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I want to implement a linux like paging system, I read the source code, load the gdt, go into PM, and mapping first 8M to

0xC0000000, and start use virtual address, all work good. But when I set page directory(because I want to map all of the

address space),virtual machine(vmware, bochs, virtual pc) give a CPU fault, I find out I can read the content the page

directory, but can not
write!(virtual pc and vmware can write the empty entries, but bochs can not write the whole page directory). I takes 4 days
to test my code, at last I find I can reload the page directory, load the same page directory at different page, but can not
load a different page directory.........

void setup_paging()
{
unsigned long * pde;
unsigned long * pte;
unsigned long pde_idx, pte_idx, pfn;
unsigned long * pgd_base = page_dir; // page_dir address 0xC0107000

pde_idx = pgd_index(PAGE_OFFSET); // pde_idx = 0xC00
pfn = 0; // map all of the phy addr
pde = pgd_base + pde_idx; // pde address = 0xC0107C00
for (; pde_idx < 1024; pde++, pde_idx++) {
pte = allocate_page(); // get one page from kernel end to first 8M
*pde = ((unsigned long)pte) | 0x27; // << This program dead at this place
for (pte_idx = 0; pte_idx < 1024; pte++, pte_idx++, pfn++) {
if (pfn >= max_pfn) // max_pfn = 0x2000
goto out;
*pte = ((pfn<<12)+0xC0000000) | 0x63;
}
}
out:
load_cr3(pgd_base); // movl $0x107000, %ecx; movl %ecx, %cr3\n
__flush_tlb_all(); // movl %cr3, %eax; movl %eax, %cr3
printk("All of the page table init successfully!\n");
}

Before executing the function:
the page_dir is:
0x108000 # at offset 0x0
0x109000
.....
0x108000 # at offset 0xC00
0x109000
registers:
cr0:0x80000011
cr3:0x107000

My gdt:
gdt:
.fill GDT_ENTRY_BOOT_CS,8,0
.word 0xFFFF # 4Gb
.word 0 # base address = 0
.word 0x9A00 # system, read/exec
.word 0x00CF # granularity=4K

.word 0xFFFF # 4Gb
.word 0 # base address = 0
.word 0x9200 # system, read/write
.word 0x00CF # granularity=4K

.word 0xFFFF # 4Gb
.word 0 # base address = 0
.word 0xfa00 # user, read/exec
.word 0x00CF # granularity=4K

.word 0xFFFF # 4Gb
.word 0 # base address = 0
.word 0xf200 # user, read/write
.word 0x00CF # granularity=4K

The full source code at http://pickup.mofile.com/0120118765010663

Are you identity mapping you PTE and PDE, because if your not then when you enable paging, it will (tripple) fault. Try looking at: http://www.mega-tokyo.com/osfaq/HigherHalfWithGdt it uses a nice little trick so the kernel always thinks its at 0xC0000000 regardless of whether being paged there or not.

Peace

I already enable paging, and begin executing above 0xC0000000. Now I want to set pdes again, and reload cr3 because at the booting I only set and load the pdes of the first 8M address. Do I need to set some bit in some register or others......

I just edit the appropreate PTE-PDE entried and use the invlpg opcode if you using i386 (as opposed to i486 onwards) you should reloads cr3 instead.

Peace

My code can run in bochs with no problem, but can not run in VPC and VMware. In bochs My cr0=0x80000011, in VPC and VMware cr0=0x80000013, so I clear the MP flag and test again:VMware auto reseted, and VPC found a ramdom processor fault as before then reset, however bochs can execute successfully, I print the page directory and page table, found no difference......

I know I can init the whole address space at the beginning, then avoid this problem, but when I start coding threads and process I will meet cr3 again......

My full source code at
http://pickup.mofile.com/0120118765010663