* powerpc VDSO files being unnecessarily rebuilt
@ 2020-12-17 2:56 Michael Ellerman
2020-12-17 9:23 ` Masahiro Yamada
0 siblings, 1 reply; 3+ messages in thread
From: Michael Ellerman @ 2020-12-17 2:56 UTC (permalink / raw)
To: linuxppc-dev, Masahiro Yamada, Christophe Leroy, linux-kbuild
Hi all,
Since the merge of the C VDSO I see we are repeatedly rebuilding some
files in the VDSO, eg:
$ make V=2
make[1]: Entering directory '/home/michael/linux/build~'
GEN Makefile
CALL /home/michael/linux/scripts/checksyscalls.sh - due to target missing
CALL /home/michael/linux/scripts/atomic/check-atomics.sh - due to target missing
CHK include/generated/compile.h
CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to vgettimeofday.o not in $(targets)
This then causes multiple other files to be rebuilt.
So the obvious fix is to add it to targets:
diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile
index d365810a689a..5386532866ce 100644
--- a/arch/powerpc/kernel/vdso64/Makefile
+++ b/arch/powerpc/kernel/vdso64/Makefile
@@ -5,6 +5,7 @@ ARCH_REL_TYPE_ABS := R_PPC_JUMP_SLOT|R_PPC_GLOB_DAT|R_PPC_ADDR32|R_PPC_ADDR24|R_
include $(srctree)/lib/vdso/Makefile
obj-vdso64 = sigtramp.o gettimeofday.o datapage.o cacheflush.o note.o getcpu.o
+targets := $(obj-vdso64) vdso64.so.dbg
ifneq ($(c-gettimeofday-y),)
CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
@@ -13,11 +14,11 @@ ifneq ($(c-gettimeofday-y),)
CFLAGS_vgettimeofday.o += -DDISABLE_BRANCH_PROFILING
CFLAGS_vgettimeofday.o += -ffreestanding -fasynchronous-unwind-tables
CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE)
+ targets += vgettimeofday.o
endif
# Build rules
-targets := $(obj-vdso64) vdso64.so.dbg
obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64))
GCOV_PROFILE := n
But then I see it still rebuilt:
CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to command line change
I'm not changing the command line, and AFAICS the .cmd file is not
changing either:
$ make V=2
...
CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to command line change
$ sha256sum build\~/arch/powerpc/kernel/vdso64/vgettimeofday.o
7f635546bc2768c7b929d3de1724d83285f3cd54394fcd7104f8b1301d689d65 build~/arch/powerpc/kernel/vdso64/vgettimeofday.o
$ make V=2
...
CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to command line change
$ sha256sum build\~/arch/powerpc/kernel/vdso64/vgettimeofday.o
7f635546bc2768c7b929d3de1724d83285f3cd54394fcd7104f8b1301d689d65 build~/arch/powerpc/kernel/vdso64/vgettimeofday.o
So any hints on what I'm missing here?
cheers
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: powerpc VDSO files being unnecessarily rebuilt
2020-12-17 2:56 powerpc VDSO files being unnecessarily rebuilt Michael Ellerman
@ 2020-12-17 9:23 ` Masahiro Yamada
2020-12-17 16:40 ` Masahiro Yamada
0 siblings, 1 reply; 3+ messages in thread
From: Masahiro Yamada @ 2020-12-17 9:23 UTC (permalink / raw)
To: Michael Ellerman; +Cc: linuxppc-dev, Linux Kbuild mailing list
On Thu, Dec 17, 2020 at 11:56 AM Michael Ellerman <mpe@ellerman.id.au> wrote:
>
> Hi all,
>
> Since the merge of the C VDSO I see we are repeatedly rebuilding some
> files in the VDSO, eg:
>
> $ make V=2
> make[1]: Entering directory '/home/michael/linux/build~'
> GEN Makefile
> CALL /home/michael/linux/scripts/checksyscalls.sh - due to target missing
> CALL /home/michael/linux/scripts/atomic/check-atomics.sh - due to target missing
> CHK include/generated/compile.h
> CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to vgettimeofday.o not in $(targets)
>
> This then causes multiple other files to be rebuilt.
