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improve padding extra

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This commit is contained in:
Daan Leijen 2021-12-09 16:04:22 -08:00
parent a84df3795a
commit 8c04558af8
5 changed files with 58 additions and 26 deletions
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34
include/mimalloc-types.h
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@ -60,16 +60,20 @@ terms of the MIT license. A copy of the license can be found in the file
#define MI_PADDING 1
#endif
#if !defined(MI_PADDING_EXTRA) // use extra padding bytes?
#define MI_PADDING_EXTRA (64)
#if !defined(MI_DEBUG_TRACE) // store stack trace at each allocation
#define MI_DEBUG_TRACE MI_DEBUG
#endif
#if !defined(MI_DEBUG_TRACE) // store stack trace at each allocation
#define MI_DEBUG_TRACE 1
#if !defined(MI_DEBUG_TRACE_LEN)
#define MI_DEBUG_TRACE_LEN (7) // store up to N frames if tracing is enabled
#endif
#if !defined(MI_DEBUG_TRACE_LEN) // store stack trace at each allocation
#define MI_DEBUG_TRACE_LEN (6) // store up to N frames
#if !defined(MI_PADDING_EXTRA) // use extra padding bytes? (so a stack trace can be preserved or next block corruption prevented)
#if MI_DEBUG_TRACE > 0
#define MI_PADDING_EXTRA (128)
#else
#define MI_PADDING_EXTRA (0)
#endif
#endif
@ -366,18 +370,26 @@ typedef struct mi_random_cxt_s {
// In debug mode there is a padding structure at the end of the blocks to check for buffer overflows
#if (MI_PADDING)
typedef struct mi_padding_s {
uint32_t canary; // encoded block value to check validity of the padding (in case of overflow)
uint32_t delta; // padding bytes before the block. (mi_usable_size(p) - delta == exact allocated bytes)
#if MI_PADDING_EXTRA > 0
uint32_t canary_lo;
uint8_t extra[MI_PADDING_EXTRA];
#endif
uint32_t canary; // encoded block value to check validity of the delat (in case of overflow)
uint32_t delta; // padding bytes before the block. (mi_usable_size(p) - delta == exact allocated bytes)
#if (MI_DEBUG_TRACE > 0)
void* strace[MI_DEBUG_TRACE_LEN]; // stack trace at allocation time
#endif
} mi_padding_t;
#define MI_PADDING_SIZE (sizeof(mi_padding_t) + MI_PADDING_EXTRA)
#define MI_PADDING_MINSIZE (8) // 2*sizeof(uint32_t)
#define MI_PADDING_SIZE (sizeof(mi_padding_t))
#else
#define MI_PADDING_SIZE 0
#define MI_PADDING_MINSIZE (0)
#define MI_PADDING_SIZE (0)
#endif
#define MI_PAGES_DIRECT (MI_SMALL_WSIZE_MAX + 1)
// add 2 more for minimal padding (MI_PADDING && !MI_DEBUG_TRACE && MI_PADDING_EXTRA==0)
// see `init.c` where all are initialized with an empty page and the check at `heap_malloc_small`.
#define MI_PAGES_DIRECT (MI_SMALL_WSIZE_MAX + 1 + 2)
// A heap owns a set of pages.