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authorPeter Zijlstra <peterz@infradead.org>2020-08-18 15:57:51 +0200
committerIngo Molnar <mingo@kernel.org>2020-09-01 09:58:06 +0200
commita945c8345ec0decb2f1a7f19a8c5e60bcb1dd1eb (patch)
tree11d4ff482c11945ef30fe5c88493a2b49202ad27 /kernel/static_call.c
parent6c3fce794e9d2a5ce3a948962d0808a459c40a84 (diff)
static_call: Allow early init
In order to use static_call() to wire up x86_pmu, we need to initialize earlier, specifically before memory allocation works; copy some of the tricks from jump_label to enable this. Primarily we overload key->next to store a sites pointer when there are no modules, this avoids having to use kmalloc() to initialize the sites and allows us to run much earlier. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Link: https://lore.kernel.org/r/20200818135805.220737930@infradead.org
Diffstat (limited to 'kernel/static_call.c')
-rw-r--r--kernel/static_call.c70
1 files changed, 66 insertions, 4 deletions
diff --git a/kernel/static_call.c b/kernel/static_call.c
index d98e0e4272c1..f8362b3f8fd5 100644
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -94,10 +94,31 @@ static inline void static_call_sort_entries(struct static_call_site *start,
static_call_site_cmp, static_call_site_swap);
}
+static inline bool static_call_key_has_mods(struct static_call_key *key)
+{
+ return !(key->type & 1);
+}
+
+static inline struct static_call_mod *static_call_key_next(struct static_call_key *key)
+{
+ if (!static_call_key_has_mods(key))
+ return NULL;
+
+ return key->mods;
+}
+
+static inline struct static_call_site *static_call_key_sites(struct static_call_key *key)
+{
+ if (static_call_key_has_mods(key))
+ return NULL;
+
+ return (struct static_call_site *)(key->type & ~1);
+}
+
void __static_call_update(struct static_call_key *key, void *tramp, void *func)
{
struct static_call_site *site, *stop;
- struct static_call_mod *site_mod;
+ struct static_call_mod *site_mod, first;
cpus_read_lock();
static_call_lock();
@@ -116,13 +137,22 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
if (WARN_ON_ONCE(!static_call_initialized))
goto done;
- for (site_mod = key->mods; site_mod; site_mod = site_mod->next) {
+ first = (struct static_call_mod){
+ .next = static_call_key_next(key),
+ .mod = NULL,
+ .sites = static_call_key_sites(key),
+ };
+
+ for (site_mod = &first; site_mod; site_mod = site_mod->next) {
struct module *mod = site_mod->mod;
if (!site_mod->sites) {
/*
* This can happen if the static call key is defined in
* a module which doesn't use it.
+ *
+ * It also happens in the has_mods case, where the
+ * 'first' entry has no sites associated with it.
*/
continue;
}
@@ -192,16 +222,48 @@ static int __static_call_init(struct module *mod,
if (key != prev_key) {
prev_key = key;
+ /*
+ * For vmlinux (!mod) avoid the allocation by storing
+ * the sites pointer in the key itself. Also see
+ * __static_call_update()'s @first.
+ *
+ * This allows architectures (eg. x86) to call
+ * static_call_init() before memory allocation works.
+ */
+ if (!mod) {
+ key->sites = site;
+ key->type |= 1;
+ goto do_transform;
+ }
+
site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
if (!site_mod)
return -ENOMEM;
+ /*
+ * When the key has a direct sites pointer, extract
+ * that into an explicit struct static_call_mod, so we
+ * can have a list of modules.
+ */
+ if (static_call_key_sites(key)) {
+ site_mod->mod = NULL;
+ site_mod->next = NULL;
+ site_mod->sites = static_call_key_sites(key);
+
+ key->mods = site_mod;
+
+ site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
+ if (!site_mod)
+ return -ENOMEM;
+ }
+
site_mod->mod = mod;
site_mod->sites = site;
- site_mod->next = key->mods;
+ site_mod->next = static_call_key_next(key);
key->mods = site_mod;
}
+do_transform:
arch_static_call_transform(site_addr, NULL, key->func,
static_call_is_tail(site));
}
@@ -348,7 +410,7 @@ int static_call_text_reserved(void *start, void *end)
return __static_call_mod_text_reserved(start, end);
}
-static void __init static_call_init(void)
+void __init static_call_init(void)
{
int ret;