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.
