Re: [PATCH 2/2 v2] tracing/syscalls: support for syscalls tracingon x86-64

[Ingo Molnar]

* Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Fri, 13 Mar 2009 15:42:12 +0100 Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:
> 
> > +static struct syscall_metadata *find_syscall_meta(unsigned long *syscall)
> > +{
> > +	struct syscall_metadata *start;
> > +	struct syscall_metadata *stop;
> > +	char str[KSYM_SYMBOL_LEN];
> > +
> > +
> > +	start = (struct syscall_metadata *)__start_syscalls_metadata;
> > +	stop = (struct syscall_metadata *)__stop_syscalls_metadata;
> > +	kallsyms_lookup((unsigned long) syscall, NULL, NULL, NULL, str);
> > +
> > +	for ( ; start < stop; start++) {
> > +		if (start->name && !strcmp(start->name, str))
> > +			return start;
> > +	}
> > +	return NULL;
> > +}
> 
> afacit this feature can be enabled when CONFIG_KALLSYMS=n.  
> Does that make sense?

It does not make much sense - the function will return NULL and 
we wont do any tracing. Frederic: FTRACE_SYSCALLS should either 
select KALLSYMS in kernel/trace/Kconfig, like the STACK_TRACER 
and FUNCTION_TRACER already does. Or perhaps, for really 
puritane tracing, we should emit simplified, non-symbolic trace 
data in the !KALLSYMS case.

	Ingo
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