Messages in this thread | | | From | David Laight <> | Subject | RE: [RFC PATCH v2 6/8] tools/nolibc/stdlib: Implement `malloc()`, `calloc()`, `realloc()` and `free()` | Date | Tue, 22 Mar 2022 11:52:43 +0000 |
| |
From: Ammar Faizi > Sent: 22 March 2022 10:21 > > 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__));
Doesn't that need (number) in the attribute?
> +}; > > /* 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;
If you do (say): len = ROUNDUP(len + sizeof *heap, 4096) you can optimise a lot of the realloc() calls.
I actually wonder if compiling a mini-libc.a and then linking the programs against it might be better than all these static functions? -ffunction-sections can help a bit (where supported).
David
> + > + 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
- Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
| |