linux-kernel - Re: [PATCH] tracing/x86: Update syscall trace events to handle new x86 syscall func names

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Date:   Tue, 17 Apr 2018 13:35:27 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Dominik Brodowski <linux@...inikbrodowski.net>
Subject: Re: [PATCH] tracing/x86: Update syscall trace events to handle new
 x86 syscall func names

Em Tue, Apr 17, 2018 at 11:54:40AM -0400, Steven Rostedt escreveu:
> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> 
> Arnaldo noticed that the latest kernel is missing the syscall event system
> directory in x86. I bisected it down to d5a00528b58c ("syscalls/core,
> syscalls/x86: Rename struct pt_regs-based sys_*() to __x64_sys_*()").
> 
> The system call trace events are special, as there is only one trace event
> for all system calls (the raw_syscalls). But a macro that wraps the system
> calls creates meta data for them that copies the name to find the system
> call that maps to the system call table (the number). At boot up, it does a
> kallsyms lookup for this mapping. If it does not find a function, then that
> system call is ignored.
> 
> Because the x86 system calls had "__x86_" appended to the "sys" for the
> names, they do not match the default compare algorithm. As this was a
> problem for power pc, the algorithm can be overwritten by the architecture.
> The solution is to have x86 have its own algorithm to do the compare and
> this brings back the system call trace events.
> 
> Reported-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> Fixes: d5a00528b58c ("syscalls/core, syscalls/x86: Rename struct pt_regs-based sys_*() to __x64_sys_*()")
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

[root@...et ~]# perf test openat
 2: Detect openat syscall event                           : Ok
 3: Detect openat syscall event on all cpus               : Ok
15: syscalls:sys_enter_openat event fields                : Ok
[root@...et ~]#

[root@...et ~]# perf trace -e nanosleep,syscalls:*nanosleep sleep 1
     0.000 (         ): syscalls:sys_enter_nanosleep:rqtp: 0x7ffd9f737950, rmtp: 0x00000000
     0.009 (         ): sleep/7905 nanosleep(rqtp: 0x7ffd9f737950                                        ) ...
  1000.204 (         ): syscalls:sys_exit_nanosleep:0x0
     0.009 (1000.217 ms): sleep/7905  ... [continued]: nanosleep()) = 0
[root@...et ~]#

Works, so the regression seems to be fixed, without looking at the code
that much:

Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>

- Arnaldo