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Re: PATCH] PR target/65612: Multiversioning doesn't work with DSO nor PIE

From: "H.J. Lu" <hjl dot tools at gmail dot com>
To: Jack Howarth <howarth dot at dot gcc at gmail dot com>
Cc: Ian Lance Taylor <ian at airs dot com>, Jakub Jelinek <jakub at redhat dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Uros Bizjak <ubizjak at gmail dot com>, Iain Sandoe <iain at codesourcery dot com>, Mike Stump <mikestump at comcast dot net>
Date: Tue, 14 Apr 2015 08:07:49 -0700
Subject: Re: PATCH] PR target/65612: Multiversioning doesn't work with DSO nor PIE
Authentication-results: sourceware.org; auth=none
References: <20150330022527 dot GA4148 at gmail dot com> <CAMe9rOrUpMmt8XyqO9fXZB-Bn+tRs-AKHTaQzu7jeGCZFXen8g at mail dot gmail dot com> <CAMe9rOp_LfJ8C4Xh4NoRD=rTutNCeqwN_OV=8+c5rFfnRHbV_g at mail dot gmail dot com> <CAMe9rOrGCRJhWpNT0hMJwKCG2+vaDsaRou7JV0tdjiANnmRm=g at mail dot gmail dot com> <CAJMcOU8nON6S=+be8C94F_tB8-VPCusa8VrEq_f5P2PZCdk7vg at mail dot gmail dot com> <CAMe9rOo2ORmyvndySKr3vzEQmZScpKQfnVVw7HW94BXvPFJqdQ at mail dot gmail dot com> <20150331053855 dot GB2121 at tucnak dot redhat dot com> <CAMe9rOrm=9gkqjFwEX8GVtri3t2mSmgOqfm_Q+LizCJqbLSAKQ at mail dot gmail dot com> <CAJMcOU_Pjryr7TxKx9zYKBtVEvBj8bmXDr=UBqShyE0CPr-cOA at mail dot gmail dot com> <CAMe9rOoRkeyw9SMuEev_ATE932UNhJBUPUd+Z81Qc1L+VpVkxw at mail dot gmail dot com> <CAJMcOU915GeWmwhTOvqXPQddZfYdJdVGQJUbMWXTEiz4y0QW9w at mail dot gmail dot com> <CAMe9rOp9kPZFhEE=seWX_VXC0NndYxtJ8Opt-kkCMSteeTuRuA at mail dot gmail dot com> <CAJMcOU8xHsE6ZyVSHy90AUgkSpY8FfG53xT+jGO=TALo27ViSA at mail dot gmail dot com> <CAMe9rOqAjsLAr+iVspN5XBdnaVtW_AJuMyOb3K6mVRKKh-sQXg at mail dot gmail dot com> <CAJMcOU9hcqopdDfpYbP5d=JLVVLUMnvqZWPQt14kH3T6DgVB8w at mail dot gmail dot com>

