diff options
Diffstat (limited to 'src/include/utils/memutils_internal.h')
| -rw-r--r-- | src/include/utils/memutils_internal.h | 40 |
1 files changed, 14 insertions, 26 deletions
diff --git a/src/include/utils/memutils_internal.h b/src/include/utils/memutils_internal.h index 377cee7a841..bc2cbdd5061 100644 --- a/src/include/utils/memutils_internal.h +++ b/src/include/utils/memutils_internal.h @@ -74,15 +74,26 @@ extern void SlabCheck(MemoryContext context); * MemoryContextMethodID * A unique identifier for each MemoryContext implementation which * indicates the index into the mcxt_methods[] array. See mcxt.c. - * The maximum value for this enum is constrained by - * MEMORY_CONTEXT_METHODID_MASK. If an enum value higher than that is - * required then MEMORY_CONTEXT_METHODID_BITS will need to be increased. + * + * For robust error detection, ensure that MemoryContextMethodID has a value + * for each possible bit-pattern of MEMORY_CONTEXT_METHODID_MASK, and make + * dummy entries for unused IDs in the mcxt_methods[] array. We also try + * to avoid using bit-patterns as valid IDs if they are likely to occur in + * garbage data, or if they could falsely match on chunks that are really from + * malloc not palloc. (We can't tell that for most malloc implementations, + * but it happens that glibc stores flag bits in the same place where we put + * the MemoryContextMethodID, so the possible values are predictable for it.) */ typedef enum MemoryContextMethodID { + MCTX_UNUSED1_ID, /* 000 occurs in never-used memory */ + MCTX_UNUSED2_ID, /* glibc malloc'd chunks usually match 001 */ + MCTX_UNUSED3_ID, /* glibc malloc'd chunks > 128kB match 010 */ MCTX_ASET_ID, MCTX_GENERATION_ID, MCTX_SLAB_ID, + MCTX_UNUSED4_ID, /* available */ + MCTX_UNUSED5_ID /* 111 occurs in wipe_mem'd memory */ } MemoryContextMethodID; /* @@ -104,27 +115,4 @@ extern void MemoryContextCreate(MemoryContext node, MemoryContext parent, const char *name); -/* - * GetMemoryChunkMethodID - * Return the MemoryContextMethodID from the uint64 chunk header which - * directly precedes 'pointer'. - */ -static inline MemoryContextMethodID -GetMemoryChunkMethodID(void *pointer) -{ - uint64 header; - - /* - * Try to detect bogus pointers handed to us, poorly though we can. - * Presumably, a pointer that isn't MAXALIGNED isn't pointing at an - * allocated chunk. - */ - Assert(pointer != NULL); - Assert(pointer == (void *) MAXALIGN(pointer)); - - header = *((uint64 *) ((char *) pointer - sizeof(uint64))); - - return (MemoryContextMethodID) (header & MEMORY_CONTEXT_METHODID_MASK); -} - #endif /* MEMUTILS_INTERNAL_H */ |