LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
* [PATCH 1/3] retpolines: Only enable retpoline when compiler support it
@ 2018-10-30  6:55 Zhenzhong Duan
  2018-10-30  8:32 ` Peter Zijlstra
  2018-10-30  9:39 ` Masahiro Yamada
  0 siblings, 2 replies; 6+ messages in thread
From: Zhenzhong Duan @ 2018-10-30  6:55 UTC (permalink / raw)
  To: Linux-Kernel
  Cc: mingo, luto, konrad.wilk, dwmw, tglx, Srinivas REDDY Eeda, bp,
	daniel, yamada.masahiro, michal.lkml, peterz, hpa

Since retpoline capable compilers are widely available, make
CONFIG_RETPOLINE hard depend on it.

Change KBUILD to use CONFIG_RETPOLINE_SUPPORT to avoid conflict with
CONFIG_RETPOLINE which is used by kernel.

With all that stuff, the check of RETPOLINE is changed to
CONFIG_RETPOLINE.

This change is based on suggestion in https://lkml.org/lkml/2018/9/18/1016

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
---
 Documentation/admin-guide/kernel-parameters.txt |  2 +-
 arch/x86/Kconfig                                |  8 ++++----
 arch/x86/Makefile                               |  5 +++--
 arch/x86/entry/vdso/Makefile                    |  4 ++--
 arch/x86/include/asm/nospec-branch.h            | 10 ++++++----
 arch/x86/kernel/cpu/bugs.c                      |  2 +-
 arch/x86/kernel/vmlinux.lds.S                   |  2 +-
 arch/x86/lib/Makefile                           |  2 +-
 arch/x86/lib/retpoline.S                        |  2 ++
 scripts/Makefile.build                          |  2 +-
 10 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e129cd8..c26264e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4187,7 +4187,7 @@
 			Selecting 'on' will, and 'auto' may, choose a
 			mitigation method at run time according to the
 			CPU, the available microcode, the setting of the
-			CONFIG_RETPOLINE configuration option, and the
+			CONFIG_RETPOLINE_SUPPORT configuration option, and the
 			compiler with which the kernel was built.
 
 			Specific mitigations can also be selected manually:
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cbd5f28..766563f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -433,7 +433,7 @@ config GOLDFISH
        def_bool y
        depends on X86_GOLDFISH
 
-config RETPOLINE
+config RETPOLINE_SUPPORT
 	bool "Avoid speculative indirect branches in kernel"
 	default y
 	select STACK_VALIDATION if HAVE_STACK_VALIDATION
@@ -443,9 +443,9 @@ config RETPOLINE
 	  branches. Requires a compiler with -mindirect-branch=thunk-extern
 	  support for full protection. The kernel may run slower.
 
-	  Without compiler support, at least indirect branches in assembler
-	  code are eliminated. Since this includes the syscall entry path,
-	  it is not entirely pointless.
+	  Since retpoline capable compilers are widely available, kernel doesn't
+	  use CONFIG_RETPOLINE_SUPPORT directly but use CONFIG_RETPOLINE which
+	  is enabled when compiler support retpoline.
 
 config INTEL_RDT
 	bool "Intel Resource Director Technology support"
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 5b562e4..7ed35b1 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -221,9 +221,10 @@ KBUILD_CFLAGS += -Wno-sign-compare
 KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
 
 # Avoid indirect branches in kernel to deal with Spectre
-ifdef CONFIG_RETPOLINE
+ifdef CONFIG_RETPOLINE_SUPPORT
 ifneq ($(RETPOLINE_CFLAGS),)
-  KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
+  KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DCONFIG_RETPOLINE
+  KBUILD_AFLAGS += -DCONFIG_RETPOLINE
 endif
 endif
 
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 141d415..87acde1 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -70,7 +70,7 @@ CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
        -fno-omit-frame-pointer -foptimize-sibling-calls \
        -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
 
