diff options
Diffstat (limited to 'libc/stdlib/malloc')
| -rw-r--r-- | libc/stdlib/malloc/free.c | 120 | ||||
| -rw-r--r-- | libc/stdlib/malloc/heap.h | 46 | ||||
| -rw-r--r-- | libc/stdlib/malloc/malloc.c | 86 | ||||
| -rw-r--r-- | libc/stdlib/malloc/malloc.h | 41 |
4 files changed, 264 insertions, 29 deletions
diff --git a/libc/stdlib/malloc/free.c b/libc/stdlib/malloc/free.c index c8c687964..6c3211360 100644 --- a/libc/stdlib/malloc/free.c +++ b/libc/stdlib/malloc/free.c @@ -19,12 +19,11 @@ #include "heap.h" -void -free (void *mem) +static void +free_to_heap (void *mem, struct heap *heap) { size_t size; struct heap_free_area *fa; - struct heap *heap = &__malloc_heap; /* Check for special cases. */ if (unlikely (! mem)) @@ -38,7 +37,7 @@ free (void *mem) size = MALLOC_SIZE (mem); mem = MALLOC_BASE (mem); - __malloc_lock (); + __heap_lock (heap); /* Put MEM back in the heap, and get the free-area it was placed in. */ fa = __heap_free (heap, mem, size); @@ -47,15 +46,20 @@ free (void *mem) unmapped. */ if (HEAP_FREE_AREA_SIZE (fa) < MALLOC_UNMAP_THRESHOLD) /* Nope, nothing left to do, just release the lock. */ - __malloc_unlock (); + __heap_unlock (heap); else /* Yup, try to unmap FA. */ { unsigned long start = (unsigned long)HEAP_FREE_AREA_START (fa); unsigned long end = (unsigned long)HEAP_FREE_AREA_END (fa); #ifndef MALLOC_USE_SBRK +# ifdef __UCLIBC_UCLINUX_BROKEN_MUNMAP__ + struct malloc_mmb *mmb, *prev_mmb; + unsigned long mmb_start, mmb_end; +# else /* !__UCLIBC_UCLINUX_BROKEN_MUNMAP__ */ unsigned long unmap_start, unmap_end; -#endif +# endif /* __UCLIBC_UCLINUX_BROKEN_MUNMAP__ */ +#endif /* !MALLOC_USE_SBRK */ #ifdef MALLOC_USE_SBRK /* Get the sbrk lock so that the two possible calls to sbrk below @@ -75,7 +79,7 @@ free (void *mem) MALLOC_DEBUG (" not unmapping: 0x%lx - 0x%lx (%ld bytes)\n", start, end, end - start); __malloc_unlock_sbrk (); - __malloc_unlock (); + __heap_unlock (heap); return; } #endif @@ -102,7 +106,7 @@ free (void *mem) #ifdef MALLOC_USE_SBRK /* Release the main lock; we're still holding the sbrk lock. */ - __malloc_unlock (); + __heap_unlock (heap); /* Lower the brk. */ sbrk (start - end); /* Release the sbrk lock too; now we hold no locks. */ @@ -110,6 +114,94 @@ free (void *mem) #else /* !MALLOC_USE_SBRK */ +# ifdef __UCLIBC_UCLINUX_BROKEN_MUNMAP__ + /* Using the uClinux broken munmap, we have to only munmap blocks + exactly as we got them from mmap, so scan through our list of + mmapped blocks, and return them in order. */ + + MALLOC_MMB_DEBUG (" walking mmb list for region 0x%x[%d]...\n", start, end - start); + + prev_mmb = 0; + mmb = __malloc_mmapped_blocks; + while (mmb + && ((mmb_end = (mmb_start = (unsigned long)mmb->mem) + mmb->size) + <= end)) + { + MALLOC_MMB_DEBUG (" considering mmb at 0x%x: 0x%x[%d]\n", + (unsigned)mmb, mmb_start, mmb_end - mmb_start); + + if (mmb_start >= start + /* If the space between START and MMB_START is non-zero, but + too small to return to the heap, we can't unmap MMB. */ + && (start == mmb_start + || mmb_start - start > HEAP_MIN_FREE_AREA_SIZE)) + { + struct malloc_mmb *next_mmb = mmb->next; + + if (mmb_end != end && mmb_end + HEAP_MIN_FREE_AREA_SIZE > end) + /* There's too little space left at the end to deallocate + this block, so give up. */ + break; + + MALLOC_MMB_DEBUG (" unmapping mmb at 0x%x: 0x%x[%d]\n", + (unsigned)mmb, mmb_start, mmb_end - mmb_start); + + if (mmb_start != start) + /* We're going to unmap a part of the heap that begins after + start, so put the intervening region back into the heap. */ + { + MALLOC_MMB_DEBUG (" putting intervening region back into heap: 0x%x[%d]\n", + start, mmb_start - start); + __heap_free (heap, (void *)start, mmb_start - start); + } + + /* Unlink MMB from the list. */ + if (prev_mmb) + prev_mmb->next = next_mmb; + else + __malloc_mmapped_blocks = next_mmb; + + /* Release the descriptor block we used. */ + free_to_heap (mmb, &__malloc_mmb_heap); + + /* Do the actual munmap. */ + __heap_unlock (heap); + munmap ((void *)mmb_start, mmb_end - mmb_start); + __heap_lock (heap); + + /* Start searching again from the end of that block. */ + start = mmb_end; + +# ifdef __UCLIBC_HAS_THREADS__ + /* In a multi-threaded program, it's possible that PREV_MMB has + been invalidated by another thread when we released the + heap lock to do the munmap system call, so just start over + from the beginning of the list. It sucks, but oh well; + it's probably not worth the bother to do better. */ + prev_mmb = 0; + mmb = __malloc_mmapped_blocks; +# else + mmb = next_mmb; +# endif + } + else + { + prev_mmb = mmb; + mmb = mmb->next; + } + } + + if (start != end) + /* Hmm, well there's something we couldn't unmap, so put it back + into the heap. */ + { + MALLOC_MMB_DEBUG (" putting tail region back into heap: 0x%x[%d]\n", + start, end - start); + __heap_free (heap, (void *)start, end - start); + } + +# else /* !__UCLIBC_UCLINUX_BROKEN_MUNMAP__ */ + /* MEM/LEN may not be page-aligned, so we have to page-align them, and return any left-over bits on the end to the heap. */ unmap_start = MALLOC_ROUND_UP_TO_PAGE_SIZE (start); @@ -133,13 +225,21 @@ free (void *mem) __heap_free (heap, (void *)unmap_end, end - unmap_end); } - /* Release the malloc lock before we do the system call. */ - __malloc_unlock (); + /* Release the heap lock before we do the system call. */ + __heap_unlock (heap); if (unmap_end > unmap_start) /* Finally, actually unmap the memory. */ munmap ((void *)unmap_start, unmap_end - unmap_start); +# endif /* __UCLIBC_UCLINUX_BROKEN_MUNMAP__ */ + #endif /* MALLOC_USE_SBRK */ } } + +void +free (void *mem) +{ + free_to_heap (mem, &__malloc_heap); +} diff --git a/libc/stdlib/malloc/heap.h b/libc/stdlib/malloc/heap.h index d8e8335b6..42cde5227 100644 --- a/libc/stdlib/malloc/heap.h +++ b/libc/stdlib/malloc/heap.h @@ -14,6 +14,13 @@ #include <features.h> +/* On multi-threaded systems, the heap includes a lock. */ +#ifdef __UCLIBC_HAS_THREADS__ +# include <pthread.h> +# define HEAP_USE_LOCKING +#endif + + /* The heap allocates in multiples of, and aligned to, HEAP_GRANULARITY. HEAP_GRANULARITY must be a power of 2. Malloc depends on this being the same as MALLOC_ALIGNMENT. */ @@ -26,9 +33,26 @@ struct heap { /* A list of memory in the heap available for allocation. */ struct heap_free_area *free_areas; + +#ifdef HEAP_USE_LOCKING + /* A lock that can be used by callers to control access to the heap. + The heap code _does not_ use this lock, it's merely here for the + convenience of users! */ + extern heap_mutex_t lock; +#endif }; -#define HEAP_INIT { 0 } +/* The HEAP_INIT macro can be used as a static initializer for a heap + variable. The HEAP_INIT_WITH_FA variant is used to initialize a heap + with an initial static free-area; its argument FA should be declared + using HEAP_DECLARE_STATIC_FREE_AREA. */ +#ifdef HEAP_USE_LOCKING +# define HEAP_INIT { 0, PTHREAD_MUTEX_INITIALIZER } +# define HEAP_INIT_WITH_FA(fa) { &fa._fa, PTHREAD_MUTEX_INITIALIZER } +#else +# define HEAP_INIT { 0 } +# define HEAP_INIT_WITH_FA(fa) { &fa._fa } +#endif /* A free-list area `header'. These are actually stored at the _ends_ of free areas (to make allocating from the beginning of the area simpler), @@ -47,6 +71,16 @@ struct heap_free_area /* Return the size of the frea area FA. */ #define