[PATCH] S390: Fix build with gcc configured with --enable-default-pie. [BZ #21537]

[PATCH] S390: Fix build with gcc configured with --enable-default-pie. [BZ #21537]

[Stefan Liebler]

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Hi,

Building glibc with gcc configured with --enable-default-pie failed on s390
due to assembler messages:
../sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S:44:
Error: junk at end of line, first unrecognized character is `@'

HIDDEN_JUMPTARGET was expanded to exit@PLT@GOTOFF.
If SHARED is not defined, HIDDEN_JUMPTARGET is defined to JUMPTARGET
in sysdeps/s390/s390-32/sysdep.h.  There it expanded to exit@PLT
in non SHARED case as PIC is defined if gcc is configured with
--enable-default-pie. Thus I've changed the "ifdef PIC" to "ifdef SHARED"
as we do not want PLTs in the static obj files.  I've also changed this
in sysdeps/s390/s390-64/sysdep.h.

I've also adjusted sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S.
If glibc is configured with --disable-hidden-plt, then NO_HIDDEN is defined.
In SHARED case HIDDEN_JUMPTARGET would be expanded to exit@PLT@GOTOFF
instead of __GI_exit@GOTOFF.
Now we jump to:
- __GI_exit if SHARED is defined
- exit@PLT if SHARED and NO_HIDDEN is defined
- exit if both are not defined.
On s390 31bit we have to setup GOT pointer in r12 if we use a PLT stub.
Therefore I use SYSCALL_PIC_SETUP from sysdep.h and added the missing 
semicolons.

Question about glibc configure flag --disable-hidden-plt:
Is this option supported or is it used by somebody?
It defines NO_HIDDEN which influences the definition of HIDDEN_JUMPTARGET.
I've tried to build glibc with this configure flag on s390, but it fails 
due to several reasons.

The glibc internal symbols of the ifunc'ed symbols are generated by 
using __hidden_ver1 which does not exist if NO_HIDDEN is defined. Thus 
for further testing I've used --disable-multi-arch to avoid the ifuncs.

Furthermore I get undefined references to __GI_memset/cpy/move
due to asm ("memxyz = __GI_memxyz"); in sysdeps/generic/symbol-hacks.h.

There are also undefined references to __nss_next2 and 
__inet6_scopeid_pton while linking nscd/nscd. Usually libc.so contains 
those symbols: xyz@@GLIBC_PRIVATE.
But with --disable-hidden-plt those symbols are only local.
For testing I've removed attribute_hidden at those prototypes.
Then glibc builds and the testsuite runs without fails except 
elf/check-localplt which detects the PLTs due to --disable-hidden-plt.

ChangeLog:

	[BZ #21537]
	* sysdeps/s390/s390-32/sysdep.h (JUMPTARGET, SYSCALL_PIC_SETUP):
	Check SHARED instead of PIC.
	(SYSCALL_PIC_SETUP): Add missing semicolons.
	* sysdeps/s390/s390-64/sysdep.h (JUMPTARGET, SYSCALL_PIC_SETUP):
	Check SHARED instead of PIC.
	* sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S
	(__makecontext_ret): Adjust code to jump to exit.

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commit a1d6669382f30e16edf787adfa87b6f77a309357
Author: Stefan Liebler <stli@linux.vnet.ibm.com>
Date:   Thu Jun 8 13:13:27 2017 +0200

    S390: Fix build with gcc configured with --enable-default-pie. [BZ #21537]
    
    Building glibc with gcc configured with --enable-default-pie failed on s390
    due to assembler messages:
    ../sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S:44:
    Error: junk at end of line, first unrecognized character is `@'
    
    HIDDEN_JUMPTARGET was expanded to exit@PLT@GOTOFF.
    If SHARED is not defined, HIDDEN_JUMPTARGET is defined to JUMPTARGET
    in sysdeps/s390/s390-32/sysdep.h.  There it expanded to exit@PLT
    in non SHARED case as PIC is defined if gcc is configured with
    --enable-default-pie. Thus I've changed the "ifdef PIC" to "ifdef SHARED"
    as we do not want PLTs in the static obj files.  I've also changed this
    in sysdeps/s390/s390-64/sysdep.h.
    
