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 CC: Andi Kleen --- 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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/