HEAP_FREE_AREA_SIZE(fa) ((fa)->size) +/* This rather clumsy macro allows one to declare a static free-area for + passing to HEAP_INIT_WITH_FA initializer macro. This is only use for + which NAME is allowed. */ +#define HEAP_DECLARE_STATIC_FREE_AREA(name, size) \ + static struct \ + { \ + char space[(size) - sizeof (struct heap_free_area)]; \ + struct heap_free_area _fa; \ + } name = { "", { (size), 0, 0 } } + /* Rounds SZ up to be a multiple of HEAP_GRANULARITY. */ #define HEAP_ADJUST_SIZE(sz) \ @@ -97,6 +131,16 @@ extern void __heap_dump (struct heap *heap, const char *str); extern void __heap_check (struct heap *heap, const char *str); +#ifdef HEAP_USE_LOCKING +# define __heap_lock(heap) pthread_mutex_lock (&(heap)->lock) +# define __heap_unlock(heap) pthread_mutex_unlock (&(heap)->lock) +#else /* !__UCLIBC_HAS_THREADS__ */ +/* Without threads, mutex operations are a nop. */ +# define __heap_lock(heap) (void)0 +# define __heap_unlock(heap) (void)0 +#endif /* HEAP_USE_LOCKING */ + + /* Delete the free-area FA from HEAP. */ extern inline void __heap_delete (struct heap *heap, struct heap_free_area *fa) diff --git a/libc/stdlib/malloc/malloc.c b/libc/stdlib/malloc/malloc.c index 021ed3a24..f6dd3099d 100644 --- a/libc/stdlib/malloc/malloc.c +++ b/libc/stdlib/malloc/malloc.c @@ -19,35 +19,49 @@ #include "heap.h" -/* The malloc heap. */ -struct heap __malloc_heap = HEAP_INIT; +/* The malloc heap. We provide a bit of initial static space so that + programs can do a little mallocing without mmaping in more space. */ +HEAP_DECLARE_STATIC_FREE_AREA (initial_fa, 256); +struct heap __malloc_heap = HEAP_INIT_WITH_FA (initial_fa); -#ifdef MALLOC_USE_LOCKING -/* A lock protecting the malloc heap. */ -malloc_mutex_t __malloc_lock; -# ifdef MALLOC_USE_SBRK +#if defined(MALLOC_USE_LOCKING) && defined(MALLOC_USE_SBRK) /* A lock protecting our use of sbrk. */ malloc_mutex_t __malloc_sbrk_lock; -# endif /* MALLOC_USE_SBRK */ -#endif /* MALLOC_USE_LOCKING */ +#endif /* MALLOC_USE_LOCKING && MALLOC_USE_SBRK */ #ifdef MALLOC_DEBUGGING int __malloc_debug = 0; #endif -void * -malloc (size_t size) +#ifdef __UCLIBC_UCLINUX_BROKEN_MUNMAP__ +/* A list of all malloc_mmb structures describing blocsk that + malloc has mmapped, ordered by the block address. */ +struct malloc_mmb *__malloc_mmapped_blocks = 0; + +/* A heap used for allocating malloc_mmb structures. We could allocate + them from the main heap, but that tends to cause heap fragmentation in + annoying ways. */ +HEAP_DECLARE_STATIC_FREE_AREA (initial_mmb_fa, 48); /* enough for 3 mmbs */ +struct heap __malloc_mmb_heap = HEAP_INIT_WITH_FA (initial_mmb_fa); + +# ifdef MALLOC_MMB_DEBUGGING +int __malloc_mmb_debug = 0; +# endif +#endif /* __UCLIBC_UCLINUX_BROKEN_MUNMAP__ */ + + +static void * +malloc_from_heap (size_t size, struct heap *heap) { void *mem; - struct heap *heap = &__malloc_heap; MALLOC_DEBUG ("malloc: %d bytes\n", size); /* Include extra space to record the size of the allocated block. */ size += MALLOC_HEADER_SIZE; - __malloc_lock (); + __heap_lock (heap); /* First try to get memory that's already in our heap. */ mem = __heap_alloc (heap, &size); @@ -65,14 +79,14 @@ malloc (size_t size) : MALLOC_ROUND_UP_TO_PAGE_SIZE (size)); #ifdef MALLOC_USE_SBRK - /* Get the sbrk lock while we've still got the main lock. */ + /* Get the sbrk lock while we've still got the heap lock. */ __malloc_lock_sbrk (); #endif - /* Don't hold the main lock during the syscall, so that small + /* Don't hold the heap lock during the syscall, so that small allocations in a different thread may succeed while we're blocked. */ - __malloc_unlock (); + __heap_unlock (heap); /* Allocate the