2021-04-14 10:35:40

by Nick Desaulniers

Subject: [PATCH] arm64: vdso32: drop -no-integrated-as flag

Clang can assemble these files just fine; this is a relic from the top
level Makefile conditionally adding this.

To test building:
$ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make LLVM=1 LLVM_IAS=1 \
defconfig arch/arm64/kernel/vdso32/

Signed-off-by: Nick Desaulniers <[email protected]>
---
arch/arm64/kernel/vdso32/Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
index 789ad420f16b..7812717f8b79 100644
--- a/arch/arm64/kernel/vdso32/Makefile
+++ b/arch/arm64/kernel/vdso32/Makefile
@@ -15,7 +15,7 @@ COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)

CC_COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE_COMPAT))
-CC_COMPAT_CLANG_FLAGS += -no-integrated-as -Qunused-arguments
+CC_COMPAT_CLANG_FLAGS += -Qunused-arguments
ifneq ($(COMPAT_GCC_TOOLCHAIN),)
CC_COMPAT_CLANG_FLAGS += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
endif
--
2.31.1.295.g9ea45b61b8-goog

2021-04-14 10:40:42

by Nathan Chancellor

Subject: Re: [PATCH] arm64: vdso32: drop -no-integrated-as flag

On Tue, Apr 13, 2021 at 04:06:06PM -0700, Nick Desaulniers wrote:
> Clang can assemble these files just fine; this is a relic from the top
> level Makefile conditionally adding this.
>
> To test building:
> $ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
> CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make LLVM=1 LLVM_IAS=1 \
> defconfig arch/arm64/kernel/vdso32/
>
> Signed-off-by: Nick Desaulniers <[email protected]>
> ---
> arch/arm64/kernel/vdso32/Makefile | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> index 789ad420f16b..7812717f8b79 100644
> --- a/arch/arm64/kernel/vdso32/Makefile
> +++ b/arch/arm64/kernel/vdso32/Makefile
> @@ -15,7 +15,7 @@ COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)
>
> CC_COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
> CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE_COMPAT))
> -CC_COMPAT_CLANG_FLAGS += -no-integrated-as -Qunused-arguments
> +CC_COMPAT_CLANG_FLAGS += -Qunused-arguments

Might as well just eliminate '--prefix=' and '--gcc-toolchain=' along
with the variables COMPAT_GCC_TOOLCHAIN_DIR and COMPAT_GCC_TOOLCHAIN
while you are at it, they serve no purpose without '-no-integrated-as'.

> ifneq ($(COMPAT_GCC_TOOLCHAIN),)
> CC_COMPAT_CLANG_FLAGS += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
> endif
> --
> 2.31.1.295.g9ea45b61b8-goog
>
>

2021-04-15 00:49:41

by Nick Desaulniers

Subject: [PATCH v2] arm64: vdso32: drop -no-integrated-as flag

Clang can assemble these files just fine; this is a relic from the top
level Makefile conditionally adding this. We no longer need --prefix,
--gcc-toolchain, or -Qunused-arguments flags either with this change, so
remove those too.

To test building:
$ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make LLVM=1 LLVM_IAS=1 \
defconfig arch/arm64/kernel/vdso32/

Suggested-by: Nathan Chancellor <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
---
Changes V1 -> V2:
* Remove --prefix, --gcc-toolchain, COMPAT_GCC_TOOLCHAIN, and
COMPAT_GCC_TOOLCHAIN_DIR as per Nathan.
* Credit Nathan with Suggested-by tag.
* Remove -Qunused-arguments.
* Update commit message.

arch/arm64/kernel/vdso32/Makefile | 8 --------
1 file changed, 8 deletions(-)

diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
index 789ad420f16b..3dba0c4f8f42 100644
--- a/arch/arm64/kernel/vdso32/Makefile
+++ b/arch/arm64/kernel/vdso32/Makefile
@@ -10,15 +10,7 @@ include $(srctree)/lib/vdso/Makefile

# Same as cc-*option, but using CC_COMPAT instead of CC
ifeq ($(CONFIG_CC_IS_CLANG), y)
-COMPAT_GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE_COMPAT)elfedit))
-COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)
-
CC_COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
-CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE_COMPAT))
-CC_COMPAT_CLANG_FLAGS += -no-integrated-as -Qunused-arguments
-ifneq ($(COMPAT_GCC_TOOLCHAIN),)
-CC_COMPAT_CLANG_FLAGS += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
-endif

CC_COMPAT ?= $(CC)
CC_COMPAT += $(CC_COMPAT_CLANG_FLAGS)
--
2.31.1.295.g9ea45b61b8-goog

