diff options
| -rw-r--r-- | arch/x86_64/Kconfig.debug | 10 | ||||
| -rw-r--r-- | arch/x86_64/mm/init.c | 23 | ||||
| -rw-r--r-- | include/asm-x86_64/cacheflush.h | 4 |
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 */ |