RISC-V: Fix the static-PIE non-relocated object check

  The value of l_scope is only valid post relocation, so this original
check was triggering undefined behavior.  Instead just directly check to
see if the object has been relocated, at which point using l_scope is
safe.

Reported-by: Andreas Schwab <schwab@suse.de>
Closes: BZ #31317
Fixes: e0590f41fe ("RISC-V: Enable static-pie.")
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
---
 sysdeps/riscv/dl-machine.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
  

Hi Palmer,

Thanks for your patch. I have did the full tests with the same change
as this patch on my qemu-system. There's no regression introduced.

Also test this change with mold linker. It passed.

Thanks,
Yanzhang

> -----Original Message-----
> From: Palmer Dabbelt <palmer@rivosinc.com>
> Sent: Friday, February 23, 2024 7:24 AM
> To: libc-alpha@sourceware.org
> Cc: schwab@suse.de; Wang, Yanzhang <yanzhang.wang@intel.com>;
> adhemerval.zanella@linaro.org; Palmer Dabbelt <palmer@rivosinc.com>
> Subject: [PATCH] RISC-V: Fix the static-PIE non-relocated object check
> 
> The value of l_scope is only valid post relocation, so this original check
> was triggering undefined behavior.  Instead just directly check to see if
> the object has been relocated, at which point using l_scope is safe.
> 
> Reported-by: Andreas Schwab <schwab@suse.de>
> Closes: BZ #31317
> Fixes: e0590f41fe ("RISC-V: Enable static-pie.")
> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
> ---
>  sysdeps/riscv/dl-machine.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sysdeps/riscv/dl-machine.h b/sysdeps/riscv/dl-machine.h index
> 0cbb476c05..b2f28697f7 100644
> --- a/sysdeps/riscv/dl-machine.h
> +++ b/sysdeps/riscv/dl-machine.h
> @@ -348,7 +348,7 @@ elf_machine_runtime_setup (struct link_map *l, struct
> r_scope_elem *scope[],
>        gotplt[1] = (ElfW(Addr)) l;
>      }
> 
> -  if (l->l_type == lt_executable && l->l_scope != NULL)
> +  if (l->l_type == lt_executable && l->l_relocated)
>      {
>        /* The __global_pointer$ may not be defined by the linker if the
>  	 $gp register does not be used to access the global variable
> --
> 2.43.0
  

On Thu, 22 Feb 2024 18:16:47 PST (-0800), yanzhang.wang@intel.com wrote:
> Hi Palmer,
>
> Thanks for your patch. I have did the full tests with the same change
> as this patch on my qemu-system. There's no regression introduced.
>
> Also test this change with mold linker. It passed.

Awesome, thanks.  I don't have a good setup for this so I was sort of 
just trying to figure it out from poking aroud the code and whatever 
Andres said.

Are you OK posting a Tested-by?  This will probably get backported, so 
best to get that stuff sorted out.

>
> Thanks,
> Yanzhang
>
>> -----Original Message-----
>> From: Palmer Dabbelt <palmer@rivosinc.com>
>> Sent: Friday, February 23, 2024 7:24 AM
>> To: libc-alpha@sourceware.org
>> Cc: schwab@suse.de; Wang, Yanzhang <yanzhang.wang@intel.com>;
>> adhemerval.zanella@linaro.org; Palmer Dabbelt <palmer@rivosinc.com>
>> Subject: [PATCH] RISC-V: Fix the static-PIE non-relocated object check
>> 
>> The value of l_scope is only valid post relocation, so this original check
>> was triggering undefined behavior.  Instead just directly check to see if
>> the object has been relocated, at which point using l_scope is safe.
>> 
>> Reported-by: Andreas Schwab <schwab@suse.de>
>> Closes: BZ #31317
>> Fixes: e0590f41fe ("RISC-V: Enable static-pie.")
>> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
>> ---
>>  sysdeps/riscv/dl-machine.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/sysdeps/riscv/dl-machine.h b/sysdeps/riscv/dl-machine.h index
>> 0cbb476c05..b2f28697f7 100644
>> --- a/sysdeps/riscv/dl-machine.h
>> +++ b/sysdeps/riscv/dl-machine.h
>> @@ -348,7 +348,7 @@ elf_machine_runtime_setup (struct link_map *l, struct
>> r_scope_elem *scope[],
>>        gotplt[1] = (ElfW(Addr)) l;
>>      }
>> 
>> -  if (l->l_type == lt_executable && l->l_scope != NULL)
>> +  if (l->l_type == lt_executable && l->l_relocated)
>>      {
>>        /* The __global_pointer$ may not be defined by the linker if the
>>  	 $gp register does not be used to access the global variable
>> --
>> 2.43.0
  

