[PATCH] build: Fix build with Ubuntu

[PATCH] build: Fix build with Ubuntu

[Andrew Cooper]

This supercedes "x86/build: Unilaterally disable -fcf-protection"

Andrew Cooper (2):
  x86/build: move -fno-asynchronous-unwind-tables into EMBEDDED_EXTRA_CFLAGS
  x86/build: Unilaterally disable -fcf-protection

 Config.mk                            | 3 ++-
 tools/tests/x86_emulator/testcase.mk | 2 +-
 xen/arch/x86/arch.mk                 | 2 +-
 xen/arch/x86/boot/build32.mk         | 2 +-
 4 files changed, 5 insertions(+), 4 deletions(-)

-- 
2.11.0

[PATCH] x86/build: move -fno-asynchronous-unwind-tables into EMBEDDED_EXTRA_CFLAGS

[Andrew Cooper]

Users of EMBEDDED_EXTRA_CFLAGS already use -fno-asynchronous-unwind-tables, or
ought to.  This shrinks the size of the rombios 32bit stubs in guest memory.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wl@xen.org>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: George Dunlap <George.Dunlap@eu.citrix.com>
CC: Ian Jackson <ian.jackson@citrix.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien@xen.org>
---
 Config.mk                            | 2 +-
 tools/tests/x86_emulator/testcase.mk | 2 +-
 xen/arch/x86/arch.mk                 | 2 +-
 xen/arch/x86/boot/build32.mk         | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Config.mk b/Config.mk
index 3621162ae4..b0f16680f3 100644
--- a/Config.mk
+++ b/Config.mk
@@ -204,7 +204,7 @@ APPEND_LDFLAGS += $(foreach i, $(APPEND_LIB), -L$(i))
 APPEND_CFLAGS += $(foreach i, $(APPEND_INCLUDES), -I$(i))
 
 EMBEDDED_EXTRA_CFLAGS := -nopie -fno-stack-protector -fno-stack-protector-all
-EMBEDDED_EXTRA_CFLAGS += -fno-exceptions
+EMBEDDED_EXTRA_CFLAGS += -fno-exceptions -fno-asynchronous-unwind-tables
 
 XEN_EXTFILES_URL ?= http://xenbits.xen.org/xen-extfiles
 # All the files at that location were downloaded from elsewhere on
diff --git a/tools/tests/x86_emulator/testcase.mk b/tools/tests/x86_emulator/testcase.mk
index a565d15524..dafeb6caf7 100644
--- a/tools/tests/x86_emulator/testcase.mk
+++ b/tools/tests/x86_emulator/testcase.mk
@@ -4,7 +4,7 @@ include $(XEN_ROOT)/tools/Rules.mk
 
 $(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
 
-CFLAGS += -fno-builtin -fno-asynchronous-unwind-tables -g0 $($(TESTCASE)-cflags)
+CFLAGS += -fno-builtin -g0 $($(TESTCASE)-cflags)
 
 .PHONY: all
 all: $(TESTCASE).bin
diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk
index 2a51553edb..62b7c97007 100644
--- a/xen/arch/x86/arch.mk
+++ b/xen/arch/x86/arch.mk
@@ -56,7 +56,7 @@ $(call as-option-add,CFLAGS,CC,\
 $(call as-option-add,CFLAGS,CC,\
     ".L1: .L2: .nops (.L2 - .L1)$$(comma)9",-DHAVE_AS_NOPS_DIRECTIVE)
 
-CFLAGS += -mno-red-zone -fpic -fno-asynchronous-unwind-tables
+CFLAGS += -mno-red-zone -fpic
 
 # Xen doesn't use SSE interally.  If the compiler supports it, also skip the
 # SSE setup for variadic function calls.
diff --git a/xen/arch/x86/boot/build32.mk b/xen/arch/x86/boot/build32.mk
index 48c7407c00..5851ebff5f 100644
--- a/xen/arch/x86/boot/build32.mk
+++ b/xen/arch/x86/boot/build32.mk
@@ -4,7 +4,7 @@ include $(XEN_ROOT)/Config.mk
 
 $(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
 
-CFLAGS += -Werror -fno-asynchronous-unwind-tables -fno-builtin -g0 -msoft-float
+CFLAGS += -Werror -fno-builtin -g0 -msoft-float
 CFLAGS += -I$(XEN_ROOT)/xen/include
 CFLAGS := $(filter-out -flto,$(CFLAGS)) 
 
-- 
2.11.0

Re: [PATCH] x86/build: move -fno-asynchronous-unwind-tables into EMBEDDED_EXTRA_CFLAGS

[Jan Beulich]

On 13.05.2020 15:55, Andrew Cooper wrote:
> Users of EMBEDDED_EXTRA_CFLAGS already use -fno-asynchronous-unwind-tables, or
> ought to.

