In arch/x86/kernel/head_64.S, I add another level page table, make pmd point to the new page table. However, after compile and boot it, the kernel cannot work and always reboot.
I try many kind of port, it still cannot work normally.
Here is the context of my modified code :
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/* Automate the creation of 1 to 1 mapping pmd entries */
#define PMDS(START, PERM, COUNT) \
i = 0 ; \
.rept (COUNT) ; \
.quad (START) + (i << PMD_SHIFT) + (PERM) ; \
i = i + 1 ; \
.endr
#define PTDS(START, PERM, COUNT) \
i = 0 ; \
.rept (COUNT) ; \
.quad (START) + (i << PAGE_SHIFT) + (PERM) ; \
i = i + 1 ; \
.endr
.data
/*
* This default setting generates an ident mapping at address 0x100000
* and a mapping for the kernel that precisely maps virtual address
* 0xffffffff80000000 to physical address 0x000000. (always using
* 2Mbyte large pages provided by PAE mode)
*/
NEXT_PAGE(init_level4_pgt)
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
.org init_level4_pgt + L4_PAGE_OFFSET*8, 0
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
.org init_level4_pgt + L4_START_KERNEL*8, 0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
NEXT_PAGE(level3_ident_pgt)
.quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
.fill 511,8,0
NEXT_PAGE(level3_kernel_pgt)
.fill L3_START_KERNEL,8,0
/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
.quad level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE
.quad level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
NEXT_PAGE(level2_fixmap_pgt)
.fill 506,8,0
.quad level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
/* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
.fill 5,8,0
NEXT_PAGE(level1_fixmap_pgt)
.fill 512,8,0
NEXT_PAGE(level2_ident_pgt)
/* Since I easily can, map the first 1G.
* Don't set NX because code runs from these pages.
*/
PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
NEXT_PAGE(level2_kernel_pgt)
/*
* 512 MB kernel mapping. We spend a full page on this pagetable
* anyway.
*
* The kernel code+data+bss must not be bigger than that.
*
* (NOTE: at +512MB starts the module area, see MODULES_VADDR.
* If you want to increase this then increase MODULES_VADDR
* too.)
*/
/* PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
KERNEL_IMAGE_SIZE/PMD_SIZE)*/
#define NEW_PMD_PORT (0x0 | _PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED)
PMDS(level1_kernel_pgt - __START_KERNEL_map, NEW_PMD_PORT, PTRS_PER_PMD)
NEXT_PAGE(level1_kernel_pgt)
#define NEW_PTD_PORT (0x0 | _PAGE_PRESENT | _PAGE_RW | |_PAGE_USER | _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_GLOBAL)
PTDS(0, NEW_PTD_PORT, KERNEL_IMAGE_SIZE/PAGE_SIZE)
NEXT_PAGE(level2_spare_pgt)
.fill 512, 8, 0
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