Messages in this thread | | | Date | Mon, 9 Nov 2015 13:51:53 -0600 | From | Josh Poimboeuf <> | Subject | Re: [PATCH 4/4] module: clean up RO/NX handling. |
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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?
> } > > -static void set_section_ro_nx(void *base, > - unsigned long text_size, > - unsigned long ro_size, > - unsigned long total_size, > - int (*set_ro)(unsigned long start, int num_pages), > - int (*set_nx)(unsigned long start, int num_pages)) > +static void frob_rodata(const struct module_layout *layout, > + int (*set_memory)(unsigned long start, int num_pages)) > { > - /* begin and end PFNs of the current subsection */ > - unsigned long begin_pfn; > - unsigned long end_pfn; > - > - /* > - * Set RO for module text and RO-data: > - * - Always protect first page. > - * - Do not protect last partial page. > - */ > - if (ro_size > 0) > - set_page_attributes(base, base + ro_size, set_ro); > + BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1)); > + BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1)); > + BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1)); > + set_memory((unsigned long)layout->base + layout->text_size, > + (layout->ro_size - layout->text_size) >> PAGE_SHIFT); > +}
Same here, what if ro_size == text_size (no rodata)?
> > - /* > - * Set NX permissions for module data: > - * - Do not protect first partial page. > - * - Always protect last page. > - */ > - if (total_size > text_size) { > - begin_pfn = PFN_UP((unsigned long)base + text_size); > - end_pfn = PFN_UP((unsigned long)base + total_size); > - if (end_pfn > begin_pfn) > - set_nx(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn); > - } > +static void frob_writable_data(const struct module_layout *layout, > + int (*set_memory)(unsigned long start, int num_pages)) > +{ > + BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1)); > + BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1)); > + BUG_ON((unsigned long)layout->size & (PAGE_SIZE-1)); > + set_memory((unsigned long)layout->base + layout->ro_size, > + (layout->size - layout->ro_size) >> PAGE_SHIFT); > }
Ditto for size == ro_size (no writable data).
-- Josh
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