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Re: [PATCH] x86/cet: Fix build on newer versions of GCC
- To: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Tue, 17 Aug 2021 12:17:31 +0100
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- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Tue, 17 Aug 2021 11:17:44 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 17/08/2021 12:14, Marek Marczykowski-Górecki wrote:
> On Tue, Aug 17, 2021 at 11:56:56AM +0100, Andrew Cooper wrote:
>> Some versions of GCC complain with:
>>
>> traps.c:405:22: error: 'get_shstk_bottom' defined but not used
>> [-Werror=unused-function]
>> static unsigned long get_shstk_bottom(unsigned long sp)
>> ^~~~~~~~~~~~~~~~
>> cc1: all warnings being treated as errors
>>
>> Change #ifdef to if ( IS_ENABLED(...) ) to make the sole user of
>> get_shstk_bottom() visible to the compiler.
>>
>> Fixes: 35727551c070 ("x86/cet: Fix shskt manipulation error with
>> BUGFRAME_{warn,run_fn}")
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> ---
>> CC: Jan Beulich <JBeulich@xxxxxxxx>
>> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> CC: Wei Liu <wl@xxxxxxx>
>> CC: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
>>
>> Not actually tested. I don't seem to have a new enough GCC to hand.
> I have just compile-tested it and it seems to fix the issue (indeed it
> failed before with CONFIG_XEN_SHSTK disabled).
Oh, thanks!
>
>> Most of the delta here is indentation. This diff is more easily reviewed
>> with
>> `git show --ignore-all-space`
> Wouldn't this make the compiler include the code even if
> CONFIG_XEN_SHSTK is disabled (not a huge issue...)? Or is it smart
> enough to optimize it out in that case?
Its a trivial dead-code elimination example, and yes - the compiler is
smart enough.
~Andrew
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