Re: [PATCH v10 perf, bpf-next 1/9] perf, bpf: Introduce PERF_RECORD_KSYMBOL

[Peter Zijlstra]

On Wed, Jan 16, 2019 at 08:29:23AM -0800, Song Liu wrote:
> +/* callback function to generate ksymbol name */
> +typedef int (perf_ksymbol_get_name_f)(char *name, int name_len, void *data);
> +extern void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len,
> +                            bool unregister,
> +                            perf_ksymbol_get_name_f get_name, void *data);
> +

I'm not liking the getname thing.. I know that's what BPF does, but can
we please do that in the caller or something?


--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1114,11 +1114,8 @@ static inline void perf_event_task_sched
 
 extern void perf_event_mmap(struct vm_area_struct *vma);
 
-/* callback function to generate ksymbol name */
-typedef int (perf_ksymbol_get_name_f)(char *name, int name_len, void *data);
 extern void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len,
-                              bool unregister,
-                              perf_ksymbol_get_name_f get_name, void *data);
+                              bool unregister, const char *name);
 
 extern struct perf_guest_info_callbacks *perf_guest_cbs;
 extern int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks 
*callbacks);
@@ -1341,11 +1338,8 @@ static inline int perf_unregister_guest_
 
 static inline void perf_event_mmap(struct vm_area_struct *vma)         { }
 
-typedef int (perf_ksymbol_get_name_f)(char *name, int name_len, void *data);
 static inline void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len,
-                                     bool unregister,
-                                     perf_ksymbol_get_name_f get_name,
-                                     void *data)                       { }
+                                     bool unregister, const char *name) { }
 static inline void perf_event_exec(void)                               { }
 static inline void perf_event_comm(struct task_struct *tsk, bool exec) { }
 static inline void perf_event_namespaces(struct task_struct *tsk)      { }
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7698,8 +7698,7 @@ static void perf_event_ksymbol_output(st
        perf_output_end(&handle);
 }
 
-void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len, bool unregister,
-                       perf_ksymbol_get_name_f get_name, void *data)
+void perf_event_ksymbol(u16 ksym_type, u64 addr, u32 len, bool unregister, 
const char *sym)
 {
        struct perf_ksymbol_event ksymbol_event;
        char name[KSYM_NAME_LEN];
@@ -7713,7 +7712,7 @@ void perf_event_ksymbol(u16 ksym_type, u
            ksym_type == PERF_RECORD_KSYMBOL_TYPE_UNKNOWN)
                goto err;
 
-       get_name(name, KSYM_NAME_LEN, data);
+       strlcpy(name, sym, KSYM_NAME_LEN);
        name_len = strlen(name) + 1;
        while (!IS_ALIGNED(name_len, sizeof(u64)))
                name[name_len++] = '\0';