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 --- arch/i386/mm/init.c | 60 ++++++++++++++++++++++++++++++++---------- include/asm-i386/cacheflush.h | 9 ++++++ 2 files changed, 56 insertions(+), 13 deletions(-) Index: linux-2.6-lttng/arch/i386/mm/init.c =================================================================== --- linux-2.6-lttng.orig/arch/i386/mm/init.c 2007-07-13 17:01:24.000000000 -0400 +++ linux-2.6-lttng/arch/i386/mm/init.c 2007-07-13 17:02:31.000000000 -0400 @@ -31,6 +31,7 @@ #include #include #include +#include #include #include @@ -53,6 +54,10 @@ static int noinline do_test_wp_bit(void); +#ifdef CONFIG_DEBUG_RODATA +static int rodata_marked; +#endif + /* * Creates a middle page table and puts a pointer to it in the * given global directory entry. This only returns the gd entry @@ -796,24 +801,16 @@ } #ifdef CONFIG_DEBUG_RODATA - void mark_rodata_ro(void) { unsigned long start = PFN_ALIGN(_text); unsigned long size = PFN_ALIGN(_etext) - start; -#ifndef CONFIG_KPROBES -#ifdef CONFIG_HOTPLUG_CPU - /* It must still be possible to apply SMP alternatives. */ - if (num_possible_cpus() <= 1) -#endif - { - change_page_attr(virt_to_page(start), - size >> PAGE_SHIFT, PAGE_KERNEL_RX); - printk("Write protecting the kernel text: %luk\n", size >> 10); - kernel_text_is_ro = 1; - } -#endif + change_page_attr(virt_to_page(start), + size >> PAGE_SHIFT, PAGE_KERNEL_RX); + printk("Write protecting the kernel text: %luk\n", size >> 10); + kernel_text_is_ro = 1; + start += size; size = (unsigned long)__end_rodata - start; change_page_attr(virt_to_page(start), @@ -828,9 +825,46 @@ * of who is the culprit. */ global_flush_tlb(); + rodata_marked = 1; +} + +/* + * Lock the kernel text for mutual write exclusion. + * Make sure the pages are writable. + */ +void __kprobes kernel_text_mark_rw(unsigned long address, size_t len) +{ + if (rodata_marked && 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); #endif +void __kprobes kernel_text_unmark(unsigned long address, size_t len) +{ + if (rodata_marked && 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_RX); + mb(); + global_flush_tlb(); + mb(); + } +} +EXPORT_SYMBOL_GPL(kernel_text_unmark); + void free_init_pages(char *what, unsigned long begin, unsigned long end) { unsigned long addr; Index: linux-2.6-lttng/include/asm-i386/cacheflush.h =================================================================== --- linux-2.6-lttng.orig/include/asm-i386/cacheflush.h 2007-07-13 17:01:24.000000000 -0400 +++ linux-2.6-lttng/include/asm-i386/cacheflush.h 2007-07-13 17:01:26.000000000 -0400 @@ -36,4 +36,13 @@ void mark_rodata_ro(void); #endif +#if defined(CONFIG_DEBUG_RODATA) +/* 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 /* _I386_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/