diff options
| -rw-r--r-- | src/malloc/expand_heap.c | 71 | ||||
| -rw-r--r-- | src/malloc/malloc.c | 64 | ||||
| -rw-r--r-- | src/malloc/malloc_impl.h | 2 |
3 files changed, 64 insertions, 73 deletions
diff --git a/src/malloc/expand_heap.c b/src/malloc/expand_heap.c deleted file mode 100644 index e6a3d7a0..00000000 --- a/src/malloc/expand_heap.c +++ /dev/null @@ -1,71 +0,0 @@ -#include <limits.h> -#include <stdint.h> -#include <errno.h> -#include <sys/mman.h> -#include "libc.h" -#include "syscall.h" -#include "malloc_impl.h" - -/* This function returns true if the interval [old,new] - * intersects the 'len'-sized interval below &libc.auxv - * (interpreted as the main-thread stack) or below &b - * (the current stack). It is used to defend against - * buggy brk implementations that can cross the stack. */ - -static int traverses_stack_p(uintptr_t old, uintptr_t new) -{ - const uintptr_t len = 8<<20; - uintptr_t a, b; - - b = (uintptr_t)libc.auxv; - a = b > len ? b-len : 0; - if (new>a && old<b) return 1; - - b = (uintptr_t)&b; - a = b > len ? b-len : 0; - if (new>a && old<b) return 1; - - return 0; -} - -/* Expand the heap in-place if brk can be used, or otherwise via mmap, - * using an exponential lower bound on growth by mmap to make - * fragmentation asymptotically irrelevant. The size argument is both - * an input and an output, since the caller needs to know the size - * allocated, which will be larger than requested due to page alignment - * and mmap minimum size rules. The caller is responsible for locking - * to prevent concurrent calls. */ - -void *__expand_heap(size_t *pn) -{ - static uintptr_t brk; - static unsigned mmap_step; - size_t n = *pn; - - if (n > SIZE_MAX/2 - PAGE_SIZE) { - errno = ENOMEM; - return 0; - } - n += -n & PAGE_SIZE-1; - - if (!brk) { - brk = __syscall(SYS_brk, 0); - brk += -brk & PAGE_SIZE-1; - } - - if (n < SIZE_MAX-brk && !traverses_stack_p(brk, brk+n) - && __syscall(SYS_brk, brk+n)==brk+n) { - *pn = n; - brk += n; - return (void *)(brk-n); - } - - size_t min = (size_t)PAGE_SIZE << mmap_step/2; - if (n < min) n = min; - void *area = __mmap(0, n, PROT_READ|PROT_WRITE, - MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); - if (area == MAP_FAILED) return 0; - *pn = n; - mmap_step++; - return area; -} diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c index 20598ec3..df3ea1be 100644 --- a/src/malloc/malloc.c +++ b/src/malloc/malloc.c @@ -126,6 +126,70 @@ void __dump_heap(int x) } #endif +/* This function returns true if the interval [old,new] + * intersects the 'len'-sized interval below &libc.auxv + * (interpreted as the main-thread stack) or below &b + * (the current stack). It is used to defend against + * buggy brk implementations that can cross the stack. */ + +static int traverses_stack_p(uintptr_t old, uintptr_t new) +{ + const uintptr_t len = 8<<20; + uintptr_t a, b; + + b = (uintptr_t)libc.auxv; + a = b > len ? b-len : 0; + if (new>a && old<b) return 1; + + b = (uintptr_t)&b; + a = b > len ? b-len : 0; + if (new>a && old<b) return 1; + + return 0; +} + +/* Expand the heap in-place if brk can be used, or otherwise via mmap, + * using an exponential lower bound on growth by mmap to make + * fragmentation asymptotically irrelevant. The size argument is both + * an input and an output, since the caller needs to know the size + * allocated, which will be larger than requested due to page alignment + * and mmap minimum size rules. The caller is responsible for locking + * to prevent concurrent calls. */ + +static void *__expand_heap(size_t *pn) +{ + static uintptr_t brk; + static unsigned mmap_step; + size_t n = *pn; + + if (n > SIZE_MAX/2 - PAGE_SIZE) { + errno = ENOMEM; + return 0; + } + n += -n & PAGE_SIZE-1; + + if (!brk) { + brk = __syscall(SYS_brk, 0); + brk += -brk & PAGE_SIZE-1; + } + + if (n < SIZE_MAX-brk && !traverses_stack_p(brk, brk+n) + && __syscall(SYS_brk, brk+n)==brk+n) { + *pn = n; + brk += n; + return (void *)(brk-n); + } + + size_t min = (size_t)PAGE_SIZE << mmap_step/2; + if (n < min) n = min; + void *area = __mmap(0, n, PROT_READ|PROT_WRITE, + MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); + if (area == MAP_FAILED) return 0; + *pn = n; + mmap_step++; + return area; +} + static struct chunk *expand_heap(size_t n) { static void *end; diff --git a/src/malloc/malloc_impl.h b/src/malloc/malloc_impl.h index 6a92c1c6..e1cf4774 100644 --- a/src/malloc/malloc_impl.h +++ b/src/malloc/malloc_impl.h @@ -4,8 +4,6 @@ #include <sys/mman.h> #include "dynlink.h" -hidden void *__expand_heap(size_t *); - struct chunk { size_t psize, csize; struct chunk *next, *prev; |