Two patches to fix building with a cf-protection toolchain.  The first
handles the case where the compiler fails to run with "error:
‘-mindirect-branch’ and ‘-fcf-protection’ are not compatible".

The second fixes a runtime error that prevented Xen booting in legacy
mode.

I still haven't figured out exactly what is wrong with rombios and/or
ipxe.

Jason Andryuk (2):
  xen/x86: Disable fcf-protection when necessary to build
  x86/boot: Drop .note.gnu.properties in build32.lds

 xen/arch/x86/arch.mk          | 11 ++++++++++-
 xen/arch/x86/boot/build32.lds |  5 +++++
 2 files changed, 15 insertions(+), 1 deletion(-)

-- 
2.25.1

On 12.05.20 05:39, Jason Andryuk wrote:
> Two patches to fix building with a cf-protection toolchain.  The first
> handles the case where the compiler fails to run with "error:
> ‘-mindirect-branch’ and ‘-fcf-protection’ are not compatible".
> 
> The second fixes a runtime error that prevented Xen booting in legacy
> mode.

That might be better than just disabling fcf-protection as well (which was done
in Ubuntu lacking a better solution).

Not sure it was already hit but that additional .note section breaks the build
of the emulator as generated headers become gigantic:

https://git.launchpad.net/ubuntu/+source/xen/tree/debian/patches/1001-strip-note-gnu-property.patch?h=ubuntu/focal

-Stefan
> 
> I still haven't figured out exactly what is wrong with rombios and/or
> ipxe.
> 
> Jason Andryuk (2):
>   xen/x86: Disable fcf-protection when necessary to build
>   x86/boot: Drop .note.gnu.properties in build32.lds
> 
>  xen/arch/x86/arch.mk          | 11 ++++++++++-
>  xen/arch/x86/boot/build32.lds |  5 +++++
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 

On 12/05/2020 08:17, Stefan Bader wrote:
> On 12.05.20 05:39, Jason Andryuk wrote:
>> Two patches to fix building with a cf-protection toolchain.  The first
>> handles the case where the compiler fails to run with "error:
>> ‘-mindirect-branch’ and ‘-fcf-protection’ are not compatible".
>>
>> The second fixes a runtime error that prevented Xen booting in legacy
>> mode.
> That might be better than just disabling fcf-protection as well (which was done
> in Ubuntu lacking a better solution).

It is a GCC bug

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654

Fixed for 10, and 9.4

>
> Not sure it was already hit but that additional .note section breaks the build
> of the emulator as generated headers become gigantic:
>
> https://git.launchpad.net/ubuntu/+source/xen/tree/debian/patches/1001-strip-note-gnu-property.patch?h=ubuntu/focal

4.6G of notes?!?  That is surely a toolchain bug.

~Andrew

On 12.05.20 20:47, Andrew Cooper wrote:
> On 12/05/2020 08:17, Stefan Bader wrote:
>> On 12.05.20 05:39, Jason Andryuk wrote:
>>> Two patches to fix building with a cf-protection toolchain.  The first
>>> handles the case where the compiler fails to run with "error:
>>> ‘-mindirect-branch’ and ‘-fcf-protection’ are not compatible".
>>>
>>> The second fixes a runtime error that prevented Xen booting in legacy
>>> mode.
>> That might be better than just disabling fcf-protection as well (which was done
>> in Ubuntu lacking a better solution).
> 
> It is a GCC bug
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
> 
> Fixed for 10, and 9.4

Ah, thanks. And yes, should have reported sooner but, as always, one runs into
those things while in a hurry, with not enough time. We were glad to have
something that did work somehow.

> 
>>
>> Not sure it was already hit but that additional .note section breaks the build
>> of the emulator as generated headers become gigantic:
>>
>> https://git.launchpad.net/ubuntu/+source/xen/tree/debian/patches/1001-strip-note-gnu-property.patch?h=ubuntu/focal
> 
> 4.6G of notes?!?  That is surely a toolchain bug.

No, sorry if that was unclear. The .notes themselves are just about some Kb or
so per object file. Problem is that each object file gets converted into a hex
array header file. And this does multiply the resulting header file sizes.
So the .h files generated are 4.6G in size. And there were a couple of those,
all included into one .c file. Which ended in the compiler running out of memory
on a 32GB system.

> 
> ~Andrew
> 

On 13.05.2020 07:41, Stefan Bader wrote:
> On 12.05.20 20:47, Andrew Cooper wrote:
>> On 12/05/2020 08:17, Stefan Bader wrote:
>>> Not sure it was already hit but that additional .note section breaks the build
>>> of the emulator as generated headers become gigantic:
>>>
>>> https://git.launchpad.net/ubuntu/+source/xen/tree/debian/patches/1001-strip-note-gnu-property.patch?h=ubuntu/focal
>>
>> 4.6G of notes?!?  That is surely a toolchain bug.
> 
> No, sorry if that was unclear. The .notes themselves are just about some Kb or
> so per object file. Problem is that each object file gets converted into a hex
> array header file. And this does multiply the resulting header file sizes.
> So the .h files generated are 4.6G in size. And there were a couple of those,
> all included into one .c file. Which ended in the compiler running out of memory
> on a 32GB system.

But as per the link above it's still 3Mb notes per object,
which still seems insane.

Jan