-ifdef CONFIG_RETPOLINE
+ifdef CONFIG_RETPOLINE_SUPPORT
 ifneq ($(RETPOLINE_VDSO_CFLAGS),)
   CFL += $(RETPOLINE_VDSO_CFLAGS)
 endif
@@ -145,7 +145,7 @@ KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
 KBUILD_CFLAGS_32 += -fno-omit-frame-pointer
 KBUILD_CFLAGS_32 += -DDISABLE_BRANCH_PROFILING
 
-ifdef CONFIG_RETPOLINE
+ifdef CONFIG_RETPOLINE_SUPPORT
 ifneq ($(RETPOLINE_VDSO_CFLAGS),)
   KBUILD_CFLAGS_32 += $(RETPOLINE_VDSO_CFLAGS)
 endif
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 80dc144..8b09cbb 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -162,11 +162,12 @@
 	_ASM_PTR " 999b\n\t"					\
 	".popsection\n\t"
 
-#if defined(CONFIG_X86_64) && defined(RETPOLINE)
+#ifdef CONFIG_RETPOLINE
+#ifdef CONFIG_X86_64
 
 /*
- * Since the inline asm uses the %V modifier which is only in newer GCC,
- * the 64-bit one is dependent on RETPOLINE not CONFIG_RETPOLINE.
+ * Inline asm uses the %V modifier which is only in newer GCC
+ * which is ensured when CONFIG_RETPOLINE is defined.
  */
 # define CALL_NOSPEC						\
 	ANNOTATE_NOSPEC_ALTERNATIVE				\
@@ -181,7 +182,7 @@
 	X86_FEATURE_RETPOLINE_AMD)
 # define THUNK_TARGET(addr) [thunk_target] "r" (addr)
 
-#elif defined(CONFIG_X86_32) && defined(CONFIG_RETPOLINE)
+#else /* CONFIG_X86_32 */
 /*
  * For i386 we use the original ret-equivalent retpoline, because
  * otherwise we'll run out of registers. We don't care about CET
@@ -211,6 +212,7 @@
 	X86_FEATURE_RETPOLINE_AMD)
 
 # define THUNK_TARGET(addr) [thunk_target] "rm" (addr)
+#endif
 #else /* No retpoline for C / inline asm */
 # define CALL_NOSPEC "call *%[thunk_target]\n"
 # define THUNK_TARGET(addr) [thunk_target] "rm" (addr)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index c37e66e..d0108fb 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -252,7 +252,7 @@ static void __init spec2_print_if_secure(const char *reason)
 
 static inline bool retp_compiler(void)
 {
-	return __is_defined(RETPOLINE);
+	return __is_defined(CONFIG_RETPOLINE);
 }
 
 static inline bool match_option(const char *arg, int arglen, const char *opt)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 0d618ee..07533f7 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -136,7 +136,7 @@ SECTIONS
 		*(.fixup)
 		*(.gnu.warning)
 
-#ifdef CONFIG_RETPOLINE
+#ifdef CONFIG_RETPOLINE_SUPPORT
 		__indirect_thunk_start = .;
 		*(.text.__x86.indirect_thunk)
 		__indirect_thunk_end = .;
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 25a972c..edfa7ab 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -27,7 +27,7 @@ lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
 lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o insn-eval.o
 lib-$(CONFIG_RANDOMIZE_BASE) += kaslr.o
 lib-$(CONFIG_FUNCTION_ERROR_INJECTION)	+= error-inject.o
-lib-$(CONFIG_RETPOLINE) += retpoline.o
+lib-$(CONFIG_RETPOLINE_SUPPORT) += retpoline.o
 
 obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o
 
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index c909961..81366ad 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 
+#ifdef CONFIG_RETPOLINE
 #include <linux/stringify.h>
 #include <linux/linkage.h>
 #include <asm/dwarf2.h>
@@ -46,3 +47,4 @@ GENERATE_THUNK(r13)
 GENERATE_THUNK(r14)
 GENERATE_THUNK(r15)
 #endif
+#endif
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 54da4b0..259d9c6 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -247,7 +247,7 @@ endif
 ifdef CONFIG_GCOV_KERNEL
 objtool_args += --no-unreachable
 endif
-ifdef CONFIG_RETPOLINE
+ifdef CONFIG_RETPOLINE_SUPPORT
 ifneq ($(RETPOLINE_CFLAGS),)
   objtool_args += --retpoline
 endif
-- 
1.8.3.1

