On Mon, 30 Sep 2024 14:46:59 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> On Tue, 17 Sep 2024 09:26:25 +0100 > Will Deacon <w...@kernel.org> wrote: > > > On Sun, Sep 15, 2024 at 04:46:14AM -0400, Steven Rostedt wrote: > > > Can I get an Acked-by from the AARCH64 maintainers for this patch? > > > > Sorry, I wasn't CC'd on the thread, so I missed this. > > Here's the lore link that starts it all: > > > https://lore.kernel.org/all/172615368656.133222.2336770908714920670.stgit@devnote2/ > > There's also a v15: > > > https://lore.kernel.org/linux-trace-kernel/172639136989.366111.11359590127009702129.stgit@devnote2/ > > > > > > On Fri, 13 Sep 2024 00:08:40 +0900 > > > "Masami Hiramatsu (Google)" <mhira...@kernel.org> wrote: > > > > > > > From: Masami Hiramatsu (Google) <mhira...@kernel.org> > > > > > > > > Pass ftrace_regs to the fgraph_ops::entryfunc(). If ftrace_regs is not > > > > available, it passes a NULL instead. User callback function can access > > > > some registers (including return address) via this ftrace_regs. > > > > Under which circumstances is 'ftrace_regs' NULL? > > When the arch does not define: HAVE_DYNAMIC_FTRACE_WITH_ARGS or > HAVE_DYNAMIC_FTRACE_WITH_REGS > > If HAVE_DYNAMIC_FTRACE_WITH_REGS is defined but not the WITH_ARGS, and the > ops used to register the function callback does not set > FTRACE_OPS_FL_SAVE_REGS. > > Otherwise it should be set. I will add this condition in the description in next version. Thank you, > > > > > The arm64 implementation of ftrace_graph_func() is: > > > > > > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > > > > index a650f5e11fc5..bc647b725e6a 100644 > > > > --- a/arch/arm64/kernel/ftrace.c > > > > +++ b/arch/arm64/kernel/ftrace.c > > > > @@ -481,7 +481,25 @@ void prepare_ftrace_return(unsigned long > > > > self_addr, unsigned long *parent, > > > > void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, > > > > struct ftrace_ops *op, struct ftrace_regs *fregs) > > > > { > > > > - prepare_ftrace_return(ip, &fregs->lr, fregs->fp); > > > > + unsigned long return_hooker = (unsigned long)&return_to_handler; > > > > + unsigned long frame_pointer = fregs->fp; > > > > Which dereferences the unchecked pointer here ^^. > > Just above the visible portion of the patch, we have: > > #ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS > void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, > struct ftrace_ops *op, struct ftrace_regs *fregs) > { > > Which means fregs will be available. The "WITH_ARGS" config tells us that > the arch will supply the function with valid fregs to the ftrace callback > (which this is). > > -- Steve > -- Masami Hiramatsu (Google) <mhira...@kernel.org>
