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feat(malloc): add allocation tracing support, fix realloc copy size bug
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@ssimek
ssimek committed Feb 12, 2025
1 parent f775179 commit b25298c
Showing 1 changed file with 42 additions and 44 deletions.
86 changes: 42 additions & 44 deletions targets/cortex-m/malloc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -13,28 +13,19 @@

#include <base/base.h>

#include <base/alloc_trace.h>

#include <malloc_internal.h>

#define DIAG_ALLOC 1
#define DIAG_HEAP 2
#define DIAG_FREECHAIN 4

//#define MALLOC_DIAG DIAG_ALLOC
//#define MALLOC_DIAG DIAG_ALLOC | DIAG_HEAP

#define MYDBG(...) DBGCL("malloc", __VA_ARGS__)

ALWAYS_INLINE static uint32_t __LR()
{
uint32_t res;
__asm volatile ("mov %0,lr" : "=r" (res));
return res;
}

#if TRACE || MINITRACE
#define CAPTURE_LR() UNUSED auto __lr = __LR() & ~1;
#else
#define CAPTURE_LR()
#endif
#define __lr __builtin_return_address(0)

#if MALLOC_DIAG
#define MYDIAG(flag, ...) if ((MALLOC_DIAG) & (flag)) { MYDBG(__VA_ARGS__); }
Expand Down Expand Up @@ -68,30 +59,33 @@ void dump_free_chain()
#define dump_free_chain()
#endif

#define SMALLEST_BLOCK (sizeof(intptr_t) * 2)
#define BLOCK_ALIGNMENT 16
#define REQUIRED_BLOCK(n) (((n) + sizeof(size_t) + BLOCK_ALIGNMENT - 1) & ~(BLOCK_ALIGNMENT - 1))
#define MEM_SIZE(ptr) (((size_t*)(ptr))[-1])
#define BLOCK_ADDR(ptr) ((size_t*)(ptr) - 1)
#define HEADER_SIZE (sizeof(size_t) + ALLOC_TRACE_OVERHEAD)
#define REQUIRED_BLOCK(n) (((n) + HEADER_SIZE + BLOCK_ALIGNMENT - 1) & ~(BLOCK_ALIGNMENT - 1))
#define SMALLEST_BLOCK REQUIRED_BLOCK(1)
#define BLOCK_ADDR(ptr) ((char*)(ptr) - HEADER_SIZE)
#define MEM_SIZE(ptr) (*(size_t*)BLOCK_ADDR(ptr))

void* mtrim(void* ptr, size_t size)
{
if (!size)
{
return ptr;
}

PLATFORM_CRITICAL_SECTION();

if (size)
size = REQUIRED_BLOCK(size);
size_t cur = MEM_SIZE(ptr);
if (cur >= size + SMALLEST_BLOCK)
{
CAPTURE_LR();
size = REQUIRED_BLOCK(size);
size_t cur = MEM_SIZE(ptr);
if (cur > size + SMALLEST_BLOCK)
{
// there is space to be trimmed - we divide the allocated block in two and free the second part
MEM_SIZE(ptr) = size; // new size of the first block
void* p2 = (uint8_t*)ptr + size;
MEM_SIZE(p2) = cur - size; // remainder to be freed
MYDIAG(DIAG_ALLOC, "-[%p] %p-%d=%d +%p=%d", __lr, BLOCK_ADDR(ptr), cur - size, size, BLOCK_ADDR(p2), cur - size);
free(p2);
}
// there is space to be trimmed - we divide the allocated block in two and free the second part
MEM_SIZE(ptr) = size; // new size of the first block
void* p2 = (uint8_t*)ptr + size;
MEM_SIZE(p2) = cur - size; // remainder to be freed
MYDIAG(DIAG_ALLOC, "-[%p] %p-%d=%d +%p=%d", __lr, BLOCK_ADDR(ptr), cur - size, size, BLOCK_ADDR(p2), cur - size);
__trace_alloc(p2, cur - size); // must do this to avoid free before alloc
free(p2);
}

return ptr;
Expand All @@ -107,20 +101,23 @@ void* realloc(void* ptr, size_t size)
}

size_t curSize = MEM_SIZE(ptr);
ASSERT(curSize <= __heap.Total()); // catch corrupted memory ASAP
size_t increment = REQUIRED_BLOCK(size) - curSize;
if (int(increment) <= -int(SMALLEST_BLOCK))
{
// trim the block
MYDIAG(DIAG_ALLOC, "~[%p] %p %d>%d", __lr, ptr, curSize, curSize + increment);
return mtrim(ptr, size);
}
if (int(increment) <= 0)
{
// no change needed/possible
MYDIAG(DIAG_ALLOC, "~[%p] %p %d==%d", __lr, ptr, curSize, curSize + increment);
return ptr;
}

