Re: [RFC PATCH v2 20/21] x86: Add support for CONFIG_CFI_CLANG
From: Sami Tolvanen <samitolvanen@google.com>
Date: 2022-05-17 20:36:59
Also in:
linux-hardening, lkml, llvm
On Mon, May 16, 2022 at 11:44 PM Peter Zijlstra [off-list ref] wrote:
On Mon, May 16, 2022 at 03:03:02PM -0700, Sami Tolvanen wrote:quoted
On Mon, May 16, 2022 at 2:44 PM Peter Zijlstra [off-list ref] wrote:quoted
On Mon, May 16, 2022 at 09:32:55PM +0000, David Laight wrote:quoted
quoted
The compiler always generates this specific instruction sequence.Yes, but there are several ways to encode 'cmpl imm,-6(reg)'.Yes, but we don't care. This *always* uses the 32bit immediate form. Even if the immediate is small.Yes, that part is not a problem, but it's a valid point that LLVM might not always use r8-r15 here, so I will have to check for the REX prefix before blindly attempting to decode the instruction.LLVM has always used r11 for indirect calls, will that change?
No, this won't change register allocation, but I will have to ensure that the compiler won't do any unnecessary register shuffling for the check itself. Sami _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel