ftrace: Convert graph filter to use hash tables

Use ftrace_hash instead of a static array of a fixed size.  This is
useful when a graph filter pattern matches to a large number of
functions.  Now hash lookup is done with preemption disabled to protect
from the hash being changed/freed.

Link: http://lkml.kernel.org/r/20170120024447.26097-3-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0470e37..2d554a0 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4378,7 +4378,7 @@ __setup("ftrace_filter=", set_ftrace_filter);
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 static char ftrace_graph_buf[FTRACE_FILTER_SIZE] __initdata;
 static char ftrace_graph_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
-static int ftrace_set_func(unsigned long *array, int *idx, int size, char *buffer);
+static int ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer);
 
 static unsigned long save_global_trampoline;
 static unsigned long save_global_flags;
@@ -4401,18 +4401,17 @@ static void __init set_ftrace_early_graph(char *buf, int enable)
 {
        int ret;
        char *func;
-       unsigned long *table = ftrace_graph_funcs;
-       int *count = &ftrace_graph_count;
+       struct ftrace_hash *hash;
 
-       if (!enable) {
-               table = ftrace_graph_notrace_funcs;
-               count = &ftrace_graph_notrace_count;
-       }
+       if (enable)
+               hash = ftrace_graph_hash;
+       else
+               hash = ftrace_graph_notrace_hash;
 
        while (buf) {
                func = strsep(&buf, ",");
                /* we allow only one expression at a time */
-               ret = ftrace_set_func(table, count, FTRACE_GRAPH_MAX_FUNCS, func);
+               ret = ftrace_graph_set_hash(hash, func);
                if (ret)
                        printk(KERN_DEBUG "ftrace: function %s not "
                                          "traceable\n", func);
@@ -4536,15 +4535,20 @@ static const struct file_operations ftrace_notrace_fops = {
 
 static DEFINE_MUTEX(graph_lock);
 
-int ftrace_graph_count;
-int ftrace_graph_notrace_count;
-unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS] __read_mostly;
-unsigned long ftrace_graph_notrace_funcs[FTRACE_GRAPH_MAX_FUNCS] __read_mostly;
+struct ftrace_hash *ftrace_graph_hash = EMPTY_HASH;
+struct ftrace_hash *ftrace_graph_notrace_hash = EMPTY_HASH;
+
+enum graph_filter_type {
+       GRAPH_FILTER_NOTRACE    = 0,
+       GRAPH_FILTER_FUNCTION,
+};
 
 struct ftrace_graph_data {
-       unsigned long *table;
-       size_t size;
-       int *count;
+       struct ftrace_hash *hash;
+       struct ftrace_func_entry *entry;
+       int idx;   /* for hash table iteration */
+       enum graph_filter_type type;
+       struct ftrace_hash *new_hash;
        const struct seq_operations *seq_ops;
 };
 
@@ -4552,10 +4556,31 @@ static void *
 __g_next(struct seq_file *m, loff_t *pos)
 {
        struct ftrace_graph_data *fgd = m->private;
+       struct ftrace_func_entry *entry = fgd->entry;
+       struct hlist_head *head;
+       int i, idx = fgd->idx;
 
-       if (*pos >= *fgd->count)
+       if (*pos >= fgd->hash->count)
                return NULL;
-       return &fgd->table[*pos];
+
+       if (entry) {
+               hlist_for_each_entry_continue(entry, hlist) {
+                       fgd->entry = entry;
+                       return entry;
+               }
+
+               idx++;
+       }
+
+       for (i = idx; i < 1 << fgd->hash->size_bits; i++) {
+               head = &fgd->hash->buckets[i];
+               hlist_for_each_entry(entry, head, hlist) {
+                       fgd->entry = entry;
+                       fgd->idx = i;
+                       return entry;
+               }
+       }
+       return NULL;
 }
 
 static void *
@@ -4572,9 +4597,11 @@ static void *g_start(struct seq_file *m, loff_t *pos)
        mutex_lock(&graph_lock);
 
        /* Nothing, tell g_show to print all functions are enabled */
-       if (!*fgd->count && !*pos)
+       if (ftrace_hash_empty(fgd->hash) && !*pos)
                return (void *)1;
 
+       fgd->idx = 0;
+       fgd->entry = NULL;
        return __g_next(m, pos);
 }
 
@@ -4585,22 +4612,22 @@ static void g_stop(struct seq_file *m, void *p)
 
 static int g_show(struct seq_file *m, void *v)
 {
-       unsigned long *ptr = v;
+       struct ftrace_func_entry *entry = v;
 
-       if (!ptr)
+       if (!entry)
                return 0;
 
-       if (ptr == (unsigned long *)1) {
+       if (entry == (void *)1) {
                struct ftrace_graph_data *fgd = m->private;
 
-               if (fgd->table == ftrace_graph_funcs)
+               if (fgd->type == GRAPH_FILTER_FUNCTION)
                        seq_puts(m, "#### all functions enabled ####\n");
                else
                        seq_puts(m, "#### no functions disabled ####\n");
                return 0;
        }
 
