Re: [PATCH v2] x86/build: fix compiler support check for CONFIG_RETPOLINE

2018-12-18 Thread Gi-Oh Kim 
On Wed, Dec 5, 2018 at 8:11 AM Zhenzhong Duan  wrote:
>
>
> On 2018/12/5 14:27, Masahiro Yamada wrote:
> > It is troublesome to add a diagnostic like this to the Makefile
> > parse stage because the top-level Makefile could be parsed with
> > a stale include/config/auto.conf.
> >
> > Once you are hit by the error about non-retpoline compiler, the
> > compilation still breaks even after disabling CONFIG_RETPOLINE.
> >
> > The easiest fix is to move this check to the "archprepare" like commit
> > 829fe4aa9ac1 ("x86: Allow generating user-space headers without a
> > compiler") did.
> >
> > Link: https://lkml.org/lkml/2018/12/4/206
> > Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on 
> > compiler support")
> > Reported-by: Meelis Roos 
> > Signed-off-by: Masahiro Yamada 
> > ---
> >
> > Changes in v2:
> >- Revive ifdef CONFIG_RETPOLINE surrounding the KBUILD_CFLAGS addition
> >- Rephase the commit log a bit, hoping the cause of the issue will be 
> > clearer
> >
> >   arch/x86/Makefile | 10 +++---
> >   1 file changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> > index f5d7f41..75ef499 100644
> > --- a/arch/x86/Makefile
> > +++ b/arch/x86/Makefile
> > @@ -220,9 +220,6 @@ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
> >
> >   # Avoid indirect branches in kernel to deal with Spectre
> >   ifdef CONFIG_RETPOLINE
> > -ifeq ($(RETPOLINE_CFLAGS),)
> > -  $(error You are building kernel with non-retpoline compiler, please 
> > update your compiler.)
> > -endif
> > KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
> >   endif
> >
> > @@ -307,6 +304,13 @@ ifndef CC_HAVE_ASM_GOTO
> >   @echo Compiler lacks asm-goto support.
> >   @exit 1
> >   endif
> > +ifdef CONFIG_RETPOLINE
> > +ifeq ($(RETPOLINE_CFLAGS),)
> > + @echo "You are building kernel with non-retpoline compiler." >&2
> > + @echo "Please update your compiler." >&2
> > + @false
> > +endif
> > +endif
> >
> >   archclean:
> >   $(Q)rm -rf $(objtree)/arch/i386
> Acked-by: Zhenzhong Duan 
>
> --
> Regards
> Zhenzhong
>

Hi,

I think this patch needs to be merged to linux-stable 4.14.y branch.
Following is what I did to reproduce the problem.
The problem is gone after applying the patch.

1. I created and installed a headers package as following.
make -j7 deb-pkg
cd ..
sudo dpkg -i linux-headers-4.14.89+_4.14.89+-18_amd64.deb

2. I managed to re-produce the same problem as following.
gohkim@ws00837:~/study/drv$ make -C /usr/src/linux-headers-4.14.89+/
kernelrelease
make: Entering directory '/usr/src/linux-headers-4.14.89+'
arch/x86/Makefile:245: *** You are building kernel with non-retpoline
compiler, please update your compiler.. Stop.
make: Leaving directory '/usr/src/linux-headers-4.14.89+'

3. Weird thing is that it works fine if I use sudo command.
gohkim@ws00837:~/study/drv$ sudo make -C
/usr/src/linux-headers-4.14.89+/ kernelrelease
make: Entering directory '/usr/src/linux-headers-4.14.89+'
  HOSTCC  scripts/kconfig/conf.o
  HOSTCC  scripts/kconfig/zconf.tab.o
  HOSTLD  scripts/kconfig/conf
scripts/kconfig/conf  --silentoldconfig Kconfig
4.14.89
make: Leaving directory '/usr/src/linux-headers-4.14.89+'


-- 
GIOH KIM
Linux Kernel Entwickler

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D - 10405 Berlin

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Re: [PATCH v2] x86/build: fix compiler support check for CONFIG_RETPOLINE

2018-12-04 Thread Zhenzhong Duan 



On 2018/12/5 14:27, Masahiro Yamada wrote:

It is troublesome to add a diagnostic like this to the Makefile
parse stage because the top-level Makefile could be parsed with
a stale include/config/auto.conf.

Once you are hit by the error about non-retpoline compiler, the
compilation still breaks even after disabling CONFIG_RETPOLINE.

