linux-kernel - [PATCH] x86: leave _brk

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Date:	Fri, 27 Feb 2009 17:51:22 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: [PATCH] x86: leave _brk_end defined

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>

highmap_end_pfn refers to _brk_end, so leave it as normal data with a
meaningful value.  Make extend_brk() check for a NULL _brk_start to
look for uses after the brk memory has been reserved and locked down.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 arch/x86/kernel/setup.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 1d4fe19..11c4198 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -116,7 +116,7 @@ unsigned int boot_cpu_id __read_mostly;
 
 extern char __brk_base[];
 __initdata unsigned long _brk_start = (unsigned long)__brk_base;
-__initdata unsigned long _brk_end = (unsigned long)&__brk_base;
+unsigned long _brk_end = (unsigned long)&__brk_base;
 
 #ifdef CONFIG_X86_64
 int default_cpu_present_to_apicid(int mps_cpu)
@@ -337,6 +337,7 @@ void * __init extend_brk(size_t size, size_t align)
 	size_t mask = align - 1;
 	void *ret;
 
+	BUG_ON(_brk_start == 0);
 	BUG_ON(align & mask);
 
 	_brk_end = (_brk_end + mask) & ~mask;
@@ -352,7 +353,7 @@ static void __init reserve_brk(void)
 	if (_brk_end > _brk_start)
 		reserve_early(__pa(_brk_start), __pa(_brk_end), "BRK");
 
-	_brk_end = _brk_start = 0xdeadb00c + POISON_POINTER_DELTA;
+	_brk_start = 0;
 }
 
 static void __init reserve_initrd(void)
-- 
1.6.0.6

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