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#include <frame.h>
#include <dbglog.h>
#include <mutex.h>
// TODO: buddy allocator
// this is a simple bitmap allocator
#define INDEX_FROM_BIT(a) ((a)/(8*4))
#define OFFSET_FROM_BIT(a) ((a)%(8*4))
static uint32_t *frame_bitset;
static uint32_t nframes, nused_frames;
static uint32_t begin_search_at;
void frame_init_allocator(size_t total_ram, void** kernel_data_end) {
nframes = PAGE_ID(total_ram);
// Statically allocate space after kernel data end
frame_bitset = (uint32_t*)ALIGN4_UP((size_t)*kernel_data_end);
*kernel_data_end = (void*)((size_t)frame_bitset + ALIGN4_UP(nframes / 8));
for (size_t i = 0; i < ALIGN4_UP(nframes / 8)/4; i++)
frame_bitset[i] = 0;
nused_frames = 0;
size_t kernel_pages = PAGE_ALIGN_UP((size_t)*kernel_data_end - K_HIGHHALF_ADDR)/PAGE_SIZE;
for (size_t i = 0; i < kernel_pages; i++) {
size_t idx = INDEX_FROM_BIT(i);
size_t ofs = OFFSET_FROM_BIT(i);
frame_bitset[idx] |= (0x1 << ofs);
nused_frames++;
}
begin_search_at = INDEX_FROM_BIT(kernel_pages);
}
STATIC_MUTEX(frame_allocator_mutex);
uint32_t frame_alloc(size_t n) {
if (n > 32) return 0;
mutex_lock(&frame_allocator_mutex);
for (uint32_t i = begin_search_at; i < INDEX_FROM_BIT(nframes); i++) {
if (frame_bitset[i] == 0xFFFFFFFF) {
if (i == begin_search_at) begin_search_at++;
continue;
}
for (uint32_t j = 0; j < 32 - n + 1; j++) {
uint32_t to_test = (0xFFFFFFFF >> (32 - n)) << j;
if (!(frame_bitset[i]&to_test)) {
frame_bitset[i] |= to_test;
nused_frames += n;
mutex_unlock(&frame_allocator_mutex);
/*dbg_printf("AF 0x%p\n", i * 32 + j);*/
return i * 32 + j;
}
}
}
mutex_unlock(&frame_allocator_mutex);
return 0;
}
void frame_free(uint32_t base, size_t n) {
mutex_lock(&frame_allocator_mutex);
for (size_t i = 0; i < n; i++) {
/*dbg_printf("FF 0x%p\n", base + i);*/
uint32_t idx = INDEX_FROM_BIT(base + i);
uint32_t ofs = OFFSET_FROM_BIT(base + i);
if (frame_bitset[idx] & (0x1 << ofs)) {
frame_bitset[idx] &= ~(0x1 << ofs);
nused_frames--;
}
}
if (INDEX_FROM_BIT(base) < begin_search_at)
begin_search_at = INDEX_FROM_BIT(base);
mutex_unlock(&frame_allocator_mutex);
}
void dbg_print_frame_stats() {
dbg_printf("Used frames: %d/%d\n", nused_frames, nframes);
}
/* vim: set ts=4 sw=4 tw=0 noet :*/
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