On Thu, Apr 03, 2014 at 07:15:19PM -0700, Kees Cook wrote:
> diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
> index 34e56647dcee..4ae343c1e2a3 100644
> --- a/arch/arm/kernel/ftrace.c
> +++ b/arch/arm/kernel/ftrace.c
> @@ -14,6 +14,7 @@
>
> #include <linux/ftrace.h>
> #include <linux/uaccess.h>
> +#include <linux/stop_machine.h>
>
> #include <asm/cacheflush.h>
> #include <asm/opcodes.h>
> @@ -34,6 +35,22 @@
>
> #define OLD_NOP 0xe1a00000 /* mov r0, r0 */
>
> +static int __ftrace_modify_code(void *data)
This is in the CONFIG_OLD_MCOUNT ifdef, but should be in the outer ifdef
(CONFIG_DYNAMIC_FTRACE) instead, otherwise it will not get enabled for
for example Thumb-2 kernels. This was wrong in my example patch too.
> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> index 8539eb2a01ad..3baac4ad165f 100644
> --- a/arch/arm/mm/init.c
> +++ b/arch/arm/mm/init.c
> @@ -681,30 +716,52 @@ static inline bool arch_has_strict_perms(void)
> return true;
> }
>
> +#define set_section_perms(perms, field) {
> \
> + size_t i; \
> + unsigned long addr; \
> + \
> + if (!arch_has_strict_perms()) \
> + return; \
> + \
> + for (i = 0; i < ARRAY_SIZE(perms); i++) { \
> + if (!IS_ALIGNED(perms[i].start, SECTION_SIZE) || \
> + !IS_ALIGNED(perms[i].end, SECTION_SIZE)) { \
> + pr_err("BUG: section %lx-%lx not aligned to %lx\n", \
> + perms[i].start, perms[i].end, \
> + SECTION_SIZE); \
> + continue; \
> + } \
> + \
> + for (addr = perms[i].start; \
> + addr < perms[i].end; \
> + addr += SECTION_SIZE) \
> + section_update(addr, perms[i].mask, \
> + perms[i].field); \
> + } \
> +}
> +
> static inline void fix_kernmem_perms(void)
> {
> - unsigned long addr;
> - unsigned int i;
> + set_section_perms(nx_perms, prot);
> +}
>
> - if (!arch_has_strict_perms())
> - return;
> +#ifdef CONFIG_DEBUG_RODATA
> +void mark_rodata_ro(void)
> +{
> + set_section_perms(ro_perms, prot);
> +}
>
> - for (i = 0; i < ARRAY_SIZE(section_perms); i++) {
> - if (!IS_ALIGNED(section_perms[i].start, SECTION_SIZE) ||
> - !IS_ALIGNED(section_perms[i].end, SECTION_SIZE)) {
> - pr_err("BUG: section %lx-%lx not aligned to %lx\n",
> - section_perms[i].start, section_perms[i].end,
> - SECTION_SIZE);
> - continue;
> - }
> +void set_kernel_text_rw(void)
> +{
> + set_section_perms(ro_perms, clear);
> +}
You need a TLB flush. I had a flush_tlb_all() in my example patch,
http://lists.infradead.org/pipermail/linux-arm-kernel/2014-April/244335.html,
but the following is probably nicer (on top of this patch):
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 9bea524..a92c45a 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -741,6 +741,8 @@ static inline bool arch_has_strict_perms(void)
addr += SECTION_SIZE) \
section_update(addr, perms[i].mask, \
perms[i].field); \
+ \
+ flush_tlb_kernel_range(perms[i].start, perms[i].end); \
} \
}
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