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modules: add ro_after_init support
Add ro_after_init support for modules by adding a new page-aligned section in the module layout (after rodata) for ro_after_init data and enabling RO protection for that section after module init runs. Signed-off-by: Jessica Yu <jeyu@redhat.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Jessica Yu
Rusty Russell
parent
bdc9f37355
commit
444d13ff10
4 changed files with 60 additions and 15 deletions
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@ -298,6 +298,8 @@ struct module_layout {
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unsigned int text_size;
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/* Size of RO section of the module (text+rodata) */
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unsigned int ro_size;
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/* Size of RO after init section */
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unsigned int ro_after_init_size;
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#ifdef CONFIG_MODULES_TREE_LOOKUP
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struct mod_tree_node mtn;
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@ -765,12 +767,12 @@ extern int module_sysfs_initialized;
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#ifdef CONFIG_DEBUG_SET_MODULE_RONX
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extern void set_all_modules_text_rw(void);
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extern void set_all_modules_text_ro(void);
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extern void module_enable_ro(const struct module *mod);
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extern void module_enable_ro(const struct module *mod, bool after_init);
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extern void module_disable_ro(const struct module *mod);
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#else
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static inline void set_all_modules_text_rw(void) { }
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static inline void set_all_modules_text_ro(void) { }
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static inline void module_enable_ro(const struct module *mod) { }
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static inline void module_enable_ro(const struct module *mod, bool after_init) { }
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static inline void module_disable_ro(const struct module *mod) { }
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#endif
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@ -286,6 +286,7 @@ typedef struct elf64_phdr {
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#define SHF_ALLOC 0x2
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#define SHF_EXECINSTR 0x4
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#define SHF_RELA_LIVEPATCH 0x00100000
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#define SHF_RO_AFTER_INIT 0x00200000
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#define SHF_MASKPROC 0xf0000000
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/* special section indexes */
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@ -309,7 +309,7 @@ static int klp_write_object_relocations(struct module *pmod,
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break;
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}
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module_enable_ro(pmod);
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module_enable_ro(pmod, true);
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return ret;
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}
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@ -1857,10 +1857,11 @@ static void mod_sysfs_teardown(struct module *mod)
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* from modification and any data from execution.
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*
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* General layout of module is:
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* [text] [read-only-data] [writable data]
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* text_size -----^ ^ ^
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* ro_size ------------------------| |
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* size -------------------------------------------|
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* [text] [read-only-data] [ro-after-init] [writable data]
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* text_size -----^ ^ ^ ^
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* ro_size ------------------------| | |
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* ro_after_init_size -----------------------------| |
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* size -----------------------------------------------------------|
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*
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* These values are always page-aligned (as is base)
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*/
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@ -1883,14 +1884,24 @@ static void frob_rodata(const struct module_layout *layout,
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(layout->ro_size - layout->text_size) >> PAGE_SHIFT);
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}
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static void frob_ro_after_init(const struct module_layout *layout,
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int (*set_memory)(unsigned long start, int num_pages))
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{
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BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
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BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));
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BUG_ON((unsigned long)layout->ro_after_init_size & (PAGE_SIZE-1));
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set_memory((unsigned long)layout->base + layout->ro_size,
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(layout->ro_after_init_size - layout->ro_size) >> PAGE_SHIFT);
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}
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static void frob_writable_data(const struct module_layout *layout,
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int (*set_memory)(unsigned long start, int num_pages))
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{
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BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
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BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));
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BUG_ON((unsigned long)layout->ro_after_init_size & (PAGE_SIZE-1));
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BUG_ON((unsigned long)layout->size & (PAGE_SIZE-1));
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set_memory((unsigned long)layout->base + layout->ro_size,
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(layout->size - layout->ro_size) >> PAGE_SHIFT);
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set_memory((unsigned long)layout->base + layout->ro_after_init_size,
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(layout->size - layout->ro_after_init_size) >> PAGE_SHIFT);
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}
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/* livepatching wants to disable read-only so it can frob module. */
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@ -1898,21 +1909,26 @@ void module_disable_ro(const struct module *mod)
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{
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frob_text(&mod->core_layout, set_memory_rw);
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frob_rodata(&mod->core_layout, set_memory_rw);
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frob_ro_after_init(&mod->core_layout, set_memory_rw);
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frob_text(&mod->init_layout, set_memory_rw);
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frob_rodata(&mod->init_layout, set_memory_rw);
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}
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void module_enable_ro(const struct module *mod)
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void module_enable_ro(const struct module *mod, bool after_init)
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{
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frob_text(&mod->core_layout, set_memory_ro);
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frob_rodata(&mod->core_layout, set_memory_ro);
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frob_text(&mod->init_layout, set_memory_ro);
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frob_rodata(&mod->init_layout, set_memory_ro);
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if (after_init)
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frob_ro_after_init(&mod->core_layout, set_memory_ro);
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}
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static void module_enable_nx(const struct module *mod)
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{