// try to find if there is a free block immediately following the current block
free_list* wantFree = (free_list*)((char*)BLOCK_ADDR(ptr) + curSize);
free_list* wantFree = (free_list*)(BLOCK_ADDR(ptr) + curSize);
free_list** pp = &__heap.free;
for (free_list* p = *pp; p; pp = &p->next, p = p->next)
{
Expand Down Expand Up @@ -155,7 +152,8 @@ void* realloc(void* ptr, size_t size)

// fallback: allocate a whole new block
void* pNew = _malloc_impl(size, false);
memcpy(pNew, ptr, curSize);
MYDIAG(DIAG_ALLOC, "~[%p] %p>%p %d>%d", __lr, ptr, pNew, curSize, MEM_SIZE(pNew));
memcpy(pNew, ptr, curSize - HEADER_SIZE);
free(ptr);
return pNew;
}
Expand All @@ -170,8 +168,6 @@ void* _malloc_impl(size_t size, bool clear)
if (!size)
return NULL;

CAPTURE_LR();

PLATFORM_CRITICAL_SECTION();

size = REQUIRED_BLOCK(size);
Expand Down Expand Up @@ -235,15 +231,16 @@ void* _malloc_impl(size_t size, bool clear)
*(size_t*)((intptr_t)res + i) = 0;
}
}
return (size_t*)res + 1;

res = (char*)res + sizeof(size_t) + ALLOC_TRACE_OVERHEAD;
__trace_alloc(res, size - ALLOC_TRACE_OVERHEAD);
return res;
}

int __dbglines;

void* malloc_once(size_t size)
{
CAPTURE_LR();

PLATFORM_CRITICAL_SECTION();

void* ptr = (uint8_t*)__heap.limit - size;
Expand All @@ -264,13 +261,14 @@ void free(void* ptr)
if (!ptr)
return;

CAPTURE_LR();

PLATFORM_CRITICAL_SECTION();

__trace_free(ptr);

free_list** pp = &__heap.free;
ptr = (size_t*)ptr - 1;
ptr = BLOCK_ADDR(ptr);
size_t size = *(size_t*)ptr;
ASSERT(size <= __heap.Total()); // catch corrupted memory ASAP
void* end = (uint8_t*)ptr + size;
free_list* cur = (free_list*)ptr;

Expand All @@ -279,9 +277,9 @@ void free(void* ptr)
if (p == end)
{
// the block being freed is immediately before another free block
MYDIAG(DIAG_ALLOC, "-[%p] %p+%p=%d+%d", __lr, cur, p, size, p->size);
cur->next = p->next;
cur->size = p->size + size;
MYDIAG(DIAG_ALLOC, "-[%p] %p+%p=%d", __lr, cur, p, cur->size);
goto done;
}

Expand All @@ -291,24 +289,24 @@ void free(void* ptr)
if (p->next == end)
{
// ...and is immediately followed by yet another free block
MYDIAG(DIAG_ALLOC, "-[%p] %p+%p+%p=%d+%d+%d", __lr, cur, p, p->next, size, p->size, p->next->size);
p->size += size + p->next->size;
MYDIAG(DIAG_ALLOC, "-[%p] %p+%p+%p=%d", __lr, cur, p, p->next, p->size);
p->next = p->next->next;
}
else
{
MYDIAG(DIAG_ALLOC, "-[%p] %p+%p=%d+%d", __lr, cur, p, size, p->size);
p->size += size;
MYDIAG(DIAG_ALLOC, "-[%p] %p+%p=%d", __lr, cur, p, p->size);
}
cur = p;
goto done;
}
}

// we've created a new free block
MYDIAG(DIAG_ALLOC, "-[%p] %p=%d", __lr, cur, size);
cur->next = *pp;
cur->size = size;
MYDIAG(DIAG_ALLOC, "-[%p] %p=%d", __lr, cur, size);

done:
__heap.fragments += size;
Expand Down

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