On Tue, Mar 31, 2015 at 11:33 AM, Jack Howarth <howarth.at.gcc@gmail.com> wrote:
> On Tue, Mar 31, 2015 at 1:00 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Tue, Mar 31, 2015 at 9:39 AM, Jack Howarth <howarth.at.gcc@gmail.com> wrote:
>>> On Tue, Mar 31, 2015 at 12:14 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>> On Tue, Mar 31, 2015 at 9:09 AM, Jack Howarth <howarth.at.gcc@gmail.com> wrote:
>>>>> H.J.,
>>>>>     Did you attach the correct version of the patch? I don't see
>>>>> anything conditional on linux.
>>>>>             Jack
>>>>
>>>> My patch will build and install libgcc_nonshared.a for all targets.  If you
>>>> don't link against it, nothing is changed.  On Linux, it is used via the
>>>> init_spec change.
>>>
>>> Isn't...
>>>
>>> diff --git a/gcc/gcc.c b/gcc/gcc.c
>>> index d956c36..3fbd549 100644
>>> --- a/gcc/gcc.c
>>> +++ b/gcc/gcc.c
>>> @@ -1566,6 +1566,7 @@ init_spec (void)
>>>         if (in_sep && *p == '-' && strncmp (p, "-lgcc", 5) == 0)
>>>           {
>>>             init_gcc_specs (&obstack,
>>> +                           "-lgcc_nonshared "
>>>                             "-lgcc_s"
>>>  #ifdef USE_LIBUNWIND_EXCEPTIONS
>>>                             " -lunwind"
>>> @@ -1591,6 +1592,7 @@ init_spec (void)
>>>             /* Ug.  We don't know shared library extensions.  Hope that
>>>                systems that use this form don't do shared libraries.  */
>>>             init_gcc_specs (&obstack,
>>> +                           "libgcc_nonshared.a%s "
>>>                             "-lgcc_s",
>>>                             "libgcc.a%s",
>>>                             "libgcc_eh.a%s"
>>>
>>> problematic for Solaris? I am unfamiliar with the Solaris spec
>>> handling but sol2.h doesn't seem to have any instances of -lgcc which
>>> might imply they use the stock compiler invocation which will now have
>>> a non-existent libgcc_nonshared static library.
>>
>> libgcc_nonshared.a is built and installed for all targets.
>>
>>>      Also, are you leaving the cpu symbols in libgcc.a on non-linux
>>> targets? If not, the linkage failure reported in
>>> https://gcc.gnu.org/ml/gcc-patches/2015-03/msg01668.html will occur,
>>> no?
>>
>> My current patch doesn't change what are in libgcc.a.  It
>> adds libgcc_nonshared.a for all targets, which contains
>> the same cpuinfo.o as in libgcc.a or a dummy .o if libgcc.a
>> doesn't have cpuinfo.o.
>
>
> I can confirm that the most current patch bootstraps on
> x86_64-apple-darwin14 and that all of the new tests show up as
> unsupported in the test suite.
>           Jack

I am re-posting this patch.  OK for trunk?

Thanks.

-- 
H.J.

From 9ddf859ba7112c3459f709fbb7aaaf9eabf485b6 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Sun, 29 Mar 2015 18:03:49 -0700
Subject: [PATCH] Hide __cpu_indicator_init/__cpu_model from linker

We shouldn't call external function, __cpu_indicator_init, while an object
is being relocated since its .got.plt section hasn't been updated.  It
works for non-PIE since no update on .got.plt section is required.  This
patch hides __cpu_indicator_init/__cpu_model from linker to force linker
to resolve __cpu_indicator_init/__cpu_model to their hidden definitions
in libgcc_nonshared.a while providing backward binary compatibility.  The
new libgcc_nonshared.a is always linked togther with -lgcc_s and -lgcc.

gcc/

	PR target/65612
	* gcc.c (init_spec): Add -lgcc_nonshared/libgcc_nonshared.a%s
	to -lgcc_s.

gcc/testsuite/

	PR target/65612
	* g++.dg/ext/mv18.C: New test.
	* g++.dg/ext/mv19.C: Likewise.
	* g++.dg/ext/mv20.C: Likewise.
	* g++.dg/ext/mv21.C: Likewise.
	* g++.dg/ext/mv22.C: Likewise.
	* g++.dg/ext/mv23.C: Likewise.

