linux-kernel - Re: [PATCH 2/2] kprobe: fix: Add ftrace_ops_assist

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Date:   Wed, 11 Jul 2018 15:56:28 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Francis Deslauriers <francis.deslauriers@...icios.com>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        torvalds@...ux-foundation.org
Subject: Re: [PATCH 2/2] kprobe: fix: Add ftrace_ops_assist_func to kprobe
 blacklist

On Wed, 11 Jul 2018 15:34:30 -0400
Francis Deslauriers <francis.deslauriers@...icios.com> wrote:

> Hi Steven,
> I tested it and it prevents the kernel crash I am witnessing.
> As for the side-effect that Masami mentioned regarding not being able to probe
> function inside the trace_kprobe.c file, I suggest we move the target
> function in
> its own separate compile unit so it can be compiled with the ftrace cflags.
> See patch below.
> 

The patch below looks fine and so does Masami's. But there's too many
patches within emails (not separated out). I have no idea what to
apply. I'm not going to apply anything that is not sent as a proper
patch (ie. any patch within a separate thread, like the patch below).

-- Steve


> Thanks
> Francis
> 
> >From d5a3645bd0046f28275d6b60207958f2751c1f47 Mon Sep 17 00:00:00 2001  
> From: Francis Deslauriers <francis.deslauriers@...icios.com>
> Date: Wed, 11 Jul 2018 12:34:22 -0400
> Subject: [PATCH] selftest/ftrace: Move kprobe selftest function to separate
>  compile unit
> 
> Move selftest function to its own compile unit so it can be compiled
> with the ftrace cflags (CC_FLAGS_FTRACE) allowing it to be probed
> during the ftrace startup tests.
> 
> Signed-off-by: Francis Deslauriers <francis.deslauriers@...icios.com>
> ---
>  kernel/trace/Makefile                |  5 +++++
>  kernel/trace/trace_kprobe.c          | 12 +-----------
>  kernel/trace/trace_kprobe_selftest.c | 10 ++++++++++
>  kernel/trace/trace_kprobe_selftest.h |  7 +++++++
>  4 files changed, 23 insertions(+), 11 deletions(-)
>  create mode 100644 kernel/trace/trace_kprobe_selftest.c
>  create mode 100644 kernel/trace/trace_kprobe_selftest.h
> 
> diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
> index e2538c7..e38771e 100644
> --- a/kernel/trace/Makefile
> +++ b/kernel/trace/Makefile
> @@ -13,6 +13,11 @@ obj-y += trace_selftest_dynamic.o
>  endif
>  endif
> 
> +ifdef CONFIG_FTRACE_STARTUP_TEST
> +CFLAGS_trace_kprobe_selftest.o = $(CC_FLAGS_FTRACE)
> +obj-$(CONFIG_KPROBE_EVENTS) += trace_kprobe_selftest.o
> +endif
> +
>  # If unlikely tracing is enabled, do not trace these files
>  ifdef CONFIG_TRACING_BRANCHES
>  KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 952dc2a..3fe966f 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -24,6 +24,7 @@
>  #include <linux/error-injection.h>
> 
>  #include "trace_probe.h"
> +#include "trace_kprobe_selftest.h"
> 
>  #define KPROBE_EVENT_SYSTEM "kprobes"
>  #define KRETPROBE_MAXACTIVE_MAX 4096
> @@ -1560,17 +1561,6 @@ fs_initcall(init_kprobe_trace);
> 
> 
>  #ifdef CONFIG_FTRACE_STARTUP_TEST
> -/*
> - * The "__used" keeps gcc from removing the function symbol
> - * from the kallsyms table. 'noinline' makes sure that there
> - * isn't an inlined version used by the test method below
> - */
> -static __used __init noinline int
> -kprobe_trace_selftest_target(int a1, int a2, int a3, int a4, int a5, int a6)
> -{
> - return a1 + a2 + a3 + a4 + a5 + a6;
> -}
> -
>  static __init struct trace_event_file *
>  find_trace_probe_file(struct trace_kprobe *tk, struct trace_array *tr)
>  {
> diff --git a/kernel/trace/trace_kprobe_selftest.c
> b/kernel/trace/trace_kprobe_selftest.c
> new file mode 100644
> index 0000000..a3d2090
> --- /dev/null
> +++ b/kernel/trace/trace_kprobe_selftest.c
> @@ -0,0 +1,10 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Function used during the kprobe self test. This function is in a seperate
> + * compile unit so it can be compile with CC_FLAGS_FTRACE to ensure that it
> + * can be probed by the selftests.
> + */
> +int kprobe_trace_selftest_target(int a1, int a2, int a3, int a4, int
> a5, int a6)
> +{
> + return a1 + a2 + a3 + a4 + a5 + a6;
> +}
> diff --git a/kernel/trace/trace_kprobe_selftest.h
> b/kernel/trace/trace_kprobe_selftest.h
> new file mode 100644
> index 0000000..9243d4e
> --- /dev/null
> +++ b/kernel/trace/trace_kprobe_selftest.h
> @@ -0,0 +1,7 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Function used during the kprobe self test. This function is in a seperate
> + * compile unit so it can be compile with CC_FLAGS_FTRACE to ensure that it
> + * can be probed by the selftests.
> + */
> +int kprobe_trace_selftest_target(int a1, int a2, int a3, int a4, int
> a5, int a6);