[PATCH 2/8] ftrace: Remove the legacy _ftrace_direct API

Florent Revest
2023-02-01T16:36:42Z

This API relies on a single global ops, used for all direct calls
registered with it. However, to implement arm64 direct calls, we need
each ops to point to a single direct call trampoline.

Signed-off-by: Florent Revest <revest@chromium.org>
---
include/linux/ftrace.h | 32 ----
kernel/trace/ftrace.c | 393 -----------------------------------------
2 files changed, 425 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 366c730beaa3..2d7c85e47c2d 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -397,14 +397,6 @@ struct ftrace_func_entry {

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
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,
- unsigned long new_addr);
unsigned long ftrace_find_rec_direct(unsigned long ip);
int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
@@ -414,30 +406,6 @@ int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr
#else
struct ftrace_ops;
# define ftrace_direct_func_count 0
-static inline int register_ftrace_direct(unsigned long ip, unsigned long addr)
-{
- return -ENOTSUPP;
-}
-static inline int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
-{
- return -ENOTSUPP;
-}
-static inline int modify_ftrace_direct(unsigned long ip,
- unsigned long old_addr, unsigned long new_addr)
-{
- 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,
- unsigned long new_addr)
-{
- return -ENODEV;
-}
static inline unsigned long ftrace_find_rec_direct(unsigned long ip)
{
return 0;
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index e634b80f49d1..5efe201428fa 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2585,20 +2585,6 @@ static void call_direct_funcs(unsigned long ip, unsigned long pip,

arch_ftrace_set_direct_caller(fregs, addr);
}
-
-struct ftrace_ops direct_ops = {
- .func = call_direct_funcs,
- .flags = FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS
- | FTRACE_OPS_FL_PERMANENT,
- /*
- * By declaring the main trampoline as this trampoline
- * it will never have one allocated for it. Allocated
- * trampolines should not call direct functions.
- * The direct_ops should only be called by the builtin
- * ftrace_regs_caller trampoline.
- */
- .trampoline = FTRACE_REGS_ADDR,
-};
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */

/**
@@ -5295,387 +5281,8 @@ struct ftrace_direct_func {

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;
-}
-
-static struct ftrace_direct_func *ftrace_alloc_direct_func(unsigned long addr)
-{
- struct ftrace_direct_func *direct;
-
- direct = kmalloc(sizeof(*direct), GFP_KERNEL);
- if (!direct)
- return NULL;
- direct->addr = addr;
- direct->count = 0;
- list_add_rcu(&direct->next, &ftrace_direct_funcs);
- ftrace_direct_func_count++;
- return direct;
-}
-
static int register_ftrace_function_nolock(struct ftrace_ops *ops);