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH 1/3] retpolines: Only enable retpoline when compiler support it
  2018-10-30  6:55 [PATCH 1/3] retpolines: Only enable retpoline when compiler support it Zhenzhong Duan
@ 2018-10-30  8:32 ` Peter Zijlstra
  2018-10-31  4:58   ` Zhenzhong Duan
  2018-10-30  9:39 ` Masahiro Yamada
  1 sibling, 1 reply; 6+ messages in thread
From: Peter Zijlstra @ 2018-10-30  8:32 UTC (permalink / raw)
  To: Zhenzhong Duan
  Cc: Linux-Kernel, mingo, luto, konrad.wilk, dwmw, tglx,
	Srinivas REDDY Eeda, bp, daniel, yamada.masahiro, michal.lkml,
	hpa

On Mon, Oct 29, 2018 at 11:55:04PM -0700, Zhenzhong Duan wrote:
> Since retpoline capable compilers are widely available, make
> CONFIG_RETPOLINE hard depend on it.
> 
> Change KBUILD to use CONFIG_RETPOLINE_SUPPORT to avoid conflict with
> CONFIG_RETPOLINE which is used by kernel.
> 
> With all that stuff, the check of RETPOLINE is changed to
> CONFIG_RETPOLINE.

So what happens when we select CONFIG_RETPOLINE but do not have
RETPOLINE_SUPPORT ? From a quick reading we'll silently build a
!retpoline kernel. I would expect a build failure.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH 1/3] retpolines: Only enable retpoline when compiler support it
  2018-10-30  6:55 [PATCH 1/3] retpolines: Only enable retpoline when compiler support it Zhenzhong Duan
  2018-10-30  8:32 ` Peter Zijlstra
@ 2018-10-30  9:39 ` Masahiro Yamada
  2018-10-30 10:09   ` Peter Zijlstra
  1 sibling, 1 reply; 6+ messages in thread
From: Masahiro Yamada @ 2018-10-30  9:39 UTC (permalink / raw)
  To: zhenzhong.duan
  Cc: Linux Kernel Mailing List, Ingo Molnar, Andy Lutomirski,
	konrad.wilk, David Woodhouse, Thomas Gleixner, srinivas.eeda,
	Borislav Petkov, Daniel Borkmann, Michal Marek,
	Peter Zijlstra (Intel),
	H. Peter Anvin

Hi,



On Tue, Oct 30, 2018 at 3:57 PM Zhenzhong Duan
<zhenzhong.duan@oracle.com> wrote:
>
> Since retpoline capable compilers are widely available, make
> CONFIG_RETPOLINE hard depend on it.
>
> Change KBUILD to use CONFIG_RETPOLINE_SUPPORT to avoid conflict with
> CONFIG_RETPOLINE which is used by kernel.
>
> With all that stuff, the check of RETPOLINE is changed to
> CONFIG_RETPOLINE.
>
> This change is based on suggestion in https://lkml.org/lkml/2018/9/18/1016
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: David Woodhouse <dwmw@amazon.co.uk>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: Michal Marek <michal.lkml@markovi.net>
> ---


Instead of adding another CONFIG option,
does it make sense to add compiler support checks
to 'depends on' syntax ?


config RETPOLINE
         bool "Avoid speculative indirect branches in kernel"
         depends on $(cc-option,-mindirect-branch=thunk-extern
-mindirect-branch-register) || \
                    $(cc-option,-mretpoline-external-thunk)
         default y
         select STACK_VALIDATION if HAVE_STACK_VALIDATION






