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static_call: Allow early init

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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
This commit is contained in:
Peter Zijlstra
2020-08-18 15:57:51 +02:00
committed by Ingo Molnar
parent 6c3fce794e
commit a945c8345e
4 changed files with 85 additions and 7 deletions
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70
kernel/static_call.c
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@@ -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;