-/**
- * register_ftrace_direct - Call a custom trampoline directly
- * @ip: The address of the nop at the beginning of a function
- * @addr: The address of the trampoline to call at @ip
- *
- * This is used to connect a direct call from the nop location (@ip)
- * at the start of ftrace traced functions. The location that it calls
- * (@addr) must be able to handle a direct call, and save the parameters
- * of the function being traced, and restore them (or inject new ones
- * if needed), before returning.
- *
- * Returns:
- * 0 on success
- * -EBUSY - Another direct function is already attached (there can be only one)
- * -ENODEV - @ip does not point to a ftrace nop location (or not supported)
- * -ENOMEM - There was an allocation failure.
- */
-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;
- int ret = -ENODEV;
-
- mutex_lock(&direct_mutex);
-
- ip = ftrace_location(ip);
- if (!ip)
- goto out_unlock;
-
- /* See if there's a direct function at @ip already */
- ret = -EBUSY;
- if (ftrace_find_rec_direct(ip))
- goto out_unlock;
-
- ret = -ENODEV;
- rec = lookup_rec(ip, ip);
- if (!rec)
- goto out_unlock;
-
- /*
- * Check if the rec says it has a direct call but we didn't
- * find one earlier?
- */
- if (WARN_ON(rec->flags & FTRACE_FL_DIRECT))
- goto out_unlock;
-
- /* Make sure the ip points to the exact record */
- if (ip != rec->ip) {
- ip = rec->ip;
- /* Need to check this ip for a direct. */
- if (ftrace_find_rec_direct(ip))
- goto out_unlock;
- }
-
- ret = -ENOMEM;
- direct = ftrace_find_direct_func(addr);
- if (!direct) {
- direct = ftrace_alloc_direct_func(addr);
- if (!direct)
- goto out_unlock;
- }
-
- entry = ftrace_add_rec_direct(ip, addr, &free_hash);
- if (!entry)
- goto out_unlock;
-
- ret = ftrace_set_filter_ip(&direct_ops, ip, 0, 0);
-
- if (!ret && !(direct_ops.flags & FTRACE_OPS_FL_ENABLED)) {
- ret = register_ftrace_function_nolock(&direct_ops);
- if (ret)
- ftrace_set_filter_ip(&direct_ops, ip, 1, 0);
- }
-
- if (ret) {
- remove_hash_entry(direct_functions, entry);
- 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);
-
- if (free_hash) {
- synchronize_rcu_tasks();
- free_ftrace_hash(free_hash);
- }
-
- return ret;
-}
-EXPORT_SYMBOL_GPL(register_ftrace_direct);
-
-static struct ftrace_func_entry *find_direct_entry(unsigned long *ip,
- struct dyn_ftrace **recp)
-{
- struct ftrace_func_entry *entry;
- struct dyn_ftrace *rec;
-
- rec = lookup_rec(*ip, *ip);
- if (!rec)
- return NULL;
-
- entry = __ftrace_lookup_ip(direct_functions, rec->ip);
- if (!entry) {
- WARN_ON(rec->flags & FTRACE_FL_DIRECT);
- return NULL;
- }
-
- WARN_ON(!(rec->flags & FTRACE_FL_DIRECT));
-
- /* Passed in ip just needs to be on the call site */
- *ip = rec->ip;
-
- if (recp)
- *recp = rec;
-
- return entry;
-}
-
-int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
-{
- struct ftrace_direct_func *direct;
- struct ftrace_func_entry *entry;
- struct ftrace_hash *hash;
- int ret = -ENODEV;
-
- mutex_lock(&direct_mutex);
-
- ip = ftrace_location(ip);
- if (!ip)
- goto out_unlock;
-
- entry = find_direct_entry(&ip, NULL);
- if (!entry)
- goto out_unlock;
-
- hash = direct_ops.func_hash->filter_hash;
- if (hash->count == 1)
- unregister_ftrace_function(&direct_ops);
-
- ret = ftrace_set_filter_ip(&direct_ops, ip, 1, 0);
-
- 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--;
- }
- }
- out_unlock:
- mutex_unlock(&direct_mutex);
-
- return ret;
-}
-EXPORT_SYMBOL_GPL(unregister_ftrace_direct);
-
-static struct ftrace_ops stub_ops = {
- .func = ftrace_stub,
-};
-
-/**
- * ftrace_modify_direct_caller - modify ftrace nop directly
- * @entry: The ftrace hash entry of the direct helper for @rec
- * @rec: The record representing the function site to patch
- * @old_addr: The location that the site at @rec->ip currently calls
- * @new_addr: The location that the site at @rec->ip should call
- *
- * An architecture may overwrite this function to optimize the
- * changing of the direct callback on an ftrace nop location.
- * This is called with the ftrace_lock mutex held, and no other
- * ftrace callbacks are on the associated record (@rec). Thus,
