linux-kernel - Re: [PATCH v10 perf, bpf-next 1/9] perf, bpf: Introduce PERF_RECORD

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Date:   Thu, 17 Jan 2019 13:48:24 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Song Liu <songliubraving@...com>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        acme@...nel.org, ast@...nel.org, daniel@...earbox.net,
        kernel-team@...com, dsahern@...il.com
Subject: Re: [PATCH v10 perf, bpf-next 1/9] perf, bpf: Introduce
 PERF_RECORD_KSYMBOL

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';