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

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

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