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Message-Id: <a5801f46f1ef1f291249b8c924adf6822c8e7e50.1606412433.git.naveen.n.rao@linux.vnet.ibm.com>
Date: Thu, 26 Nov 2020 23:38:41 +0530
From: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To: Steven Rostedt <rostedt@...dmis.org>,
Michael Ellerman <mpe@...erman.id.au>
Cc: <linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>
Subject: [RFC PATCH 04/14] ftrace: Remove ftrace_find_direct_func()
This is a revert of commit 013bf0da047481 ("ftrace: Add
ftrace_find_direct_func()")
ftrace_find_direct_func() was meant for use in the function graph tracer
by architecture specific code. However, commit ff205766dbbee0 ("ftrace:
Fix function_graph tracer interaction with BPF trampoline") disabled
function graph tracer for direct calls leaving this without any users.
In addition, modify_ftrace_direct() allowed redirecting the direct call
to a different trampoline that was never registered through
register_ftrace_direct(). This meant that ftrace_direct_funcs didn't
capture all trampolines.
Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
---
include/linux/ftrace.h | 5 ---
kernel/trace/ftrace.c | 84 ++----------------------------------------
2 files changed, 4 insertions(+), 85 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 1bd3a0356ae478..46b4b7ee28c41f 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -285,7 +285,6 @@ extern int ftrace_direct_func_count;
int register_ftrace_direct(unsigned long ip, unsigned long addr);
int unregister_ftrace_direct(unsigned long ip, unsigned long addr);
int modify_ftrace_direct(unsigned long ip, unsigned long old_addr, unsigned long new_addr);
-struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr);
int ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
struct dyn_ftrace *rec,
unsigned long old_addr,
@@ -306,10 +305,6 @@ static inline int modify_ftrace_direct(unsigned long ip,
{
return -ENOTSUPP;
}
-static inline struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr)
-{
- return NULL;
-}
static inline int ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
struct dyn_ftrace *rec,
unsigned long old_addr,
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 3844a4a1346a9c..7476f2458b6d95 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5005,46 +5005,6 @@ ftrace_set_addr(struct ftrace_ops *ops, unsigned long ip, int remove,
}
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
-
-struct ftrace_direct_func {
- struct list_head next;
- unsigned long addr;
- int count;
-};
-
-static LIST_HEAD(ftrace_direct_funcs);
-
-/**
- * ftrace_find_direct_func - test an address if it is a registered direct caller
- * @addr: The address of a registered direct caller
- *
- * This searches to see if a ftrace direct caller has been registered
- * at a specific address, and if so, it returns a descriptor for it.
- *
- * This can be used by architecture code to see if an address is
- * a direct caller (trampoline) attached to a fentry/mcount location.
- * This is useful for the function_graph tracer, as it may need to
- * do adjustments if it traced a location that also has a direct
- * trampoline attached to it.
- */
-struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr)
-{
- struct ftrace_direct_func *entry;
- bool found = false;
-
- /* May be called by fgraph trampoline (protected by rcu tasks) */
- list_for_each_entry_rcu(entry, &ftrace_direct_funcs, next) {
- if (entry->addr == addr) {
- found = true;
- break;
- }
- }
- if (found)
- return entry;
-
- return NULL;
-}
-
/**
* register_ftrace_direct - Call a custom trampoline directly
* @ip: The address of the nop at the beginning of a function
@@ -5064,7 +5024,6 @@ struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr)
*/
int register_ftrace_direct(unsigned long ip, unsigned long addr)
{
- struct ftrace_direct_func *direct;
struct ftrace_func_entry *entry;
struct ftrace_hash *free_hash = NULL;
struct dyn_ftrace *rec;
@@ -5118,19 +5077,7 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
if (!entry)
goto out_unlock;
- direct = ftrace_find_direct_func(addr);
- if (!direct) {
- direct = kmalloc(sizeof(*direct), GFP_KERNEL);
- if (!direct) {
- kfree(entry);
- goto out_unlock;
- }
- direct->addr = addr;
- direct->count = 0;
- list_add_rcu(&direct->next, &ftrace_direct_funcs);
- ftrace_direct_func_count++;
- }
-
+ ftrace_direct_func_count++;
entry->ip = ip;
entry->direct = addr;
__add_hash_entry(direct_functions, entry);
@@ -5145,18 +5092,8 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
if (ret) {
remove_hash_entry(direct_functions, entry);
+ ftrace_direct_func_count--;
kfree(entry);
- if (!direct->count) {
- list_del_rcu(&direct->next);
- synchronize_rcu_tasks();
- kfree(direct);
- if (free_hash)
- free_ftrace_hash(free_hash);
- free_hash = NULL;
- ftrace_direct_func_count--;
- }
- } else {
- direct->count++;
}
out_unlock:
mutex_unlock(&direct_mutex);
@@ -5199,7 +5136,6 @@ static struct ftrace_func_entry *find_direct_entry(unsigned long *ip,
int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
{
- struct ftrace_direct_func *direct;
struct ftrace_func_entry *entry;
int ret = -ENODEV;
@@ -5217,20 +5153,8 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
WARN_ON(ret);
remove_hash_entry(direct_functions, entry);
-
- direct = ftrace_find_direct_func(addr);
- if (!WARN_ON(!direct)) {
- /* This is the good path (see the ! before WARN) */
- direct->count--;
- WARN_ON(direct->count < 0);
- if (!direct->count) {
- list_del_rcu(&direct->next);
- synchronize_rcu_tasks();
- kfree(direct);
- kfree(entry);
- ftrace_direct_func_count--;
- }
- }
+ ftrace_direct_func_count--;
+ kfree(entry);
out_unlock:
mutex_unlock(&direct_mutex);
--
2.25.4
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