[PATCH RFC 08/10] jump_label: Handle module writable address

[Rick Edgecombe]

Since modules can have a separate writable address during loading,
do the nop application at the writable address.

As long as info is on hand about if the operations is happening during
a module load, don't do a full text_poke() when writing data to a
writable address.

Signed-off-by: Rick Edgecombe <rick.p.edgeco...@intel.com>
---
 arch/x86/kernel/jump_label.c | 18 ++++++++++++++++--
 kernel/jump_label.c          |  2 +-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index 5ba8477c2cb7..7a50148a63dd 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -63,6 +63,18 @@ static inline void __jump_label_transform(struct jump_entry 
*entry,
                                          int init)
 {
        const void *opcode = __jump_label_set_jump_code(entry, type, init);
+       unsigned long addr = jump_entry_code(entry);
+       struct module *mod = __module_address(addr);
+       bool mod_writable = false;
+
+       if (mod) {
+               struct perm_allocation *alloc = module_get_allocation(mod, 
addr);
+
+               if (perm_is_writable(alloc)) {
+                       addr = perm_writable_addr(alloc, addr);
+                       mod_writable = true;
+               }
+       }
 
        /*
         * As long as only a single processor is running and the code is still
@@ -74,9 +86,11 @@ static inline void __jump_label_transform(struct jump_entry 
*entry,
         * At the time the change is being done, just ignore whether we
         * are doing nop -> jump or jump -> nop transition, and assume
         * always nop being the 'currently valid' instruction
+        *
+        * If this is a module being loaded, text_poke_early can also be used.
         */
-       if (init || system_state == SYSTEM_BOOTING) {
-               text_poke_early((void *)jump_entry_code(entry), opcode,
+       if (init || system_state == SYSTEM_BOOTING || mod_writable) {
+               text_poke_early((void *)addr, opcode,
                                JUMP_LABEL_NOP_SIZE);
                return;
        }
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 015ef903ce8c..3919e78fce12 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -595,7 +595,7 @@ static void __jump_label_mod_update(struct static_key *key)
  */
 void jump_label_apply_nops(struct module *mod)
 {
-       struct jump_entry *iter_start = mod->jump_entries;
+       struct jump_entry *iter_start = 
module_adjust_writable_addr(mod->jump_entries);
        struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
        struct jump_entry *iter;
 
-- 
2.20.1