diff options
| -rw-r--r-- | libmaple/syscalls.c | 47 |
1 files changed, 31 insertions, 16 deletions
diff --git a/libmaple/syscalls.c b/libmaple/syscalls.c index ae80010..f28202c 100644 --- a/libmaple/syscalls.c +++ b/libmaple/syscalls.c @@ -25,32 +25,47 @@ *****************************************************************************/ #include "libmaple.h" + #include <sys/stat.h> +#include <errno.h> -/* _end is set in the linker command file */ -extern caddr_t _end; +/* Set by the linker script */ +extern int _end; +/* FIXME these should be determined by the linker script. + * + * Doing so will allow the heap to be configured on a per-board basis. + * Current values are just stopgaps for a heap in built-in SRAM. + * + * STACK_RESERVED_BYTES is just a hack to ensure a minimum stack size. + * It should probably go away as well. */ +#define STACK_RESERVED_BYTES 1024 +#define HEAP_START ((caddr_t)&_end) +#define HEAP_END ((caddr_t)((uint32)STM32_SRAM_END - \ + STACK_RESERVED_BYTES)) /* - * sbrk -- changes heap size size. Get nbytes more - * RAM. We just increment a pointer in what's - * left of memory on the board. + * _sbrk -- Increment the program break. + * + * Get incr bytes more RAM (for use by the heap). malloc() and + * friends call this function behind the scenes. */ -caddr_t _sbrk(int nbytes) { - static caddr_t heap_ptr = NULL; - caddr_t base; +caddr_t _sbrk(int incr) { + static caddr_t pbreak = NULL; /* current program break */ + caddr_t ret; - if (heap_ptr == NULL) { - heap_ptr = (caddr_t)&_end; + if (pbreak == NULL) { + pbreak = HEAP_START; } - if ((STACK_TOP - (unsigned int)heap_ptr) >= 0) { - base = heap_ptr; - heap_ptr += nbytes; - return (base); - } else { - return ((caddr_t)-1); + if ((HEAP_END - pbreak < incr) || (pbreak - HEAP_START < -incr)) { + errno = ENOMEM; + return (caddr_t)-1; } + + ret = pbreak; + pbreak += incr; + return ret; } int _open(const char *path, int flags, ...) { |