On Wed, 11 Jul 2018 15:34:30 -0400 Francis Deslauriers <francis.deslauri...@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. Ah, good catch. > > Thanks > Francis > > From d5a3645bd0046f28275d6b60207958f2751c1f47 Mon Sep 17 00:00:00 2001 > From: Francis Deslauriers <francis.deslauri...@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. Looks good to me. Acked-by: Masami Hiramatsu <mhira...@kernel.org> Thanks! > > Signed-off-by: Francis Deslauriers <francis.deslauri...@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); > -- > 2.7.4 > > > Le mar. 3 juill. 2018, à 18 h 31, Steven Rostedt <rost...@goodmis.org> a > écrit : > > > > Mathieu and Francis, > > > > Looking back, this thread never got further. Would Masami's patch work > > for you? > > > > -- Steve > > > > > > On Sat, 17 Mar 2018 10:22:11 +0900 > > Masami Hiramatsu <mhira...@kernel.org> wrote: > > > > > On Sat, 17 Mar 2018 09:13:34 +0900 > > > Masami Hiramatsu <mhira...@kernel.org> wrote: > > > > > > > On Fri, 16 Mar 2018 13:53:01 -0400 (EDT) > > > > Mathieu Desnoyers <mathieu.desnoy...@efficios.com> wrote: > > > > > > > > > ----- On Mar 16, 2018, at 12:48 PM, rostedt rost...@goodmis.org wrote: > > > > > > > > > > > On Fri, 16 Mar 2018 12:41:34 -0400 > > > > > > Steven Rostedt <rost...@goodmis.org> wrote: > > > > > > > > > > > >> Yes, kprobes are dangerous. I'm not saying it shouldn't be fixed, > > > > > >> I'm > > > > > >> saying that I don't have time to fix it now, but would be happy to > > > > > >> accept patches if someone else does so. > > > > > > > > > > > > And looking at what I replied before for the original patch. It > > > > > > would > > > > > > probably be a good idea to blacklist directories. Like we do with > > > > > > function tracing. We probably should black list both kernel/tracing > > > > > > and > > > > > > kernel/events from being probed. > > > > > > > > > > > > Did this come up at plumbers? You were there too, I don't remember > > > > > > discussing it there. > > > > > > > > > > I don't remember this coming up last Plumbers nor KS neither, given > > > > > that we were focused on other topics. > > > > > > > > > > Would the general approach you envision be based on emitting all code > > > > > generated by compilation of all objects under kernel/tracing and > > > > > kernel/events into a specific "nokprobes" text section of the kernel ? > > > > > Perhaps we could create a specific linker scripts for those > > > > > directories, > > > > > or do you have in mind a neater way to do this ? > > > > > > > > .kprobes.text section still exists. As I pointed in previous mail, I > > > > don't > > > > think we have to put all those code into that section. But if you want, > > > > it is acceptable to have a kconfig which push most of those ftrace > > > > related > > > > code into .kprobes.text section. > > > > > > Or, we can check it by ftrace_location_range() as below patch. > > > > > > Note that as a side-effect, we can not trace functions in trace_kprobe.c > > > anymore, and this means it is hard to me to make a testcase of kprobe > > > events. > > > It was the easiest (and maintainable) way to make test cases... sigh. > > > > > > ----- > > > tracing: kprobes: Prohibit probing on notrace function > > > > > > From: Masami Hiramatsu <mhira...@kernel.org> > > > > > > Prohibit kprobe-events probing on notrace function. > > > Since probing on the notrace function can cause recursive > > > event call. In most case those are just skipped, but > > > in some case it falls into infinit recursive call. > > > > > > Signed-off-by: Masami Hiramatsu <mhira...@kernel.org> > > > --- > > > kernel/trace/trace_kprobe.c | 23 +++++++++++++++++++++++ > > > 1 file changed, 23 insertions(+) > > > > > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > > > index 5ce9b8cf7be3..7404b012e51a 100644 > > > --- a/kernel/trace/trace_kprobe.c > > > +++ b/kernel/trace/trace_kprobe.c > > > @@ -487,6 +487,23 @@ disable_trace_kprobe(struct trace_kprobe *tk, struct > > > trace_event_file *file) > > > return ret; > > > } > > > > > > +#ifdef CONFIG_KPROBES_ON_FTRACE > > > +static bool within_notrace_func(struct trace_kprobe *tk) > > > +{ > > > + unsigned long offset, size, addr; > > > + > > > + addr = kallsyms_lookup_name(trace_kprobe_symbol(tk)); > > > + addr += trace_kprobe_offset(tk); > > > + > > > + if (!kallsyms_lookup_size_offset(addr, &size, &offset)) > > > + return true; /* Out of range. */ > > > + > > > + return !ftrace_location_range(addr - offset, addr - offset + size); > > > +} > > > +#else > > > +#define within_notrace_func(tk) (false) > > > +#endif > > > + > > > /* Internal register function - just handle k*probes and flags */ > > > static int __register_trace_kprobe(struct trace_kprobe *tk) > > > { > > > @@ -495,6 +512,12 @@ static int __register_trace_kprobe(struct > > > trace_kprobe *tk) > > > if (trace_probe_is_registered(&tk->tp)) > > > return -EINVAL; > > > > > > + if (within_notrace_func(tk)) { > > > + pr_warn("Could not probe notrace function %s\n", > > > + trace_kprobe_symbol(tk)); > > > + return -EINVAL; > > > + } > > > + > > > for (i = 0; i < tk->tp.nr_args; i++) > > > traceprobe_update_arg(&tk->tp.args[i]); > > > > > > > > > > > -- > Francis Deslauriers > Software developer > EfficiOS inc. -- Masami Hiramatsu <mhira...@kernel.org>