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[PATCH] x86/altcall: silence undue warning
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 1 Mar 2022 12:36:08 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Tue, 01 Mar 2022 11:36:25 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Suitable compiler options are passed only when the actual feature
(XEN_IBT) is enabled, not when merely the compiler capability was found
to be available.
Fixes: 12e3410e071e ("x86/altcall: Check and optimise altcall targets")
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Furthermore, is "Optimised away ..." really appropriate in what
37ed5da851b8 ("x86/altcall: Optimise away endbr64 instruction where
possible") added? If this really was an optimization (rather than
hardening), shouldn't we purge ENDBR also when !cpu_has_xen_ibt, and
then ideally all of them? Whereas if this is mainly about hardening,
wouldn't the message better say "Purged" or "Clobbered"?
--- a/xen/arch/x86/alternative.c
+++ b/xen/arch/x86/alternative.c
@@ -295,7 +295,7 @@ static void init_or_livepatch _apply_alt
* marginal perf improvement which saves on instruction
* decode bandwidth.
*/
- if ( IS_ENABLED(CONFIG_HAS_CC_CET_IBT) )
+ if ( IS_ENABLED(CONFIG_XEN_IBT) )
{
if ( is_endbr64(dest) )
dest += ENDBR64_LEN;
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