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authorRich Felker <dalias@aerifal.cx>2018-04-17 18:36:19 -0400
committerRich Felker <dalias@aerifal.cx>2018-04-18 14:22:49 -0400
commitc9f415d7ea2dace5bf77f6518b6afc36bb7a5732 (patch)
tree53e90cc28b51fd50185527bfbd71411e1ef05843 /src/malloc
parentc1014a812c90bab3c9c989863e4ebb129e987de6 (diff)
downloadmusl-c9f415d7ea2dace5bf77f6518b6afc36bb7a5732.tar.gz
allow interposition/replacement of allocator (malloc)
replacement is subject to conditions on the replacement functions. they may only call functions which are async-signal-safe, as specified either by POSIX or as an implementation-defined extension. if any allocator functions are replaced, at least malloc, realloc, and free must be provided. if calloc is not provided, it will behave as malloc+memset. any of the memalign-family functions not provided will fail with ENOMEM. in order to implement the above properties, calloc and __memalign check that they are using their own malloc or free, respectively. choice to check malloc or free is based on considerations of supporting __simple_malloc. in order to make this work, calloc is split into separate versions for __simple_malloc and full malloc; commit ba819787ee93ceae94efd274f7849e317c1bff58 already did most of the split anyway, and completing it saves an extra call frame. previously, use of -Bsymbolic-functions made dynamic interposition impossible. now, we are using an explicit dynamic-list, so add allocator functions to the list. most are not referenced anyway, but all are added for completeness.
Diffstat (limited to 'src/malloc')
-rw-r--r--src/malloc/calloc.c13
-rw-r--r--src/malloc/lite_malloc.c12
-rw-r--r--src/malloc/malloc.c22
-rw-r--r--src/malloc/memalign.c6
4 files changed, 30 insertions, 23 deletions
diff --git a/src/malloc/calloc.c b/src/malloc/calloc.c
deleted file mode 100644
index 436c0b03..00000000
--- a/src/malloc/calloc.c
+++ /dev/null
@@ -1,13 +0,0 @@
-#include <stdlib.h>
-#include <errno.h>
-
-void *__malloc0(size_t);
-
-void *calloc(size_t m, size_t n)
-{
- if (n && m > (size_t)-1/n) {
- errno = ENOMEM;
- return 0;
- }
- return __malloc0(n * m);
-}
diff --git a/src/malloc/lite_malloc.c b/src/malloc/lite_malloc.c
index 701f60b4..29cccb10 100644
--- a/src/malloc/lite_malloc.c
+++ b/src/malloc/lite_malloc.c
@@ -47,4 +47,14 @@ static void *__simple_malloc(size_t n)
}
weak_alias(__simple_malloc, malloc);
-weak_alias(__simple_malloc, __malloc0);
+
+static void *__simple_calloc(size_t m, size_t n)
+{
+ if (n && m > (size_t)-1/n || malloc != __simple_malloc) {
+ errno = ENOMEM;
+ return 0;
+ }
+ return __simple_malloc(n * m);
+}
+
+weak_alias(__simple_calloc, calloc);
diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c
index 991300cc..5a56e0c5 100644
--- a/src/malloc/malloc.c
+++ b/src/malloc/malloc.c
@@ -368,6 +368,8 @@ void *malloc(size_t n)
return CHUNK_TO_MEM(c);
}
+weak_alias(malloc, __internal_malloc);
+
static size_t mal0_clear(char *p, size_t pagesz, size_t n)
{
#ifdef __GNUC__
@@ -386,13 +388,21 @@ static size_t mal0_clear(char *p, size_t pagesz, size_t n)
}
}
-void *__malloc0(size_t n)
+void *calloc(size_t m, size_t n)
{
+ if (n && m > (size_t)-1/n) {
+ errno = ENOMEM;
+ return 0;
+ }
+ n *= m;
void *p = malloc(n);
- if (!p || IS_MMAPPED(MEM_TO_CHUNK(p)))
- return p;
- if (n >= PAGE_SIZE)
- n = mal0_clear(p, PAGE_SIZE, n);
+ if (!p) return p;
+ if (malloc == __internal_malloc) {
+ if (IS_MMAPPED(MEM_TO_CHUNK(p)))
+ return p;
+ if (n >= PAGE_SIZE)
+ n = mal0_clear(p, PAGE_SIZE, n);
+ }
return memset(p, 0, n);
}
@@ -558,6 +568,8 @@ void free(void *p)
bin_chunk(self);
}
+weak_alias(free, __internal_free);
+
void __malloc_donate(char *start, char *end)
{
size_t align_start_up = (SIZE_ALIGN-1) & (-(uintptr_t)start - OVERHEAD);
diff --git a/src/malloc/memalign.c b/src/malloc/memalign.c
index 006bd21c..35b67599 100644
--- a/src/malloc/memalign.c
+++ b/src/malloc/memalign.c
@@ -3,9 +3,7 @@
#include <errno.h>
#include "libc.h"
-/* This function should work with most dlmalloc-like chunk bookkeeping
- * systems, but it's only guaranteed to work with the native implementation
- * used in this library. */
+void __internal_free(void *);
void *__memalign(size_t align, size_t len)
{
@@ -17,7 +15,7 @@ void *__memalign(size_t align, size_t len)
return NULL;
}
- if (len > SIZE_MAX - align) {
+ if (len > SIZE_MAX - align || free != __internal_free) {
errno = ENOMEM;
return NULL;
}