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Diffstat (limited to 'src/basic/alloc-util.h')
-rw-r--r-- | src/basic/alloc-util.h | 276 |
1 files changed, 276 insertions, 0 deletions
diff --git a/src/basic/alloc-util.h b/src/basic/alloc-util.h new file mode 100644 index 0000000..136d2b3 --- /dev/null +++ b/src/basic/alloc-util.h @@ -0,0 +1,276 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +#pragma once + +#include <alloca.h> +#include <malloc.h> +#include <stddef.h> +#include <stdlib.h> +#include <string.h> + +#include "macro.h" + +#if HAS_FEATURE_MEMORY_SANITIZER +# include <sanitizer/msan_interface.h> +#endif + +typedef void (*free_func_t)(void *p); +typedef void* (*mfree_func_t)(void *p); + +/* If for some reason more than 4M are allocated on the stack, let's abort immediately. It's better than + * proceeding and smashing the stack limits. Note that by default RLIMIT_STACK is 8M on Linux. */ +#define ALLOCA_MAX (4U*1024U*1024U) + +#define new(t, n) ((t*) malloc_multiply((n), sizeof(t))) + +#define new0(t, n) ((t*) calloc((n) ?: 1, sizeof(t))) + +#define alloca_safe(n) \ + ({ \ + size_t _nn_ = n; \ + assert(_nn_ <= ALLOCA_MAX); \ + alloca(_nn_ == 0 ? 1 : _nn_); \ + }) \ + +#define newa(t, n) \ + ({ \ + size_t _n_ = n; \ + assert(!size_multiply_overflow(sizeof(t), _n_)); \ + (t*) alloca_safe(sizeof(t)*_n_); \ + }) + +#define newa0(t, n) \ + ({ \ + size_t _n_ = n; \ + assert(!size_multiply_overflow(sizeof(t), _n_)); \ + (t*) alloca0((sizeof(t)*_n_)); \ + }) + +#define newdup(t, p, n) ((t*) memdup_multiply(p, (n), sizeof(t))) + +#define newdup_suffix0(t, p, n) ((t*) memdup_suffix0_multiply(p, (n), sizeof(t))) + +#define malloc0(n) (calloc(1, (n) ?: 1)) + +#define free_and_replace_full(a, b, free_func) \ + ({ \ + typeof(a)* _a = &(a); \ + typeof(b)* _b = &(b); \ + free_func(*_a); \ + *_a = *_b; \ + *_b = NULL; \ + 0; \ + }) + +#define free_and_replace(a, b) \ + free_and_replace_full(a, b, free) + +/* This is similar to free_and_replace_full(), but NULL is not assigned to 'b', and its reference counter is + * increased. */ +#define unref_and_replace_full(a, b, ref_func, unref_func) \ + ({ \ + typeof(a)* _a = &(a); \ + typeof(b) _b = ref_func(b); \ + unref_func(*_a); \ + *_a = _b; \ + 0; \ + }) + +void* memdup(const void *p, size_t l) _alloc_(2); +void* memdup_suffix0(const void *p, size_t l); /* We can't use _alloc_() here, since we return a buffer one byte larger than the specified size */ + +#define memdupa(p, l) \ + ({ \ + void *_q_; \ + size_t _l_ = l; \ + _q_ = alloca_safe(_l_); \ + memcpy_safe(_q_, p, _l_); \ + }) + +#define memdupa_suffix0(p, l) \ + ({ \ + void *_q_; \ + size_t _l_ = l; \ + _q_ = alloca_safe(_l_ + 1); \ + ((uint8_t*) _q_)[_l_] = 0; \ + memcpy_safe(_q_, p, _l_); \ + }) + +static inline void unsetp(void *p) { + /* A trivial "destructor" that can be used in cases where we want to + * unset a pointer from a _cleanup_ function. */ + + *(void**)p = NULL; +} + +static inline void freep(void *p) { + *(void**)p = mfree(*(void**) p); +} + +#define _cleanup_free_ _cleanup_(freep) + +static inline bool size_multiply_overflow(size_t size, size_t need) { + return _unlikely_(need != 0 && size > (SIZE_MAX / need)); +} + +_malloc_ _alloc_(1, 2) static inline void *malloc_multiply(size_t need, size_t size) { + if (size_multiply_overflow(size, need)) + return NULL; + + return malloc(size * need ?: 1); +} + +#if !HAVE_REALLOCARRAY +_alloc_(2, 3) static inline void *reallocarray(void *p, size_t need, size_t size) { + if (size_multiply_overflow(size, need)) + return NULL; + + return realloc(p, size * need ?: 1); +} +#endif + +_alloc_(2, 3) static inline void *memdup_multiply(const void *p, size_t need, size_t size) { + if (size_multiply_overflow(size, need)) + return NULL; + + return memdup(p, size * need); +} + +/* Note that we can't decorate this function with _alloc_() since the returned memory area is one byte larger + * than the product of its parameters. */ +static inline void *memdup_suffix0_multiply(const void *p, size_t need, size_t size) { + if (size_multiply_overflow(size, need)) + return NULL; + + return memdup_suffix0(p, size * need); +} + +void* greedy_realloc(void **p, size_t need, size_t size); +void* greedy_realloc0(void **p, size_t need, size_t size); +void* greedy_realloc_append(void **p, size_t *n_p, const void *from, size_t n_from, size_t size); + +#define