+++ Jessica Yu [25/07/16 05:25 -0400]:
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@xxxxxxxxxx>
---
include/linux/module.h | 6 +++--
include/uapi/linux/elf.h | 1 +
kernel/livepatch/core.c | 2 +-
kernel/module.c | 66 +++++++++++++++++++++++++++++++++++++++---------
4 files changed, 60 insertions(+), 15 deletions(-)
diff --git a/include/linux/module.h b/include/linux/module.h
index f777164..5255c2f 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -311,6 +311,8 @@ struct module_layout {
unsigned int text_size;
/* Size of RO section of the module (text+rodata) */
unsigned int ro_size;
+ /* Size of RO after init section */
+ unsigned int ro_after_init_size;
#ifdef CONFIG_MODULES_TREE_LOOKUP
struct mod_tree_node mtn;
@@ -788,12 +790,12 @@ extern int module_sysfs_initialized;
#ifdef CONFIG_DEBUG_SET_MODULE_RONX
extern void set_all_modules_text_rw(void);
extern void set_all_modules_text_ro(void);
-extern void module_enable_ro(const struct module *mod);
+extern void module_enable_ro(const struct module *mod, bool after_init);
extern void module_disable_ro(const struct module *mod);
#else
static inline void set_all_modules_text_rw(void) { }
static inline void set_all_modules_text_ro(void) { }
-static inline void module_enable_ro(const struct module *mod) { }
+static inline void module_enable_ro(const struct module *mod, bool after_init) { }
static inline void module_disable_ro(const struct module *mod) { }
#endif
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index cb4a72f..70b172ba 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -286,6 +286,7 @@ typedef struct elf64_phdr {
#define SHF_ALLOC 0x2
#define SHF_EXECINSTR 0x4
#define SHF_RELA_LIVEPATCH 0x00100000
+#define SHF_RO_AFTER_INIT 0x00200000
#define SHF_MASKPROC 0xf0000000
/* special section indexes */
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 5c2bc10..8bbe507 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -309,7 +309,7 @@ static int klp_write_object_relocations(struct module *pmod,
break;
}
- module_enable_ro(pmod);
+ module_enable_ro(pmod, true);
There is a slight quirk here in that klp_init_object_loaded() (which
calls klp_write_object_relocations()) can be called either during
patch module init (during patch registration) or after init (e.g.,
when a previously unloaded to-be-patched module is loaded). AFAIK
patch modules themselves don't use .data..ro_after_init sections, so
it's probably fine to set after_init to be true here for now. But I
still need to think some more about the case where we try to patch
data from another module marked __ro_after_init.
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