[RFC PATCH 3/3] add r_debug multiple namespaces support

[Carlos O'Donell]

On 6/26/20 5:05 PM, Florian Weimer via Libc-alpha wrote:
> * Daniel Walker via Libc-alpha:
> 
>> diff --git a/elf/link.h b/elf/link.h
>> index 0048ad5d4d..5a42511636 100644
>> --- a/elf/link.h
>> +++ b/elf/link.h
>> @@ -61,6 +61,10 @@ struct r_debug
>>        } r_state;
>>  
>>      ElfW(Addr) r_ldbase;	/* Base address the linker is loaded at.  */
>> +
>> +    /* Link to next r_debug struct. Each r_debug struct represents a
>> +       different namespace.  The first r_debug struct is the default.  */
>> +    struct r_debug *next;
>>    };
>>  
>>  /* This is the instance of that structure used by the dynamic linker.  */
> 
> How has this patch been tested?  I expect that it will cause an abilist
> mismatch for the _r_debug symbol in the dynamic linker.
> 
> If we go this route to add this capability, I think we have to add a new
> symbol version for the _r_debug symbol, and keep the old one at the
> previous size.
> 
> How is your compatibility experience with the size and version change?
> How many tools need updating before they work again?
> 
> A different approach would add another symbol (parallel to _r_debug) to
> store this data.  This would avoid the need for any immediate tool
> updates.

I mention this in my response to the cover letter in this series.

This patch is probably unacceptable as-is because of application
expectations.

-- 
Cheers,
Carlos.