The easiest fix is to move this check to the "archprepare" like commit
829fe4aa9ac1 ("x86: Allow generating user-space headers without a
compiler") did.

Link: https://lkml.org/lkml/2018/12/4/206
Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler 
support")
Reported-by: Meelis Roos 
Signed-off-by: Masahiro Yamada 
---

Changes in v2:
   - Revive ifdef CONFIG_RETPOLINE surrounding the KBUILD_CFLAGS addition
   - Rephase the commit log a bit, hoping the cause of the issue will be clearer

  arch/x86/Makefile | 10 +++---
  1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index f5d7f41..75ef499 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -220,9 +220,6 @@ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
  
  # Avoid indirect branches in kernel to deal with Spectre

  ifdef CONFIG_RETPOLINE
-ifeq ($(RETPOLINE_CFLAGS),)
-  $(error You are building kernel with non-retpoline compiler, please update 
your compiler.)
-endif
KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
  endif
  
@@ -307,6 +304,13 @@ ifndef CC_HAVE_ASM_GOTO

@echo Compiler lacks asm-goto support.
@exit 1
  endif
+ifdef CONFIG_RETPOLINE
+ifeq ($(RETPOLINE_CFLAGS),)
+   @echo "You are building kernel with non-retpoline compiler." >&2
+   @echo "Please update your compiler." >&2
+   @false
+endif
+endif
  
  archclean:

$(Q)rm -rf $(objtree)/arch/i386

Acked-by: Zhenzhong Duan 

--
Regards
Zhenzhong

Re: [PATCH v2] x86/build: fix compiler support check for CONFIG_RETPOLINE

2018-12-04 Thread Zhenzhong Duan 



On 2018/12/5 14:27, Masahiro Yamada wrote:

It is troublesome to add a diagnostic like this to the Makefile
parse stage because the top-level Makefile could be parsed with
a stale include/config/auto.conf.

Once you are hit by the error about non-retpoline compiler, the
compilation still breaks even after disabling CONFIG_RETPOLINE.

The easiest fix is to move this check to the "archprepare" like commit
829fe4aa9ac1 ("x86: Allow generating user-space headers without a
compiler") did.

Link: https://lkml.org/lkml/2018/12/4/206
Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler 
support")
Reported-by: Meelis Roos 
Signed-off-by: Masahiro Yamada 
---

Changes in v2:
   - Revive ifdef CONFIG_RETPOLINE surrounding the KBUILD_CFLAGS addition
   - Rephase the commit log a bit, hoping the cause of the issue will be clearer

  arch/x86/Makefile | 10 +++---
  1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index f5d7f41..75ef499 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -220,9 +220,6 @@ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
  
  # Avoid indirect branches in kernel to deal with Spectre

  ifdef CONFIG_RETPOLINE
-ifeq ($(RETPOLINE_CFLAGS),)
-  $(error You are building kernel with non-retpoline compiler, please update 
your compiler.)
-endif
KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
  endif
  
@@ -307,6 +304,13 @@ ifndef CC_HAVE_ASM_GOTO

@echo Compiler lacks asm-goto support.
@exit 1
  endif
+ifdef CONFIG_RETPOLINE
+ifeq ($(RETPOLINE_CFLAGS),)
+   @echo "You are building kernel with non-retpoline compiler." >&2
+   @echo "Please update your compiler." >&2
+   @false
+endif
+endif
  
  archclean:

$(Q)rm -rf $(objtree)/arch/i386

Acked-by: Zhenzhong Duan 

--
Regards
Zhenzhong

Re: [PATCH v2] x86/build: fix compiler support check for CONFIG_RETPOLINE

2018-12-04 Thread Meelis Roos 

05.12.18 08:27 Masahiro Yamada kirjutas:

The easiest fix is to move this check to the "archprepare" like commit
829fe4aa9ac1 ("x86: Allow generating user-space headers without a
compiler") did.

Link: https://lkml.org/lkml/2018/12/4/206
Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler 
support")
Reported-by: Meelis Roos 
Signed-off-by: Masahiro Yamada 
---

Changes in v2:
   - Revive ifdef CONFIG_RETPOLINE surrounding the KBUILD_CFLAGS addition
   - Rephase the commit log a bit, hoping the cause of the issue will be clearer


Works for me - first it did

scripts/kconfig/conf  --syncconfig Kconfig

and then started compiling. The #define is gone from include/linux.

Thank you!

