+/**
+ * @file dmm.c
+ * @author Lunaixsky
+ * @brief Dynamic memory manager dedicated to kernel heap. It is not portable at
+ * this moment. Implicit free list implementation.
+ * @version 0.1
+ * @date 2022-02-28
+ *
+ * @copyright Copyright (c) Lunaixsky 2022
+ *
+ */
+
#include <lunaix/mm/dmm.h>
+#include <lunaix/mm/page.h>
#include <lunaix/mm/vmm.h>
-// This is a temporary design.
-// We can do better when we are ready for multitasking
-void
-lxsbrk(void* current, void* next) {
- // TODO: sbrk
+#include <lunaix/assert.h>
+#include <lunaix/constants.h>
+#include <lunaix/spike.h>
+
+#define M_ALLOCATED 0x1
+#define M_PREV_FREE 0x2
+
+#define M_NOT_ALLOCATED 0x0
+#define M_PREV_ALLOCATED 0x0
+
+#define CHUNK_S(header) ((header) & ~0x3)
+#define CHUNK_PF(header) ((header)&M_PREV_FREE)
+#define CHUNK_A(header) ((header)&M_ALLOCATED)
+
+#define PACK(size, flags) (((size) & ~0x3) | (flags))
+
+#define SW(p, w) (*((uint32_t*)(p)) = w)
+#define LW(p) (*((uint32_t*)(p)))
+
+#define HPTR(bp) ((uint32_t*)(bp)-1)
+#define BPTR(bp) ((uint8_t*)(bp) + WSIZE)
+#define FPTR(hp, size) ((uint32_t*)(hp + size - WSIZE))
+#define NEXT_CHK(hp) ((uint8_t*)(hp) + CHUNK_S(LW(hp)))
+
+#define BOUNDARY 4
+#define WSIZE 4
+
+extern uint8_t __kernel_heap_start;
+
+void* current_heap_top = NULL;
+
+void*
+coalesce(uint8_t* chunk_ptr);
+
+void*
+lx_grow_heap(size_t sz);
+
+void place_chunk(uint8_t* ptr, size_t size);
+
+int
+dmm_init()
+{
+ assert((uintptr_t)&__kernel_heap_start % BOUNDARY == 0);
+
+ current_heap_top = &__kernel_heap_start;
+ uint8_t* heap_start = &__kernel_heap_start;
+
+ vmm_alloc_page(current_heap_top, PG_PREM_RW);
+
+ SW(heap_start, PACK(4, M_ALLOCATED));
+ SW(heap_start + WSIZE, PACK(0, M_ALLOCATED));
+ current_heap_top += WSIZE;
+
+ return lx_grow_heap(HEAP_INIT_SIZE);
}
-void
-lxmalloc(size_t size) {
- // TODO: Malloc
+int
+lxsbrk(void* addr)
+{
+ return lxbrk(addr - current_heap_top) != NULL;
+}
+
+void*
+lxbrk(size_t size)
+{
+ if (size == 0) {
+ return NULL;
+ }
+
+ // plus WSIZE is the overhead for epilogue marker
+ size += WSIZE;
+ void* next = current_heap_top + ROUNDUP((uintptr_t)size, WSIZE);
+
+ if (next >= K_STACK_START) {
+ return NULL;
+ }
+
+ // Check the invariant
+ assert(size % BOUNDARY == 0)
+
+ uintptr_t heap_top_pg = PG_ALIGN(current_heap_top);
+ if (heap_top_pg != PG_ALIGN(next))
+ {
+ // if next do require new pages to be allocated
+ if (!vmm_alloc_pages(heap_top_pg + PG_SIZE, ROUNDUP(size, PG_SIZE), PG_PRESENT | PG_WRITE)) {
+ return NULL;
+ }
+
+ }
+
+ uintptr_t old = current_heap_top;
+ current_heap_top = next - WSIZE;
+ return old;
+}
+
+void*
+lx_grow_heap(size_t sz) {
+ uintptr_t start;
+
+ sz = ROUNDUP(sz, BOUNDARY);
+ if (!(start = lxbrk(sz))) {
+ return NULL;
+ }
+
+ uint32_t old_marker = *((uint32_t*)start);
+ uint32_t free_hdr = PACK(sz, CHUNK_PF(old_marker));
+ SW(start, free_hdr);
+ SW(FPTR(start, sz), free_hdr);
+ SW(NEXT_CHK(start), PACK(0, M_ALLOCATED | M_PREV_FREE));
+
+ return coalesce(start);
+}
+
+void*
+lx_malloc(size_t size)
+{
+ // Simplest first fit approach.
