* [PATCH] um: Allow builds with Clang
@ 2022-02-17 0:28 Kees Cook
2022-02-17 0:37 ` Nathan Chancellor
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Kees Cook @ 2022-02-17 0:28 UTC (permalink / raw)
To: Jeff Dike
Cc: Kees Cook, Richard Weinberger, Anton Ivanov, Masahiro Yamada,
Nick Desaulniers, Nathan Chancellor, David Gow, linux-um,
linux-kbuild, linux-kselftest, kunit-dev, llvm, linux-kernel,
x86, linux-hardening
Add x86-64 target for Clang+um and update user-offsets.c to use
Clang-friendly assembler, similar to the fix from commit cf0c3e68aa81
("kbuild: fix asm-offset generation to work with clang").
This lets me run KUnit tests with Clang:
$ ./tools/testing/kunit/kunit.py config --make_options LLVM=1
...
$ ./tools/testing/kunit/kunit.py run --make_options LLVM=1
...
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: David Gow <davidgow@google.com>
Cc: linux-um@lists.infradead.org
Cc: linux-kbuild@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: kunit-dev@googlegroups.com
Cc: llvm@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/um/user-offsets.c | 4 ++--
scripts/Makefile.clang | 1 +
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
index bae61554abcc..d9071827b515 100644
--- a/arch/x86/um/user-offsets.c
+++ b/arch/x86/um/user-offsets.c
@@ -10,10 +10,10 @@
#include <asm/types.h>
#define DEFINE(sym, val) \
- asm volatile("\n->" #sym " %0 " #val : : "i" (val))
+ asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val))
#define DEFINE_LONGS(sym, val) \
- asm volatile("\n->" #sym " %0 " #val : : "i" (val/sizeof(unsigned long)))
+ asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val/sizeof(unsigned long)))
void foo(void)
{
diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
index 51fc23e2e9e5..857b23de51c6 100644
--- a/scripts/Makefile.clang
+++ b/scripts/Makefile.clang
@@ -10,6 +10,7 @@ CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu
CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu
CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu
CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu
+CLANG_TARGET_FLAGS_um := x86_64-linux-gnu
CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH))
ifeq ($(CROSS_COMPILE),)
--
2.30.2
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] um: Allow builds with Clang
2022-02-17 0:28 [PATCH] um: Allow builds with Clang Kees Cook
@ 2022-02-17 0:37 ` Nathan Chancellor
2022-02-17 2:59 ` David Gow
2022-02-17 4:54 ` Masahiro Yamada
2 siblings, 0 replies; 6+ messages in thread
From: Nathan Chancellor @ 2022-02-17 0:37 UTC (permalink / raw)
To: Kees Cook
Cc: Jeff Dike, Richard Weinberger, Anton Ivanov, Masahiro Yamada,
Nick Desaulniers, David Gow, linux-um, linux-kbuild,
linux-kselftest, kunit-dev, llvm, linux-kernel, x86,
linux-hardening
On Wed, Feb 16, 2022 at 04:28:43PM -0800, Kees Cook wrote:
> Add x86-64 target for Clang+um and update user-offsets.c to use
> Clang-friendly assembler, similar to the fix from commit cf0c3e68aa81
Clang-friendly assembly?
> ("kbuild: fix asm-offset generation to work with clang").
>
> This lets me run KUnit tests with Clang:
>
> $ ./tools/testing/kunit/kunit.py config --make_options LLVM=1
> ...
> $ ./tools/testing/kunit/kunit.py run --make_options LLVM=1
> ...
>
> Cc: Jeff Dike <jdike@addtoit.com>
> Cc: Richard Weinberger <richard@nod.at>
> Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: David Gow <davidgow@google.com>
> Cc: linux-um@lists.infradead.org
> Cc: linux-kbuild@vger.kernel.org
> Cc: linux-kselftest@vger.kernel.org
> Cc: kunit-dev@googlegroups.com
> Cc: llvm@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>
I am not super familiar with UML but this seems reasonable.
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
One small nit below if you have to send a v2, not sure it is worth it
otherwise.
