Messages in this thread Patch in this message |  | | From | Ammar Faizi <> | Subject | [RFC PATCH v1 5/6] tools/nolibc/stdlib: Implement `malloc()`, `calloc()`, `realloc()` and `free()` | Date | Sun, 20 Mar 2022 16:37:49 +0700 |
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Implement basic dynamic allocator functions. These functions are currently only available on architectures that have nolibc mmap() syscall implemented. These are not a super-fast memory allocator, but at least they can satisfy basic needs for having heap without libc.
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org> --- tools/include/nolibc/stdlib.h | 79 +++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+)
diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h index 733105c574ee..13600e73404d 100644 --- a/tools/include/nolibc/stdlib.h +++ b/tools/include/nolibc/stdlib.h @@ -10,8 +10,24 @@ #include "std.h" #include "arch.h" #include "types.h" +#include "string.h" #include "sys.h" +struct nolibc_heap { + size_t len; + char user_p[] __attribute__((__aligned__)); +}; + +#ifndef offsetof +#define offsetof(TYPE, FIELD) ((size_t) &((TYPE *)0)->FIELD) +#endif + +#ifndef container_of +#define container_of(PTR, TYPE, FIELD) ({ \ + __typeof__(((TYPE *)0)->FIELD) *__FIELD_PTR = (PTR); \ + (TYPE *)((char *) __FIELD_PTR - offsetof(TYPE, FIELD)); \ +}) +#endif /* Buffer used to store int-to-ASCII conversions. Will only be implemented if * any of the related functions is implemented. The area is large enough to @@ -60,6 +76,18 @@ int atoi(const char *s) return atol(s); } +static __attribute__((unused)) +void free(void *ptr) +{ + struct nolibc_heap *heap; + + if (!ptr) + return; + + heap = container_of(ptr, struct nolibc_heap, user_p); + munmap(heap, heap->len); +} + /* Converts the unsigned long integer <in> to its hex representation into * buffer <buffer>, which must be long enough to store the number and the * trailing zero (17 bytes for "ffffffffffffffff" or 9 for "ffffffff"). The @@ -182,6 +210,57 @@ char *ltoa(long in) return itoa_buffer; } +static inline __attribute__((unused)) +void *malloc(size_t len) +{ + struct nolibc_heap *heap; + + heap = mmap(NULL, sizeof(*heap) + len, PROT_READ|PROT_WRITE, + MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); + if (__builtin_expect(heap == MAP_FAILED, 0)) + return NULL; + + heap->len = sizeof(*heap) + len; + return heap->user_p; +} + +static inline __attribute__((unused)) +void *calloc(size_t size, size_t nmemb) +{ + void *orig; + size_t res = 0; + + if (__builtin_expect(__builtin_mul_overflow(nmemb, size, &res), 0)) { + SET_ERRNO(ENOMEM); + return NULL; + } + + /* + * No need to zero the heap, the MAP_ANONYMOUS in malloc() + * already does it. + */ + return malloc(res); +} + +static inline __attribute__((unused)) +void *realloc(void *old_ptr, size_t new_size) +{ + struct nolibc_heap *heap; + void *ret; + + if (!old_ptr) + return malloc(new_size); + + ret = malloc(new_size); + if (__builtin_expect(!ret, 0)) + return NULL; + + heap = container_of(old_ptr, struct nolibc_heap, user_p); + memcpy(ret, heap->user_p, heap->len); + munmap(heap, heap->len); + return ret; +} + /* converts unsigned long integer <in> to a string using the static itoa_buffer * and returns the pointer to that string. */ -- Ammar Faizi
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