It's not really well defined what they're supposed to be used for
(and where it's not supposed to be used). I notice in particular
a use in stubdom/Makefile which I'm unsure whether it indeed wants
this adjustment. Therefore ...

>  This shrinks the size of the rombios 32bit stubs in guest memory.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>
with the request that Samuel also ack (or otherwise) the change
from a stubdom perspective.

Jan

Re: [PATCH] x86/build: move -fno-asynchronous-unwind-tables into EMBEDDED_EXTRA_CFLAGS

[Samuel Thibault]

Hello,

Jan Beulich, le mer. 13 mai 2020 16:11:00 +0200, a ecrit:
> On 13.05.2020 15:55, Andrew Cooper wrote:
> > Users of EMBEDDED_EXTRA_CFLAGS already use -fno-asynchronous-unwind-tables, or
> > ought to.
> 
> It's not really well defined what they're supposed to be used for
> (and where it's not supposed to be used). I notice in particular
> a use in stubdom/Makefile which I'm unsure whether it indeed wants
> this adjustment. Therefore ...

I don't know why this is there in mini-os. It dates back 2005
8afe079be ('Mini-OS cleanups. Bug fixes in x86_64 assembly code.')

It indeed looks to me like a general option to minimize binary size, so
I'd say it is fine to make its activation general.

> >  This shrinks the size of the rombios 32bit stubs in guest memory.
> > 
> > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> 
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
> with the request that Samuel also ack (or otherwise) the change
> from a stubdom perspective.

Samuel

[PATCH] x86/build: Unilaterally disable -fcf-protection

[Andrew Cooper]

Xen doesn't support CET-IBT yet.  At a minimum, logic is required to enable it
for supervisor use, but the livepatch functionality needs to learn not to
overwrite ENDBR64 instructions.

Furthermore, Ubuntu enables -fcf-protection by default, along with a buggy
version of GCC-9 which objects to it in combination with
-mindirect-branch=thunk-extern (Fixed in GCC 10, 9.4).

Various objects (Xen boot path, Rombios 32 stubs) require .text to be at the
beginning of the object.  These paths explode when .note.gnu.properties gets
put ahead of .text and we end up executing the notes data.

Disable -fcf-protection for all embedded objects.

Reported-by: Jason Andryuk <jandryuk@gmail.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wl@xen.org>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Jason Andryuk <jandryuk@gmail.com>
CC: Stefan Bader <stefan.bader@canonical.com>

v2:
 * Fix Rombios 32 stubs as well.
---
 Config.mk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Config.mk b/Config.mk
index b0f16680f3..7d556aed30 100644
--- a/Config.mk
+++ b/Config.mk
@@ -205,6 +205,7 @@ APPEND_CFLAGS += $(foreach i, $(APPEND_INCLUDES), -I$(i))
 
 EMBEDDED_EXTRA_CFLAGS := -nopie -fno-stack-protector -fno-stack-protector-all
 EMBEDDED_EXTRA_CFLAGS += -fno-exceptions -fno-asynchronous-unwind-tables
+EMBEDDED_EXTRA_CFLAGS += -fcf-protection=none
 
 XEN_EXTFILES_URL ?= http://xenbits.xen.org/xen-extfiles
 # All the files at that location were downloaded from elsewhere on
-- 
2.11.0

Re: [PATCH] x86/build: Unilaterally disable -fcf-protection

[Jan Beulich]

On 13.05.2020 15:55, Andrew Cooper wrote:
> Xen doesn't support CET-IBT yet.  At a minimum, logic is required to enable it
> for supervisor use, but the livepatch functionality needs to learn not to
> overwrite ENDBR64 instructions.
> 
> Furthermore, Ubuntu enables -fcf-protection by default, along with a buggy
> version of GCC-9 which objects to it in combination with
> -mindirect-branch=thunk-extern (Fixed in GCC 10, 9.4).
> 
> Various objects (Xen boot path, Rombios 32 stubs) require .text to be at the
> beginning of the object.  These paths explode when .note.gnu.properties gets
> put ahead of .text and we end up executing the notes data.
> 
> Disable -fcf-protection for all embedded objects.
> 
> Reported-by: Jason Andryuk <jandryuk@gmail.com>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

For the immediate purpose
Reviewed-by: Jan Beulich <jbeulich@suse.com>

I wonder however ...