new heap block. */ #ifdef MALLOC_USE_SBRK @@ -106,23 +120,53 @@ malloc (size_t size) #endif /* MALLOC_USE_SBRK */ - /* Get back the main lock. */ - __malloc_lock (); + /* Get back the heap lock. */ + __heap_lock (heap); if (likely (block != (void *)-1)) { +#if !defined(MALLOC_USE_SBRK) && defined(__UCLIBC_UCLINUX_BROKEN_MUNMAP__) + struct malloc_mmb *mmb, *prev_mmb, *new_mmb; +#endif /* !MALLOC_USE_SBRK && __UCLIBC_UCLINUX_BROKEN_MUNMAP__ */ + MALLOC_DEBUG (" adding memory: 0x%lx - 0x%lx (%d bytes)\n", (long)block, (long)block + block_size, block_size); /* Put BLOCK into the heap. */ __heap_free (heap, block, block_size); +#if !defined(MALLOC_USE_SBRK) && defined(__UCLIBC_UCLINUX_BROKEN_MUNMAP__) + /* Insert a record of this allocation in sorted order into the + __malloc_mmapped_blocks list. */ + + for (prev_mmb = 0, mmb = __malloc_mmapped_blocks; + mmb; + prev_mmb = mmb, mmb = mmb->next) + if (block < mmb->mem) + break; + + new_mmb = malloc_from_heap (sizeof *new_mmb, &__malloc_mmb_heap); + new_mmb->next = mmb; + new_mmb->mem = block; + new_mmb->size = block_size; + + MALLOC_MMB_DEBUG (" new mmb at 0x%x: 0x%x[%d]\n", + (unsigned)new_mmb, + (unsigned)new_mmb->mem, block_size); + + if (prev_mmb) + prev_mmb->next = new_mmb; + else + __malloc_mmapped_blocks = new_mmb; + +#endif /* !MALLOC_USE_SBRK && __UCLIBC_UCLINUX_BROKEN_MUNMAP__ */ + /* Try again to allocate. */ mem = __heap_alloc (heap, &size); } } - __malloc_unlock (); + __heap_unlock (heap); if (likely (mem)) /* Record the size of the block and get the user address. */ @@ -135,3 +179,9 @@ malloc (size_t size) return mem; } + +void * +malloc (size_t size) +{ + return malloc_from_heap (size, &__malloc_heap); +} diff --git a/libc/stdlib/malloc/malloc.h b/libc/stdlib/malloc/malloc.h index 4071a4ffb..9c7f047d3 100644 --- a/libc/stdlib/malloc/malloc.h +++ b/libc/stdlib/malloc/malloc.h @@ -48,6 +48,47 @@ #endif +/* The current implementation of munmap in uClinux doesn't work correctly: + it requires that ever call to munmap exactly match a corresponding call + to mmap (that is, it doesn't allow you to unmap only part of a + previously allocated block, or to unmap two contiguous blocks with a + single call to munmap). This behavior is broken, and uClinux should be + fixed; however, until it is, we add code to work around the problem in + malloc. */ +#ifdef __UCLIBC_UCLINUX_BROKEN_MUNMAP__ + +/* A structure recording a block of memory mmapped by malloc. */ +struct malloc_mmb +{ + void *mem; /* the mmapped block */ + size_t size; /* its size */ + struct malloc_mmb *next; +}; + +/* A list of all malloc_mmb structures describing blocsk that malloc has + mmapped, ordered by the block address. */ +extern struct malloc_mmb *__malloc_mmapped_blocks; + +/* A heap used for allocating malloc_mmb structures. We could allocate + them from the main heap, but that tends to cause heap fragmentation in + annoying ways. */ +extern struct heap __malloc_mmb_heap; + +/* Define MALLOC_MMB_DEBUGGING to cause malloc to emit debugging info about + about mmap block allocation/freeing by the `uclinux broken munmap' code + to stderr, when the variable __malloc_mmb_debug is set to true. */ +#ifdef MALLOC_MMB_DEBUGGING +#include <stdio.h> +extern int __malloc_mmb_debug; +#define MALLOC_MMB_DEBUG(fmt, args...) \ + (__malloc_mmb_debug ? fprintf (stderr, fmt , ##args) : 0) +#else /* !MALLOC_MMB_DEBUGGING */ +#define MALLOC_MMB_DEBUG(fmt, args...) (void)0 +#endif /* MALLOC_MMB_DEBUGGING */ + +#endif /* __UCLIBC_UCLINUX_BROKEN_MUNMAP__ */ + + /* The size of a malloc allocation is stored in a size_t word MALLOC_ALIGNMENT bytes prior to the start address of the allocation: |