-- 
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH 1/3] retpolines: Only enable retpoline when compiler support it
  2018-10-30  9:39 ` Masahiro Yamada
@ 2018-10-30 10:09   ` Peter Zijlstra
  2018-10-31  5:55     ` Zhenzhong Duan
  0 siblings, 1 reply; 6+ messages in thread
From: Peter Zijlstra @ 2018-10-30 10:09 UTC (permalink / raw)
  To: Masahiro Yamada
  Cc: zhenzhong.duan, Linux Kernel Mailing List, Ingo Molnar,
	Andy Lutomirski, konrad.wilk, David Woodhouse, Thomas Gleixner,
	srinivas.eeda, Borislav Petkov, Daniel Borkmann, Michal Marek,
	H. Peter Anvin

On Tue, Oct 30, 2018 at 06:39:24PM +0900, Masahiro Yamada wrote:
> Hi,
> 
> 
> 
> On Tue, Oct 30, 2018 at 3:57 PM Zhenzhong Duan
> <zhenzhong.duan@oracle.com> wrote:
> >
> > Since retpoline capable compilers are widely available, make
> > CONFIG_RETPOLINE hard depend on it.
> >
> > Change KBUILD to use CONFIG_RETPOLINE_SUPPORT to avoid conflict with
> > CONFIG_RETPOLINE which is used by kernel.
> >
> > With all that stuff, the check of RETPOLINE is changed to
> > CONFIG_RETPOLINE.
> >
> > This change is based on suggestion in https://lkml.org/lkml/2018/9/18/1016
> >
> > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Borislav Petkov <bp@suse.de>
> > Cc: Daniel Borkmann <daniel@iogearbox.net>
> > Cc: David Woodhouse <dwmw@amazon.co.uk>
> > Cc: H. Peter Anvin <hpa@zytor.com>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > Cc: Andy Lutomirski <luto@kernel.org>
> > Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> > Cc: Michal Marek <michal.lkml@markovi.net>
> > ---
> 
> 
> Instead of adding another CONFIG option,
> does it make sense to add compiler support checks
> to 'depends on' syntax ?
> 
> 
> config RETPOLINE
>          bool "Avoid speculative indirect branches in kernel"
>          depends on $(cc-option,-mindirect-branch=thunk-extern
> -mindirect-branch-register) || \
>                     $(cc-option,-mretpoline-external-thunk)
>          default y
>          select STACK_VALIDATION if HAVE_STACK_VALIDATION

That seems to be what we did for stackprotector, which is similar in
that it used to fail the build. So yes, this seems sane.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH 1/3] retpolines: Only enable retpoline when compiler support it
  2018-10-30  8:32 ` Peter Zijlstra
@ 2018-10-31  4:58   ` Zhenzhong Duan
  0 siblings, 0 replies; 6+ messages in thread
From: Zhenzhong Duan @ 2018-10-31  4:58 UTC (permalink / raw)
  To: Peter Zijlstra
  Cc: Linux-Kernel, mingo, luto, konrad.wilk, dwmw, tglx,
	Srinivas REDDY Eeda, bp, daniel, yamada.masahiro, michal.lkml,
	hpa

On 2018/10/30 16:32, Peter Zijlstra wrote:
> On Mon, Oct 29, 2018 at 11:55:04PM -0700, Zhenzhong Duan wrote:
>> Since retpoline capable compilers are widely available, make
>> CONFIG_RETPOLINE hard depend on it.
>>
>> Change KBUILD to use CONFIG_RETPOLINE_SUPPORT to avoid conflict with
>> CONFIG_RETPOLINE which is used by kernel.
>>
>> With all that stuff, the check of RETPOLINE is changed to
>> CONFIG_RETPOLINE.
> 
> So what happens when we select CONFIG_RETPOLINE but do not have
> RETPOLINE_SUPPORT ? From a quick reading we'll silently build a
> !retpoline kernel. I would expect a build failure.

CONFIG_RETPOLINE is only defined when CONFIG_RETPOLINE_SUPPORT is 
selected. See below chunk.

