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ftrace: Add comments to ftrace_hash_move() and friends

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Describe what ftrace_hash_move() does and add some more comments to some
other functions to make it easier to understand.

Link: https://lore.kernel.org/linux-trace-kernel/20240605180409.179520305@goodmis.org

Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2024-06-05 14:03:39 -04:00
parent 1a88c07167
commit d66bb33479
1 changed files with 23 additions and 1 deletions
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24
kernel/trace/ftrace.c
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@ -169,6 +169,7 @@ static inline void ftrace_ops_init(struct ftrace_ops *ops)
#endif #endif
} }
/* Call this function for when a callback filters on set_ftrace_pid */
static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip, static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs) struct ftrace_ops *op, struct ftrace_regs *fregs)
{ {
@ -1318,7 +1319,7 @@ static struct ftrace_hash *alloc_ftrace_hash(int size_bits)
return hash; return hash;
} }
/* Used to save filters on functions for modules not loaded yet */
static int ftrace_add_mod(struct trace_array *tr, static int ftrace_add_mod(struct trace_array *tr,
const char *func, const char *module, const char *func, const char *module,
int enable) int enable)
@ -1430,6 +1431,7 @@ static struct ftrace_hash *__move_hash(struct ftrace_hash *src, int size)
return new_hash; return new_hash;
} }
/* Move the @src entries to a newly allocated hash */
static struct ftrace_hash * static struct ftrace_hash *
__ftrace_hash_move(struct ftrace_hash *src) __ftrace_hash_move(struct ftrace_hash *src)
{ {
@ -1444,6 +1446,26 @@ __ftrace_hash_move(struct ftrace_hash *src)
return __move_hash(src, size); return __move_hash(src, size);
} }
/**
* ftrace_hash_move - move a new hash to a filter and do updates
* @ops: The ops with the hash that @dst points to
* @enable: True if for the filter hash, false for the notrace hash
* @dst: Points to the @ops hash that should be updated
* @src: The hash to update @dst with
*
* This is called when an ftrace_ops hash is being updated and the
* the kernel needs to reflect this. Note, this only updates the kernel
* function callbacks if the @ops is enabled (not to be confused with
* @enable above). If the @ops is enabled, its hash determines what
* callbacks get called. This function gets called when the @ops hash
* is updated and it requires new callbacks.
*
* On success the elements of @src is moved to @dst, and @dst is updated
* properly, as well as the functions determined by the @ops hashes
* are now calling the @ops callback function.
*
* Regardless of return type, @src should be freed with free_ftrace_hash().
*/
static int static int
ftrace_hash_move(struct ftrace_ops *ops, int enable, ftrace_hash_move(struct ftrace_ops *ops, int enable,
struct ftrace_hash **dst, struct ftrace_hash *src) struct ftrace_hash **dst, struct ftrace_hash *src)