diff mbox series

ifuncmain6pie: Remove the circular IFUNC dependency [BZ #20019]

Message ID CAMe9rOryuOAHN=7yk8Ym=qEqseznYwN+ZSOnMep5eS8299TpYA@mail.gmail.com
State Committed
Headers show
Series ifuncmain6pie: Remove the circular IFUNC dependency [BZ #20019] | expand

Commit Message

H.J. Lu Jan. 4, 2021, 10:38 p.m. UTC
On Mon, Jan 4, 2021 at 1:20 PM Carlos O'Donell <carlos@redhat.com> wrote:
>
...
> >
> > [hjl@gnu-cfl-2 build-x86_64-linux]$ ./elf/ifuncmain6pie --direct
> > ./elf/ifuncmain6pie: IFUNC symbol 'foo' referenced in
> > '/export/build/gnu/tools-build/glibc/build-x86_64-linux/elf/ifuncmod6.so'
> > is defined in the executable and creates an unsatisfiable circular
> > dependency.
> > [hjl@gnu-cfl-2 build-x86_64-linux]$
> >
> > The message is correct.  Should we update the testcase to avoid it?
>
> Yes, but it is still possible to support this with lazy binding?
>
> Should ifuncmain6pie be explicitly compiled with -Wl,-z,lazy to
> bypass selection from the toolchain?

The problem is non-JUMP_SLOT relocations.  Here is a patch to
remove them.   OK for master?

Thanks.

Comments

Adhemerval Zanella Netto Jan. 13, 2021, 7:43 p.m. UTC | #1
On 04/01/2021 19:38, H.J. Lu via Libc-alpha wrote:
> On Mon, Jan 4, 2021 at 1:20 PM Carlos O'Donell <carlos@redhat.com> wrote:
>>
> ...
>>>
>>> [hjl@gnu-cfl-2 build-x86_64-linux]$ ./elf/ifuncmain6pie --direct
>>> ./elf/ifuncmain6pie: IFUNC symbol 'foo' referenced in
>>> '/export/build/gnu/tools-build/glibc/build-x86_64-linux/elf/ifuncmod6.so'
>>> is defined in the executable and creates an unsatisfiable circular
>>> dependency.
>>> [hjl@gnu-cfl-2 build-x86_64-linux]$
>>>
>>> The message is correct.  Should we update the testcase to avoid it?
>>
>> Yes, but it is still possible to support this with lazy binding?
>>
>> Should ifuncmain6pie be explicitly compiled with -Wl,-z,lazy to
>> bypass selection from the toolchain?
> 
> The problem is non-JUMP_SLOT relocations.  Here is a patch to
> remove them.   OK for master?
> 
> Thanks.
> 

I am getting a failure for elf/ifuncmain6pie for a couple of days:

$ ./testrun.sh elf/ifuncmain6pie
elf/ifuncmain6pie: IFUNC symbol 'foo' referenced in '/home/azanella/Projects/glibc/build/x86_64-linux-gnu/elf/ifuncmod6.so' is defined in the executable and creates an unsatisfiable circular dependency.

The patch looks ok for 2.33.

However, I think it should be been added along with 6ea5b57afa5
fix in first place. Why hasn't it shown in your make check? Does the
failure depend on a binutils version?


