module: clean up RO/NX handling.
Modules have three sections: text, rodata and writable data. The code
handled the case where these overlapped, however they never can:
debug_align() ensures they are always page-aligned.
This is why we got away with manually traversing the pages in
set_all_modules_text_rw() without rounding.
We create three helper functions: frob_text(), frob_rodata() and
frob_writable_data(). We then call these explicitly at every point,
so it's clear what we're doing.
We also expose module_enable_ro() and module_disable_ro() for
livepatch to use.
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/kernel/module.c b/kernel/module.c
index a0a3d6d..7721212 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -80,15 +80,6 @@
# define debug_align(X) (X)
#endif
-/*
- * Given BASE and SIZE this macro calculates the number of pages the
- * memory regions occupies
- */
-#define MOD_NUMBER_OF_PAGES(BASE, SIZE) (((SIZE) > 0) ? \
- (PFN_DOWN((unsigned long)(BASE) + (SIZE) - 1) - \
- PFN_DOWN((unsigned long)BASE) + 1) \
- : (0UL))
-
/* If this is set, the section belongs in the init part of the module */
#define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
@@ -1858,74 +1849,75 @@
/*
* 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);
}
-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);
-
- /*
- * 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);
- }
+ 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);
}
-static void set_module_core_ro_nx(struct module *mod)
+static void frob_writable_data(const struct module_layout *layout,
+ int (*set_memory)(unsigned long start, int num_pages))
{
- set_section_ro_nx(mod->core_layout.base, mod->core_layout.text_size,
- mod->core_layout.ro_size, mod->core_layout.size,
- set_memory_ro, set_memory_nx);
+ 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);
}
-static void unset_module_core_ro_nx(struct module *mod)
+/* livepatching wants to disable read-only so it can frob module. */
+void module_disable_ro(const struct module *mod)
{
- set_section_ro_nx(mod->core_layout.base, mod->core_layout.text_size,
- mod->core_layout.ro_size, mod->core_layout.size,
- set_memory_rw, set_memory_x);
+ frob_text(&mod->core_layout, set_memory_rw);
+ frob_rodata(&mod->core_layout, set_memory_rw);
+ frob_text(&mod->init_layout, set_memory_rw);
+ frob_rodata(&mod->init_layout, set_memory_rw);
}
-static void set_module_init_ro_nx(struct module *mod)
+void module_enable_ro(const struct module *mod)
{
- set_section_ro_nx(mod->init_layout.base, mod->init_layout.text_size,
- mod->init_layout.ro_size, mod->init_layout.size,
- set_memory_ro, set_memory_nx);
+ frob_text(&mod->core_layout, set_memory_ro);
+ frob_rodata(&mod->core_layout, set_memory_ro);
+ frob_text(&mod->init_layout, set_memory_ro);
+ frob_rodata(&mod->init_layout, set_memory_ro);
}
-static void unset_module_init_ro_nx(struct module *mod)
+static void module_enable_nx(const struct module *mod)
{
- set_section_ro_nx(mod->init_layout.base, mod->init_layout.text_size,
- mod->init_layout.ro_size, mod->init_layout.size,
- set_memory_rw, set_memory_x);
+ frob_rodata(&mod->core_layout, set_memory_nx);
+ frob_writable_data(&mod->core_layout, set_memory_nx);
+ frob_rodata(&mod->init_layout, set_memory_nx);
+ frob_writable_data(&mod->init_layout, set_memory_nx);
+}
+
+static void module_disable_nx(const struct module *mod)
+{
+ frob_rodata(&mod->core_layout, set_memory_x);
+ frob_writable_data(&mod->core_layout, set_memory_x);
+ frob_rodata(&mod->init_layout, set_memory_x);
