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

[Richard Biener <richard dot guenther at gmail dot com>]

On Sat, Feb 28, 2015 at 5:42 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> 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 adds
> -mcopyreloc-in-pie to give user an option to turn it off to avoid problem
> at link-time.  OK for trunk?

I wonder if the linker can fix this up?  That is, turn the relocation into
a valid one?

Richard.

> Thanks.
>
>
> H.J.
> ---
> 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..7fd4e77 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 linker
> +used to build GCC supports it.
> +
>  @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
>
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