GREEDY_REALLOC(array, need) \ + greedy_realloc((void**) &(array), (need), sizeof((array)[0])) + +#define GREEDY_REALLOC0(array, need) \ + greedy_realloc0((void**) &(array), (need), sizeof((array)[0])) + +#define GREEDY_REALLOC_APPEND(array, n_array, from, n_from) \ + greedy_realloc_append((void**) &(array), (size_t*) &(n_array), (from), (n_from), sizeof((array)[0])) + +#define alloca0(n) \ + ({ \ + char *_new_; \ + size_t _len_ = n; \ + _new_ = alloca_safe(_len_); \ + memset(_new_, 0, _len_); \ + }) + +/* It's not clear what alignment glibc/gcc alloca() guarantee, hence provide a guaranteed safe version */ +#define alloca_align(size, align) \ + ({ \ + void *_ptr_; \ + size_t _mask_ = (align) - 1; \ + size_t _size_ = size; \ + _ptr_ = alloca_safe(_size_ + _mask_); \ + (void*)(((uintptr_t)_ptr_ + _mask_) & ~_mask_); \ + }) + +#define alloca0_align(size, align) \ + ({ \ + void *_new_; \ + size_t _xsize_ = (size); \ + _new_ = alloca_align(_xsize_, (align)); \ + memset(_new_, 0, _xsize_); \ + }) + +#if HAS_FEATURE_MEMORY_SANITIZER +# define msan_unpoison(r, s) __msan_unpoison(r, s) +#else +# define msan_unpoison(r, s) +#endif + +/* Dummy allocator to tell the compiler that the new size of p is newsize. The implementation returns the + * pointer as is; the only reason for its existence is as a conduit for the _alloc_ attribute. This must not + * be inlined (hence a non-static function with _noinline_ because LTO otherwise tries to inline it) because + * gcc then loses the attributes on the function. + * See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96503 */ +void *expand_to_usable(void *p, size_t newsize) _alloc_(2) _returns_nonnull_ _noinline_; + +static inline size_t malloc_sizeof_safe(void **xp) { + if (_unlikely_(!xp || !*xp)) + return 0; + + size_t sz = malloc_usable_size(*xp); + *xp = expand_to_usable(*xp, sz); + /* GCC doesn't see the _returns_nonnull_ when built with ubsan, so yet another hint to make it doubly + * clear that expand_to_usable won't return NULL. + * See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79265 */ + if (!*xp) + assert_not_reached(); + return sz; +} + +/* This returns the number of usable bytes in a malloc()ed region as per malloc_usable_size(), which may + * return a value larger than the size that was actually allocated. Access to that additional memory is + * discouraged because it violates the C standard; a compiler cannot see that this as valid. To help the + * compiler out, the MALLOC_SIZEOF_SAFE macro 'allocates' the usable size using a dummy allocator function + * expand_to_usable. There is a possibility of malloc_usable_size() returning different values during the + * lifetime of an object, which may cause problems, but the glibc allocator does not do that at the moment. */ +#define MALLOC_SIZEOF_SAFE(x) \ + malloc_sizeof_safe((void**) &__builtin_choose_expr(__builtin_constant_p(x), (void*) { NULL }, (x))) + +/* Inspired by ELEMENTSOF() but operates on malloc()'ed memory areas: typesafely returns the number of items + * that fit into the specified memory block */ +#define MALLOC_ELEMENTSOF(x) \ + (__builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(x), typeof(&*(x))), \ + MALLOC_SIZEOF_SAFE(x)/sizeof((x)[0]), \ + VOID_0)) + +/* These are like strdupa()/strndupa(), but honour ALLOCA_MAX */ +#define strdupa_safe(s) \ + ({ \ + const char *_t = (s); \ + (char*) memdupa_suffix0(_t, strlen(_t)); \ + }) + +#define strndupa_safe(s, n) \ + ({ \ + const char *_t = (s); \ + (char*) memdupa_suffix0(_t, strnlen(_t, (n))); \ + }) + +/* Free every element of the array. */ +static inline void free_many(void **p, size_t n) { + assert(p || n == 0); + + FOREACH_ARRAY(i, p, n) + *i = mfree(*i); +} + +/* Typesafe wrapper for char** rather than void**. Unfortunately C won't implicitly cast this. */ +static inline void free_many_charp(char **c, size_t n) { + free_many((void**) c, n); +} + +_alloc_(2) static inline void *realloc0(void *p, size_t new_size) { + size_t old_size; + void *q; + + /* Like realloc(), but initializes anything appended to zero */ + + old_size = MALLOC_SIZEOF_SAFE(p); + + q = realloc(p, new_size); + if (!q) + return NULL; + + new_size = MALLOC_SIZEOF_SAFE(q); /* Update with actually allocated space */ + + if (new_size > old_size) + memset((uint8_t*) q + old_size, 0, new_size - old_size); + + return q; +} + +#include "memory-util.h" |