Interface to use for code patching : makes sure the page is writable
between calls to kernel_text_mark_rw() and kernel_text_unmark().
Signed-off-by: Mathieu Desnoyers <[EMAIL PROTECTED]>
CC: Andi Kleen <[EMAIL PROTECTED]>
---
arch/x86_64/mm/init.c | 72 +++++++++++++++++++++++++++++-----------
include/asm-x86_64/cacheflush.h | 7 +++
2 files changed, 60 insertions(+), 19 deletions(-)
Index: linux-2.6-lttng/arch/x86_64/mm/init.c
===================================================================
--- linux-2.6-lttng.orig/arch/x86_64/mm/init.c 2007-08-12 09:33:55.000000000
-0400
+++ linux-2.6-lttng/arch/x86_64/mm/init.c 2007-08-12 10:04:13.000000000
-0400
@@ -103,7 +103,7 @@ static __init void *spp_getpage(void)
{
void *ptr;
if (after_bootmem)
- ptr = (void *) get_zeroed_page(GFP_ATOMIC);
+ ptr = (void *) get_zeroed_page(GFP_KERNEL);
else
ptr = alloc_bootmem_pages(PAGE_SIZE);
if (!ptr || ((unsigned long)ptr & ~PAGE_MASK))
@@ -598,25 +598,11 @@ void free_initmem(void)
void mark_rodata_ro(void)
{
- unsigned long start = (unsigned long)_stext, end;
+ unsigned long start = PFN_ALIGN(_stext);
+ unsigned long end = PFN_ALIGN(__end_rodata);
-#ifdef CONFIG_HOTPLUG_CPU
- /* It must still be possible to apply SMP alternatives. */
- if (num_possible_cpus() > 1)
- start = (unsigned long)_etext;
-#endif
-
-#ifdef CONFIG_KPROBES
- start = (unsigned long)__start_rodata;
-#endif
-
- end = (unsigned long)__end_rodata;
- start = (start + PAGE_SIZE - 1) & PAGE_MASK;
- end &= PAGE_MASK;
- if (end <= start)
- return;
-
- change_page_attr_addr(start, (end - start) >> PAGE_SHIFT,
PAGE_KERNEL_RO);
+ 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);
@@ -629,6 +615,54 @@ void mark_rodata_ro(void)
*/
global_flush_tlb();
}
+
+/**
+ * kernel_text_mark_rw - Change kernel core text flags to RW
+ * @address: location of the code
+ * @len: size of code to mark
+ *
+ * Change kernel text flags to RW. Useful for code patching.
+ */
+
+void kernel_text_mark_rw(unsigned long address, size_t len)
+{
+ if (address >= PFN_ALIGN(_text)
+ && (address + len) <= PFN_ALIGN(_etext)) {
+ unsigned long nr_pages;
+ nr_pages = ((address + len) >> PAGE_SHIFT)
+ - (address >> PAGE_SHIFT) + 1;
+ change_page_attr(virt_to_page(address), nr_pages,
+ PAGE_KERNEL_EXEC);
+ mb();
+ global_flush_tlb();
+ mb();
+ }
+}
+EXPORT_SYMBOL_GPL(kernel_text_mark_rw);
+
+/**
+ * kernel_text_unmark - Unmap a kernel text rw mapping.
+ * @address: location of the mapping
+ * @len: size of code to mark
+ *
+ * Remove RW flag from kernel text.
+ */
+
+void kernel_text_unmark(unsigned long address, size_t len)
+{
+ if (address >= PFN_ALIGN(_text)
+ && (address + len) <= PFN_ALIGN(_etext)) {
+ unsigned long nr_pages;
+ nr_pages = ((address + len) >> PAGE_SHIFT)
+ - (address >> PAGE_SHIFT) + 1;
+ mb();
+ change_page_attr(virt_to_page(address), nr_pages,
+ PAGE_KERNEL_RO);
+ mb();
+ global_flush_tlb();
+ }
+}
+EXPORT_SYMBOL_GPL(kernel_text_unmark);
#endif
#ifdef CONFIG_BLK_DEV_INITRD
Index: linux-2.6-lttng/include/asm-x86_64/cacheflush.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-x86_64/cacheflush.h 2007-08-12
09:33:55.000000000 -0400
+++ linux-2.6-lttng/include/asm-x86_64/cacheflush.h 2007-08-12
09:34:07.000000000 -0400
@@ -31,6 +31,13 @@ void clflush_cache_range(void *addr, int
#ifdef CONFIG_DEBUG_RODATA
void mark_rodata_ro(void);
+
+/* mark kernel text pages writable */
+extern void kernel_text_mark_rw(unsigned long address, size_t len);
+extern void kernel_text_unmark(unsigned long address, size_t len);
+#else
+void kernel_text_mark_rw(unsigned long address, size_t len) { }
+void kernel_text_unmark(unsigned long address, size_t len) { }
#endif
#endif /* _X8664_CACHEFLUSH_H */
--
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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