#include <k/mem.h>
#include <k/core.h>
#include <k/def.h>
#include <k/type.h>
/* heapa.c - kmheapa() "heap alloc"
* ~ lexi hale <lexi@hale.su>
* kmheapa() allocates a pointer on the heap à la libc malloc()
* see also: kmheapf() "heap free"
*/
/* arch specific headers */
#ifdef KFenv_posix
# include <posix/posix.h>
#endif
/* we define all our platform functions here, whether or not
* they're for the correct platform - only the ones that are
* called by the preprocessed form of the code will actually
* be linked, linker errors are our friend here! */
extern void* kmem_platform_mmap(void* addr,
unsigned long sz, unsigned long prot, unsigned long flags,
unsigned long fd, unsigned long off);
void* kmheapa(sz len) {
/* allocate an object on the heap and return
* a pointer, or NULL if the allocation failed. */
union {
void* raw;
ubyte* byte;
kmbox* header;
} region;
/* we need to allocate space for the
* header and for the actual object */
sz region_size = sizeof(kmbox) + len;
# ifdef KFenv_posix
/* posix APIs - we've got it easy. currently for
* nonlinear heap allocation kmheapa simply uses
* m(un)map and lets the kernel worry about it. it
* may ultimately be worth replacing this with a
* more sophisticated implementation, most likely an
* existing allocator like jemalloc, though i'm wary
* of including outside code - it creates a licensing
* mess and i'd prefer libk to be AGPLv3 across the
* board. possibility: include hooks for multiple
* allocators, allowing the user to select & link in
* her preferred allocator at compile time? */
/* because munmap needs to be informed of the size of
* the region we are going to unmap, we need to store
* that information in the region that we are mapping.
* the user will receive an adjusted pointer that can
* be adjusted to point a field of type size_t that
* contains the size of the allocated space.*/
region.byte = kmem_platform_mmap(null, region_size,
posix_prot_read | posix_prot_write,
posix_flag_anonymous | posix_map_shared, -1, 0);
/* impl note: while per manpage fd is "ignored"
* for MAP_ANONYMOUS, "some implementations" require
* a value of -1 */
if (region.raw == (void*) -1) return null;
/* worth retrieving errno? discuss */
# else
Knoimpl(kmheapa,KVos);
# error missing implementation
# endif
void* const object = (region.byte + sizeof (kmbox));
region.header -> kind = kmkind_heap;
region.header -> size = len;
return object;
}