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Re: PING^3: [PATCH]: New configure options that make the compiler use -fPIE and -pie as default option


On Thu, May 21, 2015 at 7:13 AM, Rainer Orth
<ro@cebitec.uni-bielefeld.de> wrote:
> "H.J. Lu" <hjl.tools@gmail.com> writes:
>
>> Here is the complete patch.  Tested on Linux/x86-64.  It is also
>> available on hjl/pie/master branch in git mirror.
>
> As always, please keep generated files like configure and config.in out
> of the submission: it simplifies review.

Will do.

> diff --git a/gcc/Makefile.in b/gcc/Makefile.in
> index ab9b637..e429274 100644
> --- a/gcc/Makefile.in
> +++ b/gcc/Makefile.in
> @@ -253,6 +253,12 @@ LINKER = $(CC)
>  LINKER_FLAGS = $(CFLAGS)
>  endif
>
> +# We don't want to compile the compiler with -fPIE, it make PCH fail.
>                                                             ^s
> +COMPILER += @NO_PIE_CFLAGS@
>
> @@ -750,6 +756,8 @@ CC_FOR_BUILD = @CC_FOR_BUILD@
>  CXX_FOR_BUILD = @CXX_FOR_BUILD@
>  BUILD_CFLAGS= @BUILD_CFLAGS@ -DGENERATOR_FILE
>  BUILD_CXXFLAGS = @BUILD_CXXFLAGS@ -DGENERATOR_FILE
> +BUILD_CFLAGS += @NO_PIE_CFLAGS@
> +BUILD_CXXFLAGS += @NO_PIE_CFLAGS@
>
> Here and in several other places, you use += instead of just adding
> @NO_PIE_CFLAGS@ to the existing BUILD_CFLAGS variable.  Please lets
> keep to the existing idiom instead of randomly introducing another.

I used += because

1.  There are things:

# library is not introduced.  If HOST_LIBS is not set, link with
# $(CXX) to pick up -lstdc++.
ifeq ($(HOST_LIBS),)
LINKER = $(CXX)
LINKER_FLAGS = $(CXXFLAGS)
else
LINKER = $(CC)
LINKER_FLAGS = $(CFLAGS)
endif

Use "+=" only needs one line.

2. There are many usages of  "+=" in Makefile.in already.

> @@ -761,6 +769,7 @@ BUILD_LINKERFLAGS = $(BUILD_CXXFLAGS)
>
>  # Native linker and preprocessor flags.  For x-fragment overrides.
>  BUILD_LDFLAGS=@BUILD_LDFLAGS@
> +BUILD_LDFLAGS += @NO_PIE_FLAG@
>
> Likewise.
>
>  BUILD_CPPFLAGS= -I. -I$(@D) -I$(srcdir) -I$(srcdir)/$(@D) \
>                 -I$(srcdir)/../include @INCINTL@ $(CPPINC) $(CPPFLAGS)
>
> @@ -1864,6 +1873,12 @@ libgcc.mvars: config.status Makefile specs xgcc$(exeext)
>         echo GCC_CFLAGS = '$(GCC_CFLAGS)' >> tmp-libgcc.mvars
>         echo INHIBIT_LIBC_CFLAGS = '$(INHIBIT_LIBC_CFLAGS)' >> tmp-libgcc.mvars
>         echo TARGET_SYSTEM_ROOT = '$(TARGET_SYSTEM_ROOT)' >> tmp-libgcc.mvars
> +       if test @enable_default_pie@ = yes; then \
> +         NO_PIE_CFLAGS="-fno-PIE"; \
>
> Why literal -fno-PIE instead of @NO_PIE_CFLAGS@?

Joseph already commented on it.

> +       else \
> +         NO_PIE_CFLAGS=; \
> +       fi; \
> +       echo NO_PIE_CFLAGS = "$$NO_PIE_CFLAGS" >> tmp-libgcc.mvars
>
>         mv tmp-libgcc.mvars libgcc.mvars
>
> Besides, we're trying to get away from libgcc.mvars, moving the
> detection to libgcc proper.  It would be nice to do so here.

It will happen when libgcc.mvars is removed/moved. I don't want
to duplicate the logic in libgcc/configure now.

> diff --git a/gcc/ada/gcc-interface/Makefile.in b/gcc/ada/gcc-interface/Makefile.in
> index ecc443e..90aedb5 100644
> --- a/gcc/ada/gcc-interface/Makefile.in
> +++ b/gcc/ada/gcc-interface/Makefile.in
> @@ -267,6 +267,9 @@ TOOLS_LIBS = ../link.o ../targext.o ../../ggc-none.o ../../libcommon-target.a \
>    ../../libcommon.a ../../../libcpp/libcpp.a $(LIBGNAT) $(LIBINTL) $(LIBICONV) \
>    ../$(LIBBACKTRACE) ../$(LIBIBERTY) $(SYSLIBS) $(TGT_LIB)
>
> +# Add -no-pie to TOOLS_LIBS since some of them are compiled with -fno-PIE.
> +TOOLS_LIBS += @NO_PIE_FLAG@
>
> Again, avoid +=
>
> diff --git a/gcc/config/sol2.h b/gcc/config/sol2.h
> index 4dceb16..adf6f3b 100644
> --- a/gcc/config/sol2.h
> +++ b/gcc/config/sol2.h
> @@ -127,7 +127,7 @@ along with GCC; see the file COPYING3.  If not see
>  #define ASM_SPEC_BASE \
>  "%{v:-V} %{Qy:} %{!Qn:-Qy} %{Ym,*} -s %(asm_cpu)"
>
> -#define ASM_PIC_SPEC " %{fpic|fpie|fPIC|fPIE:-K PIC}"
> +#define ASM_PIC_SPEC " %{" FPIE_OR_FPIC_SPEC ":-K PIC}"
>
>  #undef ASM_CPU_DEFAULT_SPEC
>  #define ASM_CPU_DEFAULT_SPEC \
>
> This is ok once the rest goes in.  I haven't reviewed the other
> target-specific parts, though.
>
> diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
> index 04332c1..437a534 100644
> --- a/gcc/doc/install.texi
> +++ b/gcc/doc/install.texi
> @@ -1585,6 +1585,9 @@ not be built.
>  Specify that the run-time libraries for stack smashing protection
>  should not be built.
>
> +@item --enable-default-pie
> +Turn on @option{-fPIE} and @option{-pie} by default.
> +
>  @item --disable-libquadmath
>  Specify that the GCC quad-precision math library should not be built.
>  On some systems, the library is required to be linkable when building
>
> This option was added in a seemingly completely random place, between
> options to enable/disable runtime libs.  Please find a better place.

I will move it to before "@item --enable-secureplt". If you aren't
happy with it,
can you suggest a better place?

> diff --git a/gcc/opts.c b/gcc/opts.c
> index 9deb8df..4b6d978 100644
> --- a/gcc/opts.c
> +++ b/gcc/opts.c
> @@ -739,8 +739,22 @@ finish_options (struct gcc_options *opts, struct gcc_options *opts_set,
>        opts->x_flag_section_anchors = 0;
>      }
>
> +#ifndef ENABLE_DEFAULT_PIE
> +#undef DEFAULT_FLAG_PIE
> +#define DEFAULT_FLAG_PIE 0
> +#endif
> +
>
> Couldn't this be done in defaults.h, too?  It seems confusing to provide
> DEFAULT_FLAG_PIE defaults both here and in defaults.h.

I will try.

Thanks.


-- 
H.J.


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