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SubjectRe: [RFC][PATCH 1/2] tracing/ftrace: syscall tracing infrastructure

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> +static const struct syscall_trace_entry syscall_trace_entries[] = {
> + /* For open, the first argument is a string, hence the given mask */
> + [SYSCALL_TRACE_OPEN] = SYS_TRACE_ENTRY(open, 3, 0x1),
> + [SYSCALL_TRACE_CLOSE] = SYS_TRACE_ENTRY(close, 1, 0),
> + [SYSCALL_TRACE_READ] = SYS_TRACE_ENTRY(read, 3, 0),
> + [SYSCALL_TRACE_WRITE] = SYS_TRACE_ENTRY(read, 3, 0),
> +};

s/read/write in the last entry i guess.

But i think the whole concept of duplicating the syscall table
is the wrong way around.

Note that we dont have to build this information at all - in
2.6.29-rc1 all syscalls got wrapper macros:

SYSCALL_DEFINE1(nice, int, increment)
SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
unsigned long __user *, user_mask_ptr)

We also have the syscall table itself.

So what we can do: by changing the SYSCALL_DEFINEX() macros we
can emit the following information into a table:

(syscall_fn_address, syscall_name_string, #of arguments, array
of argument names and type sizeof()s)

then during bootup we can match up the sys_call_table[] to the
secondary table we built, so that we can order the secondary
table based on syscall NR. 99% of the syscalls will match up
just fine.

Ingo


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