On Thu, 2018-07-12 at 16:03 +0200, Ingo Molnar wrote:

* Yu-cheng Yu [off-list ref] wrote:

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diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index e2ee403865eb..ac2bc3a18427 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c

@@ -49,7 +49,9 @@ enum x86_regset {

 	REGSET_IOPERM64 = REGSET_XFP,
 	REGSET_XSTATE,
 	REGSET_TLS,
+	REGSET_CET64 = REGSET_TLS,
 	REGSET_IOPERM32,
+	REGSET_CET32,
 };

Why does REGSET_CET64 alias on REGSET_TLS?

In x86_64_regsets[], there is no [REGSET_TLS].  The core dump code
cannot handle holes in the array.

Is there a fundamental (ABI) reason for that?

What I did was, ran Linux with 'slub_debug', and forced a core dump
(kill -abrt <pid>), then there was a red zone warning in the dmesg.
My feeling is there could be issues in the core dump code.  These
enum's are only local to arch/x86/kernel/ptrace.c and not exported.
I am not aware this is in the ABI.

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to "CET" (which is a well-known acronym for "Central European Time"),
not to CFE?

I don't know if I can change that, will find out.

So what I'd suggest is something pretty simple: to use CFT/cft in kernel internal 
names, except for the Intel feature bit and any MSR enumeration which can be CET 
if Intel named it that way, and a short comment explaining the acronym difference.

Or something like that.

Ok, I will make changes in the next version and probably revise
from that if still not optimal.

Yu-cheng