    I've also adjusted sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S.
    If glibc is configured with --disable-hidden-plt, then NO_HIDDEN is defined.
    In SHARED case HIDDEN_JUMPTARGET would be expanded to exit@PLT@GOTOFF
    instead of __GI_exit@GOTOFF.
    Now we jump to:
    - __GI_exit if SHARED is defined
    - exit@PLT if SHARED and NO_HIDDEN is defined
    - exit if both are not defined.
    On s390 31bit we have to setup GOT pointer in r12 if we use a PLT stub.
    Therefore I use SYSCALL_PIC_SETUP from sysdep.h and added the missing semicolons.
    
    ChangeLog:
    
    	[BZ #21537]
    	* sysdeps/s390/s390-32/sysdep.h (JUMPTARGET, SYSCALL_PIC_SETUP):
    	Check SHARED instead of PIC.
    	(SYSCALL_PIC_SETUP): Add missing semicolons.
    	* sysdeps/s390/s390-64/sysdep.h (JUMPTARGET, SYSCALL_PIC_SETUP):
    	Check SHARED instead of PIC.
    	* sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S
    	(__makecontext_ret): Adjust code to jump to exit.

diff --git a/sysdeps/s390/s390-32/sysdep.h b/sysdeps/s390/s390-32/sysdep.h
index 15a4e3e..60cf1e7 100644
--- a/sysdeps/s390/s390-32/sysdep.h
+++ b/sysdeps/s390/s390-32/sysdep.h
@@ -82,14 +82,14 @@ lose: SYSCALL_PIC_SETUP				\
   END (name)
 
 #undef JUMPTARGET
-#ifdef PIC
+#ifdef SHARED
 #define JUMPTARGET(name)	name##@PLT
 #define SYSCALL_PIC_SETUP             \
-    bras  %r12,1f                     \
-0:  .long _GLOBAL_OFFSET_TABLE_-0b    \
+    bras  %r12,1f;		      \
+0:  .long _GLOBAL_OFFSET_TABLE_-0b;   \
 1:  al    %r12,0(%r12)
 #else
-#define JUMPTARGET(name)   	name
+#define JUMPTARGET(name)	name
 #define SYSCALL_PIC_SETUP	/* Nothing.  */
 #endif
 
diff --git a/sysdeps/s390/s390-64/sysdep.h b/sysdeps/s390/s390-64/sysdep.h
index a4dfc67..419cd01 100644
--- a/sysdeps/s390/s390-64/sysdep.h
+++ b/sysdeps/s390/s390-64/sysdep.h
@@ -77,7 +77,7 @@ lose: SYSCALL_PIC_SETUP			\
   END (name)
 
 #undef JUMPTARGET
-#ifdef PIC
+#ifdef SHARED
 #define JUMPTARGET(name)	name##@PLT
 #define SYSCALL_PIC_SETUP \
     larl  %r12,_GLOBAL_OFFSET_TABLE_
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S b/sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S
index f32cd3c..887d841 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S
@@ -32,25 +32,18 @@ ENTRY(__makecontext_ret)
 	lr    %r2,%r8
 	br    %r9
 1:	lhi   %r2,0			/* EXIT return value.  */
-	basr	%r13,0
-2:
-#ifdef PIC
-	l       %r12,4f-2b(%r13)
-	la      %r12,0(%r12,%r13)	/* GOT pointer in r12 after this.  */
-	l       %r1,3f-2b(%r13)
-	bas     %r14,0(%r1,%r12)
-	.align  4
-3:
-	.long   HIDDEN_JUMPTARGET (exit)@GOTOFF
-4:
-	.long   _GLOBAL_OFFSET_TABLE_-2b
-#else
-	l	%r1,3f-2b(%r13)
-	basr	%r14,%r1
-	.align  4
-3:
-	.long   HIDDEN_JUMPTARGET (exit)
+#ifdef NO_HIDDEN
+	/* If SHARED and NO_HIDDEN is defined, we need to setup got pointer
+	   as HIDDEN_JUMPTARGET expands to JUMPTARGET which expands to
+	   exit@PLT.  Otherwise HIDDEN_JUMPTARGET expands to __GI_exit if
+	   SHARED is defined and to exit if SHARED is not defined.  */
+	SYSCALL_PIC_SETUP
 #endif
-	.align	2
+	basr	%r1,0
+2:
+	al	%r1,3f-2b(%r1)
+	basr	%r14,%r1		/* Call exit.  */
 	j	.+2			/* Trap if exit returns for some reason.  */
+3:
+	.long   HIDDEN_JUMPTARGET (exit) - 2b
 END(__makecontext_ret)