--
Meelis Roos

Re: [PATCH v2] x86/build: fix compiler support check for CONFIG_RETPOLINE

2018-12-04 Thread Meelis Roos 

05.12.18 08:27 Masahiro Yamada kirjutas:

The easiest fix is to move this check to the "archprepare" like commit
829fe4aa9ac1 ("x86: Allow generating user-space headers without a
compiler") did.

Link: https://lkml.org/lkml/2018/12/4/206
Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler 
support")
Reported-by: Meelis Roos 
Signed-off-by: Masahiro Yamada 
---

Changes in v2:
   - Revive ifdef CONFIG_RETPOLINE surrounding the KBUILD_CFLAGS addition
   - Rephase the commit log a bit, hoping the cause of the issue will be clearer


Works for me - first it did

scripts/kconfig/conf  --syncconfig Kconfig

and then started compiling. The #define is gone from include/linux.

Thank you!

--
Meelis Roos

[PATCH v2] x86/build: fix compiler support check for CONFIG_RETPOLINE

2018-12-04 Thread Masahiro Yamada 
It is troublesome to add a diagnostic like this to the Makefile
parse stage because the top-level Makefile could be parsed with
a stale include/config/auto.conf.

Once you are hit by the error about non-retpoline compiler, the
compilation still breaks even after disabling CONFIG_RETPOLINE.

The easiest fix is to move this check to the "archprepare" like commit
829fe4aa9ac1 ("x86: Allow generating user-space headers without a
compiler") did.

Link: https://lkml.org/lkml/2018/12/4/206
Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler 
support")
Reported-by: Meelis Roos 
Signed-off-by: Masahiro Yamada 
---

Changes in v2:
  - Revive ifdef CONFIG_RETPOLINE surrounding the KBUILD_CFLAGS addition
  - Rephase the commit log a bit, hoping the cause of the issue will be clearer

 arch/x86/Makefile | 10 +++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index f5d7f41..75ef499 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -220,9 +220,6 @@ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
 
 # Avoid indirect branches in kernel to deal with Spectre
 ifdef CONFIG_RETPOLINE
-ifeq ($(RETPOLINE_CFLAGS),)
-  $(error You are building kernel with non-retpoline compiler, please update 
your compiler.)
-endif
   KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
 endif
 
@@ -307,6 +304,13 @@ ifndef CC_HAVE_ASM_GOTO
@echo Compiler lacks asm-goto support.
@exit 1
 endif
+ifdef CONFIG_RETPOLINE
+ifeq ($(RETPOLINE_CFLAGS),)
+   @echo "You are building kernel with non-retpoline compiler." >&2
+   @echo "Please update your compiler." >&2
+   @false
+endif
+endif
 
 archclean:
$(Q)rm -rf $(objtree)/arch/i386
-- 
2.7.4

[PATCH v2] x86/build: fix compiler support check for CONFIG_RETPOLINE

2018-12-04 Thread Masahiro Yamada 
It is troublesome to add a diagnostic like this to the Makefile
parse stage because the top-level Makefile could be parsed with
a stale include/config/auto.conf.

Once you are hit by the error about non-retpoline compiler, the
compilation still breaks even after disabling CONFIG_RETPOLINE.

The easiest fix is to move this check to the "archprepare" like commit
829fe4aa9ac1 ("x86: Allow generating user-space headers without a
compiler") did.

Link: https://lkml.org/lkml/2018/12/4/206
Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler 
support")
Reported-by: Meelis Roos 
Signed-off-by: Masahiro Yamada 
---

Changes in v2:
  - Revive ifdef CONFIG_RETPOLINE surrounding the KBUILD_CFLAGS addition
  - Rephase the commit log a bit, hoping the cause of the issue will be clearer

 arch/x86/Makefile | 10 +++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index f5d7f41..75ef499 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -220,9 +220,6 @@ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
 
 # Avoid indirect branches in kernel to deal with Spectre
 ifdef CONFIG_RETPOLINE
-ifeq ($(RETPOLINE_CFLAGS),)
-  $(error You are building kernel with non-retpoline compiler, please update 
your compiler.)
-endif
   KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
 endif
 
@@ -307,6 +304,13 @@ ifndef CC_HAVE_ASM_GOTO
@echo Compiler lacks asm-goto support.
@exit 1
 endif
+ifdef CONFIG_RETPOLINE
+ifeq ($(RETPOLINE_CFLAGS),)
+   @echo "You are building kernel with non-retpoline compiler." >&2
+   @echo "Please update your compiler." >&2
+   @false
+endif
+endif
 
 archclean:
$(Q)rm -rf $(objtree)/arch/i386
-- 
2.7.4