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SubjectRe: [PATCH] [RFC] tracehook: Hook in syscall tracing markers.
Hi Paul,

> At kernel summit, the idea that syscall tracing was generally desirable
> for tracing was mentioned several times, as was the argument that kernel
> developers aren't placing markers in meaningful locations. This is a
> simple patch to try and do that for the syscall case.
>
> Presently LTTng attempts to litter these trace markers all over the
> architecture code, primarily to get around the fact that there was no
> generic way to get at this information before. Now that platforms are
> starting to do their syscall entry/exit notifiers through tracehook and
> we have the asm/syscall.h interface, all of this information can be
> generically abstracted.
>
> Signed-off-by: Paul Mundt <lethal@linux-sh.org>
>

I think marriage between tracehook and generic marker is very good idea.
at least, instruction pointer and return value are definitly useful.

but...
Have you seen Mathieu's tracepoint patch?
I recommend to use tracepoint insted use marker directly.


> ---
>
> include/linux/tracehook.h | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
> index 6186a78..481ff45 100644
> --- a/include/linux/tracehook.h
> +++ b/include/linux/tracehook.h
> @@ -49,6 +49,9 @@
> #include <linux/sched.h>
> #include <linux/ptrace.h>
> #include <linux/security.h>
> +#include <linux/marker.h>
> +#include <asm/syscall.h>
> +
> struct linux_binprm;
>
> /**
> @@ -112,6 +115,8 @@ static inline __must_check int tracehook_report_syscall_entry(
> struct pt_regs *regs)
> {
> ptrace_report_syscall(regs);
> + trace_mark(kernel_arch_syscall_entry, "syscall_id %ld ip #p%ld",
> + syscall_get_nr(NULL, regs), instruction_pointer(regs));
> return 0;
> }
>
> @@ -135,6 +140,8 @@ static inline __must_check int tracehook_report_syscall_entry(
> static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
> {
> ptrace_report_syscall(regs);
> + trace_mark(kernel_arch_syscall_exit, "ret %ld",
> + syscall_get_return_value(NULL, regs));
> }




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