Use comdat instead of .gnu.linkonce for i386 setup pic register

Message ID 1483991301-14420-1-git-send-email-adhemerval.zanella@linaro.org
State New
Headers show

Commit Message

Adhemerval Zanella Jan. 9, 2017, 7:48 p.m.
GCC has moved from using .gnu.linkonce for i386 setup pic register with
minimum current version (as for binutils minimum binutils that support
comdat).  This patch replace linkonce usage by comdat.

Checked on i686-linux-gnu.

	[BZ #20543]
	* sysdeps/i386/sysdep.h (SETUP_PIC_REG): Use comdat instead of
	gnu.linkonce section.
	(SETUP_PIC_REG_STR): Likewise.
---
 ChangeLog             | 7 +++++++
 sysdeps/i386/sysdep.h | 5 +++--
 2 files changed, 10 insertions(+), 2 deletions(-)

-- 
2.7.4

Comments

Zack Weinberg Jan. 9, 2017, 8:26 p.m. | #1
On Mon, Jan 9, 2017 at 2:48 PM, Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
> GCC has moved from using .gnu.linkonce for i386 setup pic register with

> minimum current version (as for binutils minimum binutils that support

> comdat).  This patch replace linkonce usage by comdat.


Is this change compatible with older GCC/binutils versions as well as
the new ones?

zw
Adhemerval Zanella Jan. 10, 2017, 2:02 p.m. | #2
On 09/01/2017 18:26, Zack Weinberg wrote:
> On Mon, Jan 9, 2017 at 2:48 PM, Adhemerval Zanella

> <adhemerval.zanella@linaro.org> wrote:

>> GCC has moved from using .gnu.linkonce for i386 setup pic register with

>> minimum current version (as for binutils minimum binutils that support

>> comdat).  This patch replace linkonce usage by comdat.

> 

> Is this change compatible with older GCC/binutils versions as well as

> the new ones?

> 

> zw

> 


I am trying to pinpoint when binutils added comdat support for i686 and
this [1] is the oldest thread I found.

I also checked with some ancient binutils version and version older than
2.16 I see:

test.o: In function `__x86.get_pc_thunk.bx':
test.o(.text.__x86.get_pc_thunk.bx+0x0): multiple definition of `__x86.get_pc_thunk.bx'
/usr/lib/gcc/x86_64-linux-gnu/5/../../../i386-linux-gnu/crti.o(.gnu.linkonce.t.__x86.get_pc_thunk.bx+0x0): first defined here

Which seems that the can not handle either comdat at all or the mix of
linkonce and comdat.  For binutils 2.16.1 and forward I am getting a
different issue trying to link a binary with and more recent ctri.o
(unrecognized relocation (0x2b) in section `.init', which is R_386_GOT32X
and old binutils won't generate it anyway).

So I think that either unlikely someone will use an older binutils than
the one used to glibc and even this scenario may fail with some issue
as the R_386_GOT32X.  Also, 2.16.1 is quite old and not really supported
(glibc itself required 2.22).

[1] https://gcc.gnu.org/ml/gcc/2004-05/msg00030.html
Adhemerval Zanella Jan. 17, 2017, 10:24 a.m. | #3
On 10/01/2017 12:02, Adhemerval Zanella wrote:
> 

> 

> On 09/01/2017 18:26, Zack Weinberg wrote:

>> On Mon, Jan 9, 2017 at 2:48 PM, Adhemerval Zanella

>> <adhemerval.zanella@linaro.org> wrote:

>>> GCC has moved from using .gnu.linkonce for i386 setup pic register with

>>> minimum current version (as for binutils minimum binutils that support

>>> comdat).  This patch replace linkonce usage by comdat.

>>

>> Is this change compatible with older GCC/binutils versions as well as

>> the new ones?

>>

>> zw

>>

> 

> I am trying to pinpoint when binutils added comdat support for i686 and

> this [1] is the oldest thread I found.

> 

> I also checked with some ancient binutils version and version older than

> 2.16 I see:

> 

> test.o: In function `__x86.get_pc_thunk.bx':

> test.o(.text.__x86.get_pc_thunk.bx+0x0): multiple definition of `__x86.get_pc_thunk.bx'

> /usr/lib/gcc/x86_64-linux-gnu/5/../../../i386-linux-gnu/crti.o(.gnu.linkonce.t.__x86.get_pc_thunk.bx+0x0): first defined here

> 

> Which seems that the can not handle either comdat at all or the mix of

> linkonce and comdat.  For binutils 2.16.1 and forward I am getting a

> different issue trying to link a binary with and more recent ctri.o

> (unrecognized relocation (0x2b) in section `.init', which is R_386_GOT32X

> and old binutils won't generate it anyway).

> 

> So I think that either unlikely someone will use an older binutils than

> the one used to glibc and even this scenario may fail with some issue

> as the R_386_GOT32X.  Also, 2.16.1 is quite old and not really supported

> (glibc itself required 2.22).

> 

> [1] https://gcc.gnu.org/ml/gcc/2004-05/msg00030.html

> 


Ping.
Adhemerval Zanella Jan. 24, 2017, 8:14 p.m. | #4
On 17/01/2017 08:24, Adhemerval Zanella wrote:
> 

> 

> On 10/01/2017 12:02, Adhemerval Zanella wrote:

>>

>>

>> On 09/01/2017 18:26, Zack Weinberg wrote:

>>> On Mon, Jan 9, 2017 at 2:48 PM, Adhemerval Zanella

>>> <adhemerval.zanella@linaro.org> wrote:

>>>> GCC has moved from using .gnu.linkonce for i386 setup pic register with

>>>> minimum current version (as for binutils minimum binutils that support

>>>> comdat).  This patch replace linkonce usage by comdat.

>>>

>>> Is this change compatible with older GCC/binutils versions as well as

>>> the new ones?

>>>

>>> zw

>>>

>>

>> I am trying to pinpoint when binutils added comdat support for i686 and

>> this [1] is the oldest thread I found.

>>

>> I also checked with some ancient binutils version and version older than

>> 2.16 I see:

>>

>> test.o: In function `__x86.get_pc_thunk.bx':

>> test.o(.text.__x86.get_pc_thunk.bx+0x0): multiple definition of `__x86.get_pc_thunk.bx'

>> /usr/lib/gcc/x86_64-linux-gnu/5/../../../i386-linux-gnu/crti.o(.gnu.linkonce.t.__x86.get_pc_thunk.bx+0x0): first defined here

>>

>> Which seems that the can not handle either comdat at all or the mix of

>> linkonce and comdat.  For binutils 2.16.1 and forward I am getting a

>> different issue trying to link a binary with and more recent ctri.o

>> (unrecognized relocation (0x2b) in section `.init', which is R_386_GOT32X

>> and old binutils won't generate it anyway).

>>

>> So I think that either unlikely someone will use an older binutils than

>> the one used to glibc and even this scenario may fail with some issue

>> as the R_386_GOT32X.  Also, 2.16.1 is quite old and not really supported

>> (glibc itself required 2.22).

>>

>> [1] https://gcc.gnu.org/ml/gcc/2004-05/msg00030.html

>>

> 

> Ping.

> 


Ping.
Adhemerval Zanella Feb. 16, 2017, 6:03 p.m. | #5
Ping.

On 24/01/2017 18:14, Adhemerval Zanella wrote:
> 

> 

> On 17/01/2017 08:24, Adhemerval Zanella wrote:

>>

>>

>> On 10/01/2017 12:02, Adhemerval Zanella wrote:

>>>

>>>

>>> On 09/01/2017 18:26, Zack Weinberg wrote:

>>>> On Mon, Jan 9, 2017 at 2:48 PM, Adhemerval Zanella

>>>> <adhemerval.zanella@linaro.org> wrote:

>>>>> GCC has moved from using .gnu.linkonce for i386 setup pic register with

>>>>> minimum current version (as for binutils minimum binutils that support

>>>>> comdat).  This patch replace linkonce usage by comdat.

>>>>

>>>> Is this change compatible with older GCC/binutils versions as well as

>>>> the new ones?

>>>>

>>>> zw

>>>>

>>>

>>> I am trying to pinpoint when binutils added comdat support for i686 and

>>> this [1] is the oldest thread I found.

>>>

>>> I also checked with some ancient binutils version and version older than

>>> 2.16 I see:

>>>

>>> test.o: In function `__x86.get_pc_thunk.bx':

>>> test.o(.text.__x86.get_pc_thunk.bx+0x0): multiple definition of `__x86.get_pc_thunk.bx'

>>> /usr/lib/gcc/x86_64-linux-gnu/5/../../../i386-linux-gnu/crti.o(.gnu.linkonce.t.__x86.get_pc_thunk.bx+0x0): first defined here

>>>

>>> Which seems that the can not handle either comdat at all or the mix of

>>> linkonce and comdat.  For binutils 2.16.1 and forward I am getting a

>>> different issue trying to link a binary with and more recent ctri.o

>>> (unrecognized relocation (0x2b) in section `.init', which is R_386_GOT32X

>>> and old binutils won't generate it anyway).

>>>

>>> So I think that either unlikely someone will use an older binutils than

>>> the one used to glibc and even this scenario may fail with some issue

>>> as the R_386_GOT32X.  Also, 2.16.1 is quite old and not really supported

>>> (glibc itself required 2.22).

>>>

>>> [1] https://gcc.gnu.org/ml/gcc/2004-05/msg00030.html

>>>

>>

>> Ping.

>>

> 

> Ping.

>

Patch hide | download patch | download mbox

diff --git a/sysdeps/i386/sysdep.h b/sysdeps/i386/sysdep.h
index d2b0860..35d65a4 100644
--- a/sysdeps/i386/sysdep.h
+++ b/sysdeps/i386/sysdep.h
@@ -97,7 +97,7 @@  lose: SYSCALL_PIC_SETUP							      \
 
 # define SETUP_PIC_REG(reg) \
   .ifndef GET_PC_THUNK(reg);						      \
-  .section .gnu.linkonce.t.GET_PC_THUNK(reg),"ax",@progbits;		      \
+  .section .text.GET_PC_THUNK(reg),"axG",@progbits,GET_PC_THUNK(reg),comdat;  \
   .globl GET_PC_THUNK(reg);						      \
   .hidden GET_PC_THUNK(reg);						      \
   .p2align 4;								      \
@@ -140,7 +140,8 @@  GET_PC_THUNK(reg):							      \
 
 # define SETUP_PIC_REG_STR(reg)						\
   ".ifndef " GET_PC_THUNK_STR (reg) "\n"				\
-  ".section .gnu.linkonce.t." GET_PC_THUNK_STR (reg) ",\"ax\",@progbits\n" \
+  ".section .text." GET_PC_THUNK_STR (reg) ",\"axG\",@progbits,"	\
+    GET_PC_THUNK_STR (reg) ",comdat\n"					\
   ".globl " GET_PC_THUNK_STR (reg) "\n"					\
   ".hidden " GET_PC_THUNK_STR (reg) "\n"				\
   ".p2align 4\n"							\