Re: [PATCH 2/2] tracing: Document HAVE_FTRACE_SYSCALLS needs

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:

> Document the arch needed requirements to get the support for syscalls
> tracing.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Cc: Jason Baron <jbaron@xxxxxxxxxx>
> Cc: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Cc: Paul Mundt <lethal@xxxxxxxxxxxx>
> ---
>  Documentation/trace/ftrace-design.txt |   11 ++++++++++-
>  1 files changed, 10 insertions(+), 1 deletions(-)
> 
> diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
> index 7003e10..04ab61c 100644
> --- a/Documentation/trace/ftrace-design.txt
> +++ b/Documentation/trace/ftrace-design.txt
> @@ -216,7 +216,16 @@ If you can't trace NMI functions, then skip this option.
>  HAVE_FTRACE_SYSCALLS
>  ---------------------
>  
> -<details to be filled>
> +You need very few things to get the syscalls tracing in an arch.
> +
> +- Have a NR_syscalls variable in <asm/unistd.h> that provides the number
> +  of syscalls supported by the arch.
> +- Implement arch_syscall_addr() that resolves a syscall address from a
> +  syscall number.
> +- Support the TIF_SYSCALL_TRACEPOINT thread flags
> +- Put the trace_sys_enter() and trace_sys_exit() tracepoints calls from ptrace
> +  in the ptrace syscalls tracing path.
> +- Tag this arch as HAVE_FTRACE_SYSCALLS.

HAVE_FTRACE_SYSCALLS is not actually used anywhere.

	Ingo
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