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Date:   Sat, 18 May 2019 19:22:11 +0530
From:   Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
To:     Joe Lawrence <joe.lawrence@redhat.com>
Cc:     live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
        jikos@kernel.org, jpoimboe@redhat.com, pmladek@suse.com,
        tglx@linutronix.de
Subject: Re: [PATCH] stacktrace: fix CONFIG_ARCH_STACKWALK
 stack_trace_save_tsk_reliable return
References: <20190517185117.24642-1-joe.lawrence@redhat.com>
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On Fri, May 17, 2019 at 02:51:17PM -0400, Joe Lawrence wrote:
> Miroslav reported that the livepatch self-tests were failing,
> specifically a case in which the consistency model ensures that we do
> not patch a current executing function, "TEST: busy target module".
> 
> Recent renovations to stack_trace_save_tsk_reliable() left it returning
> only an -ERRNO success indication in some configuration combinations:
> 
>   klp_check_stack()
>     ret = stack_trace_save_tsk_reliable()
>       #ifdef CONFIG_ARCH_STACKWALK && CONFIG_HAVE_RELIABLE_STACKTRACE
>         stack_trace_save_tsk_reliable()
>           ret = arch_stack_walk_reliable()
>             return 0
>             return -EINVAL
>           ...
>           return ret;
>     ...
>     if (ret < 0)
>       /* stack_trace_save_tsk_reliable error */
>     nr_entries = ret;                               << 0
> 
> Previously (and currently for !CONFIG_ARCH_STACKWALK &&
> CONFIG_HAVE_RELIABLE_STACKTRACE) stack_trace_save_tsk_reliable()
> returned the number of entries that it consumed in the passed storage
> array.
> 
> In the case of the above config and trace, be sure to return the
> stacktrace_cookie.len on stack_trace_save_tsk_reliable() success.
> 
> Fixes: 25e39e32b0a3f ("livepatch: Simplify stack trace retrieval")
> Reported-by: Miroslav Benes <mbenes@suse.cz>
> Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>

Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>