Re: [PATCH 06/18] tracing: Ftrace dynamic ftrace_event_call support

From: Masami Hiramatsu
Date: Thu Aug 27 2009 - 11:04:44 EST

Frederic Weisbecker wrote:
On Thu, Aug 27, 2009 at 10:47:24AM +0800, Li Zefan wrote:
-int trace_define_field(struct ftrace_event_call *call, const char *type,
- const char *name, int offset, int size, int is_signed,
+int trace_define_field(struct ftrace_event_call *call, char *type,
+ char *name, int offset, int size, int is_signed,
int filter_type)

I don't see why you remove "const"?

Because kprobes uses dynamically allocated strings as names.
That said, I should turn it back to const, it's indeed more sane.
I don't remember exactly the reason of this. I had to resolve several
conflicts between Masami's patchset and tracing/core, but I did
wrong in this part, indeed.

Ah, it should be a regression. My patches were based on an old ftrace
which used char * instead of const char *, before Li enhanced it.

Thank you for pointing it out!

struct ftrace_event_field *field;
@@ -92,9 +92,7 @@ int trace_define_common_fields(struct ftrace_event_call *call)


for (i = 0; i< meta->nb_args; i++) {
- ret = trace_define_field(call, meta->types[i],
- meta->args[i], offset,
+ ret = trace_define_field(call, (char *)meta->types[i],
+ (char *)meta->args[i], offset,

This is not good..


sizeof(unsigned long), 0,
offset += sizeof(unsigned long);
@@ -277,13 +277,13 @@ void ftrace_syscall_exit(struct pt_regs *regs, long ret)
trace_current_buffer_unlock_commit(event, 0, 0);


-int reg_event_syscall_exit(void *ptr)
+int reg_event_syscall_exit(struct ftrace_event_call *call)
int ret = 0;
int num;
char *name;

- name = (char *)ptr;
+ name = (char *)call->data;

nitpick: implicit cast is fine.

num = syscall_name_to_nr(name);
if (num< 0 || num>= FTRACE_SYSCALL_MAX)
return -ENOSYS;
@@ -342,12 +342,12 @@ int reg_event_syscall_exit(void *ptr)
return ret;

-void unreg_event_syscall_exit(void *ptr)
+void unreg_event_syscall_exit(struct ftrace_event_call *call)
int num;
char *name;

- name = (char *)ptr;
+ name = (char *)call->data;


Ok, I'll send a delta patch to fix these.


num = syscall_name_to_nr(name);
if (num< 0 || num>= FTRACE_SYSCALL_MAX)

Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@xxxxxxxxxx

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at