summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorAlexander Monakov <amonakov@ispras.ru>2018-04-16 20:54:36 +0300
committerRich Felker <dalias@aerifal.cx>2018-04-17 19:23:00 -0400
commitce7ae11acfd9db8eb92cc6823c132e1825918d92 (patch)
tree209dc86f7454ff68af570afb3ad29e2bbc1a1a27
parentd889cc3463edc92869676c1eec34a8f52d942adb (diff)
downloadmusl-ce7ae11acfd9db8eb92cc6823c132e1825918d92.tar.gz
ldso, malloc: implement reclaim_gaps via __malloc_donate
Split 'free' into unmap_chunk and bin_chunk, use the latter to introduce __malloc_donate and use it in reclaim_gaps instead of calling 'free'.
-rw-r--r--ldso/dynlink.c16
-rw-r--r--src/malloc/malloc.c61
2 files changed, 47 insertions, 30 deletions
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 9bf6924b..b9ff41bc 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -476,23 +476,15 @@ static void redo_lazy_relocs()
/* A huge hack: to make up for the wastefulness of shared libraries
* needing at least a page of dirty memory even if they have no global
* data, we reclaim the gaps at the beginning and end of writable maps
- * and "donate" them to the heap by setting up minimal malloc
- * structures and then freeing them. */
+ * and "donate" them to the heap. */
static void reclaim(struct dso *dso, size_t start, size_t end)
{
- size_t *a, *z;
+ void __malloc_donate(char *, char *);
if (start >= dso->relro_start && start < dso->relro_end) start = dso->relro_end;
if (end >= dso->relro_start && end < dso->relro_end) end = dso->relro_start;
- start = start + 6*sizeof(size_t)-1 & -4*sizeof(size_t);
- end = (end & -4*sizeof(size_t)) - 2*sizeof(size_t);
- if (start>end || end-start < 4*sizeof(size_t)) return;
- a = laddr(dso, start);
- z = laddr(dso, end);
- a[-2] = 1;
- a[-1] = z[0] = end-start + 2*sizeof(size_t) | 1;
- z[1] = 1;
- free(a);
+ if (start >= end) return;
+ __malloc_donate(laddr(dso, start), laddr(dso, end));
}
static void reclaim_gaps(struct dso *dso)
diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c
index db19bc34..6605ec3a 100644
--- a/src/malloc/malloc.c
+++ b/src/malloc/malloc.c
@@ -299,6 +299,8 @@ static int pretrim(struct chunk *self, size_t n, int i, int j)
return 1;
}
+static void bin_chunk(struct chunk *);
+
static void trim(struct chunk *self, size_t n)
{
size_t n1 = CHUNK_SIZE(self);
@@ -314,7 +316,7 @@ static void trim(struct chunk *self, size_t n)
next->psize = n1-n | C_INUSE;
self->csize = n | C_INUSE;
- free(CHUNK_TO_MEM(split));
+ bin_chunk(split);
}
void *malloc(size_t n)
@@ -465,29 +467,14 @@ copy_free_ret:
return new;
}
-void free(void *p)
+static void bin_chunk(struct chunk *self)
{
- struct chunk *self, *next;
+ struct chunk *next = NEXT_CHUNK(self);
size_t final_size, new_size, size;
int reclaim=0;
int i;
- if (!p) return;
-
- self = MEM_TO_CHUNK(p);
-
- if (IS_MMAPPED(self)) {
- size_t extra = self->psize;
- char *base = (char *)self - extra;
- size_t len = CHUNK_SIZE(self) + extra;
- /* Crash on double free */
- if (extra & 1) a_crash();
- __munmap(base, len);
- return;
- }
-
final_size = new_size = CHUNK_SIZE(self);
- next = NEXT_CHUNK(self);
/* Crash on corrupted footer (likely from buffer overflow) */
if (next->psize != self->csize) a_crash();
@@ -548,3 +535,41 @@ void free(void *p)
unlock_bin(i);
}
+
+static void unmap_chunk(struct chunk *self)
+{
+ size_t extra = self->psize;
+ char *base = (char *)self - extra;
+ size_t len = CHUNK_SIZE(self) + extra;
+ /* Crash on double free */
+ if (extra & 1) a_crash();
+ __munmap(base, len);
+}
+
+void free(void *p)
+{
+ if (!p) return;
+
+ struct chunk *self = MEM_TO_CHUNK(p);
+
+ if (IS_MMAPPED(self))
+ unmap_chunk(self);
+ else
+ bin_chunk(self);
+}
+
+void __malloc_donate(char *start, char *end)
+{
+ size_t align_start_up = (SIZE_ALIGN-1) & (-(uintptr_t)start - OVERHEAD);
+ size_t align_end_down = (SIZE_ALIGN-1) & (uintptr_t)end;
+
+ if (end - start <= OVERHEAD + align_start_up + align_end_down)
+ return;
+ start += align_start_up + OVERHEAD;
+ end -= align_end_down;
+
+ struct chunk *c = MEM_TO_CHUNK(start), *n = MEM_TO_CHUNK(end);
+ c->psize = n->csize = C_INUSE;
+ c->csize = n->psize = C_INUSE | (end-start);
+ bin_chunk(c);
+}