Re: [PATCH v9 09/10] x86: use / "support" UDB

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 05/12/2025 1:13 pm, Jan Beulich wrote:
> On 05.12.2025 13:40, Andrew Cooper wrote:
>> On 05/12/2025 12:01 pm, Andrew Cooper wrote:
>>> On 24/11/2025 3:01 pm, Jan Beulich wrote:
>>>> --- a/xen/arch/x86/include/asm/bug.h
>>>> +++ b/xen/arch/x86/include/asm/bug.h
>>>> @@ -21,7 +21,7 @@
>>>>  
>>>>  #ifndef __ASSEMBLY__
>>>>  
>>>> -#define BUG_INSTR       "ud2"
>>>> +#define BUG_INSTR       ".byte 0xd6" /* UDB */
>>>>  #define BUG_ASM_CONST   "c"
>>>>  
>>>>  #else  /* !__ASSEMBLY__ */
>>>> @@ -37,7 +37,7 @@
>>>>          .error "Invalid BUGFRAME index"
>>>>      .endif
>>>>  
>>>> -    .L\@ud: ud2a
>>>> +    .L\@ud: .byte 0xd6 /* UDB */
>> P.S. Presumably binutils is going to learn a udb mnemonic at some
>> point?  Can we include a version number in the comment?
> I has already learned it, so it'll be available from 2.46 onwards. I've
> added a comment, but aiui we'd then need to also cover Clang's integrated
> assembler (if and when that gains support). In the meantime I've made both
> comments say "UDB, requiring gas 2.46".

Thanks.  Clang Trunk doesn't currently know it.

https://godbolt.org/z/ccrhzq95h

~Andrew