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Date: Thu, 3 May 2018 12:15:38 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Julia Cartwright <julia@...com>
Cc: <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] trace-cmd: add plugin for decoding
syscalls/sys_enter_futex
On Wed, 6 Dec 2017 20:56:49 -0600
Julia Cartwright <julia@...com> wrote:
> The futex syscall is a complicated one. It supports thirteen
> multiplexed operations, each with different semantics and encodings for
> the syscalls six arguments.
>
> Manually decoding these arguments is tedious and error prone.
>
> This plugin provides symbolic names for futex operations, futex flags,
> and tries to be intelligent about the intent of specific arguments (for
> example, waking operations use 'val' as an integer count, not just an
> arbitrary value).
>
> It doesn't do a full decode of the FUTEX_WAKE_OP's 'val3' argument,
> however, this is a good starting point.
>
> Signed-off-by: Julia Cartwright <julia@...com>
Hi Julia,
I missed this patch. I just applied it and will be pushing it out soon.
Thanks!
-- Steve
> ---
> Makefile | 1 +
> plugin_futex.c | 135 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 136 insertions(+)
> create mode 100644 plugin_futex.c
>
> diff --git a/Makefile b/Makefile
> index 5c35143c8867..58b957d9a578 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -365,6 +365,7 @@ PLUGIN_OBJS += plugin_kvm.o
> PLUGIN_OBJS += plugin_mac80211.o
> PLUGIN_OBJS += plugin_sched_switch.o
> PLUGIN_OBJS += plugin_function.o
> +PLUGIN_OBJS += plugin_futex.o
> PLUGIN_OBJS += plugin_xen.o
> PLUGIN_OBJS += plugin_scsi.o
> PLUGIN_OBJS += plugin_cfg80211.o
> diff --git a/plugin_futex.c b/plugin_futex.c
> new file mode 100644
> index 000000000000..b12c92d91a86
> --- /dev/null
> +++ b/plugin_futex.c
> @@ -0,0 +1,135 @@
> +/*
> + * Copyright (C) 2017 National Instruments Corp.
> + *
> + * Author: Julia Cartwright <julia@...com>
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation;
> + * version 2.1 of the License (not later!)
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this program; if not, see <http://www.gnu.org/licenses>
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + */
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <linux/futex.h>
> +
> +#include "trace-cmd.h"
> +
> +struct futex_args {
> + unsigned long long uaddr;
> + unsigned long long op;
> + unsigned long long val;
> + unsigned long long utime; /* or val2 */
> + unsigned long long uaddr2;
> + unsigned long long val3;
> +};
> +
> +struct futex_op {
> + const char *name;
> + const char *fmt_val;
> + const char *fmt_utime;
> + const char *fmt_uaddr2;
> + const char *fmt_val3;
> +};
> +
> +static const struct futex_op futex_op_tbl[] = {
> + { "FUTEX_WAIT", " val=0x%08llx", " utime=0x%08llx", NULL, NULL },
> + { "FUTEX_WAKE", " val=%llu", NULL, NULL, NULL },
> + { "FUTEX_FD", " val=%llu", NULL, NULL, NULL },
> + { "FUTEX_REQUEUE", " val=%llu", " val2=%llu", " uaddr2=0x%08llx", NULL },
> + { "FUTEX_CMP_REQUEUE", " val=%llu", " val2=%llu", " uaddr2=0x%08llx", " val3=0x%08llx" },
> + { "FUTEX_WAKE_OP", " val=%llu", " val2=%llu", " uaddr2=0x%08llx", " val3=0x%08llx" },
> + { "FUTEX_LOCK_PI", NULL, " utime=0x%08llx", NULL, NULL },
> + { "FUTEX_UNLOCK_PI", NULL, NULL, NULL, NULL },
> + { "FUTEX_TRYLOCK_PI", NULL, NULL, NULL, NULL },
> + { "FUTEX_WAIT_BITSET", " val=0x%08llx", " utime=0x%08llx", NULL, " val3=0x%08llx" },
> + { "FUTEX_WAKE_BITSET", " val=%llu", NULL, NULL, " val3=0x%08llx" },
> + { "FUTEX_WAIT_REQUEUE_PI", " val=0x%08llx", " utime=0x%08llx", " uaddr2=0x%08llx", " val3=0x%08llx" },
> + { "FUTEX_CMP_REQUEUE_PI", " val=%llu", " val2=%llu", " uaddr2=0x%08llx", " val3=0x%08llx" },
> +};
> +
> +
> +static void futex_print(struct trace_seq *s, const struct futex_args *args,
> + const struct futex_op *fop)
> +{
> + trace_seq_printf(s, " uaddr=0x%08llx", args->uaddr);
> +
> + if (fop->fmt_val)
> + trace_seq_printf(s, fop->fmt_val, args->val);
> +
> + if (fop->fmt_utime)
> + trace_seq_printf(s,fop->fmt_utime, args->utime);
> +
> + if (fop->fmt_uaddr2)
> + trace_seq_printf(s, fop->fmt_uaddr2, args->uaddr2);
> +
> + if (fop->fmt_val3)
> + trace_seq_printf(s, fop->fmt_val3, args->val3);
> +}
> +
> +static int futex_handler(struct trace_seq *s, struct pevent_record *record,
> + struct event_format *event, void *context)
> +{
> + const struct futex_op *fop;
> + struct futex_args args;
> + unsigned long long cmd;
> +
> + if (pevent_get_field_val(s, event, "uaddr", record, &args.uaddr, 1))
> + return 1;
> +
> + if (pevent_get_field_val(s, event, "op", record, &args.op, 1))
> + return 1;
> +
> + if (pevent_get_field_val(s, event, "val", record, &args.val, 1))
> + return 1;
> +
> + if (pevent_get_field_val(s, event, "utime", record, &args.utime, 1))
> + return 1;
> +
> + if (pevent_get_field_val(s, event, "uaddr2", record, &args.uaddr2, 1))
> + return 1;
> +
> + if (pevent_get_field_val(s, event, "val3", record, &args.val3, 1))
> + return 1;
> +
> + cmd = args.op & FUTEX_CMD_MASK;
> + if (cmd >= ARRAY_SIZE(futex_op_tbl))
> + return 1;
> +
> + fop = &futex_op_tbl[cmd];
> +
> + trace_seq_printf(s, "op=%s", fop->name);
> +
> + if (args.op & FUTEX_PRIVATE_FLAG)
> + trace_seq_puts(s, "|FUTEX_PRIVATE_FLAG");
> +
> + if (args.op & FUTEX_CLOCK_REALTIME)
> + trace_seq_puts(s, "|FUTEX_CLOCK_REALTIME");
> +
> + futex_print(s, &args, fop);
> + return 0;
> +}
> +
> +int PEVENT_PLUGIN_LOADER(struct pevent *pevent)
> +{
> + pevent_register_event_handler(pevent, -1, "syscalls", "sys_enter_futex",
> + futex_handler, NULL);
> + return 0;
> +}
> +
> +void PEVENT_PLUGIN_UNLOADER(struct pevent *pevent)
> +{
> + pevent_unregister_event_handler(pevent, -1, "syscalls", "sys_enter_futex",
> + futex_handler, NULL);
> +}
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