> ---
> arch/x86/um/user-offsets.c | 4 ++--
> scripts/Makefile.clang | 1 +
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
> index bae61554abcc..d9071827b515 100644
> --- a/arch/x86/um/user-offsets.c
> +++ b/arch/x86/um/user-offsets.c
> @@ -10,10 +10,10 @@
> #include <asm/types.h>
>
> #define DEFINE(sym, val) \
> - asm volatile("\n->" #sym " %0 " #val : : "i" (val))
> + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val))
>
> #define DEFINE_LONGS(sym, val) \
> - asm volatile("\n->" #sym " %0 " #val : : "i" (val/sizeof(unsigned long)))
> + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val/sizeof(unsigned long)))
>
> void foo(void)
> {
> diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
> index 51fc23e2e9e5..857b23de51c6 100644
> --- a/scripts/Makefile.clang
> +++ b/scripts/Makefile.clang
> @@ -10,6 +10,7 @@ CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu
> CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu
> CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu
> CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu
> +CLANG_TARGET_FLAGS_um := x86_64-linux-gnu
It might be nice to keep this in alphabetical order.
> CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH))
>
> ifeq ($(CROSS_COMPILE),)
> --
> 2.30.2
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] um: Allow builds with Clang
2022-02-17 0:28 [PATCH] um: Allow builds with Clang Kees Cook
2022-02-17 0:37 ` Nathan Chancellor
@ 2022-02-17 2:59 ` David Gow
2022-02-17 4:54 ` Masahiro Yamada
2 siblings, 0 replies; 6+ messages in thread
From: David Gow @ 2022-02-17 2:59 UTC (permalink / raw)
To: Kees Cook
Cc: Jeff Dike, Richard Weinberger, Anton Ivanov, Masahiro Yamada,
Nick Desaulniers, Nathan Chancellor, linux-um, linux-kbuild,
open list:KERNEL SELFTEST FRAMEWORK, KUnit Development, llvm,
Linux Kernel Mailing List, x86, linux-hardening
On Thu, Feb 17, 2022 at 8:28 AM Kees Cook <keescook@chromium.org> wrote:
>
> Add x86-64 target for Clang+um and update user-offsets.c to use
> Clang-friendly assembler, similar to the fix from commit cf0c3e68aa81
> ("kbuild: fix asm-offset generation to work with clang").
>
> This lets me run KUnit tests with Clang:
>
> $ ./tools/testing/kunit/kunit.py config --make_options LLVM=1
> ...
> $ ./tools/testing/kunit/kunit.py run --make_options LLVM=1
> ...
>
> Cc: Jeff Dike <jdike@addtoit.com>
> Cc: Richard Weinberger <richard@nod.at>
> Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: David Gow <davidgow@google.com>
> Cc: linux-um@lists.infradead.org
> Cc: linux-kbuild@vger.kernel.org
> Cc: linux-kselftest@vger.kernel.org
> Cc: kunit-dev@googlegroups.com
> Cc: llvm@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
Thanks, this worked fine for me, with one small note:
I get the following warning with clang (13.0.1) under UML (but not
under x86_64):
clang: warning: argument unused during compilation:
'-mno-global-merge' [-Wunused-command-line-argument]
It's not really a problem unless -Werror is enabled, though, so this
is still definitely an improvement over clang not working at all.
With that caveat, this is:
Tested-by: David Gow <davidgow@google.com>
Cheers,
-- David
> arch/x86/um/user-offsets.c | 4 ++--
> scripts/Makefile.clang | 1 +
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
> index bae61554abcc..d9071827b515 100644
> --- a/arch/x86/um/user-offsets.c
> +++ b/arch/x86/um/user-offsets.c
> @@ -10,10 +10,10 @@
> #include <asm/types.h>
>
> #define DEFINE(sym, val) \
> - asm volatile("\n->" #sym " %0 " #val : : "i" (val))
> + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val))
>
> #define DEFINE_LONGS(sym, val) \
> - asm volatile("\n->" #sym " %0 " #val : : "i" (val/sizeof(unsigned long)))
> + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val/sizeof(unsigned long)))
>
> void foo(void)
> {
> diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
> index 51fc23e2e9e5..857b23de51c6 100644
> --- a/scripts/Makefile.clang
> +++ b/scripts/Makefile.clang
> @@ -10,6 +10,7 @@ CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu
> CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu
> CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu
> CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu
> +CLANG_TARGET_FLAGS_um := x86_64-linux-gnu
> CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH))
>
> ifeq ($(CROSS_COMPILE),)
> --
> 2.30.2
>
> --
> You received this message because you are subscribed to the Google Groups "KUnit Development" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to kunit-dev+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/kunit-dev/20220217002843.2312603-1-keescook%40chromium.org.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] um: Allow builds with Clang
2022-02-17 0:28 [PATCH] um: Allow builds with Clang Kees Cook
2022-02-17 0:37 ` Nathan Chancellor
2022-02-17 2:59 ` David Gow
@ 2022-02-17 4:54 ` Masahiro Yamada
2022-02-17 17:41 ` Nathan Chancellor
2 siblings, 1 reply; 6+ messages in thread
From: Masahiro Yamada @ 2022-02-17 4:54 UTC (permalink / raw)
To: Kees Cook
Cc: Jeff Dike, Richard Weinberger, Anton Ivanov, Nick Desaulniers,
Nathan Chancellor, David Gow, linux-um,
Linux Kbuild mailing list, open list:KERNEL SELFTEST FRAMEWORK,
kunit-dev, llvm, Linux Kernel Mailing List, X86 ML,
linux-hardening
On Thu, Feb 17, 2022 at 9:28 AM Kees Cook <keescook@chromium.org> wrote:
>
> Add x86-64 target for Clang+um and update user-offsets.c to use
> Clang-friendly assembler, similar to the fix from commit cf0c3e68aa81
> ("kbuild: fix asm-offset generation to work with clang").
