From 22d37d84a7ab0bb4208cdc8828541a30ef0821e2 Mon Sep 17 00:00:00 2001 From: Mattias Andrée Date: Sun, 30 Aug 2015 17:36:09 +0200 Subject: add memory allocation functions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: Mattias Andrée --- src/slibc-alloc.c | 149 +++++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 143 insertions(+), 6 deletions(-) (limited to 'src/slibc-alloc.c') diff --git a/src/slibc-alloc.c b/src/slibc-alloc.c index a29b188..0cbf623 100644 --- a/src/slibc-alloc.c +++ b/src/slibc-alloc.c @@ -18,6 +18,13 @@ #include #include #include +#include +#include + + + +#define PURE_ALLOC(p) (((char*)(p)) - sizeof(size_t)) +#define PURE_SIZE(z) ((z) + sizeof(size_t)) @@ -29,7 +36,9 @@ */ void fast_free(void* segment) { - free(segment); + if (segument == NULL) + return; + munmap(PURE_ALLOC(segment), PURE_SIZE(*(size_t*)segment)); } @@ -41,10 +50,138 @@ void fast_free(void* segment) */ void secure_free(void* segment) { - if (segment) - { - explicit_bzero(segment, allocsize(segment)); - free(segment); - } + if (segument == NULL) + return; + explicit_bzero(PURE_ALLOC(segment), PURE_SIZE(allocsize(segment))); + fast_free(segment); +} + + +/** + * This function returns the allocation size of + * a memory segment. + * + * `p = malloc(n), allocsize(p)` will return `n`. + * + * @param segment The memory segment. + * @return The size of the memory segment, 0 on error. + * + * @throws EINVAL If `segment` is `NULL`. + * @throws EFAULT If `segment` is not a pointer to an allocation + * on the heap, or was not allocated with a function + * implemented in slibc. It is however not guaranteed + * that this will happen, undefined behaviour may be + * invoked instead. + */ +size_t allocsize(void* segment) +{ + if (segment == NULL) + return errno = EINVAL, 0; + return *(size_t*)PURE_ALLOC(segment); +} + + +/** + * Common code for realloc-functions, apart from `naive_realloc`. + */ +#define REALLOC(ptr, size, CLEAR_OLD, CLEAR_NEW, CLEAR_FREE) \ + size_t old_size; \ + void* new_ptr; \ + \ + if (size == 0) \ + return secure_free(ptr), NULL; \ + \ + if (ptr == NULL) \ + return CLEAR_NEW ? malloc(size) : calloc(1, size); \ + \ + old_size = allocsize(ptr); \ + if (old_size == size) \ + return ptr; \ + \ + if (CLEAR_OLD ? (old_size > size) : 0) \ + explicit_bzero(((char*)ptr) + size, old_size - size); \ + \ + new_ptr = naive_realloc(ptr); \ + if (new_ptr != ptr) \ + { \ + if (CLEAR_FREE) \ + explicit_bzero(PURE_ALLOC(ptr), PURE_SIZE(old_size)); \ + fast_free(new_ptr); \ + } \ + \ + if (CLEAR_NEW ? (old_size < size) : 0) \ + explicit_bzero(((char*)new_ptr) + old, size - old_size); \ + \ + return new_ptr + + +/** + * Variant of `realloc` that overrides newly allocated space + * with zeroes. Additionally, it will override any freed space + * with zeroes, including the old allocation if it creates a + * new allocation. + * + * @param ptr The old allocation, see `realloc` for more details. + * @param size The new allocation size, see `realloc` for more details. + * @return The new allocation, see `realloc` for more details. + * + * @throws ENOMEM The process cannot allocate more memory. + */ +void* crealloc(void* ptr, size_t size) +{ + REALLOC(ptr, size, 1, 1, 1); +} + + +/** + * This function behaves exactly like `realloc`, except it is + * guaranteed to never initialise or errors data. + * + * @param ptr The old allocation, see `realloc` for more details. + * @param size The new allocation size, see `realloc` for more details. + * @return The new allocation, see `realloc` for more details. + * + * @throws ENOMEM The process cannot allocate more memory. + */ +void* fast_realloc(void* ptr, size_t size) +{ + REALLOC(ptr, size, 0, 0, 0); +} + + +/** + * This function behaves exactly like `crealloc`, except it + * does not initialise newly allocated size. + * + * @param ptr The old allocation, see `realloc` for more details. + * @param size The new allocation size, see `realloc` for more details. + * @return The new allocation, see `realloc` for more details. + * + * @throws ENOMEM The process cannot allocate more memory. + */ +void* secure_realloc(void* ptr, size_t size) +{ + REALLOC(ptr, size, 1, 0, 1); +} + + +/** + * This function behaves exactly like `fast_realloc`, except: + * - Its haviour is undefined if `ptr` is `NULL`. + * - Its haviour is undefined `size` equals the old allocation size. + * - Its haviour is undefined if `size` is zero. + * - It will never free `ptr`. + * + * @param ptr The old allocation, see `realloc` for more details. + * @param size The new allocation size, see `realloc` for more details. + * @return The new allocation, see `realloc` for more details. + * + * @throws ENOMEM The process cannot allocate more memory. + */ +void* naive_realloc(void* ptr, size_t size) +{ + /* TODO improve implementation of naive_realloc */ + return malloc(size); + (void) ptr; } -- cgit v1.2.3-70-g09d2