Messages in this thread Patch in this message | | | From | Matt Fleming <> | Subject | [PATCH 1/6] x86/efi: PFN_ALIGN() _text and _end when calculating number of pages | Date | Mon, 23 Nov 2015 13:33:09 +0000 |
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While _text is currently aligned to PAGE_SIZE in the vmlinux linker script because it's based on CONFIG_PHYSICAL_ALIGN, it's always better to be explicit about these things to be sure no alignment bugs are lurking. There's no analogous enforcement for _end.
Dave provided an example of why the 'npages' calculation is wrong,
"Just for fun, imagine that _end=0xfff and _text=0x1001. npages would be 0."
Use PFN_ALIGN() to be sure the calculation is correctly aligned to PAGE_SIZE.
Reported-by: Dave Hansen <dave.hansen@intel.com> Reported-by: Thomas Gleixner <tglx@linutronix.de> Cc: Borislav Petkov <bp@alien8.de> Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> --- arch/x86/platform/efi/efi_64.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index a0ac0f9c307f..3a90eb72d153 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -183,7 +183,7 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages) efi_scratch.phys_stack = virt_to_phys(page_address(page)); efi_scratch.phys_stack += PAGE_SIZE; /* stack grows down */ - npages = (_end - _text) >> PAGE_SHIFT; + npages = (PFN_ALIGN(_end) - PFN_ALIGN(_text)) >> PAGE_SHIFT; text = __pa(_text); if (kernel_map_pages_in_pgd(pgd, text >> PAGE_SHIFT, text, npages, 0)) { -- 2.6.2
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