>
> This lets me run KUnit tests with Clang:
>
> $ ./tools/testing/kunit/kunit.py config --make_options LLVM=1
> ...
> $ ./tools/testing/kunit/kunit.py run --make_options LLVM=1
> ...
>
> Cc: Jeff Dike <jdike@addtoit.com>
> Cc: Richard Weinberger <richard@nod.at>
> Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: David Gow <davidgow@google.com>
> Cc: linux-um@lists.infradead.org
> Cc: linux-kbuild@vger.kernel.org
> Cc: linux-kselftest@vger.kernel.org
> Cc: kunit-dev@googlegroups.com
> Cc: llvm@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> arch/x86/um/user-offsets.c | 4 ++--
> scripts/Makefile.clang | 1 +
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
> index bae61554abcc..d9071827b515 100644
> --- a/arch/x86/um/user-offsets.c
> +++ b/arch/x86/um/user-offsets.c
> @@ -10,10 +10,10 @@
> #include <asm/types.h>
>
> #define DEFINE(sym, val) \
> - asm volatile("\n->" #sym " %0 " #val : : "i" (val))
> + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val))
>
> #define DEFINE_LONGS(sym, val) \
> - asm volatile("\n->" #sym " %0 " #val : : "i" (val/sizeof(unsigned long)))
> + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val/sizeof(unsigned long)))
>
> void foo(void)
> {
> diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
> index 51fc23e2e9e5..857b23de51c6 100644
> --- a/scripts/Makefile.clang
> +++ b/scripts/Makefile.clang
> @@ -10,6 +10,7 @@ CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu
> CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu
> CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu
> CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu
> +CLANG_TARGET_FLAGS_um := x86_64-linux-gnu
Does this work for the i386 host?
UML supports i386 and x86_64 as the host architecture as of now,
but this always compiles UML for x86_64?
> CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH))
>
> ifeq ($(CROSS_COMPILE),)
> --
> 2.30.2
>
--
Best Regards
Masahiro Yamada
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] um: Allow builds with Clang
2022-02-17 4:54 ` Masahiro Yamada
@ 2022-02-17 17:41 ` Nathan Chancellor
2022-02-18 2:19 ` Masahiro Yamada
0 siblings, 1 reply; 6+ messages in thread
From: Nathan Chancellor @ 2022-02-17 17:41 UTC (permalink / raw)
To: Masahiro Yamada
Cc: Kees Cook, Jeff Dike, Richard Weinberger, Anton Ivanov,
Nick Desaulniers, David Gow, linux-um, Linux Kbuild mailing list,
open list:KERNEL SELFTEST FRAMEWORK, kunit-dev, llvm,
Linux Kernel Mailing List, X86 ML, linux-hardening
On Thu, Feb 17, 2022 at 01:54:58PM +0900, Masahiro Yamada wrote:
> On Thu, Feb 17, 2022 at 9:28 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > Add x86-64 target for Clang+um and update user-offsets.c to use
> > Clang-friendly assembler, similar to the fix from commit cf0c3e68aa81
> > ("kbuild: fix asm-offset generation to work with clang").
> >
> > This lets me run KUnit tests with Clang:
> >
> > $ ./tools/testing/kunit/kunit.py config --make_options LLVM=1
> > ...
