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authorArjan van de Ven <arjan@infradead.org>2006-01-06 00:12:04 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-06 08:33:36 -0800
commit67df197b1a07944c2e0e40ded3d4fd07d108e110 (patch)
treeb29534a27b2c18e64c6b3d4cdc149de8978e38ba
parentc728252c7a072628bd3932ff87943d1e12423359 (diff)
[PATCH] x86/x86_64: mark rodata section read-only: x86-64 support
x86-64 specific parts to make the .rodata section read only Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/x86_64/Kconfig.debug10
-rw-r--r--arch/x86_64/mm/init.c23
-rw-r--r--include/asm-x86_64/cacheflush.h4
3 files changed, 37 insertions, 0 deletions
diff --git a/arch/x86_64/Kconfig.debug b/arch/x86_64/Kconfig.debug
index e2c6e64a85e..fcb06a50fdd 100644
--- a/arch/x86_64/Kconfig.debug
+++ b/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/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index c016dfe8478..1faae5fc1c0 100644
--- a/arch/x86_64/mm/init.c
+++ b/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/include/asm-x86_64/cacheflush.h b/include/asm-x86_64/cacheflush.h
index b3189fb229d..d32f7f58752 100644
--- a/include/asm-x86_64/cacheflush.h
+++ b/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 */