/**
* @brief invalidate all TLB entries, including global entries
*/
static void x86_tlb_global_invalidate() {
/* See Intel 3A section 4.10.4.1 */
ulong cr4 = x86_get_cr4();
if (likely(cr4 & X86_CR4_PGE)) {
x86_set_cr4(cr4 & ~X86_CR4_PGE);
x86_set_cr4(cr4);
} else {
x86_set_cr3(x86_get_cr3());
}
}
void vm_init_paging(struct multiboot_info *boot_info)
{
struct x86_cpuid_info cpuid_info;
struct frame *pgdir_frame;
struct frame *pgtab_frame;
pte_t *pgtab;
ulong_t paddr, mem_max;
/*
* Check CPUID instruction to see if large pages (PSE feature)
* is supported.
*/
PANIC_IF(!x86_cpuid(&cpuid_info), "GeekOS requires a Pentium-class CPU");
PANIC_IF(!cpuid_info.feature_info_edx.pse, "Processor does not support PSE");
cons_printf("CPU supports PSE\n");
/*
* Enable PSE by setting the PSE bit in CR4.
*/
x86_set_cr4(x86_get_cr4() | CR4_PSE);
/*
* Allocate kernel page directory.
*/
pgdir_frame = mem_alloc_frame(FRAME_KERN, 1);
s_kernel_pagedir = mem_frame_to_pa(pgdir_frame);
memset(s_kernel_pagedir, '\0', PAGE_SIZE);
/*
* We will support at most 2G of physical memory.
*/
mem_max = ((ulong_t) boot_info->mem_upper) * 1024;
if (mem_max > (1 << 31)) {
mem_max = (ulong_t) (1 << 31);
}
/*
* We need a page table for the low 4M of the kernel address space,
* since we want to leave the zero page unmapped (to catch null pointer derefs).
*/
pgtab_frame = mem_alloc_frame(FRAME_KERN, 1);
pgtab = mem_frame_to_pa(pgtab_frame);
memset(pgtab, '\0', PAGE_SIZE);
/*
* Initialize low page table, leaving page 0 unmapped
*/
for (paddr = PAGE_SIZE; paddr < VM_PT_SPAN; paddr += PAGE_SIZE) {
vm_set_pte(pgtab, VM_WRITE|VM_READ|VM_EXEC, paddr, paddr);
}
/*
* Add low page table to the kernel pagedir.
*/
vm_set_pde(s_kernel_pagedir, VM_WRITE|VM_READ|VM_EXEC, 0UL, (u32_t) pgtab);
/*
* Use 4M pages to map the rest of the low 2G of memory
*/
for (paddr = VM_PT_SPAN; paddr < mem_max; paddr += VM_PT_SPAN) {
vm_set_pde_4m(s_kernel_pagedir, VM_WRITE|VM_READ|VM_EXEC, paddr, paddr);
}
/*
* Turn on paging!
*/
x86_set_cr3((u32_t) s_kernel_pagedir); /* set the kernel page directory */
x86_set_cr0(x86_get_cr0() | CR0_PG); /* turn on the paging bit in cr0 */
cons_printf("Paging enabled\n");
}
