What I need to confirm is if the Linaro 5.3 would generate such code from a normal block of C without any kind of asm in it? Detecting the code is part of the kernel...I need to figure out where it was generated. Is Linaro 5.3 going to generate such code without explicitly writing it in?

----- Original Message -----From: Andrew Pinski Andrew.Pinski@cavium.comTo: stimits@comcast.net, Linaro Toolchain Mailman List linaro-toolchain@lists.linaro.orgSent: Mon, 05 Sep 2016 17:21:24 -0000 (UTC)Subject: RE: Question on "Using deprecated CP15 barrier instruction".

Simple answer is yes. There are a lot of assembly out there and someone (seen it in the past) could have used this barrier method in their code and not really thought it was going to change in the future.

Thanks, Andrew

From: linaro-toolchain [mailto:linaro-toolchain-bounces@lists.linaro.org]On Behalf Of stimits@comcast.netSent: Monday, September 5, 2016 8:10 AMTo: Linaro Toolchain Mailman List linaro-toolchain@lists.linaro.orgSubject: Question on "Using deprecated CP15 barrier instruction".

Hi,

For reference, the following questions refer to a Linux 3.10 aarch64 kernel (ARMv8, ARMv8-A) compiled with Linaro5.3-2016.02 (5.3-2016.02 arm64 CROSS_COMPILE and 5.3-2016.02 armhf CROSS32CC cross compiled from x86_64). This Linux kernel compile requires the full 64-bit tool chain plus the 32-bit gcc.

There is a Linux kernel file "arch/arm64/kernel/deprecated.c". Within that file is a block of code which is apparently designed to detect some sort of older obsolete 32-bit code. Specifically, the warning message is "Using deprecated CP15 barrier instruction". I wouldn't think that this kernel, when compiled with such a recent compiler, would ever introduce CP15 barrier code (from what I see barrier code was deprecated in ARMv7 and used to deal with obsolete ARMv6 code). Is there any chance the 32-bit 5.3 gcc would still generate CP15 barrier code?

Although this kernel and "most" modules are built with Linaro 5.3 I'd like to be able to narrow the cause down to existing binary modules not compiled with the 5.3 Linaro. If I can guarantee 5.3 32-bit gcc does not produce the CP15 barrier instruction then I'll know it is in pre-built binary modules. Can anyone tell me if C code compiled from Linaro version 5.3 32-bit gcc code would ever contain CP15 instructions?

Thanks!