On Mon, 21 Oct 2024 18:03:40 +0100 Will Deacon <[email protected]> wrote:
> On Wed, Oct 16, 2024 at 09:57:55AM +0900, Masami Hiramatsu (Google) wrote: > > From: Masami Hiramatsu (Google) <[email protected]> > > > > 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. > > > > Note that the ftrace_regs can be NULL when the arch does NOT define: > > HAVE_DYNAMIC_FTRACE_WITH_ARGS or HAVE_DYNAMIC_FTRACE_WITH_REGS. > > More specifically, if HAVE_DYNAMIC_FTRACE_WITH_REGS is defined but > > not the HAVE_DYNAMIC_FTRACE_WITH_ARGS, and the ftrace ops used to > > register the function callback does not set FTRACE_OPS_FL_SAVE_REGS. > > In this case, ftrace_regs can be NULL in user callback. > > > > Signed-off-by: Masami Hiramatsu (Google) <[email protected]> > > Cc: Steven Rostedt <[email protected]> > > Cc: Mark Rutland <[email protected]> > > Cc: Catalin Marinas <[email protected]> > > Cc: Will Deacon <[email protected]> > > Cc: Huacai Chen <[email protected]> > > Cc: WANG Xuerui <[email protected]> > > Cc: Michael Ellerman <[email protected]> > > Cc: Nicholas Piggin <[email protected]> > > Cc: Christophe Leroy <[email protected]> > > Cc: Naveen N Rao <[email protected]> > > Cc: Madhavan Srinivasan <[email protected]> > > Cc: Paul Walmsley <[email protected]> > > Cc: Palmer Dabbelt <[email protected]> > > Cc: Albert Ou <[email protected]> > > Cc: Thomas Gleixner <[email protected]> > > Cc: Ingo Molnar <[email protected]> > > Cc: Borislav Petkov <[email protected]> > > Cc: Dave Hansen <[email protected]> > > Cc: [email protected] > > Cc: "H. Peter Anvin" <[email protected]> > > Cc: Mathieu Desnoyers <[email protected]> > > > > --- > > Changes in v16: > > - Add a note when the ftrace_regs can be NULL. > > - Update against for the latest kernel. > > Changes in v11: > > - Update for the latest for-next branch. > > Changes in v8: > > - Just pass ftrace_regs to the handler instead of adding a new > > entryregfunc. > > - Update riscv ftrace_graph_func(). > > Changes in v3: > > - Update for new multiple fgraph. > > --- > > arch/arm64/kernel/ftrace.c | 20 +++++++++++- > > arch/loongarch/kernel/ftrace_dyn.c | 10 +++++- > > arch/powerpc/kernel/trace/ftrace.c | 2 + > > arch/powerpc/kernel/trace/ftrace_64_pg.c | 10 ++++-- > > arch/riscv/kernel/ftrace.c | 17 ++++++++++ > > arch/x86/kernel/ftrace.c | 50 > > +++++++++++++++++++++--------- > > include/linux/ftrace.h | 17 ++++++++-- > > kernel/trace/fgraph.c | 25 +++++++++------ > > kernel/trace/ftrace.c | 3 +- > > kernel/trace/trace.h | 3 +- > > kernel/trace/trace_functions_graph.c | 3 +- > > kernel/trace/trace_irqsoff.c | 3 +- > > kernel/trace/trace_sched_wakeup.c | 3 +- > > kernel/trace/trace_selftest.c | 8 +++-- > > 14 files changed, 129 insertions(+), 45 deletions(-) > > > > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > > index b2d947175cbe..a5a285f8a7ef 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, &arch_ftrace_regs(fregs)->lr, > > arch_ftrace_regs(fregs)->fp); > > + unsigned long return_hooker = (unsigned long)&return_to_handler; > > + unsigned long frame_pointer = arch_ftrace_regs(fregs)->fp; > > + unsigned long *parent = &arch_ftrace_regs(fregs)->lr; > > + unsigned long old; > > + > > + if (unlikely(atomic_read(¤t->tracing_graph_pause))) > > + return; > > + > > + /* > > + * Note: > > + * No protection against faulting at *parent, which may be seen > > + * on other archs. It's unlikely on AArch64. > > + */ > > + old = *parent; > > Sorry to pick on this line again, but the comment is very non-committal] > and I think this is something on which we need to be definitive. Agreed. I think this does not happen because it is a part of __arch_ftrace_regs, which is stored on kernel stack. I copied it from prepare_ftrace_return(), so that also need to be changed too. Let me remove this comment. Thank you, > > Either the access can fault, and we should handle it, or it will never > fault and we don't need to handle it. Saying it's unlikely means we > need to handle it :) > > Will > -- Masami Hiramatsu (Google) <[email protected]>
