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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Gatlin Newhouse <gatlin.newhouse@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Kees Cook <keescook@chromium.org>, Marco Elver <elver@google.com>,
	Andrey Konovalov <andreyknvl@gmail.com>,
	Andrey Ryabinin <ryabinin.a.a@gmail.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Baoquan He <bhe@redhat.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Changbin Du <changbin.du@huawei.com>,
	Pengfei Xu <pengfei.xu@intel.com>,
	Josh Poimboeuf <jpoimboe@kernel.org>, Xin Li <xin3.li@intel.com>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
	linux-hardening@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH] x86/traps: Enable UBSAN traps on x86
Date: Thu, 30 May 2024 01:24:56 +0100	[thread overview]
Message-ID: <c068193b-75fb-49d2-9104-775051ffd941@citrix.com> (raw)
In-Reply-To: <20240529022043.3661757-1-gatlin.newhouse@gmail.com>

On 29/05/2024 3:20 am, Gatlin Newhouse wrote:
> diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
> index a3ec87d198ac..e3fbed9073f8 100644
> --- a/arch/x86/include/asm/bug.h
> +++ b/arch/x86/include/asm/bug.h
> @@ -13,6 +13,14 @@
>  #define INSN_UD2	0x0b0f
>  #define LEN_UD2		2
>  
> +/*
> + * In clang we have UD1s reporting UBSAN failures on X86, 64 and 32bit.
> + */
> +#define INSN_UD1	0xb90f
> +#define LEN_UD1		2
> +#define INSN_REX	0x67
> +#define LEN_REX		1

That's an address size override prefix, not a REX prefix.

What information is actually encoded in this UD1 instruction?  I can't
find anything any documentation which actually discusses how the ModRM
byte is encoded.

~Andrew

  parent reply	other threads:[~2024-05-30  0:24 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-05-29  2:20 Gatlin Newhouse
2024-05-29  7:25 ` Marco Elver
2024-05-29 18:16   ` Gatlin Newhouse
2024-05-29 18:30     ` Marco Elver
2024-05-29 20:36       ` Gatlin Newhouse
2024-05-29 23:32         ` Kees Cook
2024-05-30  0:24 ` Andrew Cooper [this message]
2024-05-31 20:36   ` Gatlin Newhouse

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