Re: [Xen-devel] [PATCH] x86-64/EFI: add -fno-stack-protector to EFI build

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.08.12 at 16:30, Daniel De Graaf <dgdegra@xxxxxxxxxxxxx> wrote:
> On 08/14/2012 10:19 AM, Jan Beulich wrote:
>>>>> On 14.08.12 at 15:52, Daniel De Graaf <dgdegra@xxxxxxxxxxxxx> wrote:
>>> Otherwise, the build fails due to a missing __stack_chk_fail symbol.
>>>
>>> Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
>>> ---
>>>  xen/arch/x86/efi/Makefile | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/xen/arch/x86/efi/Makefile b/xen/arch/x86/efi/Makefile
>>> index 005e3e0..b727757 100644
>>> --- a/xen/arch/x86/efi/Makefile
>>> +++ b/xen/arch/x86/efi/Makefile
>>> @@ -1,11 +1,11 @@
>>> -CFLAGS += -fshort-wchar
>>> +CFLAGS += -fshort-wchar -fno-stack-protector
>> 
>> It shouldn't be needed here (or else the rest of the Xen build
>> should fail too). Or where would that symbol magically come
>> from?
> 
> You are correct, this change is not needed. The Xen build already adds
> -fno-stack-protector to CFLAGS, so this change would just duplicate it.
> 
>>>  obj-y += stub.o
>>>  
>>>  create = test -e $(1) || touch -t 199901010000 $(1)
>>>  
>>>  efi := $(filter y,$(x86_64)$(shell rm -f disabled))
>>> -efi := $(if $(efi),$(shell $(CC) -c -Werror check.c 2>disabled && echo y))
>>> +efi := $(if $(efi),$(shell $(CC) -fno-stack-protector -c -Werror check.c 
>>> 2>disabled && echo y))
>> 
>> I can see why it might be needed here, albeit I'm curious why
>> this is not a problem for our builds: Are you having a compiler
>> in use that had been configured in a non-standard way? Plus
>> I first want to understand why this special option isn't needed
>> for the rest of the build tree.
> 
> This build was done on Gentoo using a hardened profile, which I assume
> adds -fstack-protector to the default compiler flags. Compiler version
> string is "gcc version 4.6.3 (Gentoo Hardened 4.6.3 p1.6, pie-0.5.2)"

So I'd prefer adding $(EMBEDDED_EXTRA_CFLAGS) instead of
the explicit option then, if that's okay for you too. Mind re-
spinning the patch that way?

Jan


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