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 /include | |
| 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 'include')
| -rw-r--r-- | include/linux/ftrace.h | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 07f8c309e432..015dd1049bea 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -359,6 +359,7 @@ enum { FTRACE_OPS_FL_DIRECT = BIT(17), FTRACE_OPS_FL_SUBOP = BIT(18), FTRACE_OPS_FL_GRAPH = BIT(19), + FTRACE_OPS_FL_JMP = BIT(20), }; #ifndef CONFIG_DYNAMIC_FTRACE_WITH_ARGS @@ -577,6 +578,38 @@ static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs, unsigned long addr) { } #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_JMP +static inline bool ftrace_is_jmp(unsigned long addr) +{ + return addr & 1; +} + +static inline unsigned long ftrace_jmp_set(unsigned long addr) +{ + return addr | 1UL; +} + +static inline unsigned long ftrace_jmp_get(unsigned long addr) +{ + return addr & ~1UL; +} +#else +static inline bool ftrace_is_jmp(unsigned long addr) +{ + return false; +} + +static inline unsigned long ftrace_jmp_set(unsigned long addr) +{ + return addr; +} + +static inline unsigned long ftrace_jmp_get(unsigned long addr) +{ + return addr; +} +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_JMP */ + #ifdef CONFIG_STACK_TRACER int stack_trace_sysctl(const struct ctl_table *table, int write, void *buffer, |