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x86/boot/32: Convert the 32-bit pgtable setup code from assembly to C
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The new Xen PVH entry point requires page tables to be setup by the
kernel since it is entered with paging disabled.

Pull the common code out of head_32.S so that mk_early_pgtbl_32() can be
invoked from both the new Xen entry point and the existing startup_32()
code.

Convert resulting common code to C.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: matt@codeblueprint.co.uk
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1481215471-9639-1-git-send-email-boris.ostrovsky@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Boris Ostrovsky authored and Ingo Molnar committed Jan 6, 2017
1 parent b4ed1d1 commit 1e620f9
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Showing 3 changed files with 101 additions and 114 deletions.
32 changes: 32 additions & 0 deletions arch/x86/include/asm/pgtable_32.h
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@ struct vm_area_struct;

extern pgd_t swapper_pg_dir[1024];
extern pgd_t initial_page_table[1024];
extern pmd_t initial_pg_pmd[];

static inline void pgtable_cache_init(void) { }
static inline void check_pgt_cache(void) { }
Expand Down Expand Up @@ -75,4 +76,35 @@ do { \
#define kern_addr_valid(kaddr) (0)
#endif

/*
* This is how much memory in addition to the memory covered up to
* and including _end we need mapped initially.
* We need:
* (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
*/
#if PTRS_PER_PMD > 1
#define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
#else
#define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
#endif

/*
* Number of possible pages in the lowmem region.
*
* We shift 2 by 31 instead of 1 by 32 to the left in order to avoid a
* gas warning about overflowing shift count when gas has been compiled
* with only a host target support using a 32-bit type for internal
* representation.
*/
#define LOWMEM_PAGES ((((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))

#endif /* _ASM_X86_PGTABLE_32_H */
62 changes: 62 additions & 0 deletions arch/x86/kernel/head32.c
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Original file line number Diff line number Diff line change
Expand Up @@ -49,3 +49,65 @@ asmlinkage __visible void __init i386_start_kernel(void)

start_kernel();
}

/*
* Initialize page tables. This creates a PDE and a set of page
* 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.
*
* In PAE mode initial_page_table is statically defined to contain
* enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
* entries). The identity mapping is handled by pointing two PGD entries
* to the first kernel PMD. Note the upper half of each PMD or PTE are
* always zero at this stage.
*/
void __init mk_early_pgtbl_32(void)
{
#ifdef __pa
#undef __pa
#endif
#define __pa(x) ((unsigned long)(x) - PAGE_OFFSET)
pte_t pte, *ptep;
int i;
unsigned long *ptr;
/* Enough space to fit pagetables for the low memory linear map */
const unsigned long limit = __pa(_end) +
(PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT);
#ifdef CONFIG_X86_PAE
pmd_t pl2, *pl2p = (pmd_t *)__pa(initial_pg_pmd);
#define SET_PL2(pl2, val) { (pl2).pmd = (val); }
#else
pgd_t pl2, *pl2p = (pgd_t *)__pa(initial_page_table);
#define SET_PL2(pl2, val) { (pl2).pgd = (val); }
#endif

ptep = (pte_t *)__pa(__brk_base);
pte.pte = PTE_IDENT_ATTR;

while ((pte.pte & PTE_PFN_MASK) < limit) {

SET_PL2(pl2, (unsigned long)ptep | PDE_IDENT_ATTR);
*pl2p = pl2;
#ifndef CONFIG_X86_PAE
/* Kernel PDE entry */
*(pl2p + ((PAGE_OFFSET >> PGDIR_SHIFT))) = pl2;
#endif
for (i = 0; i < PTRS_PER_PTE; i++) {
*ptep = pte;
pte.pte += PAGE_SIZE;
ptep++;
}

pl2p++;
}

ptr = (unsigned long *)__pa(&max_pfn_mapped);
/* Can't use pte_pfn() since it's a call with CONFIG_PARAVIRT */
*ptr = (pte.pte & PTE_PFN_MASK) >> PAGE_SHIFT;

ptr = (unsigned long *)__pa(&_brk_end);
*ptr = (unsigned long)ptep + PAGE_OFFSET;
}

