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Date: Mon, 18 Apr 2022 17:42:23 -0700 From: "Paul E. McKenney" <paulmck@...nel.org> To: linux-kernel@...r.kernel.org Cc: gwml@...r.gnuweeb.org, kernel-team@...com, w@....eu, Ammar Faizi <ammarfaizi2@...weeb.org>, David Laight <David.Laight@...LAB.COM>, Willy Tarreau <w@....eu>, "Paul E . McKenney" <paulmck@...nel.org> Subject: [PATCH nolibc 59/61] tools/nolibc/stdlib: Implement `malloc()`, `calloc()`, `realloc()` and `free()` From: Ammar Faizi <ammarfaizi2@...weeb.org> 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. Cc: David Laight <David.Laight@...LAB.COM> Acked-by: Willy Tarreau <w@....eu> Signed-off-by: Ammar Faizi <ammarfaizi2@...weeb.org> Signed-off-by: Paul E. McKenney <paulmck@...nel.org> --- tools/include/nolibc/stdlib.h | 81 +++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h index 8a07e263f0d0..8fd32eaf8037 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); +} + /* getenv() 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 @@ -91,6 +108,70 @@ char *getenv(const char *name) return _getenv(name, environ); } +static __attribute__((unused)) +void *malloc(size_t len) +{ + struct nolibc_heap *heap; + + /* Always allocate memory with size multiple of 4096. */ + len = sizeof(*heap) + len; + len = (len + 4095UL) & -4096UL; + heap = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, + -1, 0); + if (__builtin_expect(heap == MAP_FAILED, 0)) + return NULL; + + heap->len = 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; + size_t user_p_len; + void *ret; + + if (!old_ptr) + return malloc(new_size); + + heap = container_of(old_ptr, struct nolibc_heap, user_p); + user_p_len = heap->len - sizeof(*heap); + /* + * Don't realloc() if @user_p_len >= @new_size, this block of + * memory is still enough to handle the @new_size. Just return + * the same pointer. + */ + if (user_p_len >= new_size) + return old_ptr; + + ret = malloc(new_size); + if (__builtin_expect(!ret, 0)) + return NULL; + + memcpy(ret, heap->user_p, heap->len); + munmap(heap, heap->len); + return ret; +} + /* 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 -- 2.31.1.189.g2e36527f23
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