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author | Linus Torvalds <torvalds@linux-foundation.org> | 2017-02-27 22:26:17 +0100 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-02-27 22:26:17 +0100 |
commit | 79b17ea740d9fab178d6a1aa15d848b5e6c01b82 (patch) | |
tree | b0c18df8713999e16bcc6e5a32cbef880efb3b10 /kernel/jump_label.c | |
parent | Merge tag 'watchdog-for-linus-v4.11' of git://git.kernel.org/pub/scm/linux/ke... (diff) | |
parent | tracing: Remove outdated ring buffer comment (diff) | |
download | linux-79b17ea740d9fab178d6a1aa15d848b5e6c01b82.tar.xz linux-79b17ea740d9fab178d6a1aa15d848b5e6c01b82.zip |
Merge tag 'trace-v4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing updates from Steven Rostedt:
"This release has no new tracing features, just clean ups, minor fixes
and small optimizations"
* tag 'trace-v4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (25 commits)
tracing: Remove outdated ring buffer comment
tracing/probes: Fix a warning message to show correct maximum length
tracing: Fix return value check in trace_benchmark_reg()
tracing: Use modern function declaration
jump_label: Reduce the size of struct static_key
tracing/probe: Show subsystem name in messages
tracing/hwlat: Update old comment about migration
timers: Make flags output in the timer_start tracepoint useful
tracing: Have traceprobe_probes_write() not access userspace unnecessarily
tracing: Have COMM event filter key be treated as a string
ftrace: Have set_graph_function handle multiple functions in one write
ftrace: Do not hold references of ftrace_graph_{notrace_}hash out of graph_lock
tracing: Reset parser->buffer to allow multiple "puts"
ftrace: Have set_graph_functions handle write with RDWR
ftrace: Reset fgd->hash in ftrace_graph_write()
ftrace: Replace (void *)1 with a meaningful macro name FTRACE_GRAPH_EMPTY
ftrace: Create a slight optimization on searching the ftrace_hash
tracing: Add ftrace_hash_key() helper function
ftrace: Convert graph filter to use hash tables
ftrace: Expose ftrace_hash_empty and ftrace_lookup_ip
...
Diffstat (limited to 'kernel/jump_label.c')
-rw-r--r-- | kernel/jump_label.c | 153 |
1 files changed, 127 insertions, 26 deletions
diff --git a/kernel/jump_label.c b/kernel/jump_label.c index a9b8cf500591..6c9cb208ac48 100644 --- a/kernel/jump_label.c +++ b/kernel/jump_label.c @@ -236,12 +236,28 @@ void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry static inline struct jump_entry *static_key_entries(struct static_key *key) { - return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK); + WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED); + return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK); } static inline bool static_key_type(struct static_key *key) { - return (unsigned long)key->entries & JUMP_TYPE_MASK; + return key->type & JUMP_TYPE_TRUE; +} + +static inline bool static_key_linked(struct static_key *key) +{ + return key->type & JUMP_TYPE_LINKED; +} + +static inline void static_key_clear_linked(struct static_key *key) +{ + key->type &= ~JUMP_TYPE_LINKED; +} + +static inline void static_key_set_linked(struct static_key *key) +{ + key->type |= JUMP_TYPE_LINKED; } static inline struct static_key *jump_entry_key(struct jump_entry *entry) @@ -254,6 +270,26 @@ static bool jump_entry_branch(struct jump_entry *entry) return (unsigned long)entry->key & 1UL; } +/*** + * A 'struct static_key' uses a union such that it either points directly + * to a table of 'struct jump_entry' or to a linked list of modules which in + * turn point to 'struct jump_entry' tables. + * + * The two lower bits of the pointer are used to keep track of which pointer + * type is in use and to store the initial branch direction, we use an access + * function which preserves these bits. + */ +static void static_key_set_entries(struct static_key *key, + struct jump_entry *entries) +{ + unsigned long type; + + WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK); + type = key->type & JUMP_TYPE_MASK; + key->entries = entries; + key->type |= type; +} + static enum jump_label_type jump_label_type(struct jump_entry *entry) { struct static_key *key = jump_entry_key(entry); @@ -313,13 +349,7 @@ void __init jump_label_init(void) continue; key = iterk; - /* - * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. - */ - *((unsigned long *)&key->entries) += (unsigned long)iter; -#ifdef CONFIG_MODULES - key->next = NULL; -#endif + static_key_set_entries(key, iter); } static_key_initialized = true; jump_label_unlock(); @@ -343,6 +373,29 @@ struct static_key_mod { struct module *mod; }; +static inline struct static_key_mod *static_key_mod(struct