Messages in this thread | | | Date | Wed, 15 Mar 2023 15:57:57 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v4 1/2] function_graph: Support recording and printing the return value of function |
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On Wed, Mar 15, 2023 at 10:13:48AM -0400, Steven Rostedt wrote: > On Wed, 15 Mar 2023 14:49:11 +0100 > Peter Zijlstra <peterz@infradead.org> wrote: > > > > diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S > > > index 1265ad519249..35ac9c58dc77 100644 > > > --- a/arch/x86/kernel/ftrace_64.S > > > +++ b/arch/x86/kernel/ftrace_64.S > > > @@ -348,6 +348,10 @@ SYM_CODE_START(return_to_handler) > > > movq %rax, (%rsp) > > > movq %rdx, 8(%rsp) > > > movq %rbp, %rdi > > > +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL > > > + /* Pass the function return value to ftrace_return_to_handler */ > > > + movq %rax, %rsi > > > +#endif > > > > > > call ftrace_return_to_handler > > > > What about the case of double register return values (when the value > > is returned in the A,D pair) ? > > Is there anything that does that in 64 bit kernels?
Note sure; but I have a patch series that introduces cmpxchg128 and friends. Most of the actual functions are __always_inline, but still, the moment a compiler decides to break out a subfunction on a u128 boundary we're in luck.
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