Messages in this thread | | | Date | Fri, 11 Oct 2019 14:26:50 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] ftrace: fix function type mismatches |
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On Thu, 10 Oct 2019 14:12:24 -0700 Kees Cook <keescook@chromium.org> wrote:
> On Mon, Oct 07, 2019 at 02:47:40PM -0700, Sami Tolvanen wrote: > > This change fixes indirect call mismatches with function and function > > graph tracing, which trip Control-Flow Integrity (CFI) checking. > > > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > Thanks for sending this! We're getting pretty close to having all the > various CFI issues cleaned up now. :)
Unfortunately, this breaks function graph tracing. There's lots of arch code that tests if the function graph tracer is set to point to the ftrace_stub. Which by the way is a nop function written in assembly.
Is there a way to do an alias or something that can fix whatever you are trying to fix?
> Reviewed-by: Kees Cook <keescook@chromium.org> > > -Kees > > > --- > > kernel/trace/fgraph.c | 9 ++++++--- > > kernel/trace/ftrace.c | 8 +++++--- > > 2 files changed, 11 insertions(+), 6 deletions(-) > > > > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c > > index 7950a0356042..ecfd4a4a106a 100644 > > --- a/kernel/trace/fgraph.c > > +++ b/kernel/trace/fgraph.c > > @@ -327,14 +327,17 @@ void ftrace_graph_sleep_time_control(bool enable) > > fgraph_sleep_time = enable; > > } > > > > +void ftrace_graph_return_stub(struct ftrace_graph_ret *trace) > > +{ > > +} > > + > > int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace) > > { > > return 0; > > } > > > > /* The callbacks that hook a function */ > > -trace_func_graph_ret_t ftrace_graph_return = > > - (trace_func_graph_ret_t)ftrace_stub; > > +trace_func_graph_ret_t ftrace_graph_return = ftrace_graph_return_stub; > > trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub; > > static trace_func_graph_ent_t __ftrace_graph_entry = ftrace_graph_entry_stub; > > > > @@ -614,7 +617,7 @@ void unregister_ftrace_graph(struct fgraph_ops *gops) > > goto out; > > > > ftrace_graph_active--; > > - ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub; > > + ftrace_graph_return = ftrace_graph_return_stub; > > ftrace_graph_entry = ftrace_graph_entry_stub; > > __ftrace_graph_entry = ftrace_graph_entry_stub; > > ftrace_shutdown(&graph_ops, FTRACE_STOP_FUNC_RET); > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > > index 62a50bf399d6..b68ee130d4a2 100644 > > --- a/kernel/trace/ftrace.c > > +++ b/kernel/trace/ftrace.c > > @@ -125,8 +125,9 @@ static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip, > > struct ftrace_ops *op, struct pt_regs *regs); > > #else > > /* See comment below, where ftrace_ops_list_func is defined */ > > -static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip); > > -#define ftrace_ops_list_func ((ftrace_func_t)ftrace_ops_no_ops) > > +static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip, > > + struct ftrace_ops *op, struct pt_regs *regs); > > +#define ftrace_ops_list_func ftrace_ops_no_ops > > #endif > > > > static inline void ftrace_ops_init(struct ftrace_ops *ops) > > @@ -6325,7 +6326,8 @@ static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip, > > } > > NOKPROBE_SYMBOL(ftrace_ops_list_func); > > #else > > -static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip) > > +static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip, > > + struct ftrace_ops *op, struct pt_regs *regs)
Also, this happens to be done because the arch only passes in the first two parameters. That's why this is called when ARCH_SUPPORTS_FTRACE_OPS is net set.
The Linux world is not x86 only!
-- Steve
> > { > > __ftrace_ops_list_func(ip, parent_ip, NULL, NULL); > > } > > -- > > 2.23.0.581.g78d2f28ef7-goog > > >
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