diff options
| author | Menglong Dong <menglong8.dong@gmail.com> | 2025-11-18 20:36:29 +0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2025-11-24 09:46:24 -0800 |
| commit | 25e4e3565d45f567f78089f38822fa64abee5230 (patch) | |
| tree | 7da2d2ce9e9ad91b86dfa5e4d6df263163a9495d /kernel/trace/ftrace.c | |
| parent | fad804002ef3cae8ca0509849d0d9539be069095 (diff) | |
ftrace: Introduce FTRACE_OPS_FL_JMP
For now, the "nop" will be replaced with a "call" instruction when a
function is hooked by the ftrace. However, sometimes the "call" can break
the RSB and introduce extra overhead. Therefore, introduce the flag
FTRACE_OPS_FL_JMP, which indicate that the ftrace_ops should be called
with a "jmp" instead of "call". For now, it is only used by the direct
call case.
When a direct ftrace_ops is marked with FTRACE_OPS_FL_JMP, the last bit of
the ops->direct_call will be set to 1. Therefore, we can tell if we should
use "jmp" for the callback in ftrace_call_replace().
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20251118123639.688444-2-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/trace/ftrace.c')
| -rw-r--r-- | kernel/trace/ftrace.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 59cfacb8a5bb..bbb37c0f8c6c 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5951,7 +5951,8 @@ static void remove_direct_functions_hash(struct ftrace_hash *hash, unsigned long for (i = 0; i < size; i++) { hlist_for_each_entry(entry, &hash->buckets[i], hlist) { del = __ftrace_lookup_ip(direct_functions, entry->ip); - if (del && del->direct == addr) { + if (del && ftrace_jmp_get(del->direct) == + ftrace_jmp_get(addr)) { remove_hash_entry(direct_functions, del); kfree(del); } @@ -6016,8 +6017,15 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr) if (ftrace_hash_empty(hash)) return -EINVAL; + /* This is a "raw" address, and this should never happen. */ + if (WARN_ON_ONCE(ftrace_is_jmp(addr))) + return -EINVAL; + mutex_lock(&direct_mutex); + if (ops->flags & FTRACE_OPS_FL_JMP) + addr = ftrace_jmp_set(addr); + /* Make sure requested entries are not already registered.. */ size = 1 << hash->size_bits; for (i = 0; i < size; i++) { @@ -6138,6 +6146,13 @@ __modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr) lockdep_assert_held_once(&direct_mutex); + /* This is a "raw" address, and this should never happen. */ + if (WARN_ON_ONCE(ftrace_is_jmp(addr))) + return -EINVAL; + + if (ops->flags & FTRACE_OPS_FL_JMP) + addr = ftrace_jmp_set(addr); + /* Enable the tmp_ops to have the same functions as the direct ops */ ftrace_ops_init(&tmp_ops); tmp_ops.func_hash = ops->func_hash; |