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Date: Wed, 1 Nov 2017 11:16:43 -0700 From: Mark Salyzyn <salyzyn@...roid.com> To: Mark Rutland <mark.rutland@....com> Cc: Robin Murphy <robin.murphy@....com>, linux-kernel@...r.kernel.org, Christoffer Dall <cdall@...aro.org>, Stefan Traby <stefan@...lo-penguin.com>, Suzuki K Poulose <suzuki.poulose@....com>, Marc Zyngier <marc.zyngier@....com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Dave Martin <Dave.Martin@....com>, linux-arm-kernel@...ts.infradead.org Subject: Re: [PATCH] arm64: write_sysreg asm illegal for aarch32 On 11/01/2017 10:56 AM, Mark Rutland wrote: > On Wed, Nov 01, 2017 at 10:49:00AM -0700, Mark Salyzyn wrote: >> 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. > This itself is the underlying issue. > > When building the compat VDSO, we must ensure that we only include > headers that make sense for 32-bit arm. > > If the build system can't do that today, we should rework it so that it > can. Anything else cannot be a complete fix. > >> 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. > ... these are just the particular symptoms this problem results in > today. > > Thanks, > Mark. Ok, will attack it and see just how bad the scale is... These ones trouble me ... there was no intent to pick up the wrong pieces. In file included from ./include/linux/time.h:4: In file included from ./include/linux/cache.h:5: In file included from ./arch/arm64/include/asm/cache.h:19: In file included from ./arch/arm64/include/asm/cachetype.h:19: In file included from ./arch/arm64/include/asm/cputype.h:94: ./arch/arm64/include/asm/sysreg.h:303:2: error: invalid input constraint 'rZ' in asm In file included from ./include/linux/hrtimer.h:18: In file included from ./include/linux/rbtree.h:34: In file included from ./include/linux/rcupdate.h:47: In file included from ./include/linux/ktime.h:25: In file included from ./include/linux/jiffies.h:8: In file included from ./include/linux/timex.h:65: In file included from ./arch/arm64/include/asm/timex.h:19: ./arch/arm64/include/asm/arch_timer.h:83:4: error: invalid input constraint 'rZ' in asm write_sysreg(cntkctl, cntkctl_el1); ^ ./arch/arm64/include/asm/sysreg.h:278:12: note: expanded from macro 'write_sysreg' : : "rZ" (__val)); -- Mark
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