-       seq_printf(m, "%ps\n", (void *)*ptr);
+       seq_printf(m, "%ps\n", (void *)entry->ip);
 
        return 0;
 }
@@ -4617,24 +4644,37 @@ __ftrace_graph_open(struct inode *inode, struct file *file,
                    struct ftrace_graph_data *fgd)
 {
        int ret = 0;
+       struct ftrace_hash *new_hash = NULL;
 
-       mutex_lock(&graph_lock);
-       if ((file->f_mode & FMODE_WRITE) &&
-           (file->f_flags & O_TRUNC)) {
-               *fgd->count = 0;
-               memset(fgd->table, 0, fgd->size * sizeof(*fgd->table));
+       if (file->f_mode & FMODE_WRITE) {
+               const int size_bits = FTRACE_HASH_DEFAULT_BITS;
+
+               if (file->f_flags & O_TRUNC)
+                       new_hash = alloc_ftrace_hash(size_bits);
+               else
+                       new_hash = alloc_and_copy_ftrace_hash(size_bits,
+                                                             fgd->hash);
+               if (!new_hash) {
+                       ret = -ENOMEM;
+                       goto out;
+               }
        }
-       mutex_unlock(&graph_lock);
 
        if (file->f_mode & FMODE_READ) {
-               ret = seq_open(file, fgd->seq_ops);
+               ret = seq_open(file, &ftrace_graph_seq_ops);
                if (!ret) {
                        struct seq_file *m = file->private_data;
                        m->private = fgd;
+               } else {
+                       /* Failed */
+                       free_ftrace_hash(new_hash);
+                       new_hash = NULL;
                }
        } else
                file->private_data = fgd;
 
+out:
+       fgd->new_hash = new_hash;
        return ret;
 }
 
@@ -4642,6 +4682,7 @@ static int
 ftrace_graph_open(struct inode *inode, struct file *file)
 {
        struct ftrace_graph_data *fgd;
+       int ret;
 
        if (unlikely(ftrace_disabled))
                return -ENODEV;
@@ -4650,18 +4691,25 @@ ftrace_graph_open(struct inode *inode, struct file *file)
        if (fgd == NULL)
                return -ENOMEM;
 
-       fgd->table = ftrace_graph_funcs;
-       fgd->size = FTRACE_GRAPH_MAX_FUNCS;
-       fgd->count = &ftrace_graph_count;
+       mutex_lock(&graph_lock);
+
+       fgd->hash = ftrace_graph_hash;
+       fgd->type = GRAPH_FILTER_FUNCTION;
        fgd->seq_ops = &ftrace_graph_seq_ops;
 
-       return __ftrace_graph_open(inode, file, fgd);
+       ret = __ftrace_graph_open(inode, file, fgd);
+       if (ret < 0)
+               kfree(fgd);
+
+       mutex_unlock(&graph_lock);
+       return ret;
 }
 
 static int
 ftrace_graph_notrace_open(struct inode *inode, struct file *file)
 {
        struct ftrace_graph_data *fgd;
+       int ret;
 
        if (unlikely(ftrace_disabled))
                return -ENODEV;
@@ -4670,45 +4718,53 @@ ftrace_graph_notrace_open(struct inode *inode, struct file *file)
        if (fgd == NULL)
                return -ENOMEM;
 
-       fgd->table = ftrace_graph_notrace_funcs;
-       fgd->size = FTRACE_GRAPH_MAX_FUNCS;
-       fgd->count = &ftrace_graph_notrace_count;
+       mutex_lock(&graph_lock);
+
+       fgd->hash = ftrace_graph_notrace_hash;
+       fgd->type = GRAPH_FILTER_NOTRACE;
        fgd->seq_ops = &ftrace_graph_seq_ops;
 
-       return __ftrace_graph_open(inode, file, fgd);
+       ret = __ftrace_graph_open(inode, file, fgd);
+       if (ret < 0)
+               kfree(fgd);
+
+       mutex_unlock(&graph_lock);
+       return ret;
 }
 
 static int
 ftrace_graph_release(struct inode *inode, struct file *file)
 {
+       struct ftrace_graph_data *fgd;
+
        if (file->f_mode & FMODE_READ) {
                struct seq_file *m = file->private_data;
 
-               kfree(m->private);
+               fgd = m->private;
                seq_release(inode, file);
        } else {
-               kfree(file->private_data);
+               fgd = file->private_data;
        }
 
+       kfree(fgd->new_hash);
+       kfree(fgd);
+
        return 0;
 }
 
 static int
-ftrace_set_func(unsigned long *array, int *idx, int size, char *buffer)
+ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
 {
        struct ftrace_glob func_g;
        struct dyn_ftrace *rec;
        struct ftrace_page *pg;
+       struct ftrace_func_entry *entry;
        int fail = 1;
        int not;
-       bool exists;
-       int i;
 
        /* decode regex */
        func_g.type = filter_parse_regex(buffer, strlen(buffer),
                                         &func_g.search, &not);
-       if (!not && *idx >= size)
-               return -EBUSY;
 
        func_g.len = strlen(func_g.search);
 
