From 44c5429a92a99d5f29c59a2bc217206709bccf35 Mon Sep 17 00:00:00 2001
From: Arjan van de Ven <arjan@infradead.org>
Date: Fri, 6 Jan 2006 00:12:04 -0800
Subject: [PATCH] --- yaml --- r: 16383 b: refs/heads/master c:
 67df197b1a07944c2e0e40ded3d4fd07d108e110 h: refs/heads/master i:   16381:
 8dfeca6f36668a31c850b2271608dc5998695a09   16379:
 a6d0973f0178987ecefcfe9cc3e36d32850c9a21   16375:
 2512522d49c0b42338cbc59f38083b81de0a3ed8   16367:
 2d5e057e812be99caf664003b3650eafb580e8c4   16351:
 eb75807eeac19a8f8c38f54ae02cc347008e4928   16319:
 bd25bb0055ae5ea7696f0a823bb8cfc766c102ab   16255:
 b69fd24aa9cbdb9b4815ace69380b43f323a2f12   16127:
 b6a4d61f841173846125f140d6c64744b95b63e1   15871:
 96b097471a5efccf41a91bd7ac0dc96c72b4d8c2   15359:
 dfd735e907a988f2f98c486fed98600a1869eb1d   14335:
 17c11290a85606a80545b40505262233069d4eee   12287:
 bd96c6237ab7f45251157c831d903d96fdddbcc0   8191:
 08f97ba64c3a1c2ff8d3b8828ffa9cf9073395bf v: v3

---
 [refs]                                |  2 +-
 trunk/arch/x86_64/Kconfig.debug       | 10 ++++++++++
 trunk/arch/x86_64/mm/init.c           | 23 +++++++++++++++++++++++
 trunk/include/asm-x86_64/cacheflush.h |  4 ++++
 4 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index f8a055346c36..8cb6f4637da7 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c728252c7a072628bd3932ff87943d1e12423359
+refs/heads/master: 67df197b1a07944c2e0e40ded3d4fd07d108e110
diff --git a/trunk/arch/x86_64/Kconfig.debug b/trunk/arch/x86_64/Kconfig.debug
index e2c6e64a85ec..fcb06a50fdd2 100644
--- a/trunk/arch/x86_64/Kconfig.debug
+++ b/trunk/arch/x86_64/Kconfig.debug
@@ -9,6 +9,16 @@ config INIT_DEBUG
 	  Fill __init and __initdata at the end of boot. This helps debugging
 	  illegal uses of __init and __initdata after initialization.
 
+config DEBUG_RODATA
+       bool "Write protect kernel read-only data structures"
+       depends on DEBUG_KERNEL
+       help
+	 Mark the kernel read-only data as write-protected in the pagetables,
+	 in order to catch accidental (and incorrect) writes to such const data.
+	 This option may have a slight performance impact because a portion
+	 of the kernel code won't be covered by a 2MB TLB anymore.
+	 If in doubt, say "N".
+
 config IOMMU_DEBUG
        depends on GART_IOMMU && DEBUG_KERNEL
        bool "Enable IOMMU debugging"
diff --git a/trunk/arch/x86_64/mm/init.c b/trunk/arch/x86_64/mm/init.c
index c016dfe84784..1faae5fc1c01 100644
--- a/trunk/arch/x86_64/mm/init.c
+++ b/trunk/arch/x86_64/mm/init.c
@@ -498,6 +498,29 @@ void free_initmem(void)
 	printk ("Freeing unused kernel memory: %luk freed\n", (__init_end - __init_begin) >> 10);
 }
 
+#ifdef CONFIG_DEBUG_RODATA
+
+extern char __start_rodata, __end_rodata;
+void mark_rodata_ro(void)
+{
+	unsigned long addr = (unsigned long)&__start_rodata;
+
+	for (; addr < (unsigned long)&__end_rodata; addr += PAGE_SIZE)
+		change_page_attr_addr(addr, 1, PAGE_KERNEL_RO);
+
+	printk ("Write protecting the kernel read-only data: %luk\n",
+			(&__end_rodata - &__start_rodata) >> 10);
+
+	/*
+	 * change_page_attr_addr() requires a global_flush_tlb() call after it.
+	 * We do this after the printk so that if something went wrong in the
+	 * change, the printk gets out at least to give a better debug hint
+	 * of who is the culprit.
+	 */
+	global_flush_tlb();
+}
+#endif
+
 #ifdef CONFIG_BLK_DEV_INITRD
 void free_initrd_mem(unsigned long start, unsigned long end)
 {
diff --git a/trunk/include/asm-x86_64/cacheflush.h b/trunk/include/asm-x86_64/cacheflush.h
index b3189fb229d1..d32f7f58752a 100644
--- a/trunk/include/asm-x86_64/cacheflush.h
+++ b/trunk/include/asm-x86_64/cacheflush.h
@@ -27,4 +27,8 @@ void global_flush_tlb(void);
 int change_page_attr(struct page *page, int numpages, pgprot_t prot);
 int change_page_attr_addr(unsigned long addr, int numpages, pgprot_t prot);
 
+#ifdef CONFIG_DEBUG_RODATA
+void mark_rodata_ro(void);
+#endif
+
 #endif /* _X8664_CACHEFLUSH_H */