+
+ uint8_t* ptr = &__kernel_heap_start;
+ // round to largest 4B aligned value
+ // and space for header
+ size = ROUNDUP(size, BOUNDARY) + WSIZE;
+ while (ptr < current_heap_top) {
+ uint32_t header = *((uint32_t*)ptr);
+ size_t chunk_size = CHUNK_S(header);
+ if (chunk_size >= size && !CHUNK_A(header)) {
+ // found!
+ place_chunk(ptr, size);
+ return BPTR(ptr);
+ }
+ ptr += chunk_size;
+ }
+
+ // if heap is full (seems to be!), then allocate more space (if it's okay...)
+ if ((ptr = lx_grow_heap(size))) {
+ place_chunk(ptr, size);
+ return BPTR(ptr);
+ }
+
+ // Well, we are officially OOM!
+ return NULL;
+}
+
+void place_chunk(uint8_t* ptr, size_t size) {
+ uint32_t header = *((uint32_t*)ptr);
+ size_t chunk_size = CHUNK_S(header);
+ *((uint32_t*)ptr) = PACK(size, CHUNK_PF(header) | M_ALLOCATED);
+ uint8_t* n_hdrptr = (uint8_t*)(ptr + size);
+ uint32_t diff = chunk_size - size;
+ if (!diff) {
+ // if the current free block is fully occupied
+ uint32_t n_hdr = LW(n_hdrptr);
+ // notify the next block about our avaliability
+ SW(n_hdrptr, n_hdr & ~0x2);
+ } else {
+ // if there is remaining free space left
+ uint32_t remainder_hdr =
+ PACK(diff, M_NOT_ALLOCATED | M_PREV_ALLOCATED);
+ SW(n_hdrptr, remainder_hdr);
+ SW(FPTR(n_hdrptr, diff), remainder_hdr);
+
+ coalesce(n_hdrptr);
+ }
}
void
-lxfree(size_t size) {
- // TODO: Free
+lx_free(void* ptr)
+{
+ if (!ptr) {
+ return;
+ }
+
+ uint8_t* chunk_ptr = (uint8_t*)ptr - WSIZE;
+ uint32_t hdr = LW(chunk_ptr);
+ uint8_t* next_hdr = chunk_ptr + CHUNK_S(hdr);
+
+ SW(chunk_ptr, hdr & ~M_ALLOCATED);
+ SW(FPTR(chunk_ptr, CHUNK_S(hdr)), hdr & ~M_ALLOCATED);
+ SW(next_hdr, LW(next_hdr) | M_PREV_FREE);
+
+ coalesce(chunk_ptr);
+}
+
+void*
+coalesce(uint8_t* chunk_ptr)
+{
+ uint32_t hdr = LW(chunk_ptr);
+ uint32_t pf = CHUNK_PF(hdr);
+ uint32_t sz = CHUNK_S(hdr);
+ uint32_t ftr = LW(chunk_ptr + sz - WSIZE);
+
+ uint32_t n_hdr = LW(chunk_ptr + sz);
+
+ if (CHUNK_A(n_hdr) && pf) {
+ // case 1: prev is free
+ uint32_t prev_ftr = LW(chunk_ptr - WSIZE);
+ size_t prev_chunk_sz = CHUNK_S(prev_ftr);
+ uint32_t new_hdr = PACK(prev_chunk_sz + sz, CHUNK_PF(prev_ftr));
+ SW(chunk_ptr - prev_chunk_sz, new_hdr);
+ SW(FPTR(chunk_ptr, sz), new_hdr);
+ chunk_ptr -= prev_chunk_sz;
+ } else if (!CHUNK_A(n_hdr) && !pf) {
+ // case 2: next is free
+ size_t next_chunk_sz = CHUNK_S(n_hdr);
+ uint32_t new_hdr = PACK(next_chunk_sz + sz, pf);
+ SW(chunk_ptr, new_hdr);
+ SW(FPTR(chunk_ptr, sz + next_chunk_sz), new_hdr);
+ } else if (!CHUNK_A(n_hdr) && pf) {
+ // case 3: both free
+ uint32_t prev_ftr = LW(chunk_ptr - WSIZE);
+ size_t next_chunk_sz = CHUNK_S(n_hdr);
+ size_t prev_chunk_sz = CHUNK_S(prev_ftr);
+ uint32_t new_hdr =
+ PACK(next_chunk_sz + prev_chunk_sz + sz, CHUNK_PF(prev_ftr));
+ SW(chunk_ptr - prev_chunk_sz, new_hdr);
+ SW(FPTR(chunk_ptr, sz + next_chunk_sz), new_hdr);
+ chunk_ptr -= prev_chunk_sz;
+ }
+
+ // case 4: prev and next are not free
+ return chunk_ptr;
}
\ No newline at end of file
git://scm.lunaixsky.com / lunaix-os.git / blobdiff