Messages in this thread | | | Date | Wed, 28 Sep 2022 00:22:21 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH] kprobes: Mark ftrace mcount handler functions nokprobe |
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On Mon, 26 Sep 2022 14:37:23 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:
> On Mon, 19 Sep 2022 16:45:33 +0800 > Liao Chang <liaochang1@huawei.com> wrote: > > > Mark ftrace mcount handler functions nokprobe since probing on these > > functions probably reaches mcount recursivly during kprobe breakpoint > > handler for some architecture(tested for riscv, arm64), and reenter > > kprobe is treated as a fatal error, causes kernel panic. > > This looks to me that the affected archs should be made more robust for this > case than to add this to the generic code.
Yeah, kprobes (arch specific code) itself shouldn't be traced by ftrace usually.
Thank you,
> > -- Steve > > > > > > Pesudo code below demonstrate this problem: > > > > mcount > > function_trace_call (probed) > > arch_breakpoint_handler > > arch_setup_singlestep [mcount] > > function_trace_call (probed) > > arch_breakpoint_handler > > reenter_kprobe > > BUG > > > > Signed-off-by: Liao Chang <liaochang1@huawei.com> > > --- > > kernel/trace/trace_functions.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c > > index 9f1bfbe105e8..440a678a8c7c 100644 > > --- a/kernel/trace/trace_functions.c > > +++ b/kernel/trace/trace_functions.c > > @@ -16,6 +16,7 @@ > > #include <linux/ftrace.h> > > #include <linux/slab.h> > > #include <linux/fs.h> > > +#include <linux/kprobes.h> > > > > #include "trace.h" > > > > @@ -194,6 +195,7 @@ function_trace_call(unsigned long ip, unsigned long parent_ip, > > > > ftrace_test_recursion_unlock(bit); > > } > > +NOKPROBE_SYMBOL(function_trace_call); > > > > #ifdef CONFIG_UNWINDER_ORC > > /* > > @@ -245,6 +247,7 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip, > > atomic_dec(&data->disabled); > > local_irq_restore(flags); > > } > > +NOKPROBE_SYMBOL(function_stack_trace_call); > > > > static inline bool is_repeat_check(struct trace_array *tr, > > struct trace_func_repeats *last_info, > > @@ -321,6 +324,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip, > > out: > > ftrace_test_recursion_unlock(bit); > > } > > +NOKPROBE_SYMBOL(function_no_repeats_trace_call); > > > > static void > > function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip, > > @@ -363,6 +367,7 @@ function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip, > > atomic_dec(&data->disabled); > > local_irq_restore(flags); > > } > > +NOKPROBE_SYMBOL(function_stack_no_repeats_trace_call); > > > > static struct tracer_opt func_opts[] = { > > #ifdef CONFIG_STACKTRACE >
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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