static_key *key) +{ + WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED)); + return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK); +} + +/*** + * key->type and key->next are the same via union. + * This sets key->next and preserves the type bits. + * + * See additional comments above static_key_set_entries(). + */ +static void static_key_set_mod(struct static_key *key, + struct static_key_mod *mod) +{ + unsigned long type; + + WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK); + type = key->type & JUMP_TYPE_MASK; + key->next = mod; + key->type |= type; +} + static int __jump_label_mod_text_reserved(void *start, void *end) { struct module *mod; @@ -365,11 +418,23 @@ static void __jump_label_mod_update(struct static_key *key) { struct static_key_mod *mod; - for (mod = key->next; mod; mod = mod->next) { - struct module *m = mod->mod; + for (mod = static_key_mod(key); mod; mod = mod->next) { + struct jump_entry *stop; + struct module *m; + + /* + * NULL if the static_key is defined in a module + * that does not use it + */ + if (!mod->entries) + continue; - __jump_label_update(key, mod->entries, - m->jump_entries + m->num_jump_entries); + m = mod->mod; + if (!m) + stop = __stop___jump_table; + else + stop = m->jump_entries + m->num_jump_entries; + __jump_label_update(key, mod->entries, stop); } } @@ -404,7 +469,7 @@ static int jump_label_add_module(struct module *mod) struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; struct jump_entry *iter; struct static_key *key = NULL; - struct static_key_mod *jlm; + struct static_key_mod *jlm, *jlm2; /* if the module doesn't have jump label entries, just return */ if (iter_start == iter_stop) @@ -421,20 +486,32 @@ static int jump_label_add_module(struct module *mod) key = iterk; if (within_module(iter->key, mod)) { - /* - * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. - */ - *((unsigned long *)&key->entries) += (unsigned long)iter; - key->next = NULL; + static_key_set_entries(key, iter); continue; } jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL); if (!jlm) return -ENOMEM; + if (!static_key_linked(key)) { + jlm2 = kzalloc(sizeof(struct static_key_mod), + GFP_KERNEL); + if (!jlm2) { + kfree(jlm); + return -ENOMEM; + } + preempt_disable(); + jlm2->mod = __module_address((unsigned long)key); + preempt_enable(); + jlm2->entries = static_key_entries(key); + jlm2->next = NULL; + static_key_set_mod(key, jlm2); + static_key_set_linked(key); + } jlm->mod = mod; jlm->entries = iter; - jlm->next = key->next; - key->next = jlm; + jlm->next = static_key_mod(key); + static_key_set_mod(key, jlm); + static_key_set_linked(key); /* Only update if we've changed from our initial state */ if (jump_label_type(iter) != jump_label_init_type(iter)) @@ -461,16 +538,34 @@ static void jump_label_del_module(struct module *mod) if (within_module(iter->key, mod)) continue; + /* No memory during module load */ + if (WARN_ON(!static_key_linked(key))) + continue; + prev = &key->next; - jlm = key->next; + jlm = static_key_mod(key); while (jlm && jlm->mod != mod) { prev = &jlm->next; jlm = jlm->next; } - if (jlm) { + /* No memory during module load */ + if (WARN_ON(!jlm)) + continue; + + if (prev == &key->next) + static_key_set_mod(key, jlm->next); + else *prev = jlm->next; + + kfree(jlm); + + jlm = static_key_mod(key); + /* if only one etry is left, fold it back into the static_key */ + if (jlm->next == NULL) { + static_key_set_entries(key, jlm->entries); + static_key_clear_linked(key); kfree(jlm); } } @@ -499,8 +594,10 @@ jump_label_module_notify(struct notifier_block *self, unsigned long val, case MODULE_STATE_COMING: jump_label_lock(); ret = jump_label_add_module(mod); - if (ret) + if (ret) { + WARN(1, "Failed to allocatote memory: jump_label may not work properly.\n"); jump_label_del_module(mod); + } jump_label_unlock(); break; case MODULE_STATE_GOING: @@ -561,11 +658,14 @@ int jump_label_text_reserved(void *start, void *end) static void jump_label_update(struct static_key *key) { struct jump_entry *stop = __stop___jump_table; - struct jump_entry *entry = static_key_entries(key); + struct jump_entry *entry; #ifdef CONFIG_MODULES struct module *mod; - __jump_label_mod_update(key); + if (static_key_linked(key)) { + __jump_label_mod_update(key); + return; + } preempt_disable(); mod = __module_address((unsigned long)key); @@ -573,6 +673,7 @@ static void jump_label_update(struct static_key *key) stop = mod->jump_entries + mod->num_jump_entries; preempt_enable(); #endif + entry = static_key_entries(key); /* if there are no users, entry can be NULL */ if (entry) __jump_label_update(key, entry, stop); |