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frob_rodata(&mod->core_layout, set_memory_nx);
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frob_ro_after_init(&mod->core_layout, set_memory_nx);
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frob_writable_data(&mod->core_layout, set_memory_nx);
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frob_rodata(&mod->init_layout, set_memory_nx);
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frob_writable_data(&mod->init_layout, set_memory_nx);
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@ -1921,6 +1937,7 @@ static void module_enable_nx(const struct module *mod)
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static void module_disable_nx(const struct module *mod)
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{
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frob_rodata(&mod->core_layout, set_memory_x);
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frob_ro_after_init(&mod->core_layout, set_memory_x);
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frob_writable_data(&mod->core_layout, set_memory_x);
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frob_rodata(&mod->init_layout, set_memory_x);
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frob_writable_data(&mod->init_layout, set_memory_x);
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@ -1963,6 +1980,8 @@ static void disable_ro_nx(const struct module_layout *layout)
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frob_text(layout, set_memory_rw);
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frob_rodata(layout, set_memory_rw);
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frob_rodata(layout, set_memory_x);
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frob_ro_after_init(layout, set_memory_rw);
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frob_ro_after_init(layout, set_memory_x);
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frob_writable_data(layout, set_memory_x);
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}
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@ -2305,6 +2324,7 @@ static void layout_sections(struct module *mod, struct load_info *info)
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* finder in the two loops below */
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{ SHF_EXECINSTR | SHF_ALLOC, ARCH_SHF_SMALL },
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{ SHF_ALLOC, SHF_WRITE | ARCH_SHF_SMALL },
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{ SHF_RO_AFTER_INIT | SHF_ALLOC, ARCH_SHF_SMALL },
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{ SHF_WRITE | SHF_ALLOC, ARCH_SHF_SMALL },
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{ ARCH_SHF_SMALL | SHF_ALLOC, 0 }
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};
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@ -2336,7 +2356,11 @@ static void layout_sections(struct module *mod, struct load_info *info)
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mod->core_layout.size = debug_align(mod->core_layout.size);
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mod->core_layout.ro_size = mod->core_layout.size;
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break;
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case 3: /* whole core */
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case 2: /* RO after init */
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mod->core_layout.size = debug_align(mod->core_layout.size);
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mod->core_layout.ro_after_init_size = mod->core_layout.size;
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break;
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case 4: /* whole core */
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mod->core_layout.size = debug_align(mod->core_layout.size);
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break;
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}
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@ -2366,7 +2390,14 @@ static void layout_sections(struct module *mod, struct load_info *info)
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mod->init_layout.size = debug_align(mod->init_layout.size);
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mod->init_layout.ro_size = mod->init_layout.size;
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break;
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case 3: /* whole init */
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case 2:
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/*
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* RO after init doesn't apply to init_layout (only
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* core_layout), so it just takes the value of ro_size.
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*/
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mod->init_layout.ro_after_init_size = mod->init_layout.ro_size;
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break;
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case 4: /* whole init */
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mod->init_layout.size = debug_align(mod->init_layout.size);
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break;
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}
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@ -3193,6 +3224,7 @@ static struct module *layout_and_allocate(struct load_info *info, int flags)
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{
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/* Module within temporary copy. */
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struct module *mod;
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unsigned int ndx;
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int err;
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mod = setup_load_info(info, flags);
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@ -3215,6 +3247,15 @@ static struct module *layout_and_allocate(struct load_info *info, int flags)
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/* We will do a special allocation for per-cpu sections later. */
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info->sechdrs[info->index.pcpu].sh_flags &= ~(unsigned long)SHF_ALLOC;
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/*
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* Mark ro_after_init section with SHF_RO_AFTER_INIT so that
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* layout_sections() can put it in the right place.
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* Note: ro_after_init sections also have SHF_{WRITE,ALLOC} set.
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*/
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ndx = find_sec(info, ".data..ro_after_init");
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if (ndx)
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info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT;
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/* Determine total sizes, and put offsets in sh_entsize. For now
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this is done generically; there doesn't appear to be any
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special cases for the architectures. */
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@ -3381,12 +3422,14 @@ static noinline int do_init_module(struct module *mod)
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/* Switch to core kallsyms now init is done: kallsyms may be walking! */
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rcu_assign_pointer(mod->kallsyms, &mod->core_kallsyms);
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#endif
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module_enable_ro(mod, true);
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mod_tree_remove_init(mod);
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disable_ro_nx(&mod->init_layout);
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module_arch_freeing_init(mod);
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mod->init_layout.base = NULL;
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mod->init_layout.size = 0;
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mod->init_layout.ro_size = 0;
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mod->init_layout.ro_after_init_size = 0;
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mod->init_layout.text_size = 0;
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/*
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* We want to free module_init, but be aware that kallsyms may be
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@ -3478,8 +3521,7 @@ static int complete_formation(struct module *mod, struct load_info *info)
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/* This relies on module_mutex for list integrity. */
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module_bug_finalize(info->hdr, info->sechdrs, mod);
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/* Set RO and NX regions */
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module_enable_ro(mod);
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module_enable_ro(mod, false);
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module_enable_nx(mod);
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/* Mark state as coming so strong_try_module_get() ignores us,
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