Messages in this thread | | | Date | Mon, 9 Nov 2015 22:27:36 -0600 | From | Josh Poimboeuf <> | Subject | Re: [PATCH 4/4] module: clean up RO/NX handling. |
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On Tue, Nov 10, 2015 at 12:27:34PM +1030, Rusty Russell wrote: > 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.
However, the frob functions are also used for init sections.
A search on my Fedora system's modules for .init.* sections shows that most modules don't have .init.rodata and .init.data, and some modules don't even have .init.text.
-- Josh
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