#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.h>
#endif
#include <error_table.h>
/* 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! */
kmres 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;
/* kmres reply is the struct that shall be returned by the
* function. if an error-condition occurs, the appropriate
* error code should be determined through system-specific
* means, the pointer value should be set to null, and the
* object should be returned immediately. if the object is
* not returned from within the system-specific section it
* will then be filled out with the appropriate values for
* a successful allocation and returned to the caller. */
kmres reply;
# 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.*/
k_platform_syscall_arg args[] = {
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, so we're setting it to that just to
* be safe. */
struct k_platform_syscall_answer r = k_platform_syscall
(k_platform_syscall_mmap, Kmsz(args), args);
if (r.error == 0) region.byte = (ubyte*)r.ret; else {
switch (r.error) {
case k_platform_error_EAGAIN: reply.cond = kmcond_bad_lock; break;
case k_platform_error_EINVAL: reply.cond = kmcond_bad_size; break;
case k_platform_error_EMFILE: reply.cond = kmcond_too_many; break;
case k_platform_error_ENOMEM: reply.cond = kmcond_no_room; break;
default: reply.cond = kmcond_fail_assert;
}
reply.raw = (void*)0;
return reply;
}
# else
Knoimpl(kmheapa,KVos);
# error missing implementation
# endif
/* if the system-specific code has not returned early,
* we assume success and return the new pointer to the
* calling function along with a success code. */
void* const object = (region.byte + sizeof (kmbox));
region.header -> kind = kmkind_heap;
region.header -> size = len;
reply.cond = kmcond_ok;
reply.raw = object;
return reply;
}