Re: [PATCH 2/2] kprobe: fix: Add ftrace_ops_assist_func to kprobe blacklist

[Francis Deslauriers <francis.deslauriers@efficios.com>]

Le mer. 11 juill. 2018, à 15 h 56, Steven Rostedt
<rostedt@goodmis.org> a écrit :
>
> On Wed, 11 Jul 2018 15:34:30 -0400
> Francis Deslauriers <francis.deslauriers@efficios.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).
>
I will put together a proper patch set with both commits.

Masami, you mentioned: "So anyway we still need to mark those functions
NOKPROBE_SYMBOL." in a reply. What functions were you talking about?
ftrace_ops_assist_func? Aren't those functions covered by your
within_notrace_func check?

Thank you,
Francis

> -- Steve
>
>
> > Thanks
> > Francis
> >
> > >From d5a3645bd0046f28275d6b60207958f2751c1f47 Mon Sep 17 00:00:00 2001
> > From: Francis Deslauriers <francis.deslauriers@efficios.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@efficios.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);
>


--
Francis Deslauriers
Software developer
EfficiOS inc.