Interface to use for code patching : uses a mutex to insure mutual edit exclusion and makes sure the page is writable. Signed-off-by: Mathieu Desnoyers --- arch/i386/mm/init.c | 52 ++++++++++++++++++++++++++++++++++-------- include/asm-i386/cacheflush.h | 4 +++ 2 files changed, 47 insertions(+), 9 deletions(-) Index: linux-2.6-lttng/arch/i386/mm/init.c =================================================================== --- linux-2.6-lttng.orig/arch/i386/mm/init.c 2007-06-18 17:42:42.000000000 -0400 +++ linux-2.6-lttng/arch/i386/mm/init.c 2007-06-18 17:56:31.000000000 -0400 @@ -31,6 +31,7 @@ #include #include #include +#include #include #include @@ -52,6 +53,9 @@ static int noinline do_test_wp_bit(void); +/* Mutex protecting text section modification (dynamic code patching) */ +static DEFINE_MUTEX(text_mutex); + /* * Creates a middle page table and puts a pointer to it in the * given global directory entry. This only returns the gd entry @@ -800,15 +804,9 @@ unsigned long start = PFN_ALIGN(_text); unsigned long size = PFN_ALIGN(_etext) - start; -#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); - } + change_page_attr(virt_to_page(start), + size >> PAGE_SHIFT, PAGE_KERNEL_RX); + printk("Write protecting the kernel text: %luk\n", size >> 10); start += size; size = (unsigned long)__end_rodata - start; @@ -827,6 +825,42 @@ } #endif +/* + * Lock the kernel text for mutual write exclusion. + * Make sure the pages are writable. + */ +void kernel_text_lock(unsigned long address, size_t len) +{ + mutex_lock(&text_mutex); +#if defined(CONFIG_DEBUG_RODATA) + if (is_kernel_text(address) && is_kernel_text(address + len)) { + 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); + global_flush_tlb(); + } +#endif +} +EXPORT_SYMBOL_GPL(kernel_text_lock); + +void kernel_text_unlock(unsigned long address, size_t len) +{ +#if defined(CONFIG_DEBUG_RODATA) + if (is_kernel_text(address) && is_kernel_text(address + len)) { + 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); + global_flush_tlb(); + } +#endif + mutex_unlock(&text_mutex); +} +EXPORT_SYMBOL_GPL(kernel_text_unlock); + 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 2007-06-18 17:42:42.000000000 -0400 +++ linux-2.6-lttng/include/asm-i386/cacheflush.h 2007-06-18 17:42:44.000000000 -0400 @@ -36,4 +36,8 @@ void mark_rodata_ro(void); #endif +/* lock kernel text and mark pages writable */ +extern void kernel_text_lock(unsigned long address, size_t len); +extern void kernel_text_unlock(unsigned long address, size_t len); + #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/