linux-kernel - [PATCH v4 1/6] x86: Page align _end to avoid pfn conversion bugs

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Date:	Fri, 27 Nov 2015 21:09:30 +0000
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H . Peter Anvin" <hpa@...or.com>
Cc:	Toshi Kani <toshi.kani@...com>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Borislav Petkov <bp@...en8.de>
Subject: [PATCH v4 1/6] x86: Page align _end to avoid pfn conversion bugs

Ingo noted that if we can guarantee _end is aligned to PAGE_SIZE we
can automatically avoid bugs along the lines of,

	size = _end - _text >> PAGE_SHIFT

which is missing a call to PFN_ALIGN(). The EFI mixed mode contains
this bug, for example.

_text is already aligned to PAGE_SIZE through the use of
LOAD_PHYSICAL_ADDR, and the BSS and BRK sections are explicitly
aligned in the linker script, so it makes sense to align _end to
match.

Reported-by: Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: "H . Peter Anvin" <hpa@...or.com>
Cc: Toshi Kani <toshi.kani@...com>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Borislav Petkov <bp@...en8.de>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
---
 arch/x86/kernel/vmlinux.lds.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 74e4bf11f562..4f1994257a18 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -325,6 +325,7 @@ SECTIONS
 		__brk_limit = .;
 	}
 
+	. = ALIGN(PAGE_SIZE);
 	_end = .;
 
         STABS_DEBUG
-- 
2.6.2

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