+ frob_writable_data(&mod->init_layout, set_memory_x);
}
/* Iterate through all modules and set each module's text as RW */
@@ -1937,16 +1929,9 @@
list_for_each_entry_rcu(mod, &modules, list) {
if (mod->state == MODULE_STATE_UNFORMED)
continue;
- if ((mod->core_layout.base) && (mod->core_layout.text_size)) {
- set_page_attributes(mod->core_layout.base,
- mod->core_layout.base + mod->core_layout.text_size,
- set_memory_rw);
- }
- if ((mod->init_layout.base) && (mod->init_layout.text_size)) {
- set_page_attributes(mod->init_layout.base,
- mod->init_layout.base + mod->init_layout.text_size,
- set_memory_rw);
- }
+
+ frob_text(&mod->core_layout, set_memory_rw);
+ frob_text(&mod->init_layout, set_memory_rw);
}
mutex_unlock(&module_mutex);
}
@@ -1960,24 +1945,25 @@
list_for_each_entry_rcu(mod, &modules, list) {
if (mod->state == MODULE_STATE_UNFORMED)
continue;
- if ((mod->core_layout.base) && (mod->core_layout.text_size)) {
- set_page_attributes(mod->core_layout.base,
- mod->core_layout.base + mod->core_layout.text_size,
- set_memory_ro);
- }
- if ((mod->init_layout.base) && (mod->init_layout.text_size)) {
- set_page_attributes(mod->init_layout.base,
- mod->init_layout.base + mod->init_layout.text_size,
- set_memory_ro);
- }
+
+ frob_text(&mod->core_layout, set_memory_ro);
+ frob_text(&mod->init_layout, set_memory_ro);
}
mutex_unlock(&module_mutex);
}
+
+static void disable_ro_nx(const struct module_layout *layout)
+{
+ frob_text(layout, set_memory_rw);
+ frob_rodata(layout, set_memory_rw);
+ frob_rodata(layout, set_memory_x);
+ frob_writable_data(layout, set_memory_x);
+}
+
#else
-static void set_module_core_ro_nx(struct module *mod) { }
-static void set_module_init_ro_nx(struct module *mod) { }
-static void unset_module_core_ro_nx(struct module *mod) { }
-static void unset_module_init_ro_nx(struct module *mod) { }
+static void disable_ro_nx(const struct module_layout *layout) { }
+static void module_enable_nx(const struct module *mod) { }
+static void module_disable_nx(const struct module *mod) { }
#endif
void __weak module_memfree(void *module_region)
@@ -2029,8 +2015,8 @@
synchronize_sched();
mutex_unlock(&module_mutex);
- /* This may be NULL, but that's OK */
- unset_module_init_ro_nx(mod);
+ /* This may be empty, but that's OK */
+ disable_ro_nx(&mod->init_layout);
module_arch_freeing_init(mod);
module_memfree(mod->init_layout.base);
kfree(mod->args);
@@ -2040,7 +2026,7 @@
lockdep_free_key_range(mod->core_layout.base, mod->core_layout.size);
/* Finally, free the core (containing the module structure) */
- unset_module_core_ro_nx(mod);
+ disable_ro_nx(&mod->core_layout);
module_memfree(mod->core_layout.base);
#ifdef CONFIG_MPU
@@ -3275,7 +3261,7 @@
mod->strtab = mod->core_strtab;
#endif
mod_tree_remove_init(mod);
- unset_module_init_ro_nx(mod);
+ disable_ro_nx(&mod->init_layout);
module_arch_freeing_init(mod);
mod->init_layout.base = NULL;
mod->init_layout.size = 0;
@@ -3370,8 +3356,8 @@
module_bug_finalize(info->hdr, info->sechdrs, mod);
/* Set RO and NX regions */
- set_module_init_ro_nx(mod);
- set_module_core_ro_nx(mod);
+ module_enable_ro(mod);
+ module_enable_nx(mod);
/* Mark state as coming so strong_try_module_get() ignores us,
* but kallsyms etc. can see us. */
@@ -3536,8 +3522,8 @@
MODULE_STATE_GOING, mod);
/* we can't deallocate the module until we clear memory protection */
- unset_module_init_ro_nx(mod);
- unset_module_core_ro_nx(mod);
+ module_disable_ro(mod);
+ module_disable_nx(mod);
ddebug_cleanup:
dynamic_debug_remove(info->debug);