Re: [PATCH 04/18] tracing/x86: Add arch_get_func_args() function

Namhyung Kim
2018-02-08T05:28:13Z

Hi Steve,

On Fri, Feb 02, 2018 at 06:05:02PM -0500, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
>
> Add function to get the function arguments from pt_regs.
>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
> arch/x86/kernel/ftrace.c | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index 01ebcb6f263e..5e845c8cf89d 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -46,6 +46,34 @@ int ftrace_arch_code_modify_post_process(void)
> return 0;
> }
>
> +int arch_get_func_args(struct pt_regs *regs,
> + int start, int end, long *args)
> +{
> +#ifdef CONFIG_X86_64
> +# define MAX_ARGS 6
> +# define INIT_REGS \
> + { regs->di, regs->si, regs->dx, \
> + regs->cx, regs->r8, regs->r9 \
> + }
> +#else
> +# define MAX_ARGS 3
> +# define INIT_REGS \
> + { regs->ax, regs->dx, regs->cx }
> +#endif
> + if (!regs)
> + return MAX_ARGS;
> +
> + {
> + long pt_args[] = INIT_REGS;
> + int i;
> +
> + for (i = start; i <= end && i < MAX_ARGS; i++)
^^^^^^^^

I expected it being 'i < end' based on your description.

Thanks,
Namhyung

> + args[i - start] = pt_args[i];
> +
> + return i - start;
> + }
> +}
> +
> union ftrace_code_union {
> char code[MCOUNT_INSN_SIZE];
> struct {
> --
> 2.15.1
>
>