> --- a/Config.mk
> +++ b/Config.mk
> @@ -205,6 +205,7 @@ APPEND_CFLAGS += $(foreach i, $(APPEND_INCLUDES), -I$(i))
>  
>  EMBEDDED_EXTRA_CFLAGS := -nopie -fno-stack-protector -fno-stack-protector-all
>  EMBEDDED_EXTRA_CFLAGS += -fno-exceptions -fno-asynchronous-unwind-tables
> +EMBEDDED_EXTRA_CFLAGS += -fcf-protection=none

... whether this isn't going to bite us once some of the consumers
of this variable want to enable some different mode.

Jan

Re: [PATCH] x86/build: Unilaterally disable -fcf-protection

[Andrew Cooper]

On 13/05/2020 15:13, Jan Beulich wrote:
> [CAUTION - EXTERNAL EMAIL] DO NOT reply, click links, or open attachments unless you have verified the sender and know the content is safe.
>
> On 13.05.2020 15:55, Andrew Cooper wrote:
>> Xen doesn't support CET-IBT yet.  At a minimum, logic is required to enable it
>> for supervisor use, but the livepatch functionality needs to learn not to
>> overwrite ENDBR64 instructions.
>>
>> Furthermore, Ubuntu enables -fcf-protection by default, along with a buggy
>> version of GCC-9 which objects to it in combination with
>> -mindirect-branch=thunk-extern (Fixed in GCC 10, 9.4).
>>
>> Various objects (Xen boot path, Rombios 32 stubs) require .text to be at the
>> beginning of the object.  These paths explode when .note.gnu.properties gets
>> put ahead of .text and we end up executing the notes data.
>>
>> Disable -fcf-protection for all embedded objects.
>>
>> Reported-by: Jason Andryuk <jandryuk@gmail.com>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> For the immediate purpose
> Reviewed-by: Jan Beulich <jbeulich@suse.com>

Thanks.

>
> I wonder however ...
>
>> --- a/Config.mk
>> +++ b/Config.mk
>> @@ -205,6 +205,7 @@ APPEND_CFLAGS += $(foreach i, $(APPEND_INCLUDES), -I$(i))
>>  
>>  EMBEDDED_EXTRA_CFLAGS := -nopie -fno-stack-protector -fno-stack-protector-all
>>  EMBEDDED_EXTRA_CFLAGS += -fno-exceptions -fno-asynchronous-unwind-tables
>> +EMBEDDED_EXTRA_CFLAGS += -fcf-protection=none
> ... whether this isn't going to bite us once some of the consumers
> of this variable want to enable some different mode.

I'm not overly happy with EMBEDDED_EXTRA_CFLAGS as a concept, but these
build fixes do need backporting.

All embedded targets may in principle use some/all of these options at
some point in the future.

~Andrew

Re: [PATCH] x86/build: Unilaterally disable -fcf-protection

[Jason Andryuk]

On Wed, May 13, 2020 at 9:56 AM Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>
> Xen doesn't support CET-IBT yet.  At a minimum, logic is required to enable it
> for supervisor use, but the livepatch functionality needs to learn not to
> overwrite ENDBR64 instructions.
>
> Furthermore, Ubuntu enables -fcf-protection by default, along with a buggy
> version of GCC-9 which objects to it in combination with
> -mindirect-branch=thunk-extern (Fixed in GCC 10, 9.4).
>
> Various objects (Xen boot path, Rombios 32 stubs) require .text to be at the
> beginning of the object.  These paths explode when .note.gnu.properties gets
> put ahead of .text and we end up executing the notes data.
>
> Disable -fcf-protection for all embedded objects.
>
> Reported-by: Jason Andryuk <jandryuk@gmail.com>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Reviewed-by: Jason Andryuk <jandryuk@gmail.com>

I have not re-tested this posting, but I tested an equivalent change
~2 weeks ago (in case that counts for Tested-by).

-Jason