Re: [rfc] x86, bts: improve X86_PTRACE_BTS help text

From: Roland Dreier
Date: Thu Oct 16 2008 - 02:57:34 EST

Thanks for improving the help text; it looks much better.

One comment:

> config X86_DS
> - bool "Debug Store support"
> - default y
> - help
> - Add support for Debug Store.
> - This allows the kernel to provide a memory buffer to the hardware
> - to store various profiling and tracing events.
> + def_bool X86_PTRACE_BTS
> + depends on X86_DEBUGCTLMSR

using def_bool here to get this turned on if X86_PTRACE_BTS is set
doesn't seem scalable to more uses of X86_DS. I would have thought that
having X86_PTRACE_BTS select X86_DS would make more sense.

Or are other users of X86_DS not planned? In which case should there be
a separate X86_DS option at all?

> + This adds a ptrace interface to the hardware's branch trace store.
> +
> + Debuggers may use it to collect an execution trace of the debugged
> + application in order to answer the question 'how did I get here?'.
> + Debuggers may trace user mode as well as kernel mode.
> +
> + Say Y unless there is no application development on this machine
> + and you want to save a small amount of code size.

This looks much better -- someone like me could read this and make an
informed decision about the config option.

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