> > $ ./tools/testing/kunit/kunit.py run --make_options LLVM=1
> > ...
> >
> > Cc: Jeff Dike <jdike@addtoit.com>
> > Cc: Richard Weinberger <richard@nod.at>
> > Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
> > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > Cc: Nick Desaulniers <ndesaulniers@google.com>
> > Cc: Nathan Chancellor <nathan@kernel.org>
> > Cc: David Gow <davidgow@google.com>
> > Cc: linux-um@lists.infradead.org
> > Cc: linux-kbuild@vger.kernel.org
> > Cc: linux-kselftest@vger.kernel.org
> > Cc: kunit-dev@googlegroups.com
> > Cc: llvm@lists.linux.dev
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > arch/x86/um/user-offsets.c | 4 ++--
> > scripts/Makefile.clang | 1 +
> > 2 files changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
> > index bae61554abcc..d9071827b515 100644
> > --- a/arch/x86/um/user-offsets.c
> > +++ b/arch/x86/um/user-offsets.c
> > @@ -10,10 +10,10 @@
> > #include <asm/types.h>
> >
> > #define DEFINE(sym, val) \
> > - asm volatile("\n->" #sym " %0 " #val : : "i" (val))
> > + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val))
> >
> > #define DEFINE_LONGS(sym, val) \
> > - asm volatile("\n->" #sym " %0 " #val : : "i" (val/sizeof(unsigned long)))
> > + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val/sizeof(unsigned long)))
> >
> > void foo(void)
> > {
> > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
> > index 51fc23e2e9e5..857b23de51c6 100644
> > --- a/scripts/Makefile.clang
> > +++ b/scripts/Makefile.clang
> > @@ -10,6 +10,7 @@ CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu
> > CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu
> > CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu
> > CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu
> > +CLANG_TARGET_FLAGS_um := x86_64-linux-gnu
>
>
> Does this work for the i386 host?
>
> UML supports i386 and x86_64 as the host architecture as of now,
> but this always compiles UML for x86_64?
I think the current code will work because arch/x86/Makefile.um includes
-m32 for CONFIG_X86_32, which will implicitly change x86_64-linux-gnu
into a 32-bit target triple:
$ echo | clang --target=x86_64-linux-gnu -x c -c -o test.o -
$ file test.o
test.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped
$ echo | clang --target=x86_64-linux-gnu -m32 -x c -c -o test.o -
$ file test.o
test.o: ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV), not stripped
In fact, we rely on this for ARCH=i386 LLVM=1 right now, as it uses
x86_64-linux-gnu for the target flag.
While UML only supports x86, maybe it is worth using SUBARCH instead of
hardcoding the triple? No strong opinion around that though.
diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
index 51fc23e2e9e5..87285b76adb2 100644
--- a/scripts/Makefile.clang
+++ b/scripts/Makefile.clang
@@ -10,6 +10,7 @@ CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu
CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu
CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu
CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu
+CLANG_TARGET_FLAGS_um := $(CLANG_TARGET_FLAGS_$(SUBARCH))
CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH))
ifeq ($(CROSS_COMPILE),)
> > CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH))
> >
> > ifeq ($(CROSS_COMPILE),)
> > --
> > 2.30.2
> >
>
>
> --
> Best Regards
> Masahiro Yamada
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] um: Allow builds with Clang
2022-02-17 17:41 ` Nathan Chancellor
@ 2022-02-18 2:19 ` Masahiro Yamada
0 siblings, 0 replies; 6+ messages in thread
From: Masahiro Yamada @ 2022-02-18 2:19 UTC (permalink / raw)
To: Nathan Chancellor
Cc: Kees Cook, Jeff Dike, Richard Weinberger, Anton Ivanov,
Nick Desaulniers, David Gow, linux-um, Linux Kbuild mailing list,
open list:KERNEL SELFTEST FRAMEWORK, kunit-dev, llvm,
Linux Kernel Mailing List, X86 ML, linux-hardening
On Fri, Feb 18, 2022 at 2:41 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> On Thu, Feb 17, 2022 at 01:54:58PM +0900, Masahiro Yamada wrote:
> > On Thu, Feb 17, 2022 at 9:28 AM Kees Cook <keescook@chromium.org> wrote:
> > >
> > > Add x86-64 target for Clang+um and update user-offsets.c to use
> > > Clang-friendly assembler, similar to the fix from commit cf0c3e68aa81
> > > ("kbuild: fix asm-offset generation to work with clang").