> diff --git a/elf/Makefile b/elf/Makefile
> index 543800f4be..c41d11693b 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -1403,6 +1403,8 @@ CFLAGS-ifuncmain7pie.c += $(pie-ccflag)
>  CFLAGS-ifuncmain9pie.c += $(pie-ccflag)
>  CFLAGS-tst-ifunc-textrel.c += $(pic-ccflag)
>  
> +LDFLAGS-ifuncmain6pie = -Wl,-z,lazy
> +
>  $(objpfx)ifuncmain1pie: $(objpfx)ifuncmod1.so
>  $(objpfx)ifuncmain1staticpie: $(objpfx)ifuncdep1pic.o
>  $(objpfx)ifuncmain1vispie: $(objpfx)ifuncmod1.so
> diff --git a/elf/ifuncmain6pie.c b/elf/ifuncmain6pie.c
> index 04faeb86ef..4a01906836 100644
> --- a/elf/ifuncmain6pie.c
> +++ b/elf/ifuncmain6pie.c
> @@ -9,7 +9,6 @@
>  #include "ifunc-sel.h"
>  
>  typedef int (*foo_p) (void);
> -extern foo_p foo_ptr;
>  
>  static int
>  one (void)
> @@ -28,20 +27,17 @@ foo_ifunc (void)
>  }
>  
>  extern int foo (void);
> -extern foo_p get_foo (void);
> +extern int call_foo (void);
>  extern foo_p get_foo_p (void);
>  
> -foo_p my_foo_ptr = foo;
> +foo_p foo_ptr = foo;
>  
>  int
>  main (void)
>  {
>    foo_p p;
>  
> -  p = get_foo ();
> -  if (p != foo)
> -    abort ();
> -  if ((*p) () != -30)
> +  if (call_foo () != -30)
>      abort ();
>  
>    p = get_foo_p ();
> @@ -52,12 +48,8 @@ main (void)
>  
>    if (foo_ptr != foo)
>      abort ();
> -  if (my_foo_ptr != foo)
> -    abort ();
>    if ((*foo_ptr) () != -30)
>      abort ();
> -  if ((*my_foo_ptr) () != -30)
> -    abort ();
>    if (foo () != -30)
>      abort ();
>  
> diff --git a/elf/ifuncmod6.c b/elf/ifuncmod6.c
> index 2e16c1d06d..2f6d0715e6 100644
> --- a/elf/ifuncmod6.c
> +++ b/elf/ifuncmod6.c
> @@ -4,7 +4,7 @@ extern int foo (void);
>  
>  typedef int (*foo_p) (void);
>  
> -foo_p foo_ptr = foo;
> +extern foo_p foo_ptr;
>  
>  foo_p
>  get_foo_p (void)
> @@ -12,8 +12,8 @@ get_foo_p (void)
>    return foo_ptr;
>  }
>  
> -foo_p
> -get_foo (void)
> +int
> +call_foo (void)
>  {
> -  return foo;
> +  return foo ();
>  }
> -- 
> 2.29.2
H.J. Lu Jan. 13, 2021, 7:48 p.m. UTC | #2
On Wed, Jan 13, 2021 at 11:43 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 04/01/2021 19:38, H.J. Lu via Libc-alpha wrote:
> > On Mon, Jan 4, 2021 at 1:20 PM Carlos O'Donell <carlos@redhat.com> wrote:
> >>
> > ...
> >>>
> >>> [hjl@gnu-cfl-2 build-x86_64-linux]$ ./elf/ifuncmain6pie --direct
> >>> ./elf/ifuncmain6pie: IFUNC symbol 'foo' referenced in
> >>> '/export/build/gnu/tools-build/glibc/build-x86_64-linux/elf/ifuncmod6.so'
> >>> is defined in the executable and creates an unsatisfiable circular
> >>> dependency.
> >>> [hjl@gnu-cfl-2 build-x86_64-linux]$
> >>>
> >>> The message is correct.  Should we update the testcase to avoid it?
> >>
> >> Yes, but it is still possible to support this with lazy binding?
> >>
> >> Should ifuncmain6pie be explicitly compiled with -Wl,-z,lazy to
> >> bypass selection from the toolchain?
> >
> > The problem is non-JUMP_SLOT relocations.  Here is a patch to
> > remove them.   OK for master?
> >
> > Thanks.
> >
>
> I am getting a failure for elf/ifuncmain6pie for a couple of days:
>
> $ ./testrun.sh elf/ifuncmain6pie
> elf/ifuncmain6pie: IFUNC symbol 'foo' referenced in '/home/azanella/Projects/glibc/build/x86_64-linux-gnu/elf/ifuncmod6.so' is defined in the executable and creates an unsatisfiable circular dependency.
>
> The patch looks ok for 2.33.

I am checking it in.  Thanks.

> However, I think it should be been added along with 6ea5b57afa5

I don't want the testcase issue to block the code fix.

> fix in first place. Why hasn't it shown in your make check? Does the
> failure depend on a binutils version?