121 changes: 7 additions & 114 deletions arch/x86/kernel/head_32.S
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#include <asm/nops.h>
#include <asm/bootparam.h>
#include <asm/export.h>
#include <asm/pgtable_32.h>

/* Physical address */
#define pa(X) ((X) - __PAGE_OFFSET)
Expand All @@ -41,43 +42,9 @@
#define X86_CAPABILITY new_cpu_data+CPUINFO_x86_capability
#define X86_VENDOR_ID new_cpu_data+CPUINFO_x86_vendor_id

/*
* This is how much memory in addition to the memory covered up to
* and including _end we need mapped initially.
* We need:
* (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
*/

#if PTRS_PER_PMD > 1
#define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
#else
#define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
#endif

#define SIZEOF_PTREGS 17*4

/*
* Number of possible pages in the lowmem region.
*
* We shift 2 by 31 instead of 1 by 32 to the left in order to avoid a
* gas warning about overflowing shift count when gas has been compiled
* with only a host target support using a 32-bit type for internal
* representation.
*/
LOWMEM_PAGES = (((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT)

/* Enough space to fit pagetables for the low memory linear map */
MAPPING_BEYOND_END = PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT

/*
* Worst-case size of the kernel mapping we need to make:
* a relocatable kernel can live anywhere in lowmem, so we need to be able
Expand Down Expand Up @@ -160,90 +127,15 @@ ENTRY(startup_32)
call load_ucode_bsp
#endif

/*
* Initialize page tables. This creates a PDE and a set of page
* 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.
*/
#ifdef CONFIG_X86_PAE

/*
* In PAE mode initial_page_table is statically defined to contain
* enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
* entries). The identity mapping is handled by pointing two PGD entries
* to the first kernel PMD.
*
* Note the upper half of each PMD or PTE are always zero at this stage.
*/

#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */

xorl %ebx,%ebx /* %ebx is kept at zero */

movl $pa(__brk_base), %edi
movl $pa(initial_pg_pmd), %edx
movl $PTE_IDENT_ATTR, %eax
10:
leal PDE_IDENT_ATTR(%edi),%ecx /* Create PMD entry */
movl %ecx,(%edx) /* Store PMD entry */
/* Upper half already zero */
addl $8,%edx
movl $512,%ecx
11:
stosl
xchgl %eax,%ebx
stosl
xchgl %eax,%ebx
addl $0x1000,%eax
loop 11b

/*
* End condition: we must map up to the end + MAPPING_BEYOND_END.
*/
movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
cmpl %ebp,%eax
jb 10b
1:
addl $__PAGE_OFFSET, %edi
movl %edi, pa(_brk_end)
shrl $12, %eax
movl %eax, pa(max_pfn_mapped)
/* Create early pagetables. */
call mk_early_pgtbl_32

/* Do early initialization of the fixmap area */
movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
#ifdef CONFIG_X86_PAE
#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
#else /* Not PAE */

page_pde_offset = (__PAGE_OFFSET >> 20);

movl $pa(__brk_base), %edi
movl $pa(initial_page_table), %edx
movl $PTE_IDENT_ATTR, %eax
10:
leal PDE_IDENT_ATTR(%edi),%ecx /* Create PDE entry */
movl %ecx,(%edx) /* Store identity PDE entry */
movl %ecx,page_pde_offset(%edx) /* Store kernel PDE entry */
addl $4,%edx
movl $1024, %ecx
11:
stosl
addl $0x1000,%eax
loop 11b
/*
* End condition: we must map up to the end + MAPPING_BEYOND_END.
*/
movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
cmpl %ebp,%eax
jb 10b
addl $__PAGE_OFFSET, %edi
movl %edi, pa(_brk_end)
shrl $12, %eax
movl %eax, pa(max_pfn_mapped)

/* Do early initialization of the fixmap area */
movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
#else
movl %eax,pa(initial_page_table+0xffc)
#endif

Expand Down Expand Up @@ -666,6 +558,7 @@ ENTRY(setup_once_ref)
__PAGE_ALIGNED_BSS
.align PAGE_SIZE
#ifdef CONFIG_X86_PAE
.globl initial_pg_pmd
initial_pg_pmd:
.fill 1024*KPMDS,4,0
#else
Expand Down

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