| Message ID | 20200529214203.673108357@infradead.org |
|---|---|
| State | Not Applicable |
| Delegated to: | David Miller |
| Headers | show |
| Series | lockdep: Change IRQ state tracking to use per-cpu variables | expand |
From: Peter Zijlstra <peterz@infradead.org> Date: Fri, 29 May 2020 23:35:51 +0200 > ../arch/sparc/include/asm/percpu_64.h:7:24: warning: call-clobbered register used for global register variable > register unsigned long __local_per_cpu_offset asm("g5"); The "-ffixed-g5" option on the command line tells gcc that we are using 'g5' as a fixed register, so some part of your build isn't using the: KBUILD_CFLAGS += -ffixed-g4 -ffixed-g5 -fcall-used-g7 -Wno-sign-compare from arch/sparc/Makefile for some reason.
On Fri, May 29, 2020 at 04:29:17PM -0700, David Miller wrote: > From: Peter Zijlstra <peterz@infradead.org> > Date: Fri, 29 May 2020 23:35:51 +0200 > > > ../arch/sparc/include/asm/percpu_64.h:7:24: warning: call-clobbered register used for global register variable > > register unsigned long __local_per_cpu_offset asm("g5"); > > The "-ffixed-g5" option on the command line tells gcc that we are > using 'g5' as a fixed register, so some part of your build isn't using > the: > > KBUILD_CFLAGS += -ffixed-g4 -ffixed-g5 -fcall-used-g7 -Wno-sign-compare > > from arch/sparc/Makefile for some reason. Thanks, that was the clue I needed. I think I see, what happens is that these headers end up in the VDSO build, and that doesn't have these CFLAGS, because userspace. Let me see what to do about that.
On Thu, Jun 04, 2020 at 06:57:03PM +0200, Peter Zijlstra wrote: > I think I see, what happens is that these headers end up in the VDSO > build, and that doesn't have these CFLAGS, because userspace. > > Let me see what to do about that. I feel like the below is cheating, but it's the best I could find :/ VDSO including kernel headers and the utter maze that our kernel headers are makes it really hard to untangle :/ This builds sparc64-defconfig and sparc64-all{no,mod}config. Dave, does this work for you, or should I try hardder? --- arch/sparc/include/asm/percpu_64.h | 2 ++ arch/sparc/include/asm/trap_block.h | 2 ++ 2 files changed, 4 insertions(+) diff --git a/arch/sparc/include/asm/percpu_64.h b/arch/sparc/include/asm/percpu_64.h index 32ef6f05cc565..a8786a4b90b6b 100644 --- a/arch/sparc/include/asm/percpu_64.h +++ b/arch/sparc/include/asm/percpu_64.h @@ -4,7 +4,9 @@ #include <linux/compiler.h> +#ifndef BUILD_VDSO register unsigned long __local_per_cpu_offset asm("g5"); +#endif #ifdef CONFIG_SMP diff --git a/arch/sparc/include/asm/trap_block.h b/arch/sparc/include/asm/trap_block.h index 0f6d0c4f66838..ace0d48e837e5 100644 --- a/arch/sparc/include/asm/trap_block.h +++ b/arch/sparc/include/asm/trap_block.h @@ -2,6 +2,8 @@ #ifndef _SPARC_TRAP_BLOCK_H #define _SPARC_TRAP_BLOCK_H +#include <linux/threads.h> + #include <asm/hypervisor.h> #include <asm/asi.h>
--- a/arch/sparc/include/asm/trap_block.h +++ b/arch/sparc/include/asm/trap_block.h @@ -2,6 +2,8 @@ #ifndef _SPARC_TRAP_BLOCK_H #define _SPARC_TRAP_BLOCK_H +#include <linux/threads.h> + #include <asm/hypervisor.h> #include <asm/asi.h>
In order to break a header dependency between lockdep and task_struct, I need per-cpu stuff from lockdep. Including <asm/percpu.h> from lockdep.h gives a build error, this patch cures that, but results in the following warning: ../arch/sparc/include/asm/percpu_64.h:7:24: warning: call-clobbered register used for global register variable register unsigned long __local_per_cpu_offset asm("g5"); But i've no idea how to fix that :/ but it does build. Not-Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- arch/sparc/include/asm/trap_block.h | 2 ++ 1 file changed, 2 insertions(+)