Re: [PATCH] PR target/65248: [5 Regression] Copy relocation in PIE against protected symbol

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Sat, Feb 28, 2015 at 5:27 PM, Sandra Loosemore
<sandra@codesourcery.com> wrote:
> On 02/28/2015 09:42 AM, H.J. Lu wrote:
>>
>> @@ -22704,6 +22705,13 @@ For systems that use the GNU C Library, the
>> default is on.
>>   Specify that the assembler should encode SSE instructions with VEX
>>   prefix.  The option @option{-mavx} turns this on by default.
>>
>> +@item -mcopyreloc-in-pie
>> +@itemx -mno-copyreloc-in-pie
>> +@opindex mcopyreloc-in-pie
>> +Use copy relocations in Position Independent Executable (PIE).  It
>> +requires linker support.  This option is turned on by default if linker
>> +used to build GCC supports it.
>> +
>
>
> How about:  "...if GCC is configured to use a linker that supports these
> relocations."
>
> I assume this is a property of the target linker, and not literally the host
> linker used to build GCC?

Yes, that is correct.  Here is the updated patch.

Thanks.

-- 
H.J.

From 91de4b11eb2d7f9b0abd83837deb510a6f69cd81 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Sat, 28 Feb 2015 08:31:36 -0800
Subject: [PATCH] Add -mcopyreloc-in-pie

Ue copy relocation in PIE improves performance.  But copy relocation
can't be used to access protected symbols defined in shared libaries
and linker in binutils 2.26 enforces doesn't allow it.  GCC doesn't
know if an external definition is protected or not.  This option gives
user an option to turn it off to avoid problem at link-time.

gcc/

	PR target/65248
	* config/i386/i386.c (ix86_option_override_internal): Set
	flag_copyreloc_in_pie to HAVE_LD_PIE_COPYRELOC if not set.
	(legitimate_pic_address_disp_p): Replace HAVE_LD_PIE_COPYRELOC
	with flag_copyreloc_in_pie.
	* config/i386/i386.opt (mcopyreloc-in-pie): New.
	* doc/invoke.texi: Document -mcopyreloc-in-pie.

gcc/testsuite/

	PR target/65248
	* gcc.target/i386/pr65248-1.c: New.
	* gcc.target/i386/pr65248-2.c: Likewise.
	* gcc.target/i386/pr65248-3.c: Likewise.
	* gcc.target/i386/pr65248-4.c: Likewise.
---
 gcc/config/i386/i386.c                    |  6 +++++-
 gcc/config/i386/i386.opt                  |  4 ++++
 gcc/doc/invoke.texi                       | 10 +++++++++-
 gcc/testsuite/gcc.target/i386/pr65248-1.c | 13 +++++++++++++
 gcc/testsuite/gcc.target/i386/pr65248-2.c | 13 +++++++++++++
 gcc/testsuite/gcc.target/i386/pr65248-3.c | 16 ++++++++++++++++
 gcc/testsuite/gcc.target/i386/pr65248-4.c | 16 ++++++++++++++++
 7 files changed, 76 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr65248-1.c
 create mode 100644 gcc/testsuite/gcc.target/i386/pr65248-2.c
 create mode 100644 gcc/testsuite/gcc.target/i386/pr65248-3.c
 create mode 100644 gcc/testsuite/gcc.target/i386/pr65248-4.c

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index bec1324..6768ee8 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -4248,6 +4248,10 @@ ix86_option_override_internal (bool main_args_p,
 #endif
    }
 
+  /* Set the default value for -mcopyreloc-in-pie.  */
+  if (opts->x_flag_copyreloc_in_pie == -1)
+    opts->x_flag_copyreloc_in_pie = HAVE_LD_PIE_COPYRELOC;
+
   if (!(opts_set->x_target_flags & MASK_VZEROUPPER))
     opts->x_target_flags |= MASK_VZEROUPPER;
   if (!ix86_tune_features[X86_TUNE_AVX256_UNALIGNED_LOAD_OPTIMAL]
@@ -13230,7 +13234,7 @@ legitimate_pic_address_disp_p (rtx disp)
 	    }
 	  else if (!SYMBOL_REF_FAR_ADDR_P (op0)
 		   && (SYMBOL_REF_LOCAL_P (op0)
-		       || (HAVE_LD_PIE_COPYRELOC
+		       || (flag_copyreloc_in_pie
 			   && flag_pie
 			   && !SYMBOL_REF_WEAK (op0)
 			   && !SYMBOL_REF_FUNCTION_P (op0)))
diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
index 301430c..55c712c 100644
--- a/gcc/config/i386/i386.opt
+++ b/gcc/config/i386/i386.opt
@@ -826,6 +826,10 @@ mfentry
 Target Report Var(flag_fentry) Init(-1)
 Emit profiling counter call at function entry before prologue.
 
