Re: x86/stacktrace: add function for detecting reliable stack traces

[Jessica Yu]

+++ Josh Poimboeuf [25/03/16 14:34 -0500]:
> For live patching and possibly other use cases, a stack trace is only
> useful if you can be assured that it's completely reliable.  Add a new
> save_stack_trace_tsk_reliable() function to achieve that.
>
> Scenarios which indicate that a stack strace may be unreliable:

s/strace/trace

> - interrupt stacks
> - preemption
> - corrupted stack data
> - newly forked tasks
> - running tasks
> - the user didn't provide a large enough entries array
>
> Also add a config option so arch-independent code can determine at build
> time whether the function is implemented.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> ---
> arch/Kconfig                 |  6 ++++++
> arch/x86/Kconfig             |  1 +
> arch/x86/kernel/dumpstack.c  | 36 ++++++++++++++++++++++++++++++++++++
> arch/x86/kernel/stacktrace.c | 32 ++++++++++++++++++++++++++++++++
> include/linux/stacktrace.h   | 20 ++++++++++++++++----
> kernel/stacktrace.c          |  4 ++--
> lib/Kconfig.debug            |  6 ++++++
> 7 files changed, 99 insertions(+), 6 deletions(-)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 81869a5..68b95f1 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -589,6 +589,12 @@ config HAVE_STACK_VALIDATION
> 	  Architecture supports the 'objtool check' host tool command, which
> 	  performs compile-time stack metadata validation.
>
> +config HAVE_RELIABLE_STACKTRACE
> +	bool
> +	help
> +	  Architecure has a save_stack_trace_tsk_reliable() function which only

s/Architecure/Architecture