2021-04-15 00:51:41

by Nathan Chancellor

Subject: Re: [PATCH v2] arm64: vdso32: drop -no-integrated-as flag

On Wed, Apr 14, 2021 at 02:45:45PM -0700, Nick Desaulniers wrote:
> Clang can assemble these files just fine; this is a relic from the top
> level Makefile conditionally adding this. We no longer need --prefix,
> --gcc-toolchain, or -Qunused-arguments flags either with this change, so
> remove those too.
>
> To test building:
> $ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
> CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make LLVM=1 LLVM_IAS=1 \
> defconfig arch/arm64/kernel/vdso32/
>
> Suggested-by: Nathan Chancellor <[email protected]>
> Signed-off-by: Nick Desaulniers <[email protected]>

Reviewed-by: Nathan Chancellor <[email protected]>

> ---
> Changes V1 -> V2:
> * Remove --prefix, --gcc-toolchain, COMPAT_GCC_TOOLCHAIN, and
> COMPAT_GCC_TOOLCHAIN_DIR as per Nathan.
> * Credit Nathan with Suggested-by tag.
> * Remove -Qunused-arguments.
> * Update commit message.
>
> arch/arm64/kernel/vdso32/Makefile | 8 --------
> 1 file changed, 8 deletions(-)
>
> diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> index 789ad420f16b..3dba0c4f8f42 100644
> --- a/arch/arm64/kernel/vdso32/Makefile
> +++ b/arch/arm64/kernel/vdso32/Makefile
> @@ -10,15 +10,7 @@ include $(srctree)/lib/vdso/Makefile
>
> # Same as cc-*option, but using CC_COMPAT instead of CC
> ifeq ($(CONFIG_CC_IS_CLANG), y)
> -COMPAT_GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE_COMPAT)elfedit))
> -COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)
> -
> CC_COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
> -CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE_COMPAT))
> -CC_COMPAT_CLANG_FLAGS += -no-integrated-as -Qunused-arguments
> -ifneq ($(COMPAT_GCC_TOOLCHAIN),)
> -CC_COMPAT_CLANG_FLAGS += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
> -endif
>
> CC_COMPAT ?= $(CC)
> CC_COMPAT += $(CC_COMPAT_CLANG_FLAGS)
> --
> 2.31.1.295.g9ea45b61b8-goog
>
>

2021-04-15 13:32:25

by Vincenzo Frascino

Subject: Re: [PATCH v2] arm64: vdso32: drop -no-integrated-as flag

On 4/14/21 10:45 PM, Nick Desaulniers wrote:
> Clang can assemble these files just fine; this is a relic from the top
> level Makefile conditionally adding this. We no longer need --prefix,
> --gcc-toolchain, or -Qunused-arguments flags either with this change, so
> remove those too.
>
> To test building:
> $ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
> CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make LLVM=1 LLVM_IAS=1 \
> defconfig arch/arm64/kernel/vdso32/
>
> Suggested-by: Nathan Chancellor <[email protected]>
> Signed-off-by: Nick Desaulniers <[email protected]>

The patch looks fine, but I have one question: the kernel requires as a minimum
Clang/LLVM version 10.0.1. Did you verify that with that version compat vDSOs
still builds and works correctly?

Otherwise:

Reviewed-by: Vincenzo Frascino <[email protected]>

> ---
> Changes V1 -> V2:
> * Remove --prefix, --gcc-toolchain, COMPAT_GCC_TOOLCHAIN, and
> COMPAT_GCC_TOOLCHAIN_DIR as per Nathan.
> * Credit Nathan with Suggested-by tag.
> * Remove -Qunused-arguments.
> * Update commit message.
>
> arch/arm64/kernel/vdso32/Makefile | 8 --------
> 1 file changed, 8 deletions(-)
>
> diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> index 789ad420f16b..3dba0c4f8f42 100644
> --- a/arch/arm64/kernel/vdso32/Makefile
> +++ b/arch/arm64/kernel/vdso32/Makefile
> @@ -10,15 +10,7 @@ include $(srctree)/lib/vdso/Makefile
>
> # Same as cc-*option, but using CC_COMPAT instead of CC
> ifeq ($(CONFIG_CC_IS_CLANG), y)
> -COMPAT_GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE_COMPAT)elfedit))
> -COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)
> -
> CC_COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
> -CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE_COMPAT))
> -CC_COMPAT_CLANG_FLAGS += -no-integrated-as -Qunused-arguments
> -ifneq ($(COMPAT_GCC_TOOLCHAIN),)
> -CC_COMPAT_CLANG_FLAGS += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
> -endif
>
> CC_COMPAT ?= $(CC)
> CC_COMPAT += $(CC_COMPAT_CLANG_FLAGS)
>

