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[malloc] Avoid false positive warnings from valgrind 

Calling discard_cache() is likely to result in a call to
free_memblock(), which will call valgrind_make_blocks_noaccess()
before returning.  This causes valgrind to report an invalid read on
the next iteration through the loop in alloc_memblock().

Fix by explicitly calling valgrind_make_blocks_defined() after
discard_cache() returns.  Also call valgrind_make_blocks_noaccess()
before calling discard_cache(), to guard against free list corruption
while executing cache discarders.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2017-09-04 14:00:32 +01:00
parent 75acb3c775
commit 42eedb04c1
1 changed files with 8 additions and 1 deletions
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9
src/core/malloc.c
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@ -284,6 +284,7 @@ void * alloc_memblock ( size_t size, size_t align, size_t offset ) {
size_t post_size;
struct memory_block *pre;
struct memory_block *post;
unsigned int discarded;
void *ptr;
/* Sanity checks */
@ -371,7 +372,13 @@ void * alloc_memblock ( size_t size, size_t align, size_t offset ) {
}
/* Try discarding some cached data to free up memory */
if ( ! discard_cache() ) {
DBGC ( &heap, "Attempting discard for %#zx (aligned %#zx+%zx), "
"used %zdkB\n", size, align, offset, ( usedmem >> 10 ) );
valgrind_make_blocks_noaccess();
discarded = discard_cache();
valgrind_make_blocks_defined();
check_blocks();
if ( ! discarded ) {
/* Nothing available to discard */
DBGC ( &heap, "Failed to allocate %#zx (aligned "
"%#zx)\n", size, align );