No.
Adhemerval Zanella Netto Jan. 14, 2021, 1:10 p.m. UTC | #3
On 13/01/2021 16:48, H.J. Lu wrote:
> On Wed, Jan 13, 2021 at 11:43 AM Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>>
>> On 04/01/2021 19:38, H.J. Lu via Libc-alpha wrote:
> 
>> However, I think it should be been added along with 6ea5b57afa5
> 
> I don't want the testcase issue to block the code fix.
> 
>> fix in first place. Why hasn't it shown in your make check? Does the
>> failure depend on a binutils version?
> 
> No.
> 

In this case I think the tests should have been disabled until we
add a proper fix.  I saw that regression for a couple of days before I 
had time to investigate and see you already posted a fix.
diff mbox series

Patch

From fe3bd3b8d7e6401dc96e2aa59f341d41d1cb4723 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Mon, 4 Jan 2021 14:25:39 -0800
Subject: [PATCH] ifuncmain6pie: Remove the circular IFUNC dependency [BZ
 #20019]

On x86, ifuncmain6pie failed with:

[hjl@gnu-cfl-2 build-i686-linux]$ ./elf/ifuncmain6pie --direct
./elf/ifuncmain6pie: IFUNC symbol 'foo' referenced in '/export/build/gnu/tools-build/glibc-32bit/build-i686-linux/elf/ifuncmod6.so' is defined in the executable and creates an unsatisfiable circular dependency.
[hjl@gnu-cfl-2 build-i686-linux]$ readelf -rW elf/ifuncmod6.so | grep foo
00003ff4  00000706 R_386_GLOB_DAT         0000400c   foo_ptr
00003ff8  00000406 R_386_GLOB_DAT         00000000   foo
0000400c  00000401 R_386_32               00000000   foo
[hjl@gnu-cfl-2 build-i686-linux]$

Remove non-JUMP_SLOT relocations against foo in ifuncmod6.so, which
trigger the circular IFUNC dependency, and build ifuncmain6pie with
-Wl,-z,lazy.
---
 elf/Makefile        |  2 ++
 elf/ifuncmain6pie.c | 14 +++-----------
 elf/ifuncmod6.c     |  8 ++++----
 3 files changed, 9 insertions(+), 15 deletions(-)

diff --git a/elf/Makefile b/elf/Makefile
index 543800f4be..c41d11693b 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -1403,6 +1403,8 @@  CFLAGS-ifuncmain7pie.c += $(pie-ccflag)
 CFLAGS-ifuncmain9pie.c += $(pie-ccflag)
 CFLAGS-tst-ifunc-textrel.c += $(pic-ccflag)
 
+LDFLAGS-ifuncmain6pie = -Wl,-z,lazy
+
 $(objpfx)ifuncmain1pie: $(objpfx)ifuncmod1.so
 $(objpfx)ifuncmain1staticpie: $(objpfx)ifuncdep1pic.o
 $(objpfx)ifuncmain1vispie: $(objpfx)ifuncmod1.so
diff --git a/elf/ifuncmain6pie.c b/elf/ifuncmain6pie.c
index 04faeb86ef..4a01906836 100644
--- a/elf/ifuncmain6pie.c
+++ b/elf/ifuncmain6pie.c
@@ -9,7 +9,6 @@ 
 #include "ifunc-sel.h"
 
 typedef int (*foo_p) (void);
-extern foo_p foo_ptr;
 
 static int
 one (void)
@@ -28,20 +27,17 @@  foo_ifunc (void)
 }
 
 extern int foo (void);
-extern foo_p get_foo (void);
+extern int call_foo (void);
 extern foo_p get_foo_p (void);
 
-foo_p my_foo_ptr = foo;
+foo_p foo_ptr = foo;
 
 int
 main (void)
 {
   foo_p p;
 
-  p = get_foo ();
-  if (p != foo)
-    abort ();
-  if ((*p) () != -30)
+  if (call_foo () != -30)
     abort ();
 
   p = get_foo_p ();
@@ -52,12 +48,8 @@  main (void)
 
   if (foo_ptr != foo)
     abort ();
-  if (my_foo_ptr != foo)
-    abort ();
   if ((*foo_ptr) () != -30)
     abort ();
-  if ((*my_foo_ptr) () != -30)
-    abort ();
   if (foo () != -30)
     abort ();
 
diff --git a/elf/ifuncmod6.c b/elf/ifuncmod6.c
index 2e16c1d06d..2f6d0715e6 100644
--- a/elf/ifuncmod6.c
+++ b/elf/ifuncmod6.c
@@ -4,7 +4,7 @@  extern int foo (void);
 
 typedef int (*foo_p) (void);
 
-foo_p foo_ptr = foo;
+extern foo_p foo_ptr;
 
 foo_p
 get_foo_p (void)
@@ -12,8 +12,8 @@  get_foo_p (void)
   return foo_ptr;
 }
 
-foo_p
-get_foo (void)
+int
+call_foo (void)
 {
-  return foo;
+  return foo ();
 }
-- 
2.29.2