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arch/i386: Add multiboot support

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This commit is contained in:
Aaron Lindsay
2012-12-24 12:44:48 -05:00
parent 62755b8f38
commit b98aa76334
6 changed files with 287 additions and 9 deletions
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96
arch/i386/kernel/mmu.c
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@ -22,9 +22,101 @@
#include <types.h>
#include <mm.h>
extern uint32 kernel_start_phys, kernel_end_phys;
extern uint32 kernel_start, kernel_end;
#define PAGE_SIZE 0x00400000
#define ROUND_DOWN_PAGE_SIZE(addr) ((typeof(addr))((uint32)(addr) & 0xff800000))
static inline int page_intersects(uint32 *page_start, uint32 *lower, uint32 *upper) {
return (lower >= page_start && lower < (page_start + PAGE_SIZE)) ||
(upper >= page_start && upper < (page_start + PAGE_SIZE)) ||
(lower < page_start && upper >= (page_start + PAGE_SIZE));
}
void mmu_reinit() {
int virt_phys_offset; /* CAUTION: 1 = 4 bytes */
uint32 *curr_tbl_entry;
uint32 *curr_addr;
uint32 *page_dir;
asm("movl %%cr3, %0" : "=r"(page_dir) : : );
virt_phys_offset = &kernel_start - &kernel_start_phys;
curr_tbl_entry = page_dir + virt_phys_offset;
//do first loop iteration outside th eloop, because we have to check against wrapping back around to know we're done
*curr_tbl_entry = 0x83;
curr_tbl_entry++;
//create identity mapping for entire address space using sections.
//BUT, if we've relocated the kernel from where it is in physical
//memory, make sure we keep those mappings correct, and we'll actually
//swap the two mappings so all of memory is addressable.
for (curr_addr = (uint32 *)PAGE_SIZE; curr_addr != 0; curr_addr += (PAGE_SIZE>>2)) {
if (page_intersects(curr_addr, &kernel_start_phys, &kernel_end_phys)) {
*curr_tbl_entry = (uint32)ROUND_DOWN_PAGE_SIZE(curr_addr + virt_phys_offset) | 0x83;
} else if (page_intersects(curr_addr, &kernel_start, &kernel_end)) {
*curr_tbl_entry = (uint32)ROUND_DOWN_PAGE_SIZE(curr_addr - virt_phys_offset) | 0x83;
} else {
*curr_tbl_entry = (uint32)curr_addr | 0x83;
}
/* Force the entries to reload */
asm("invlpg (%0)" : : "r"(curr_addr) : );
curr_tbl_entry++;
}
}
//TODO merge the rest of this file with the similar section in arch/arm. This is clearly mostly duplicated code.
int mmu_region_contains(void *lower_a, void *upper_a, void *lower_b, void *upper_b) {
return lower_b >= lower_a && upper_b <= upper_a;
}
int mmu_region_contains_single(void *lower_a, void *upper_a, void *ptr) {
return lower_a <= ptr && ptr <= upper_a;
}
#define section_round_down(ptr) (((uint32)ptr) & ~(PAGE_SIZE-1))
#define section_round_up(ptr) (((((uint32)ptr) & ~1) + (PAGE_SIZE-1) ) & ~(PAGE_SIZE-1))
/* Called once per physical memory region by bootup code. This function is
* responsible for only adding (via mm_add_free_region()) those parts of the
* memory region which are still available (i.e. aren't in the kernel and
* haven't been remapped anywhere else. */
void declare_memory_region(void *lower, void *upper) {
(void)lower;
(void)upper;
void *k_section_start_phys = (void *)section_round_down(&kernel_start_phys);
void *k_section_end_phys = (void *)(section_round_up(&kernel_end_phys) - 1);
void *k_section_start_virt = (void *)section_round_down(&kernel_start);
void *k_section_end_virt = (void *)(section_round_up(&kernel_end) - 1);
if (upper - lower < 1) {
print("Warning: declare_memory_region() called with lower=%x, upper=%x. Ignoring.\n", lower, upper);
return;
}
//TODO It's possible (though highly unlikely) that the kernel (virtual)
//is split across two different memory regions. We should probably
//handle this.
if (mmu_region_contains(lower, upper, k_section_start_phys, k_section_end_phys)) {
//Don't map any of the physical kernel's memory
declare_memory_region(lower, (void *) ((char *)k_section_start_phys - 1));
declare_memory_region((void *) ((char *)k_section_end_phys + 1), upper);
mm_add_free_region(&kernel_end, k_section_end_virt);
} else if (mmu_region_contains(lower, upper, k_section_start_virt, k_section_end_virt)) {
declare_memory_region(lower, (void *) ((char *)k_section_start_virt - 1));
declare_memory_region((void *) ((char *)k_section_end_virt + 1), upper);
} else if (mmu_region_contains_single(lower, upper, k_section_start_phys)) {
if ((void*)((char*)lower + 1) < k_section_start_phys)
declare_memory_region(lower, (void *) ((char *)k_section_start_phys - 1));
} else if (mmu_region_contains_single(lower, upper, k_section_end_phys)) {
if (k_section_end_phys < (void*)((char*)upper - 1))
declare_memory_region((void *) ((char *)k_section_end_phys + 1), upper);
} else if (mmu_region_contains_single(lower, upper, k_section_start_virt)) {
if ((void*)((char*)lower + 1) < k_section_start_virt)
declare_memory_region(lower, (void *) ((char *)k_section_start_virt - 1));
} else if (mmu_region_contains_single(lower, upper, k_section_end_virt)) {
if (k_section_end_virt < (void*)((char*)upper - 1))
declare_memory_region((void *) ((char *)k_section_end_virt + 1), upper);
} else {
mm_add_free_region(lower, upper);
}
}