+mcopyreloc-in-pie
+Target Report Var(flag_copyreloc_in_pie) Init(-1)
+Use copy relocations in Position Independent Executable (PIE)
+
 mrecord-mcount
 Target Report Var(flag_record_mcount) Init(0)
 Generate __mcount_loc section with all mcount or __fentry__ calls.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index a87376e..de228c4 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1078,7 +1078,8 @@ See RS/6000 and PowerPC Options.
 -m32 -m64 -mx32 -m16 -mlarge-data-threshold=@var{num} @gol
 -msse2avx -mfentry -mrecord-mcount -mnop-mcount -m8bit-idiv @gol
 -mavx256-split-unaligned-load -mavx256-split-unaligned-store @gol
--malign-data=@var{type} -mstack-protector-guard=@var{guard}}
+-malign-data=@var{type} -mstack-protector-guard=@var{guard}} @gol
+-mcopyreloc-in-pie
 
 @emph{x86 Windows Options}
 @gccoptlist{-mconsole -mcygwin -mno-cygwin -mdll @gol
@@ -22704,6 +22705,13 @@ For systems that use the GNU C Library, the default is on.
 Specify that the assembler should encode SSE instructions with VEX
 prefix.  The option @option{-mavx} turns this on by default.
 
+@item -mcopyreloc-in-pie
+@itemx -mno-copyreloc-in-pie
+@opindex mcopyreloc-in-pie
+Use copy relocations in Position Independent Executable (PIE).  It
+requires linker support.  This option is turned on by default if GCC
+is configured to use a linker that supports copy relocations in PIE.
+
 @item -mfentry
 @itemx -mno-fentry
 @opindex mfentry
diff --git a/gcc/testsuite/gcc.target/i386/pr65248-1.c b/gcc/testsuite/gcc.target/i386/pr65248-1.c
new file mode 100644
index 0000000..91aa6be
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr65248-1.c
@@ -0,0 +1,13 @@
+/* Check that GOTPCREL isn't used to access glob_a.  */
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fpie -mcopyreloc-in-pie" } */
+
+extern int glob_a;
+
+int foo ()
+{
+  return glob_a;
+}
+
+/* glob_a should never be accessed with a GOTPCREL.  */
+/* { dg-final { scan-assembler-not "glob_a@GOTPCREL" { target { ! ia32 } } } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr65248-2.c b/gcc/testsuite/gcc.target/i386/pr65248-2.c
new file mode 100644
index 0000000..dc8445c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr65248-2.c
@@ -0,0 +1,13 @@
+/* Check that GOTPCREL isn't used to access glob_a.  */
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fpie -mno-copyreloc-in-pie" } */
+
+int glob_a;
+
+int foo ()
+{
+  return glob_a;
+}
+
+/* glob_a should never be accessed with a GOTPCREL.  */
+/* { dg-final { scan-assembler-not "glob_a@GOTPCREL" { target { ! ia32 } } } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr65248-3.c b/gcc/testsuite/gcc.target/i386/pr65248-3.c
new file mode 100644
index 0000000..9398fd2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr65248-3.c
@@ -0,0 +1,16 @@
+/* Check that GOTPCREL is used to access glob_a.  */
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fpie -mno-copyreloc-in-pie" } */
+
+extern int glob_a;
+
+int foo ()
+{
+  if (&glob_a != 0)
+    return glob_a;
+  else
+    return 0;
+}
+
+/* weak glob_a should be accessed with a GOTPCREL.  */
+/* { dg-final { scan-assembler "glob_a@GOTPCREL" { target { ! ia32 } } } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr65248-4.c b/gcc/testsuite/gcc.target/i386/pr65248-4.c
new file mode 100644
index 0000000..6d7cc86
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr65248-4.c
@@ -0,0 +1,16 @@
+/* Check that GOTPCREL is used to access glob_a.  */
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fpie -mno-copyreloc-in-pie" } */
+
+extern int glob_a  __attribute__((weak));
+
+int foo ()
+{
+  if (&glob_a != 0)
+    return glob_a;
+  else
+    return 0;
+}
+
+/* weak glob_a should be accessed with a GOTPCREL.  */
+/* { dg-final { scan-assembler "glob_a@GOTPCREL" { target { ! ia32 } } } } */
-- 
2.1.0