[PATCH 5.10 034/126] static_call: Align static_call_is_init() patching condition

Greg Kroah-Hartman
2021-04-05T09:09:55Z

From: Peter Zijlstra <peterz@infradead.org>

[ Upstream commit 698bacefe993ad2922c9d3b1380591ad489355e9 ]

The intent is to avoid writing init code after init (because the text
might have been freed). The code is needlessly different between
jump_label and static_call and not obviously correct.

The existing code relies on the fact that the module loader clears the
init layout, such that within_module_init() always fails, while
jump_label relies on the module state which is more obvious and
matches the kernel logic.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Sumit Garg <sumit.garg@linaro.org>
Link: https://lkml.kernel.org/r/20210318113610.636651340@infradead.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/static_call.c | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/kernel/static_call.c b/kernel/static_call.c
index 49efbdc5b480..f59089a12231 100644
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -149,6 +149,7 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
};

for (site_mod = &first; site_mod; site_mod = site_mod->next) {
+ bool init = system_state < SYSTEM_RUNNING;
struct module *mod = site_mod->mod;

if (!site_mod->sites) {
@@ -168,6 +169,7 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
if (mod) {
stop = mod->static_call_sites +
mod->num_static_call_sites;
+ init = mod->state == MODULE_STATE_COMING;
}
#endif

@@ -175,16 +177,8 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
site < stop && static_call_key(site) == key; site++) {
void *site_addr = static_call_addr(site);

- if (static_call_is_init(site)) {
- /*
- * Don't write to call sites which were in
- * initmem and have since been freed.
- */
- if (!mod && system_state >= SYSTEM_RUNNING)
- continue;
- if (mod && !within_module_init((unsigned long)site_addr, mod))
- continue;
- }
+ if (!init && static_call_is_init(site))
+ continue;

if (!kernel_text_address((unsigned long)site_addr)) {
/*
--
2.30.1