLOC_PREFIX;
}
@ -143,9 +135,15 @@ void OPENSSL_free(void *orig_ptr) {
__asan_unpoison_memory_region(ptr, OPENSSL_MALLOC_PREFIX);
size_t size = *(size_t *)ptr;
OPENSSL_track_memory_free(ptr, size + OPENSSL_MALLOC_PREFIX);
if (OPENSSL_track_memory_free) {
OPENSSL_track_memory_free(ptr, size + OPENSSL_MALLOC_PREFIX);
}
OPENSSL_cleanse(ptr, size + OPENSSL_MALLOC_PREFIX);
sdallocx(ptr, size + OPENSSL_MALLOC_PREFIX, 0 /* flags */);
if (sdallocx) {
sdallocx(ptr, size + OPENSSL_MALLOC_PREFIX, 0 /* flags */);
} else {
free(ptr);
}
}
void *OPENSSL_realloc(void *orig_ptr, size_t new_size) {