ifuncmain6pie: Remove the circular IFUNC dependency [BZ #20019]
Commit Message
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
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: $(objpfx)ifuncmod1.so
> diff --git a/elf/ifuncmain6pie.c b/elf/ifuncmain6pie.c
> index 04faeb86ef..4a01906836 100644
> --- a/elf/ifuncmain6pie.c
> +++ b/elf/ifuncmain6pie.c
> @@ -9,7 +9,6 @@
> #include "ifunc-sel.h"
>
> typedef int (*foo_p) (void);
> -extern foo_p foo_ptr;
>
> static int
> one (void)
> @@ -28,20 +27,17 @@ foo_ifunc (void)
> }
>
> extern int foo (void);
> -extern foo_p get_foo (void);
> +extern int call_foo (void);
> extern foo_p get_foo_p (void);
>
> -foo_p my_foo_ptr = foo;
> +foo_p foo_ptr = foo;
>
> int
> main (void)
> {
> foo_p p;
>
> - p = get_foo ();
> - if (p != foo)
> - abort ();
> - if ((*p) () != -30)
> + if (call_foo () != -30)
> abort ();
>
> p = get_foo_p ();
> @@ -52,12 +48,8 @@ main (void)
>
> if (foo_ptr != foo)
> abort ();
> - if (my_foo_ptr != foo)
> - abort ();
> if ((*foo_ptr) () != -30)
> abort ();
> - if ((*my_foo_ptr) () != -30)
> - abort ();
> if (foo () != -30)
> abort ();
>
> diff --git a/elf/ifuncmod6.c b/elf/ifuncmod6.c
> index 2e16c1d06d..2f6d0715e6 100644
> --- a/elf/ifuncmod6.c
> +++ b/elf/ifuncmod6.c
> @@ -4,7 +4,7 @@ extern int foo (void);
>
> typedef int (*foo_p) (void);
>
> -foo_p foo_ptr = foo;
> +extern foo_p foo_ptr;
>
> foo_p
> get_foo_p (void)
> @@ -12,8 +12,8 @@ get_foo_p (void)
> return foo_ptr;
> }
>
> -foo_p
> -get_foo (void)
> +int
> +call_foo (void)
> {
> - return foo;
> + return foo ();
> }
> --
> 2.29.2
On Wed, Jan 13, 2021 at 11:43 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 04/01/2021 19:38, H.J. Lu via Libc-alpha wrote:
> > On Mon, Jan 4, 2021 at 1:20 PM Carlos O'Donell <carlos@redhat.com> wrote:
> >>
> > ...
> >>>
> >>> [hjl@gnu-cfl-2 build-x86_64-linux]$ ./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.
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.
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(-)
@@ -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
@@ -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 ();
@@ -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