>
> So the obvious fix is to add it to targets:
>
> diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile
> index d365810a689a..5386532866ce 100644
> --- a/arch/powerpc/kernel/vdso64/Makefile
> +++ b/arch/powerpc/kernel/vdso64/Makefile
> @@ -5,6 +5,7 @@ ARCH_REL_TYPE_ABS := R_PPC_JUMP_SLOT|R_PPC_GLOB_DAT|R_PPC_ADDR32|R_PPC_ADDR24|R_
> include $(srctree)/lib/vdso/Makefile
>
> obj-vdso64 = sigtramp.o gettimeofday.o datapage.o cacheflush.o note.o getcpu.o
> +targets := $(obj-vdso64) vdso64.so.dbg
>
> ifneq ($(c-gettimeofday-y),)
> CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> @@ -13,11 +14,11 @@ ifneq ($(c-gettimeofday-y),)
> CFLAGS_vgettimeofday.o += -DDISABLE_BRANCH_PROFILING
> CFLAGS_vgettimeofday.o += -ffreestanding -fasynchronous-unwind-tables
> CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE)
> + targets += vgettimeofday.o
> endif
>
> # Build rules
>
> -targets := $(obj-vdso64) vdso64.so.dbg
> obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64))
>
> GCOV_PROFILE := n
>
>
> But then I see it still rebuilt:
>
> CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to command line change
>
>
> I'm not changing the command line, and AFAICS the .cmd file is not
> changing either:
>
> $ make V=2
> ...
> CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to command line change
>
> $ sha256sum build\~/arch/powerpc/kernel/vdso64/vgettimeofday.o
> 7f635546bc2768c7b929d3de1724d83285f3cd54394fcd7104f8b1301d689d65 build~/arch/powerpc/kernel/vdso64/vgettimeofday.o
>
> $ make V=2
> ...
> CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to command line change
>
> $ sha256sum build\~/arch/powerpc/kernel/vdso64/vgettimeofday.o
> 7f635546bc2768c7b929d3de1724d83285f3cd54394fcd7104f8b1301d689d65 build~/arch/powerpc/kernel/vdso64/vgettimeofday.o
>
>
> So any hints on what I'm missing here?
>
> cheers
This is because PPC builds the vdso twice
with different command arguments.
First time:
vdso_prepare: prepare0
$(if $(CONFIG_VDSO32),$(Q)$(MAKE) \
$(build)=arch/powerpc/kernel/vdso32
include/generated/vdso32-offsets.h)
$(if $(CONFIG_PPC64),$(Q)$(MAKE) \
$(build)=arch/powerpc/kernel/vdso64
include/generated/vdso64-offsets.h)
Second time:
from arch/powerpc/kernel/Makefile
For the first build, -Werror is missing because
Kbuild directly descends into arch/powerpc/kernel/vdso[32,64]/.
For the second build,
arch/powerpc/Kbuild appends the following:
subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
--
Best Regards
Masahiro Yamada
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: powerpc VDSO files being unnecessarily rebuilt
2020-12-17 9:23 ` Masahiro Yamada
@ 2020-12-17 16:40 ` Masahiro Yamada
0 siblings, 0 replies; 3+ messages in thread
From: Masahiro Yamada @ 2020-12-17 16:40 UTC (permalink / raw)
To: Michael Ellerman; +Cc: linuxppc-dev, Linux Kbuild mailing list
On Thu, Dec 17, 2020 at 6:23 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Thu, Dec 17, 2020 at 11:56 AM Michael Ellerman <mpe@ellerman.id.au> wrote:
> >
> > Hi all,
> >
> > Since the merge of the C VDSO I see we are repeatedly rebuilding some
> > files in the VDSO, eg:
> >
> > $ make V=2
> > make[1]: Entering directory '/home/michael/linux/build~'
> > GEN Makefile
> > CALL /home/michael/linux/scripts/checksyscalls.sh - due to target missing
> > CALL /home/michael/linux/scripts/atomic/check-atomics.sh - due to target missing
> > CHK include/generated/compile.h
> > CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to vgettimeofday.o not in $(targets)
> >
> > This then causes multiple other files to be rebuilt.