@@ -4725,26 +4781,18 @@ ftrace_set_func(unsigned long *array, int *idx, int size, char *buffer)
                        continue;
 
                if (ftrace_match_record(rec, &func_g, NULL, 0)) {
-                       /* if it is in the array */
-                       exists = false;
-                       for (i = 0; i < *idx; i++) {
-                               if (array[i] == rec->ip) {
-                                       exists = true;
-                                       break;
-                               }
-                       }
+                       entry = ftrace_lookup_ip(hash, rec->ip);
 
                        if (!not) {
                                fail = 0;
-                               if (!exists) {
-                                       array[(*idx)++] = rec->ip;
-                                       if (*idx >= size)
-                                               goto out;
-                               }
+
+                               if (entry)
+                                       continue;
+                               if (add_hash_entry(hash, rec->ip) < 0)
+                                       goto out;
                        } else {
-                               if (exists) {
-                                       array[i] = array[--(*idx)];
-                                       array[*idx] = 0;
+                               if (entry) {
+                                       free_hash_entry(hash, entry);
                                        fail = 0;
                                }
                        }
@@ -4766,6 +4814,7 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
        struct trace_parser parser;
        ssize_t read, ret = 0;
        struct ftrace_graph_data *fgd = file->private_data;
+       struct ftrace_hash *old_hash, *new_hash;
 
        if (!cnt)
                return 0;
@@ -4781,10 +4830,25 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
                mutex_lock(&graph_lock);
 
                /* we allow only one expression at a time */
-               ret = ftrace_set_func(fgd->table, fgd->count, fgd->size,
-                                     parser.buffer);
+               ret = ftrace_graph_set_hash(fgd->new_hash,
+                                           parser.buffer);
+
+               old_hash = fgd->hash;
+               new_hash = __ftrace_hash_move(fgd->new_hash);
+               if (!new_hash)
+                       ret = -ENOMEM;
+
+               if (fgd->type == GRAPH_FILTER_FUNCTION)
+                       rcu_assign_pointer(ftrace_graph_hash, new_hash);
+               else
+                       rcu_assign_pointer(ftrace_graph_notrace_hash, new_hash);
 
                mutex_unlock(&graph_lock);
+
+               /* Wait till all users are no longer using the old hash */
+               synchronize_sched();
+
+               free_ftrace_hash(old_hash);
        }
 
        if (!ret)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 9001460..afbec96 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -803,51 +803,49 @@ extern void __trace_graph_return(struct trace_array *tr,
                                 unsigned long flags, int pc);
 
 #ifdef CONFIG_DYNAMIC_FTRACE
-/* TODO: make this variable */
-#define FTRACE_GRAPH_MAX_FUNCS         32
-extern int ftrace_graph_count;
-extern unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS];
-extern int ftrace_graph_notrace_count;
-extern unsigned long ftrace_graph_notrace_funcs[FTRACE_GRAPH_MAX_FUNCS];
+extern struct ftrace_hash *ftrace_graph_hash;
+extern struct ftrace_hash *ftrace_graph_notrace_hash;
 
 static inline int ftrace_graph_addr(unsigned long addr)
 {
-       int i;
-
-       if (!ftrace_graph_count)
-               return 1;
-
-       for (i = 0; i < ftrace_graph_count; i++) {
-               if (addr == ftrace_graph_funcs[i]) {
-                       /*
-                        * If no irqs are to be traced, but a set_graph_function
-                        * is set, and called by an interrupt handler, we still
-                        * want to trace it.
-                        */
-                       if (in_irq())
-                               trace_recursion_set(TRACE_IRQ_BIT);
-                       else
-                               trace_recursion_clear(TRACE_IRQ_BIT);
-                       return 1;
-               }
+       int ret = 0;
+
+       preempt_disable_notrace();
+
+       if (ftrace_hash_empty(ftrace_graph_hash)) {
+               ret = 1;
+               goto out;
        }
 
-       return 0;
+       if (ftrace_lookup_ip(ftrace_graph_hash, addr)) {
+               /*
+                * If no irqs are to be traced, but a set_graph_function
+                * is set, and called by an interrupt handler, we still
+                * want to trace it.
+                */
+               if (in_irq())
+                       trace_recursion_set(TRACE_IRQ_BIT);
+               else
+                       trace_recursion_clear(TRACE_IRQ_BIT);
+               ret = 1;
+       }
+
+out:
+       preempt_enable_notrace();
+       return ret;
 }
 
 static inline int ftrace_graph_notrace_addr(unsigned long addr)
 {
-       int i;
+       int ret = 0;
 
-       if (!ftrace_graph_notrace_count)
-               return 0;
+       preempt_disable_notrace();
 
-       for (i = 0; i < ftrace_graph_notrace_count; i++) {
-               if (addr == ftrace_graph_notrace_funcs[i])
-                       return 1;
-       }
+       if (ftrace_lookup_ip(ftrace_graph_notrace_hash, addr))
+               ret = 1;
 
-       return 0;
+       preempt_enable_notrace();
+       return ret;
 }
 #else
 static inline int ftrace_graph_addr(unsigned long addr)