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ftrace: Add modify_ftrace_direct_multi_nolock

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This is similar to modify_ftrace_direct_multi, but does not acquire
direct_mutex. This is useful when direct_mutex is already locked by the
user.

Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/bpf/20220720002126.803253-2-song@kernel.org
This commit is contained in:
Song Liu 2022-07-19 17:21:23 -07:00 • committed by Daniel Borkmann
parent f664f9c6b4
commit f96f644ab9
2 changed files with 67 additions and 24 deletions
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5
include/linux/ftrace.h
View file

@ -340,6 +340,7 @@ unsigned long ftrace_find_rec_direct(unsigned long ip);
int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr); int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr); int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr); int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr);
#else #else
struct ftrace_ops; struct ftrace_ops;
@ -384,6 +385,10 @@ static inline int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned lo
{ {
return -ENODEV; return -ENODEV;
} }
static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr)
{
return -ENODEV;
}
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS

86
kernel/trace/ftrace.c
View file

@ -5691,22 +5691,8 @@ int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
} }
EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi); EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi);
/** static int
* modify_ftrace_direct_multi - Modify an existing direct 'multi' call __modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
* to call something else
* @ops: The address of the struct ftrace_ops object
* @addr: The address of the new trampoline to call at @ops functions
*
* This is used to unregister currently registered direct caller and
* register new one @addr on functions registered in @ops object.
*
* Note there's window between ftrace_shutdown and ftrace_startup calls
* where there will be no callbacks called.
*
* Returns: zero on success. Non zero on error, which includes:
* -EINVAL - The @ops object was not properly registered.
*/
int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
{ {
struct ftrace_hash *hash; struct ftrace_hash *hash;
struct ftrace_func_entry *entry, *iter; struct ftrace_func_entry *entry, *iter;
@ -5717,12 +5703,7 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
int i, size; int i, size;
int err; int err;
if (check_direct_multi(ops)) lockdep_assert_held_once(&direct_mutex);
return -EINVAL;
if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
return -EINVAL;
mutex_lock(&direct_mutex);
/* Enable the tmp_ops to have the same functions as the direct ops */ /* Enable the tmp_ops to have the same functions as the direct ops */
ftrace_ops_init(&tmp_ops); ftrace_ops_init(&tmp_ops);
@ -5730,7 +5711,7 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
err = register_ftrace_function(&tmp_ops); err = register_ftrace_function(&tmp_ops);
if (err) if (err)
goto out_direct; return err;
/* /*
* Now the ftrace_ops_list_func() is called to do the direct callers. * Now the ftrace_ops_list_func() is called to do the direct callers.
@ -5754,7 +5735,64 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
/* Removing the tmp_ops will add the updated direct callers to the functions */ /* Removing the tmp_ops will add the updated direct callers to the functions */
unregister_ftrace_function(&tmp_ops); unregister_ftrace_function(&tmp_ops);
out_direct: return err;
}
/**
* modify_ftrace_direct_multi_nolock - Modify an existing direct 'multi' call
* to call something else
* @ops: The address of the struct ftrace_ops object
* @addr: The address of the new trampoline to call at @ops functions
*
* This is used to unregister currently registered direct caller and
* register new one @addr on functions registered in @ops object.
*
* Note there's window between ftrace_shutdown and ftrace_startup calls
* where there will be no callbacks called.
*
* Caller should already have direct_mutex locked, so we don't lock
* direct_mutex here.
*
* Returns: zero on success. Non zero on error, which includes:
* -EINVAL - The @ops object was not properly registered.
*/
int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr)
{
if (check_direct_multi(ops))
return -EINVAL;
if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
return -EINVAL;
return __modify_ftrace_direct_multi(ops, addr);
}
EXPORT_SYMBOL_GPL(modify_ftrace_direct_multi_nolock);
/**
* modify_ftrace_direct_multi - Modify an existing direct 'multi' call
* to call something else
* @ops: The address of the struct ftrace_ops object
* @addr: The address of the new trampoline to call at @ops functions
*
* This is used to unregister currently registered direct caller and
* register new one @addr on functions registered in @ops object.
*
* Note there's window between ftrace_shutdown and ftrace_startup calls
* where there will be no callbacks called.
*
* Returns: zero on success. Non zero on error, which includes:
* -EINVAL - The @ops object was not properly registered.
*/
int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
{
int err;
if (check_direct_multi(ops))
return -EINVAL;
if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
return -EINVAL;
mutex_lock(&direct_mutex);
err = __modify_ftrace_direct_multi(ops, addr);
mutex_unlock(&direct_mutex); mutex_unlock(&direct_mutex);
return err; return err;
} }