Messages in this thread Patch in this message | | | Date | Mon, 13 Dec 2021 13:54:10 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH v1 0/5] Implement livepatch on PPC32 |
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On Mon, 13 Dec 2021 17:50:52 +0000 Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
> @@ -958,6 +942,12 @@ unsigned long prepare_ftrace_return(unsigned long > parent, unsigned long ip, > out: > return parent; > } > + > +void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, > + struct ftrace_ops *op, struct ftrace_regs *fregs) > +{ > + prepare_ftrace_return(ip, kernel_stack_pointer(&fregs->regs), 0); > +}
I have for powerpc prepare_ftrace_return as:
unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip, unsigned long sp) { unsigned long return_hooker;
if (unlikely(ftrace_graph_is_dead())) goto out; if (unlikely(atomic_read(¤t->tracing_graph_pause))) goto out; return_hooker = ppc_function_entry(return_to_handler);
if (!function_graph_enter(parent, ip, 0, (unsigned long *)sp)) parent = return_hooker; out: return parent; } Which means you'll need different parameters to it than what x86 has, which has the prototype of:
void prepare_ftrace_return(unsigned long ip, unsigned long *parent, unsigned long frame_pointer)
and it does not use the frame_pointer for this case, which is why it is zero.
For powerpc though, it uses the stack pointer, so you parameters are incorrect. Looks like it should be:
prepare_ftrace_return(parent_ip, ip, kernel_stack_pointer(&fregs->regs));
And that will likely not be enough. I'll need to update the ctr register, as that is where the return address is saved. So you'll probably need it to be:
void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct ftrace_regs *fregs) { unsigned long parent; parent = prepare_ftrace_return(parent_ip, ip, kernel_stack_pointer(&fregs->regs)); fregs->regs.ctr = parent; }
-- Steve
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