On Tue, 3 Nov 2015, Josh Poimboeuf wrote:
> Subject: [PATCH] livepatch: Cleanup page permission changes
>
> Calling set_memory_rw() and set_memory_ro() for every iteration of the
> loop in klp_write_object_relocations() is messy and inefficient. Change
> all the RO pages to RW before the loop and convert them back to RO after
> the loop.
Generally speaking, I like the patch and would like to have this in 4.4
still (if worse becomes worst and we don't make it in time for merge
window, this still qualifies for -rc bugfix).
> Suggested-by: Miroslav Benes <mbe...@suse.cz>
> Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
> ---
> arch/x86/kernel/livepatch.c | 25 ++-----------------------
> kernel/livepatch/core.c | 42 +++++++++++++++++++++++++++++++++++++-----
> 2 files changed, 39 insertions(+), 28 deletions(-)
>
> diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c
> index d1d35cc..1062eff 100644
> --- a/arch/x86/kernel/livepatch.c
> +++ b/arch/x86/kernel/livepatch.c
> @@ -20,8 +20,6 @@
>
> #include <linux/module.h>
> #include <linux/uaccess.h>
> -#include <asm/cacheflush.h>
> -#include <asm/page_types.h>
> #include <asm/elf.h>
> #include <asm/livepatch.h>
>
> @@ -38,8 +36,7 @@
> int klp_write_module_reloc(struct module *mod, unsigned long type,
> unsigned long loc, unsigned long value)
> {
> - int ret, numpages, size = 4;
> - bool readonly;
> + int size = 4;
BTW I don't see a reason to have 'size' signed here.
[ ... snip ... [
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -28,6 +28,7 @@
> #include <linux/list.h>
> #include <linux/kallsyms.h>
> #include <linux/livepatch.h>
> +#include <asm/cacheflush.h>
>
> /**
> * struct klp_ops - structure for tracking registered ftrace ops structs
> @@ -131,6 +132,33 @@ static bool klp_initialized(void)
> return !!klp_root_kobj;
> }
>
> +#ifdef CONFIG_DEBUG_SET_MODULE_RONX
> +static void set_page_attributes(void *start, void *end,
> + int (*set)(unsigned long start, int num_pages))
> +{
> + unsigned long begin_pfn = PFN_DOWN((unsigned long)start);
> + unsigned long end_pfn = PFN_DOWN((unsigned long)end);
> +
> + if (end_pfn > begin_pfn)
> + set(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn);
> +}
> +static void set_module_ro_rw(struct module *mod)
> +{
> + set_page_attributes(mod->module_core,
> + mod->module_core + mod->core_ro_size,
> + set_memory_rw);
> +}
> +static void set_module_ro_ro(struct module *mod)
Honestly, I find both the function names above horrible and not really
self-explanatory (especially the _ro_ro variant). At least comment,
explaining what they are actually doing, or picking up a better name,
would make the code much more self-explanatory in my eyes.
Thanks,
--
Jiri Kosina
SUSE Labs
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