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    SubjectRe: [PATCH v4 1/2] function_graph: Support recording and printing the return value of function
    On Wed, Mar 15, 2023 at 06:39:10AM -0700, Donglin Peng wrote:
    > diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S
    > index a0ed0e4a2c0c..44a773d9de82 100644
    > --- a/arch/x86/kernel/ftrace_32.S
    > +++ b/arch/x86/kernel/ftrace_32.S
    > @@ -184,6 +184,10 @@ SYM_CODE_END(ftrace_graph_caller)
    > return_to_handler:
    > pushl %eax
    > pushl %edx
    > +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
    > + /* Pass the function return value to ftrace_return_to_handler*/
    > + movl %eax, %edx
    > +#endif
    > movl $0, %eax
    > call ftrace_return_to_handler
    > movl %eax, %ecx
    > 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) ?

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