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x86/efi: Fix kernel panic when CONFIG_DEBUG_VIRTUAL is enabled 

When CONFIG_DEBUG_VIRTUAL is enabled, all accesses to __pa(address) are
monitored to see whether address falls in direct mapping or kernel text
mapping (see Documentation/x86/x86_64/mm.txt for details), if it does
not, the kernel panics. During 1:1 mapping of EFI runtime services we access
virtual addresses which are == physical addresses, thus the 1:1 mapping
and these addresses do not fall in either of the above two regions and
hence when passed as arguments to __pa() kernel panics as reported by
Dave Hansen here https://lkml.kernel.org/r/5462999A.7090706@intel.com.

So, before calling __pa() virtual addresses should be validated which
results in skipping call to split_page_count() and that should be fine
because it is used to keep track of everything *but* 1:1 mappings.

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Reported-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Glenn P Williamson <glenn.p.williamson@intel.com>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
This commit is contained in:
Sai Praneeth 2015-10-16 16:20:27 -07:00 committed by Matt Fleming
parent 0f96a99dab
commit 2c66e24d75
1 changed files with 6 additions and 3 deletions
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9
arch/x86/mm/pageattr.c
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@ -648,9 +648,12 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
for (i = 0; i < PTRS_PER_PTE; i++, pfn += pfninc)
set_pte(&pbase[i], pfn_pte(pfn, canon_pgprot(ref_prot)));
if (pfn_range_is_mapped(PFN_DOWN(__pa(address)),
PFN_DOWN(__pa(address)) + 1))
split_page_count(level);
if (virt_addr_valid(address)) {
unsigned long pfn = PFN_DOWN(__pa(address));
if (pfn_range_is_mapped(pfn, pfn + 1))
split_page_count(level);
}
/*
* Install the new, split up pagetable.