> >
> > So the obvious fix is to add it to targets:
> >
> > diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile
> > index d365810a689a..5386532866ce 100644
> > --- a/arch/powerpc/kernel/vdso64/Makefile
> > +++ b/arch/powerpc/kernel/vdso64/Makefile
> > @@ -5,6 +5,7 @@ ARCH_REL_TYPE_ABS := R_PPC_JUMP_SLOT|R_PPC_GLOB_DAT|R_PPC_ADDR32|R_PPC_ADDR24|R_
> > include $(srctree)/lib/vdso/Makefile
> >
> > obj-vdso64 = sigtramp.o gettimeofday.o datapage.o cacheflush.o note.o getcpu.o
> > +targets := $(obj-vdso64) vdso64.so.dbg
> >
> > ifneq ($(c-gettimeofday-y),)
> > CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
> > @@ -13,11 +14,11 @@ ifneq ($(c-gettimeofday-y),)
> > CFLAGS_vgettimeofday.o += -DDISABLE_BRANCH_PROFILING
> > CFLAGS_vgettimeofday.o += -ffreestanding -fasynchronous-unwind-tables
> > CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE)
> > + targets += vgettimeofday.o
> > endif
> >
> > # Build rules
> >
> > -targets := $(obj-vdso64) vdso64.so.dbg
> > obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64))
> >
> > GCOV_PROFILE := n
> >
> >
> > But then I see it still rebuilt:
> >
> > CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to command line change
> >
> >
> > I'm not changing the command line, and AFAICS the .cmd file is not
> > changing either:
> >
> > $ make V=2
> > ...
> > CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to command line change
> >
> > $ sha256sum build\~/arch/powerpc/kernel/vdso64/vgettimeofday.o
> > 7f635546bc2768c7b929d3de1724d83285f3cd54394fcd7104f8b1301d689d65 build~/arch/powerpc/kernel/vdso64/vgettimeofday.o
> >
> > $ make V=2
> > ...
> > CC arch/powerpc/kernel/vdso64/vgettimeofday.o - due to command line change
> >
> > $ sha256sum build\~/arch/powerpc/kernel/vdso64/vgettimeofday.o
> > 7f635546bc2768c7b929d3de1724d83285f3cd54394fcd7104f8b1301d689d65 build~/arch/powerpc/kernel/vdso64/vgettimeofday.o
> >
> >
> > So any hints on what I'm missing here?
> >
> > cheers
>
>
> This is because PPC builds the vdso twice
> with different command arguments.
>
>
> First time:
>
> vdso_prepare: prepare0
> $(if $(CONFIG_VDSO32),$(Q)$(MAKE) \
> $(build)=arch/powerpc/kernel/vdso32
> include/generated/vdso32-offsets.h)
> $(if $(CONFIG_PPC64),$(Q)$(MAKE) \
> $(build)=arch/powerpc/kernel/vdso64
> include/generated/vdso64-offsets.h)
>
>
> Second time:
> from arch/powerpc/kernel/Makefile
>
>
>
>
>
> For the first build, -Werror is missing because
> Kbuild directly descends into arch/powerpc/kernel/vdso[32,64]/.
>
>
> For the second build,
>
> arch/powerpc/Kbuild appends the following:
>
> subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
>
This is very dangerous because the vdso offsets are wrong.
I think ppc followed arm64 implementation.
Let me figure out how to fix arm64 vdso.
--
Best Regards
Masahiro Yamada
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-12-17 9:23 ` Masahiro Yamada
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