--
Regards,
Vincenzo

2021-04-15 16:53:27

by Nick Desaulniers

Subject: Re: [PATCH v2] arm64: vdso32: drop -no-integrated-as flag

On Thu, Apr 15, 2021 at 6:31 AM Vincenzo Frascino
<[email protected]> wrote:
>
>
>
> On 4/14/21 10:45 PM, Nick Desaulniers wrote:
> > Clang can assemble these files just fine; this is a relic from the top
> > level Makefile conditionally adding this. We no longer need --prefix,
> > --gcc-toolchain, or -Qunused-arguments flags either with this change, so
> > remove those too.
> >
> > To test building:
> > $ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
> > CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make LLVM=1 LLVM_IAS=1 \
> > defconfig arch/arm64/kernel/vdso32/
> >
> > Suggested-by: Nathan Chancellor <[email protected]>
> > Signed-off-by: Nick Desaulniers <[email protected]>
>
> The patch looks fine, but I have one question: the kernel requires as a minimum
> Clang/LLVM version 10.0.1. Did you verify that with that version compat vDSOs
> still builds and works correctly?

Hi Vincenzo,
Great question, let's check.
$ cd path/to/llvm-project
$ git checkout origin/release/10.x
$ cd llvm/build && ninja
$ cd path/to/linux
$ b4 am https://lore.kernel.org/lkml/[email protected]/
-o - | git am -3

We can't generally build ARCH=arm64 defconfig with LLVM_IAS=1 with
clang-10, but dropping LLVM_IAS=1 it looks like we can still build
without that.

$ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-
CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make LLVM=1 -j72 defconfig
clean all
$ ls -l arch/arm64/kernel/vdso32
total 116
-rw-r----- 1 ndesaulniers primarygroup 7534 Apr 14 14:41 Makefile
-rw-r----- 1 ndesaulniers primarygroup 387 Mar 31 10:47 note.c
-rw-r----- 1 ndesaulniers primarygroup 2544 Apr 15 09:48 note.o
-rw-r----- 1 ndesaulniers primarygroup 4552 Apr 15 09:48 vdso.lds
-rw-r----- 1 ndesaulniers primarygroup 1587 Apr 1 12:55 vdso.lds.S
-rw------- 1 ndesaulniers primarygroup 3576 Apr 15 09:48 vdso.so
-rw------- 1 ndesaulniers primarygroup 24380 Apr 15 09:48 vdso.so.dbg
-rwxr-x--- 1 ndesaulniers primarygroup 24380 Apr 15 09:48 vdso.so.raw
-rw-r----- 1 ndesaulniers primarygroup 828 Apr 1 12:55 vgettimeofday.c
-rw-r----- 1 ndesaulniers primarygroup 29084 Apr 15 09:48 vgettimeofday.o

FWIW, clang-10 was missing support for R_AARCH64_PREL32, which affects
building arch/arm64/kvm/hyp/nvhe/hyp-reloc.S.

>
> Otherwise:
>
> Reviewed-by: Vincenzo Frascino <[email protected]>
>
> > ---
> > Changes V1 -> V2:
> > * Remove --prefix, --gcc-toolchain, COMPAT_GCC_TOOLCHAIN, and
> > COMPAT_GCC_TOOLCHAIN_DIR as per Nathan.
> > * Credit Nathan with Suggested-by tag.
> > * Remove -Qunused-arguments.
> > * Update commit message.
> >
> > arch/arm64/kernel/vdso32/Makefile | 8 --------
> > 1 file changed, 8 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> > index 789ad420f16b..3dba0c4f8f42 100644
> > --- a/arch/arm64/kernel/vdso32/Makefile
> > +++ b/arch/arm64/kernel/vdso32/Makefile
> > @@ -10,15 +10,7 @@ include $(srctree)/lib/vdso/Makefile
> >
> > # Same as cc-*option, but using CC_COMPAT instead of CC
> > ifeq ($(CONFIG_CC_IS_CLANG), y)
> > -COMPAT_GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE_COMPAT)elfedit))
> > -COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)
> > -
> > CC_COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
> > -CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE_COMPAT))
> > -CC_COMPAT_CLANG_FLAGS += -no-integrated-as -Qunused-arguments
> > -ifneq ($(COMPAT_GCC_TOOLCHAIN),)
> > -CC_COMPAT_CLANG_FLAGS += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
> > -endif
> >
> > CC_COMPAT ?= $(CC)
> > CC_COMPAT += $(CC_COMPAT_CLANG_FLAGS)
> >
>
> --
> Regards,
> Vincenzo



--
Thanks,
~Nick Desaulniers