Re: [Minios-devel] [UNIKRAFT PATCHv5 11/46] build: Override default pie option of GCC if possible

[Simon Kuenzer <simon.kuenzer@xxxxxxxxx>]

Hey Wei,

I accepted this patch but please help me reminding ;-) - is the check 
for '--enable-default-pie' necessary or can we always hand-over the 
'-no-pie' compile flag as soon we know GCC supports it? It probably 
won't hurt. We could maybe get rid of the console command. We could do 
this with a separate patch later.
Thanks,

Simon

On 06.09.2018 11:37, Simon Kuenzer wrote:
> Reviewed-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
>
> On 10.08.2018 09:08, Wei Chen wrote:
> > From: Wei Chen <Wei.Chen@xxxxxxx>
> >
> > On recent debian distributions (Debian/Ubuntu), the GCC enabled
> > "--enable-default-pie" configuration option by default. This will
> > case Unikraft link failed on debian/ubuntu platforms.
> > In commit:
> > "build: Add -no-pie to GCC flags"
> > "cc7eb555080775cf2cb4a595a07b6121ff0f7361"
> > I have added -no-pie to GCC flags directly to override the default
> > pie option. But as Wei Liu reminded, old version GCC doesn't
> > support -no-pie option.
> >
> > So in this patch, I checked the enbale-default-pie option and
> > GCC version, and then added -no-pie to override it.
> >
> > Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
> > ---
> >   Makefile.uk | 21 ++++++++++++++++-----
> >   1 file changed, 16 insertions(+), 5 deletions(-)
> >
> > diff --git a/Makefile.uk b/Makefile.uk
> > index b3938d0..0cc6690 100644
> > --- a/Makefile.uk
> > +++ b/Makefile.uk
> > @@ -4,15 +4,15 @@
> >   #
> >   
> > ################################################################################ 
> >
> > -ASFLAGS     += -U __linux__ -U __FreeBSD__ -U __sun__ -D__ASSEMBLY__ 
> > -no-pie
> > +ASFLAGS     += -U __linux__ -U __FreeBSD__ -U __sun__ -D__ASSEMBLY__
> >   ASINCLUDES  += -nostdinc -nostdlib -I$(CONFIG_UK_BASE)/include
> > -CFLAGS      += -U __linux__ -U __FreeBSD__ -U __sun__ -no-pie
> > +CFLAGS      += -U __linux__ -U __FreeBSD__ -U __sun__
> >   CFLAGS      += -fno-stack-protector -fno-omit-frame-pointer 
> > -fno-tree-sra
> >   CFLAGS      += -Wall -Wextra
> >   CINCLUDES   += -nostdinc -nostdlib -I$(CONFIG_UK_BASE)/include
> > -CXXFLAGS    += -U __linux__ -U __FreeBSD__ -U __sun__ -no-pie
> > +CXXFLAGS    += -U __linux__ -U __FreeBSD__ -U __sun__
> >   CXXFLAGS    += -fno-stack-protector -fno-omit-frame-pointer 
> > -fno-tree-sra
> >   CXXFLAGS    += -Wall -Wextra
> >   CXXINCLUDES += -nostdinc -nostdlib -I$(CONFIG_UK_BASE)/include
> > @@ -20,8 +20,8 @@ CXXINCLUDES += -nostdinc -nostdlib 
> > -I$(CONFIG_UK_BASE)/include
> >   # Set the text and data sections to be readable and writable. Also,
> >   # do not page-align the data segment. If the output format supports
> >   # Unix style magic numbers, mark the output as OMAGIC.
> > -LIBLDFLAGS  += -nostdinc -nostdlib -Wl,--omagic -Wl,-r -no-pie
> > -LDFLAGS     += -nostdinc -nostdlib -Wl,--omagic -Wl,--build-id=none 
> > -no-pie
> > +LIBLDFLAGS  += -nostdinc -nostdlib -Wl,--omagic -Wl,-r
> > +LDFLAGS     += -nostdinc -nostdlib -Wl,--omagic -Wl,--build-id=none
> >   CFLAGS-$(CONFIG_OPTIMIZE_NONE)            += -O0 
> > -fno-optimize-sibling-calls -fno-tree-vectorize
> >   CXXFLAGS-$(CONFIG_OPTIMIZE_NONE)          += -O0 
> > -fno-optimize-sibling-calls -fno-tree-vectorize
> > @@ -56,3 +56,14 @@ endif
> >   ASFLAGS  += -DUK_VERSION=$(UK_VERSION).$(UK_SUBVERSION) 
> > -DUK_FULLVERSION=$(UK_FULLVERSION) -DUK_CODENAME="$(UK_CODENAME)"
> >   CFLAGS   += -DUK_VERSION=$(UK_VERSION).$(UK_SUBVERSION) 
> > -DUK_FULLVERSION=$(UK_FULLVERSION) -DUK_CODENAME="$(UK_CODENAME)"
> >   CXXFLAGS += -DUK_VERSION=$(UK_VERSION).$(UK_SUBVERSION) 
> > -DUK_FULLVERSION=$(UK_FULLVERSION) -DUK_CODENAME="$(UK_CODENAME)"
> > +
> > +# Check whether the pie option is enabled by default. If possible,
> > +# add -no-pie to link flags to override default pie option.
> > +PIE_ON = $(shell $(CC) -v 2>&1 | grep -Fo "enable-default-pie")
> > +ifneq ($(PIE_ON),)
> > +ASFLAGS-$(call gcc_version_ge,6,1)    += -no-pie
> > +CFLAGS-$(call gcc_version_ge,6,1)    += -no-pie
> > +CXXFLAGS-$(call gcc_version_ge,6,1)    += -no-pie
> > +LIBLDFLAGS-$(call gcc_version_ge,6,1)    += -no-pie
> > +LDFLAGS-$(call gcc_version_ge,6,1)    += -no-pie
> > +endif
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