The glib library has a memory pool / slab allocator of its own. Mostly when running glib programs under Valgrind, we bypass it completely by setting GSLICE=always_malloc.
However, that's not optimal -- partly because it papers over the cases where a program allocates using g_slice and then invalidly frees with the normal (g_)free. So I wanted to add proper annotations to make it work nicely with Valgrind. My attempt is below. The file being patched is http://git.gnome.org/browse/glib/tree/glib/gslice.c However, it doesn't quite work as I want -- the 'superblocks' used by the slab allocator are allocated with memalign, so they are tracked by valgrind already. And thus although I seem to mostly get the right warnings at the right times, the allocation stack trace is the wrong one. For example, this test case: foo = g_slice_alloc(20); foo[20] = 0; g_slice_free1(20, foo); foo = g_slice_alloc(20); g_free(foo); ...gives this output: ==18242== Invalid write of size 1 ==18242== at 0x4005CD: main (slice.c:9) ==18242== Address 0x4f38014 is 20 bytes inside a block of size 496 alloc'd ==18242== at 0x4A04360: memalign (vg_replace_malloc.c:532) ==18242== by 0x4A043B9: posix_memalign (vg_replace_malloc.c:660) ==18242== by 0x4C6831B: slab_allocator_alloc_chunk (gslice.c:1174) ==18242== by 0x4C69A74: g_slice_alloc (gslice.c:682) ==18242== by 0x4005B5: main (slice.c:7) ==18242== ==18242== Invalid free() / delete / delete[] ==18242== at 0x4A04D72: free (vg_replace_malloc.c:325) ==18242== by 0x4005FF: main (slice.c:12) ==18242== Address 0x4f38020 is 32 bytes inside a block of size 496 alloc'd ==18242== at 0x4A04360: memalign (vg_replace_malloc.c:532) ==18242== by 0x4A043B9: posix_memalign (vg_replace_malloc.c:660) ==18242== by 0x4C6831B: slab_allocator_alloc_chunk (gslice.c:1174) ==18242== by 0x4C69A74: g_slice_alloc (gslice.c:682) ==18242== by 0x4005B5: main (slice.c:7) How can I make Valgrind *forget* that the slab allocator's superblock was originally allocated with memalign? diff --git a/glib/gslice.c b/glib/gslice.c index 05de6b3..19bdddc 100644 --- a/glib/gslice.c +++ b/glib/gslice.c @@ -52,6 +52,7 @@ #include "gthread.h" #include "gthreadprivate.h" #include "glib_trace.h" +#include "memcheck.h" /* the GSlice allocator is split up into 4 layers, roughly modelled after the slab * allocator and magazine extensions as outlined in: @@ -304,6 +305,8 @@ g_slice_init_nomessage (void) mem_assert (sys_page_size == 0); mem_assert (MIN_MAGAZINE_SIZE >= 4); + VALGRIND_CREATE_MEMPOOL(allocator, 0, 0); + #ifdef G_OS_WIN32 { SYSTEM_INFO system_info; @@ -831,11 +834,15 @@ g_slice_alloc (gsize mem_size) thread_memory_magazine1_reload (tmem, ix); } mem = thread_memory_magazine1_alloc (tmem, ix); + VALGRIND_MAKE_MEM_NOACCESS(mem, chunk_size); + VALGRIND_MEMPOOL_ALLOC(allocator, mem, mem_size); } else if (acat == 2) /* allocate through slab allocator */ { g_mutex_lock (allocator->slab_mutex); mem = slab_allocator_alloc_chunk (chunk_size); + VALGRIND_MAKE_MEM_NOACCESS(mem, chunk_size); + VALGRIND_MEMPOOL_ALLOC(allocator, mem, mem_size); g_mutex_unlock (allocator->slab_mutex); } else /* delegate to system malloc */ @@ -890,6 +897,8 @@ g_slice_free1 (gsize mem_size, } if (G_UNLIKELY (g_mem_gc_friendly)) memset (mem_block, 0, chunk_size); + VALGRIND_MEMPOOL_FREE(allocator, mem_block); + VALGRIND_MAKE_MEM_UNDEFINED(mem_block, sizeof(ChunkLink)); thread_memory_magazine2_free (tmem, ix, mem_block); } else if (acat == 2) /* allocate through slab allocator */ @@ -897,6 +906,8 @@ g_slice_free1 (gsize mem_size, if (G_UNLIKELY (g_mem_gc_friendly)) memset (mem_block, 0, chunk_size); g_mutex_lock (allocator->slab_mutex); + VALGRIND_MEMPOOL_FREE(allocator, mem_block); + VALGRIND_MAKE_MEM_UNDEFINED(mem_block, sizeof(ChunkLink)); slab_allocator_free_chunk (chunk_size, mem_block); g_mutex_unlock (allocator->slab_mutex); } @@ -951,6 +962,8 @@ g_slice_free_chain_with_offset (gsize mem_size, } if (G_UNLIKELY (g_mem_gc_friendly)) memset (current, 0, chunk_size); + VALGRIND_MEMPOOL_FREE(allocator, current); + VALGRIND_MAKE_MEM_UNDEFINED(current, sizeof(ChunkLink)); thread_memory_magazine2_free (tmem, ix, current); } } @@ -966,6 +979,8 @@ g_slice_free_chain_with_offset (gsize mem_size, abort(); if (G_UNLIKELY (g_mem_gc_friendly)) memset (current, 0, chunk_size); + VALGRIND_MEMPOOL_FREE(allocator, current); + VALGRIND_MAKE_MEM_UNDEFINED(current, sizeof(ChunkLink)); slab_allocator_free_chunk (chunk_size, current); } g_mutex_unlock (allocator->slab_mutex); -- dwmw2 ------------------------------------------------------------------------------ Beautiful is writing same markup. Internet Explorer 9 supports standards for HTML5, CSS3, SVG 1.1, ECMAScript5, and DOM L2 & L3. Spend less time writing and rewriting code and more time creating great experiences on the web. Be a part of the beta today. http://p.sf.net/sfu/beautyoftheweb _______________________________________________ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
