x86: put initial_pg_tables into .bss (2bd2753f) · Commits · 戴 / test

arch/x86/kernel/head_32.S

+14 −29

Original line number	Diff line number	Diff line
		@@ -41,41 +41,28 @@
		* This is how much memory *in addition to the memory covered up to
		* and including _end* we need mapped initially.
		* We need:
		* - one bit for each possible page, but only in low memory, which means
		* 2^32/4096/8 = 128K worst case (4G/4G split.)
		* - enough space to map all low memory, which means
		* (2^32/4096) / 1024 pages (worst case, non PAE)
		* (2^32/4096) / 512 + 4 pages (worst case for PAE)
		* - a few pages for allocator use before the kernel pagetable has
		* been set up
		* (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE)
		* (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE)
		*
		* Modulo rounding, each megabyte assigned here requires a kilobyte of
		* memory, which is currently unreclaimed.
		*
		* This should be a multiple of a page.
		*
		* KERNEL_IMAGE_SIZE should be greater than pa(_end)
		* and small than max_low_pfn, otherwise will waste some page table entries
		*/
		LOW_PAGES = (KERNEL_IMAGE_SIZE + PAGE_SIZE_asm - 1)>>PAGE_SHIFT

		/*
		* To preserve the DMA pool in PAGEALLOC kernels, we'll allocate
		* pagetables from above the 16MB DMA limit, so we'll have to set
		* up pagetables 16MB more (worst-case):
		*/
		#ifdef CONFIG_DEBUG_PAGEALLOC
		LOW_PAGES = LOW_PAGES + 0x1000000
		#endif

		#if PTRS_PER_PMD > 1
		PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PMD) + PTRS_PER_PGD
		#else
		PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PGD)
		#endif
		BOOTBITMAP_SIZE = LOW_PAGES / 8
		ALLOCATOR_SLOP = 4

		INIT_MAP_BEYOND_END = BOOTBITMAP_SIZE + (PAGE_TABLE_SIZE + ALLOCATOR_SLOP)*PAGE_SIZE_asm

		RESERVE_BRK(pagetables, PAGE_TABLE_SIZE * PAGE_SIZE)
		INIT_MAP_SIZE = (PAGE_TABLE_SIZE + ALLOCATOR_SLOP) * PAGE_SIZE_asm
		RESERVE_BRK(pagetables, INIT_MAP_SIZE)

		/*
		* 32-bit kernel entrypoint; only used by the boot CPU. On entry,
		@@ -168,10 +155,10 @@ num_subarch_entries = (. - subarch_entries) / 4

		/*
		* Initialize page tables. This creates a PDE and a set of page
		* tables, which are located immediately beyond _end. The variable
		* tables, which are located immediately beyond __brk_base. The variable
		* _brk_end is set up to point to the first "safe" location.
		* Mappings are created both at virtual address 0 (identity mapping)
		* and PAGE_OFFSET for up to _end+sizeof(page tables)+INIT_MAP_BEYOND_END.
		* and PAGE_OFFSET for up to _end.
		*
		* Note that the stack is not yet set up!
		*/
		@@ -210,10 +197,9 @@ default_entry:
		loop 11b

		/*
		* End condition: we must map up to and including INIT_MAP_BEYOND_END
		* bytes beyond the end of our own page tables.
		* End condition: we must map up to the end.
		*/
		leal (INIT_MAP_BEYOND_END+PTE_IDENT_ATTR)(%edi),%ebp
		movl $pa(_end) + PTE_IDENT_ATTR, %ebp
		cmpl %ebp,%eax
		jb 10b
		1:
		@@ -243,11 +229,9 @@ page_pde_offset = (__PAGE_OFFSET >> 20);
		addl $0x1000,%eax
		loop 11b
		/*
		* End condition: we must map up to and including INIT_MAP_BEYOND_END
		* bytes beyond the end of our own page tables; the +0x007 is
		* the attribute bits
		* End condition: we must map up to end
		*/
		leal (INIT_MAP_BEYOND_END+PTE_IDENT_ATTR)(%edi),%ebp
		movl $pa(_end) + PTE_IDENT_ATTR, %ebp
		cmpl %ebp,%eax
		jb 10b
		addl $__PAGE_OFFSET, %edi
		@@ -638,6 +622,7 @@ swapper_pg_fixmap:
		.fill 1024,4,0
		ENTRY(empty_zero_page)
		.fill 4096,1,0

		/*
		* This starts the data section.
		*/

arch/x86/kernel/vmlinux_32.lds.S

+6 −0

Original line number	Diff line number	Diff line
		@@ -210,6 +210,12 @@ SECTIONS
		DWARF_DEBUG
		}

		/*
		* Build-time check on the image size:
		*/
		ASSERT((_end - LOAD_OFFSET <= KERNEL_IMAGE_SIZE),
		"kernel image bigger than KERNEL_IMAGE_SIZE")

		#ifdef CONFIG_KEXEC
		/* Link time checks */
		#include <asm/kexec.h>

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