- * it is safe to modify the ftrace record, where it should be
- * currently calling @old_addr directly, to call @new_addr.
- *
- * This is called with direct_mutex locked.
- *
- * Safety checks should be made to make sure that the code at
- * @rec->ip is currently calling @old_addr. And this must
- * also update entry->direct to @new_addr.
- */
-int __weak ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
- struct dyn_ftrace *rec,
- unsigned long old_addr,
- unsigned long new_addr)
-{
- unsigned long ip = rec->ip;
- int ret;
-
- lockdep_assert_held(&direct_mutex);
-
- /*
- * The ftrace_lock was used to determine if the record
- * had more than one registered user to it. If it did,
- * we needed to prevent that from changing to do the quick
- * switch. But if it did not (only a direct caller was attached)
- * then this function is called. But this function can deal
- * with attached callers to the rec that we care about, and
- * since this function uses standard ftrace calls that take
- * the ftrace_lock mutex, we need to release it.
- */
- mutex_unlock(&ftrace_lock);
-
- /*
- * By setting a stub function at the same address, we force
- * the code to call the iterator and the direct_ops helper.
- * This means that @ip does not call the direct call, and
- * we can simply modify it.
- */
- ret = ftrace_set_filter_ip(&stub_ops, ip, 0, 0);
- if (ret)
- goto out_lock;
-
- ret = register_ftrace_function_nolock(&stub_ops);
- if (ret) {
- ftrace_set_filter_ip(&stub_ops, ip, 1, 0);
- goto out_lock;
- }
-
- entry->direct = new_addr;
-
- /*
- * By removing the stub, we put back the direct call, calling
- * the @new_addr.
- */
- unregister_ftrace_function(&stub_ops);
- ftrace_set_filter_ip(&stub_ops, ip, 1, 0);
-
- out_lock:
- mutex_lock(&ftrace_lock);
-
- return ret;
-}
-
-/**
- * modify_ftrace_direct - Modify an existing direct call to call something else
- * @ip: The instruction pointer to modify
- * @old_addr: The address that the current @ip calls directly
- * @new_addr: The address that the @ip should call
- *
- * This modifies a ftrace direct caller at an instruction pointer without
- * having to disable it first. The direct call will switch over to the
- * @new_addr without missing anything.
- *
- * Returns: zero on success. Non zero on error, which includes:
- * -ENODEV : the @ip given has no direct caller attached
- * -EINVAL : the @old_addr does not match the current direct caller
- */
-int modify_ftrace_direct(unsigned long ip,
- unsigned long old_addr, unsigned long new_addr)
-{
- struct ftrace_direct_func *direct, *new_direct = NULL;
- struct ftrace_func_entry *entry;
- struct dyn_ftrace *rec;
- int ret = -ENODEV;
-
- mutex_lock(&direct_mutex);
-
- mutex_lock(&ftrace_lock);
-
- ip = ftrace_location(ip);
- if (!ip)
- goto out_unlock;
-
- entry = find_direct_entry(&ip, &rec);
- if (!entry)
- goto out_unlock;
-
- ret = -EINVAL;
- if (entry->direct != old_addr)
- goto out_unlock;
-
- direct = ftrace_find_direct_func(old_addr);
- if (WARN_ON(!direct))
- goto out_unlock;
- if (direct->count > 1) {
- ret = -ENOMEM;
- new_direct = ftrace_alloc_direct_func(new_addr);
- if (!new_direct)
- goto out_unlock;
- direct->count--;
- new_direct->count++;
- } else {
- direct->addr = new_addr;
- }
-
- /*
- * If there's no other ftrace callback on the rec->ip location,
- * then it can be changed directly by the architecture.
- * If there is another caller, then we just need to change the
- * direct caller helper to point to @new_addr.
- */
- if (ftrace_rec_count(rec) == 1) {
- ret = ftrace_modify_direct_caller(entry, rec, old_addr, new_addr);
- } else {
- entry->direct = new_addr;
- ret = 0;
- }
-
- if (unlikely(ret && new_direct)) {
- direct->count++;
- list_del_rcu(&new_direct->next);
- synchronize_rcu_tasks();
- kfree(new_direct);
- ftrace_direct_func_count--;
- }
-
- out_unlock:
- mutex_unlock(&ftrace_lock);
- mutex_unlock(&direct_mutex);
- return ret;
-}
-EXPORT_SYMBOL_GPL(modify_ftrace_direct);
-
#define MULTI_FLAGS (FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS)

static int check_direct_multi(struct ftrace_ops *ops)
--
2.39.1.519.gcb327c4b5f-goog