lkml.org 
[lkml]   [2017]   [Nov]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] arm64: write_sysreg asm illegal for aarch32
From
Date
On 11/01/2017 10:14 AM, Robin Murphy wrote:
> On 01/11/17 16:58, Mark Salyzyn wrote:
>> Cross compiling to aarch32 (for vdso32) using clang correctly
>> identifies that (the unused) write_sysreg inline asm directive is
>> illegal in that architectural context:
>>
>> arch/arm64/include/asm/arch_timer.h: error: invalid input constraint 'rZ' in asm
>> write_sysreg(cntkctl, cntkctl_el1);
>> ^
>> arch/arm64/include/asm/sysreg.h: note: expanded from macro 'write_sysreg'
>> : : "rZ" (__val));
>> ^
>>
>> GCC normally checks for correctness everywhere. But uniquely for
>> unused asm, will optimize out and suppress the error report.
> It sounds more like some paths are wrong in the compat vDSO build if
> it's pulling in this header in the first place - nothing in this file is
> relevant to AArch32.
>
> Robin.
>
And yet, when you CROSS_COMPILE_ARM32 a vdso32, you have no choice but
to utilize the arm64 headers since they contain all the relevant kernel
structures and environment.

asm/arch_timer.h (remember we are using arm instructions to access
arch64 timers)

linux/time.h (really only for struct timespec())

asm/processor.h (eg: cpu_relax())

pull in a _lot_ of architectural related cruft that always somehow picks
up asm/sysreg.h somewhere in the multitude of includes to fulfill some
unused inline's needs.

-- Mark

\
 
 \ /
  Last update: 2017-11-01 18:50    [W:0.066 / U:1.584 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site