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| author | Rich Felker <dalias@aerifal.cx> | 2011-08-23 09:43:45 -0400 |
|---|---|---|
| committer | Rich Felker <dalias@aerifal.cx> | 2011-08-23 09:43:45 -0400 |
| commit | 1c8bead345eca58ddc5177a121142b527937adee (patch) | |
| tree | 75620e8cf4815c94eed8d1d69d3062b7b5893709 | |
| parent | df0b5a49406763aa4719dfad561a5de8924ecd59 (diff) | |
| download | musl-1c8bead345eca58ddc5177a121142b527937adee.tar.gz musl-1c8bead345eca58ddc5177a121142b527937adee.tar.xz musl-1c8bead345eca58ddc5177a121142b527937adee.zip | |
use new a_crash() asm to optimize double-free handler.
gcc generates extremely bad code (7 byte immediate mov) for the old null pointer write approach. it should be generating something like "xor %eax,%eax ; mov %al,(%eax)". in any case, using a dedicated crashing opcode accomplishes the same thing in one byte.
| -rw-r--r-- | src/malloc/malloc.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c index 0888afa9..abf3e8fa 100644 --- a/src/malloc/malloc.c +++ b/src/malloc/malloc.c @@ -394,7 +394,7 @@ void *realloc(void *p, size_t n) size_t oldlen = n0 + extra; size_t newlen = n + extra; /* Crash on realloc of freed chunk */ - if (extra & 1) *(volatile char *)0=0; + if (extra & 1) a_crash(); if (newlen < PAGE_SIZE && (new = malloc(n))) { memcpy(new, p, n-OVERHEAD); free(p); @@ -457,7 +457,7 @@ void free(void *p) char *base = (char *)self - extra; size_t len = CHUNK_SIZE(self) + extra; /* Crash on double free */ - if (extra & 1) *(volatile char *)0=0; + if (extra & 1) a_crash(); __munmap(base, len); return; } |