libgcc/

	PR target/65612
	* Makefile.in (LIB2ADDNONSHARED): New.
	(libgcc-nonshared-objects): Likewise.
	(libgcc_nonshared.a): Likewise.
	Check unsupported files in LIB2ADDNONSHARED.
	(iter-items): Add $(LIB2ADDNONSHARED).
	(all): Depend on libgcc_nonshared.a.
	($(libgcc-nonshared-objects)): Depend on libgcc_tm.h.
	(install-leaf): Install libgcc_nonshared.a.
	* shared-object.mk: Check empty $o.
	* config/i386/cpuinfo.c (__cpu_model): Initialize.
	(__cpu_indicator_init@GCC_4.8.0): New.
	(__cpu_model@GCC_4.8.0): Likewise.
	* config/i386/t-cpuinfo (LIB2ADDNONSHARED): New.
	* config/i386/t-linux (HOST_LIBGCC2_CFLAGS): Add
	-DUSE_ELF_SYMVER.
---
 gcc/gcc.c                       |  2 ++
 gcc/testsuite/g++.dg/ext/mv18.C |  7 +++++++
 gcc/testsuite/g++.dg/ext/mv19.C |  7 +++++++
 gcc/testsuite/g++.dg/ext/mv20.C |  7 +++++++
 gcc/testsuite/g++.dg/ext/mv21.C |  7 +++++++
 gcc/testsuite/g++.dg/ext/mv22.C |  7 +++++++
 gcc/testsuite/g++.dg/ext/mv23.C |  7 +++++++
 libgcc/Makefile.in              | 22 +++++++++++++++++++---
 libgcc/config/i386/cpuinfo.c    |  7 ++++++-
 libgcc/config/i386/t-cpuinfo    |  1 +
 libgcc/config/i386/t-linux      |  2 +-
 libgcc/shared-object.mk         |  2 ++
 12 files changed, 73 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/ext/mv18.C
 create mode 100644 gcc/testsuite/g++.dg/ext/mv19.C
 create mode 100644 gcc/testsuite/g++.dg/ext/mv20.C
 create mode 100644 gcc/testsuite/g++.dg/ext/mv21.C
 create mode 100644 gcc/testsuite/g++.dg/ext/mv22.C
 create mode 100644 gcc/testsuite/g++.dg/ext/mv23.C

diff --git a/gcc/gcc.c b/gcc/gcc.c
index d956c36..3fbd549 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -1566,6 +1566,7 @@ init_spec (void)
 	if (in_sep && *p == '-' && strncmp (p, "-lgcc", 5) == 0)
 	  {
 	    init_gcc_specs (&obstack,
+			    "-lgcc_nonshared "
 			    "-lgcc_s"
 #ifdef USE_LIBUNWIND_EXCEPTIONS
 			    " -lunwind"
@@ -1591,6 +1592,7 @@ init_spec (void)
 	    /* Ug.  We don't know shared library extensions.  Hope that
 	       systems that use this form don't do shared libraries.  */
 	    init_gcc_specs (&obstack,
+			    "libgcc_nonshared.a%s "
 			    "-lgcc_s",
 			    "libgcc.a%s",
 			    "libgcc_eh.a%s"
diff --git a/gcc/testsuite/g++.dg/ext/mv18.C b/gcc/testsuite/g++.dg/ext/mv18.C
new file mode 100644
index 0000000..1f024de
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/mv18.C
@@ -0,0 +1,7 @@
+/* Test case to check if Multiversioning works.  */
+/* { dg-do run { target i?86-*-* x86_64-*-* } } */
+/* { dg-require-ifunc "" }  */
+/* { dg-require-effective-target pie } */
+/* { dg-options "-O2 -fPIE -pie" } */
+
+#include "mv1.C"
diff --git a/gcc/testsuite/g++.dg/ext/mv19.C b/gcc/testsuite/g++.dg/ext/mv19.C
new file mode 100644
index 0000000..d1ea788
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/mv19.C
@@ -0,0 +1,7 @@
+/* Test case to check if Multiversioning works.  */
+/* { dg-do run { target i?86-*-* x86_64-*-* } } */
+/* { dg-require-ifunc "" }  */
+/* { dg-require-effective-target pie } */
+/* { dg-options "-O2 -fPIE -pie -march=x86-64" } */
+
+#include "mv14.C"
diff --git a/gcc/testsuite/g++.dg/ext/mv20.C b/gcc/testsuite/g++.dg/ext/mv20.C
new file mode 100644
index 0000000..98f7408
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/mv20.C
@@ -0,0 +1,7 @@
+/* Test case to check if Multiversioning works.  */
+/* { dg-do run { target i?86-*-* x86_64-*-* } } */
+/* { dg-require-ifunc "" }  */
+/* { dg-require-effective-target pie } */
+/* { dg-options "-O2 -fPIE -pie -march=x86-64" } */
+
+#include "mv15.C"
diff --git a/gcc/testsuite/g++.dg/ext/mv21.C b/gcc/testsuite/g++.dg/ext/mv21.C
new file mode 100644
index 0000000..9708ad9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/mv21.C
@@ -0,0 +1,7 @@
+/* Test case to check if Multiversioning works.  */
+/* { dg-do run { target i?86-*-* x86_64-*-* } } */
+/* { dg-require-ifunc "" }  */
+/* { dg-require-effective-target static } */
+/* { dg-options "-O2 -static" } */
+
+#include "mv1.C"
diff --git a/gcc/testsuite/g++.dg/ext/mv22.C b/gcc/testsuite/g++.dg/ext/mv22.C
new file mode 100644
index 0000000..2550136
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/mv22.C
@@ -0,0 +1,7 @@
+/* Test case to check if Multiversioning works.  */
+/* { dg-do run { target i?86-*-* x86_64-*-* } } */
+/* { dg-require-ifunc "" }  */
+/* { dg-require-effective-target static } */
+/* { dg-options "-O2 -static -march=x86-64" } */
+
+#include "mv14.C"
diff --git a/gcc/testsuite/g++.dg/ext/mv23.C b/gcc/testsuite/g++.dg/ext/mv23.C
new file mode 100644
index 0000000..f00afb0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/mv23.C
@@ -0,0 +1,7 @@
+/* Test case to check if Multiversioning works.  */
+/* { dg-do run { target i?86-*-* x86_64-*-* } } */
+/* { dg-require-ifunc "" }  */
+/* { dg-require-effective-target static } */
+/* { dg-options "-O2 -static -march=x86-64" } */
+
+#include "mv15.C"
diff --git a/libgcc/Makefile.in b/libgcc/Makefile.in
index 88ddfea..f78b1ac 100644
--- a/libgcc/Makefile.in
+++ b/libgcc/Makefile.in
@@ -261,6 +261,10 @@ LIB2ADD =
 # Assembler files should have names ending in `.S'.
 LIB2ADD_ST =
 
