matos/core/mem.c

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#include "mem.h"
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#include "list.h"
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#include "vga.h"
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static struct mem_desc *page_desc = (struct mem_desc *)&__ld_kernel_end;
static struct mem_desc *free_page;
static struct mem_desc *used_page;
static unsigned long bottom_mem;
static unsigned long top_mem;
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int memInit(unsigned long upper_mem)
{
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printf("Free Mem going from %d to %d\n", &__ld_kernel_end, upper_mem * 1024);
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unsigned long memdesc_end =
(unsigned long)page_desc +
((upper_mem) / (PAGE_SIZE / 1024)) * sizeof(struct mem_desc);
uint lastUsed = (memdesc_end >> PAGE_SHIFT) + 1;
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list_init(free_page);
list_init(used_page);
bottom_mem = lastUsed;
top_mem = upper_mem;
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for (uint i = 0; i < (upper_mem / (PAGE_SIZE / 1024)); i++) {
struct mem_desc *mem = &page_desc[i];
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if (i < lastUsed) {
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mem->ref = 1;
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list_add_tail(used_page, mem);
} else {
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mem->ref = 0;
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list_add_tail(free_page, mem);
}
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mem->phy_addr = i * PAGE_SIZE;
}
return 0;
}
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struct mem_desc *addr2memDesc(unsigned long addr)
{
if (addr > top_mem || addr < bottom_mem)
return NULL;
int idx = addr >> PAGE_SHIFT;
return page_desc + idx;
}
unsigned long allocPage(void)
{
if (list_is_empty(free_page))
return (unsigned long)NULL;
struct mem_desc *mem = list_pop_head(free_page);
mem->ref = 1;
list_add_tail(used_page, mem);
return mem->phy_addr;
}
int unrefPage(unsigned long addr)
{
struct mem_desc *mem = addr2memDesc(addr);
if (!mem) {
return -1;
}
mem->ref--;
if (mem->ref == 0) {
list_add_tail(free_page, mem);
}
return 0;
}