linux-kernel - [tip:x86/efi] x86/mm: Page align the '_end' symbol to avoid pfn conversion bugs

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Message-ID: <tip-21cdb6b568435738cc0b303b2b3b82742396310c@git.kernel.org>
Date:	Sun, 29 Nov 2015 01:03:44 -0800
From:	tip-bot for Matt Fleming <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	dave.hansen@...el.com, toshi.kani@...com, bp@...e.de,
	ard.biesheuvel@...aro.org, luto@...capital.net,
	dvlasenk@...hat.com, matt@...eblueprint.co.uk, hpa@...or.com,
	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	sai.praneeth.prakhya@...el.com, mingo@...nel.org,
	brgerst@...il.com, torvalds@...ux-foundation.org,
	peterz@...radead.org, bp@...en8.de
Subject: [tip:x86/efi] x86/mm: Page align the '_end'
  symbol to avoid pfn conversion bugs

Commit-ID:  21cdb6b568435738cc0b303b2b3b82742396310c
Gitweb:     http://git.kernel.org/tip/21cdb6b568435738cc0b303b2b3b82742396310c
Author:     Matt Fleming <matt@...eblueprint.co.uk>
AuthorDate: Fri, 27 Nov 2015 21:09:30 +0000
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sun, 29 Nov 2015 09:15:42 +0100

x86/mm: Page align the '_end' symbol 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>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
Acked-by: Borislav Petkov <bp@...e.de>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Toshi Kani <toshi.kani@...com>
Cc: linux-efi@...r.kernel.org
Link: http://lkml.kernel.org/r/1448658575-17029-2-git-send-email-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 74e4bf1..4f19942 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
--
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