Messages in this thread Patch in this message | | | From | Ammar Faizi <> | Subject | [RFC PATCH v2 6/8] tools/nolibc/stdlib: Implement `malloc()`, `calloc()`, `realloc()` and `free()` | Date | Tue, 22 Mar 2022 17:21:13 +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> ---
@@ Changelog:
Link: https://lore.kernel.org/lkml/20220320093750.159991-6-ammarfaizi2@gnuweeb.org RFC v1 -> RFC v2: - Move container_of() and offsetof() macro to types.h with a separate patch (comment from Willy). --- tools/include/nolibc/stdlib.h | 68 +++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+)
diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h index aca8616335e3..a0ed75431e0a 100644 --- a/tools/include/nolibc/stdlib.h +++ b/tools/include/nolibc/stdlib.h @@ -11,7 +11,12 @@ #include "arch.h" #include "types.h" #include "sys.h" +#include "string.h" +struct nolibc_heap { + size_t len; + char user_p[] __attribute__((__aligned__)); +}; /* 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 +65,18 @@ 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); +} + /* Tries to find the environment variable named <name> in the environment array * pointed to by global variable "environ" which must be declared as a char **, * and must be terminated by a NULL (it is recommended to set this variable to @@ -205,6 +222,57 @@ char *ltoa(long in) return itoa_buffer; } +static __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 __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 __attribute__((unused)) +void *realloc(void *old_ptr, size_t new_size) +{ + struct nolibc_heap *heap; + void *ret; + + ret = malloc(new_size); + if (__builtin_expect(!ret, 0)) + return NULL; + + if (!old_ptr) + return ret; + + 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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