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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>
This commit is contained in:
Boris Ostrovsky
2016-12-08 11:44:31 -05:00
committed by Ingo Molnar
parent b4ed1d15b4
commit 1e620f9b23
3 changed files with 102 additions and 115 deletions
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62
arch/x86/kernel/head32.c
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@@ -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;
}