Messages in this thread | ![/](/images/icornerl.gif) | | From | Rusty Russell <> | Subject | Re: [PATCH 4/4] module: clean up RO/NX handling. | Date | Tue, 10 Nov 2015 12:27:34 +1030 |
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Josh Poimboeuf <jpoimboe@redhat.com> writes: > On Mon, Nov 09, 2015 at 02:53:57PM +1030, Rusty Russell wrote: > >> @@ -1858,74 +1849,75 @@ static void mod_sysfs_teardown(struct module *mod) >> /* >> * LKM RO/NX protection: protect module's text/ro-data >> * from modification and any data from execution. >> + * >> + * General layout of module is: >> + * [text] [read-only-data] [writable data] >> + * text_size -----^ ^ ^ >> + * ro_size ------------------------| | >> + * size -------------------------------------------| >> + * >> + * These values are always page-aligned (as is base) >> */ >> -void set_page_attributes(void *start, void *end, int (*set)(unsigned long start, int num_pages)) >> +static void frob_text(const struct module_layout *layout, >> + int (*set_memory)(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); >> + BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1)); >> + BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1)); >> + set_memory((unsigned long)layout->base, >> + layout->text_size >> PAGE_SHIFT); > > Should the set_memory() call be skipped if text_size is 0?
Not AFAICT. And in practice: 1) Every module on my system has a .text section. 2) Every module has a rodata section (.modinfo) 3) Every module on my system has a .data section.
So I think it would be a premature optimization.
Thanks, Rusty.
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