+# List of extra C and assembler files to add to libgcc_nonshared.a.
+# Assembler files should have names ending in `.S'.
+LIB2ADDNONSHARED =
+
 # Specify the directories to be searched for header files.
 # Both . and srcdir are used, in that order,
 # so that *config.h will be found in the compilation
@@ -807,8 +811,15 @@ endif
 libgcc-objects += $(addsuffix $(objext),$(basename $(notdir $(LIB2ADD))))
 libgcc-objects += $(addsuffix $(objext),$(basename $(notdir $(LIB2ADD_ST))))
 
+# Build LIB2ADDNONSHARED.
+ifneq ($(filter-out %.c %.S %.asm,$(LIB2ADDNONSHARED)),)
+$(error Unsupported files in LIB2ADDNONSHARED.)
+endif
+
+libgcc-nonshared-objects += $(addsuffix $(objext),$(basename $(notdir $(LIB2ADDNONSHARED))))
+
 c_flags :=
-iter-items := $(LIB2ADD) $(LIB2ADD_ST)
+iter-items := $(LIB2ADD) $(LIB2ADD_ST) $(LIB2ADDNONSHARED)
 include $(iterator)
 
 ifeq ($(enable_shared),yes)
@@ -890,8 +901,9 @@ libgcc.a: $(libgcc-objects)
 libgcov.a: $(libgcov-objects)
 libunwind.a: $(libunwind-objects)
 libgcc_eh.a: $(libgcc-eh-objects)
+libgcc_nonshared.a: $(libgcc-nonshared-objects)
 
-libgcc.a libgcov.a libunwind.a libgcc_eh.a:
+libgcc.a libgcov.a libunwind.a libgcc_eh.a libgcc_nonshared.a:
 	-rm -f $@
 
 	objects="$(objects)";					\
@@ -905,7 +917,7 @@ libgcc.a libgcov.a libunwind.a libgcc_eh.a:
 
 	$(RANLIB) $@
 
-all: libgcc.a libgcov.a
+all: libgcc.a libgcc_nonshared.a libgcov.a
 
 ifneq ($(LIBUNWIND),)
 all: libunwind.a
@@ -1051,6 +1063,7 @@ libgcc-extra-parts: $(EXTRA_PARTS)
 all: $(extra-parts)
 