> > >
> > > This lets me run KUnit tests with Clang:
> > >
> > > $ ./tools/testing/kunit/kunit.py config --make_options LLVM=1
> > > ...
> > > $ ./tools/testing/kunit/kunit.py run --make_options LLVM=1
> > > ...
> > >
> > > Cc: Jeff Dike <jdike@addtoit.com>
> > > Cc: Richard Weinberger <richard@nod.at>
> > > Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
> > > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > > Cc: Nick Desaulniers <ndesaulniers@google.com>
> > > Cc: Nathan Chancellor <nathan@kernel.org>
> > > Cc: David Gow <davidgow@google.com>
> > > Cc: linux-um@lists.infradead.org
> > > Cc: linux-kbuild@vger.kernel.org
> > > Cc: linux-kselftest@vger.kernel.org
> > > Cc: kunit-dev@googlegroups.com
> > > Cc: llvm@lists.linux.dev
> > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > ---
> > > arch/x86/um/user-offsets.c | 4 ++--
> > > scripts/Makefile.clang | 1 +
> > > 2 files changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
> > > index bae61554abcc..d9071827b515 100644
> > > --- a/arch/x86/um/user-offsets.c
> > > +++ b/arch/x86/um/user-offsets.c
> > > @@ -10,10 +10,10 @@
> > > #include <asm/types.h>
> > >
> > > #define DEFINE(sym, val) \
> > > - asm volatile("\n->" #sym " %0 " #val : : "i" (val))
> > > + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val))
> > >
> > > #define DEFINE_LONGS(sym, val) \
> > > - asm volatile("\n->" #sym " %0 " #val : : "i" (val/sizeof(unsigned long)))
> > > + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val/sizeof(unsigned long)))
> > >
> > > void foo(void)
> > > {
> > > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
> > > index 51fc23e2e9e5..857b23de51c6 100644
> > > --- a/scripts/Makefile.clang
> > > +++ b/scripts/Makefile.clang
> > > @@ -10,6 +10,7 @@ CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu
> > > CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu
> > > CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu
> > > CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu
> > > +CLANG_TARGET_FLAGS_um := x86_64-linux-gnu
> >
> >
> > Does this work for the i386 host?
> >
> > UML supports i386 and x86_64 as the host architecture as of now,
> > but this always compiles UML for x86_64?
>
> I think the current code will work because arch/x86/Makefile.um includes
> -m32 for CONFIG_X86_32, which will implicitly change x86_64-linux-gnu
> into a 32-bit target triple:
Ah, you are right!
>
> $ echo | clang --target=x86_64-linux-gnu -x c -c -o test.o -
>
> $ file test.o
> test.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped
>
> $ echo | clang --target=x86_64-linux-gnu -m32 -x c -c -o test.o -
>
> $ file test.o
> test.o: ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV), not stripped
>
> In fact, we rely on this for ARCH=i386 LLVM=1 right now, as it uses
> x86_64-linux-gnu for the target flag.
>
> While UML only supports x86, maybe it is worth using SUBARCH instead of
> hardcoding the triple? No strong opinion around that though.
>
> diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
> index 51fc23e2e9e5..87285b76adb2 100644
> --- a/scripts/Makefile.clang
> +++ b/scripts/Makefile.clang
> @@ -10,6 +10,7 @@ CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu
> CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu
> CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu
> CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu
> +CLANG_TARGET_FLAGS_um := $(CLANG_TARGET_FLAGS_$(SUBARCH))
LGTM.
I also thought of not passing --target at all for ARCH=um, but
we decided to override --target all the time (for reproducibility?).
Anyway, Nathan's way is clean, and looks OK to me.
> CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH))
>
> ifeq ($(CROSS_COMPILE),)
>
> > > CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH))
> > >
> > > ifeq ($(CROSS_COMPILE),)
> > > --
> > > 2.30.2
> > >
> >
> >
> > --
> > Best Regards
> > Masahiro Yamada
--
Best Regards
Masahiro Yamada
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-02-18 2:20 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-02-17 0:28 [PATCH] um: Allow builds with Clang Kees Cook
2022-02-17 0:37 ` Nathan Chancellor
2022-02-17 2:59 ` David Gow
2022-02-17 4:54 ` Masahiro Yamada
2022-02-17 17:41 ` Nathan Chancellor
2022-02-18 2:19 ` Masahiro Yamada
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