--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -221,9 +221,10 @@ KBUILD_CFLAGS += -Wno-sign-compare
  KBUILD_CFLAGS += -fno-asynchronous-unwind-tables

  # Avoid indirect branches in kernel to deal with Spectre
-ifdef CONFIG_RETPOLINE
+ifdef CONFIG_RETPOLINE_SUPPORT
  ifneq ($(RETPOLINE_CFLAGS),)
-  KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
+  KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DCONFIG_RETPOLINE
+  KBUILD_AFLAGS += -DCONFIG_RETPOLINE
  endif
  endif


Thanks
Zhenzhong

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH 1/3] retpolines: Only enable retpoline when compiler support it
  2018-10-30 10:09   ` Peter Zijlstra
@ 2018-10-31  5:55     ` Zhenzhong Duan
  0 siblings, 0 replies; 6+ messages in thread
From: Zhenzhong Duan @ 2018-10-31  5:55 UTC (permalink / raw)
  To: Peter Zijlstra, Masahiro Yamada
  Cc: Linux Kernel Mailing List, Ingo Molnar, Andy Lutomirski,
	konrad.wilk, David Woodhouse, Thomas Gleixner, srinivas.eeda,
	Borislav Petkov, Daniel Borkmann, Michal Marek, H. Peter Anvin

On 2018/10/30 18:09, Peter Zijlstra wrote:
> On Tue, Oct 30, 2018 at 06:39:24PM +0900, Masahiro Yamada wrote:
>> Hi,
>>
>>
>>
>> On Tue, Oct 30, 2018 at 3:57 PM Zhenzhong Duan
>> <zhenzhong.duan@oracle.com> wrote:
>>>
>>> Since retpoline capable compilers are widely available, make
>>> CONFIG_RETPOLINE hard depend on it.
>>>
>>> Change KBUILD to use CONFIG_RETPOLINE_SUPPORT to avoid conflict with
>>> CONFIG_RETPOLINE which is used by kernel.
>>>
>>> With all that stuff, the check of RETPOLINE is changed to
>>> CONFIG_RETPOLINE.
>>>
>>> This change is based on suggestion in https://lkml.org/lkml/2018/9/18/1016
>>>
>>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> Cc: Peter Zijlstra <peterz@infradead.org>
>>> Cc: Borislav Petkov <bp@suse.de>
>>> Cc: Daniel Borkmann <daniel@iogearbox.net>
>>> Cc: David Woodhouse <dwmw@amazon.co.uk>
>>> Cc: H. Peter Anvin <hpa@zytor.com>
>>> Cc: Ingo Molnar <mingo@redhat.com>
>>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>>> Cc: Andy Lutomirski <luto@kernel.org>
>>> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
>>> Cc: Michal Marek <michal.lkml@markovi.net>
>>> ---
>>
>>
>> Instead of adding another CONFIG option,
>> does it make sense to add compiler support checks
>> to 'depends on' syntax ?
>>
>>
>> config RETPOLINE
>>           bool "Avoid speculative indirect branches in kernel"
>>           depends on $(cc-option,-mindirect-branch=thunk-extern
>> -mindirect-branch-register) || \
>>                      $(cc-option,-mretpoline-external-thunk)
>>           default y
>>           select STACK_VALIDATION if HAVE_STACK_VALIDATION

Looks better, thanks for suggestion.

> 
> That seems to be what we did for stackprotector, which is similar in
> that it used to fail the build. So yes, this seems sane.

Should I add a scripts/gcc-x86_64-has-retpoline.sh like what 
stackprotector does as below or there is a simpler way?

config CC_HAS_SANE_STACKPROTECTOR
         bool
         default 
$(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 
64BIT
         default 
$(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
         help
            We have to make sure stack protector is unconditionally 
disabled if
            the compiler produces broken code.

Thanks
Zhenzhong

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2018-10-31  5:55 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-10-30  6:55 [PATCH 1/3] retpolines: Only enable retpoline when compiler support it Zhenzhong Duan
2018-10-30  8:32 ` Peter Zijlstra
2018-10-31  4:58   ` Zhenzhong Duan
2018-10-30  9:39 ` Masahiro Yamada
2018-10-30 10:09   ` Peter Zijlstra
2018-10-31  5:55     ` Zhenzhong Duan

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).