 $(libgcc-objects) $(libgcc-s-objects) $(libgcc-eh-objects) \
+	$(libgcc-nonshared-objects) \
 	$(libgcov-objects) \
 	$(libunwind-objects) $(libunwind-s-objects) \
 	$(EXTRA_PARTS): libgcc_tm.h
@@ -1118,6 +1131,9 @@ install-leaf: $(install-shared) $(install-libunwind)
 	$(INSTALL_DATA) libgcc.a $(DESTDIR)$(inst_libdir)/
 	chmod 644 $(DESTDIR)$(inst_libdir)/libgcc.a
 	$(RANLIB) $(DESTDIR)$(inst_libdir)/libgcc.a
+	$(INSTALL_DATA) libgcc_nonshared.a $(DESTDIR)$(inst_libdir)/
+	chmod 644 $(DESTDIR)$(inst_libdir)/libgcc_nonshared.a
+	$(RANLIB) $(DESTDIR)$(inst_libdir)/libgcc_nonshared.a
 	$(INSTALL_DATA) libgcov.a $(DESTDIR)$(inst_libdir)/
 	chmod 644 $(DESTDIR)$(inst_libdir)/libgcov.a
 	$(RANLIB) $(DESTDIR)$(inst_libdir)/libgcov.a
diff --git a/libgcc/config/i386/cpuinfo.c b/libgcc/config/i386/cpuinfo.c
index eaf2f10..f6f91dd 100644
--- a/libgcc/config/i386/cpuinfo.c
+++ b/libgcc/config/i386/cpuinfo.c
@@ -109,7 +109,7 @@ struct __processor_model
   unsigned int __cpu_type;
   unsigned int __cpu_subtype;
   unsigned int __cpu_features[1];
-} __cpu_model;
+} __cpu_model = { };
 
 
 /* Get the specific type of AMD CPU.  */
@@ -424,3 +424,8 @@ __cpu_indicator_init (void)
 
   return 0;
 }
+
+#if defined SHARED && defined USE_ELF_SYMVER
+__asm__ (".symver __cpu_indicator_init, __cpu_indicator_init@GCC_4.8.0");
+__asm__ (".symver __cpu_model, __cpu_model@GCC_4.8.0");
+#endif
diff --git a/libgcc/config/i386/t-cpuinfo b/libgcc/config/i386/t-cpuinfo
index 31c8db9..b20ef30 100644
--- a/libgcc/config/i386/t-cpuinfo
+++ b/libgcc/config/i386/t-cpuinfo
@@ -1 +1,2 @@
 LIB2ADD += $(srcdir)/config/i386/cpuinfo.c
+LIB2ADDNONSHARED += $(srcdir)/config/i386/cpuinfo.c
diff --git a/libgcc/config/i386/t-linux b/libgcc/config/i386/t-linux
index 4f47f7b..11bb46e 100644
--- a/libgcc/config/i386/t-linux
+++ b/libgcc/config/i386/t-linux
@@ -3,4 +3,4 @@
 # t-slibgcc-elf-ver and t-linux
 SHLIB_MAPFILES = libgcc-std.ver $(srcdir)/config/i386/libgcc-glibc.ver
 
-HOST_LIBGCC2_CFLAGS += -mlong-double-80
+HOST_LIBGCC2_CFLAGS += -mlong-double-80 -DUSE_ELF_SYMVER
diff --git a/libgcc/shared-object.mk b/libgcc/shared-object.mk
index efac797..306176d 100644
--- a/libgcc/shared-object.mk
+++ b/libgcc/shared-object.mk
@@ -4,6 +4,7 @@
 o := $(firstword $(iter-items))
 iter-items := $(filter-out $o,$(iter-items))
 
+ifneq ($o,)
 base := $(basename $(notdir $o))
 
 c_flags-$o := $(c_flags)
@@ -36,3 +37,4 @@ $(base)_s$(objext): $o
 	$(gcc_s_compile) -c $(as_flags-$<) $<
 
 endif
+endif
-- 
1.9.3

Follow-Ups:
- Re: PATCH] PR target/65612: Multiversioning doesn't work with DSO nor PIE
  - From: Mike Stump

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