OK, no problem. 

> -----Original Message-----
> From: Palmer Dabbelt <palmer@rivosinc.com>
> Sent: Friday, February 23, 2024 11:07 AM
> To: Wang, Yanzhang <yanzhang.wang@intel.com>
> Cc: libc-alpha@sourceware.org; schwab@suse.de;
> adhemerval.zanella@linaro.org
> Subject: RE: [PATCH] RISC-V: Fix the static-PIE non-relocated object check
> 
> On Thu, 22 Feb 2024 18:16:47 PST (-0800), yanzhang.wang@intel.com wrote:
> > Hi Palmer,
> >
> > Thanks for your patch. I have did the full tests with the same change
> > as this patch on my qemu-system. There's no regression introduced.
> >
> > Also test this change with mold linker. It passed.
> 
> Awesome, thanks.  I don't have a good setup for this so I was sort of just
> trying to figure it out from poking aroud the code and whatever Andres said.
> 
> Are you OK posting a Tested-by?  This will probably get backported, so best
> to get that stuff sorted out.
> 
> >
> > Thanks,
> > Yanzhang
> >
> >> -----Original Message-----
> >> From: Palmer Dabbelt <palmer@rivosinc.com>
> >> Sent: Friday, February 23, 2024 7:24 AM
> >> To: libc-alpha@sourceware.org
> >> Cc: schwab@suse.de; Wang, Yanzhang <yanzhang.wang@intel.com>;
> >> adhemerval.zanella@linaro.org; Palmer Dabbelt <palmer@rivosinc.com>
> >> Subject: [PATCH] RISC-V: Fix the static-PIE non-relocated object
> >> check
> >>
> >> The value of l_scope is only valid post relocation, so this original
> >> check was triggering undefined behavior.  Instead just directly check
> >> to see if the object has been relocated, at which point using l_scope is
> safe.
> >>
> >> Reported-by: Andreas Schwab <schwab@suse.de>
> >> Closes: BZ #31317
> >> Fixes: e0590f41fe ("RISC-V: Enable static-pie.")
> >> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
> >> ---
> >>  sysdeps/riscv/dl-machine.h | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/sysdeps/riscv/dl-machine.h b/sysdeps/riscv/dl-machine.h
> >> index
> >> 0cbb476c05..b2f28697f7 100644
> >> --- a/sysdeps/riscv/dl-machine.h
> >> +++ b/sysdeps/riscv/dl-machine.h
> >> @@ -348,7 +348,7 @@ elf_machine_runtime_setup (struct link_map *l,
> >> struct r_scope_elem *scope[],
> >>        gotplt[1] = (ElfW(Addr)) l;
> >>      }
> >>
> >> -  if (l->l_type == lt_executable && l->l_scope != NULL)
> >> +  if (l->l_type == lt_executable && l->l_relocated)
> >>      {
> >>        /* The __global_pointer$ may not be defined by the linker if the
> >>  	 $gp register does not be used to access the global variable
> >> --
> >> 2.43.0
  

On Feb 22 2024, Palmer Dabbelt wrote:

> The value of l_scope is only valid post relocation, so this original
> check was triggering undefined behavior.  Instead just directly check to
> see if the object has been relocated, at which point using l_scope is
> safe.

Ok.