Re: [PATCH] S390: Fix build with gcc configured with --enable-default-pie. [BZ #21537]

[Florian Weimer]

On 06/08/2017 02:02 PM, Stefan Liebler wrote:
> Question about glibc configure flag --disable-hidden-plt:
> Is this option supported or is it used by somebody?
> It defines NO_HIDDEN which influences the definition of HIDDEN_JUMPTARGET.
> I've tried to build glibc with this configure flag on s390, but it fails
> due to several reasons.

I think we can remove --disable-hidden-plt.  It is broken on x86-64 as
well, and I think the whole thing stopped working with PLT avoidance for
hidden symbols in binutils and switching to namespace-clean names (which
are generally hidden).

Thanks,
Florian

Re: [PATCH] S390: Fix build with gcc configured with --enable-default-pie. [BZ #21537]

[Joseph Myers]

On Fri, 9 Jun 2017, Florian Weimer wrote:

> On 06/08/2017 02:02 PM, Stefan Liebler wrote:
> > Question about glibc configure flag --disable-hidden-plt:
> > Is this option supported or is it used by somebody?
> > It defines NO_HIDDEN which influences the definition of HIDDEN_JUMPTARGET.
> > I've tried to build glibc with this configure flag on s390, but it fails
> > due to several reasons.
> 
> I think we can remove --disable-hidden-plt.  It is broken on x86-64 as
> well, and I think the whole thing stopped working with PLT avoidance for
> hidden symbols in binutils and switching to namespace-clean names (which
> are generally hidden).

Do note however the unconditional definition of NO_HIDDEN in 
sysdeps/mach/hurd/configure.ac (and the corresponding comment pointing to 
a discussion of that).  We really need Hurd people to get current glibc 
working on Hurd without external patches and contribute 
build-many-glibcs.py support for it so it's possible to make sure changes 
don't break Hurd.

-- 
Joseph S. Myers
joseph@codesourcery.com

Re: [PATCH] S390: Fix build with gcc configured with --enable-default-pie. [BZ #21537]

[Andreas Schwab]

On Jun 08 2017, Stefan Liebler <stli@linux.vnet.ibm.com> wrote:

> 	[BZ #21537]
> 	* sysdeps/s390/s390-32/sysdep.h (JUMPTARGET, SYSCALL_PIC_SETUP):
> 	Check SHARED instead of PIC.
> 	(SYSCALL_PIC_SETUP): Add missing semicolons.
> 	* sysdeps/s390/s390-64/sysdep.h (JUMPTARGET, SYSCALL_PIC_SETUP):
> 	Check SHARED instead of PIC.
> 	* sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S
> 	(__makecontext_ret): Adjust code to jump to exit.

Ok.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: [PATCH] S390: Fix build with gcc configured with --enable-default-pie. [BZ #21537]

[Stefan Liebler]

On 06/12/2017 02:05 PM, Andreas Schwab wrote:
> On Jun 08 2017, Stefan Liebler <stli@linux.vnet.ibm.com> wrote:
> 
>> 	[BZ #21537]
>> 	* sysdeps/s390/s390-32/sysdep.h (JUMPTARGET, SYSCALL_PIC_SETUP):
>> 	Check SHARED instead of PIC.
>> 	(SYSCALL_PIC_SETUP): Add missing semicolons.
>> 	* sysdeps/s390/s390-64/sysdep.h (JUMPTARGET, SYSCALL_PIC_SETUP):
>> 	Check SHARED instead of PIC.
>> 	* sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S
>> 	(__makecontext_ret): Adjust code to jump to exit.
> 
> Ok.
> 
> Andreas.
> 
Committed.

Thanks.
Stefan