aclindsa/aedrix-kernel
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Enable the MMU even if the kernel is not loaded in physical memory at

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the same place it was linked against.
This commit is contained in:
Aaron Lindsay
2012-09-23 01:29:45 -04:00
parent e2a3ab602c
commit d6e3899fc1
4 changed files with 191 additions and 50 deletions
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31
kernel/mmu.c
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@ -10,20 +10,41 @@
#define cp_read(var, ...) _cp_read(var, __VA_ARGS__)
#define cp_write(var, ...) _cp_write(var, __VA_ARGS__)
#define TT_BASE_SIZE (1<<14) /* 16k */
unsigned int *kernel_start_phys, *kernel_start_virt, *kernel_end_phys, *kernel_end_virt;
void mmu_reinit() {
unsigned int *curr_tt_entry;
extern unsigned int tt_base_virtual, tt_base_physical, start;
unsigned int curr_addr;
unsigned int *curr_tt_entry;
int virt_phys_offset;
virt_phys_offset = tt_base_virtual - tt_base_physical;
kernel_start_virt = &start;
kernel_start_phys = kernel_start_virt - virt_phys_offset/4;
kernel_end_virt = (unsigned int *)(tt_base_virtual + TT_BASE_SIZE);
kernel_end_phys = (unsigned int *)(tt_base_physical + TT_BASE_SIZE);
//get the current translation table base address
cp_read(curr_tt_entry, TTBR0);
curr_tt_entry = (unsigned int *)tt_base_virtual;
//do first loop iteration outside the loop, because we have to check against wrapping back around to know we're done
*curr_tt_entry = 0xc02;
*curr_tt_entry = 0xc02; /* 0xc02 means read/write at any priviledge level, and that it's a section w/o PXN bit set */
curr_tt_entry++;
//create identity mapping for entire address space using sections
//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 twp mappings so all of memory is addressable.
for (curr_addr = 0x00100000; curr_addr != 0; curr_addr += 0x00100000) {
*curr_tt_entry = curr_addr | 0xc02;
if ((unsigned int *)curr_addr >= kernel_start_phys && (unsigned int *)curr_addr < kernel_end_phys) {
*curr_tt_entry = (curr_addr + virt_phys_offset) | 0xc02;
} else if ((unsigned int *)curr_addr >= kernel_start_virt && (unsigned int *)curr_addr < kernel_end_virt) {
*curr_tt_entry = (curr_addr - virt_phys_offset) | 0xc02;
} else {
*curr_tt_entry = curr_addr | 0xc02;
}
curr_tt_entry++;
}
}

5
kernel/start_kernel.c
View File

@ -7,8 +7,6 @@
#include <framebuffer.h>
#include <console.h>
extern const unsigned int kernel_end;
struct fb myfb;
void video(void) {
@ -64,7 +62,8 @@ int main(void) {
//setup memory
mm_init();
mm_add_free_region((void*)0x60000000, (void*)0x7FFFFFFF);
lower = (char*) &kernel_end;
mm_add_free_region((void*)0x80000000, (void*)0x800FFFFF);
lower = (char*) &kernel_end_virt;
if ((unsigned int)lower % MM_PAGE_SIZE != 0)
lower += (MM_PAGE_SIZE - ((unsigned int)lower % MM_PAGE_SIZE));
mm_add_free_region((void*)lower, (void*)0x9FFFFFFF); //subtract the memory used by the kernel