linux-kernel - [PATCH] Text Edit Lock - x86_64 Use kernel_tex_is

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Date:	Sat, 14 Jul 2007 16:16:54 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Cc:	Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>
Subject: [PATCH] Text Edit Lock - x86_64 Use kernel_tex_is_ro

Text Edit Lock - x86_64 Use kernel_tex_is_ro

It makes more sense to use the kernel_text_is_ro variable instead of
duplicating it.

And since we do not plan to call kernel_text_mark_rw()/kernel_text_unmark()
in the middle of mark_rodata_ro (we are still at boot time), there is no
need to wait until after global_flush_tlb() mark the rodata.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
CC: Andi Kleen <andi@...stfloor.org>
CC: Christoph Hellwig <hch@...radead.org>
---
 arch/x86_64/mm/init.c |   12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

Index: linux-2.6-lttng/arch/x86_64/mm/init.c
===================================================================
--- linux-2.6-lttng.orig/arch/x86_64/mm/init.c	2007-07-14 16:10:21.000000000 -0400
+++ linux-2.6-lttng/arch/x86_64/mm/init.c	2007-07-14 16:11:47.000000000 -0400
@@ -56,10 +56,6 @@ static unsigned long dma_reserve __initd
 
 DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
 
-#ifdef CONFIG_DEBUG_RODATA
-static int rodata_marked;
-#endif
-
 /*
  * NOTE: pagetable_init alloc all the fixmap pagetables contiguous on the
  * physical space so we can cache the place of the first one and move
@@ -605,13 +601,12 @@ void mark_rodata_ro(void)
 	unsigned long start = PFN_ALIGN(_stext);
 	unsigned long end = PFN_ALIGN(__end_rodata);
 
-	kernel_text_is_ro = 1;
-
 	change_page_attr_addr(start, (end - start) >> PAGE_SHIFT,
 				PAGE_KERNEL_RO);
 
 	printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
 	       (end - start) >> 10);
+	kernel_text_is_ro = 1;
 
 	/*
 	 * change_page_attr_addr() requires a global_flush_tlb() call after it.
@@ -620,7 +615,6 @@ void mark_rodata_ro(void)
 	 * of who is the culprit.
 	 */
 	global_flush_tlb();
-	rodata_marked = 1;
 }
 
 /*
@@ -628,7 +622,7 @@ void mark_rodata_ro(void)
  */
 void kernel_text_mark_rw(unsigned long address, size_t len)
 {
-	if (rodata_marked && address >= PFN_ALIGN(_text)
+	if (kernel_text_is_ro && address >= PFN_ALIGN(_text)
 			&& (address + len) <= PFN_ALIGN(_etext)) {
 		unsigned long nr_pages;
 		nr_pages = ((address + len) >> PAGE_SHIFT)
@@ -644,7 +638,7 @@ EXPORT_SYMBOL_GPL(kernel_text_mark_rw);
 
 void kernel_text_unmark(unsigned long address, size_t len)
 {
-	if (rodata_marked && address >= PFN_ALIGN(_text)
+	if (kernel_text_is_ro && address >= PFN_ALIGN(_text)
 			&& (address + len) <= PFN_ALIGN(_etext)) {
 		unsigned long nr_pages;
 		nr_pages = ((address + len) >> PAGE_SHIFT)

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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