[PATCH v3 2/8] elf: Add a tunable to control use of tagged memory

[Richard Earnshaw]

On 25/11/2020 16:53, Siddhesh Poyarekar wrote:
> On 11/25/20 10:05 PM, H.J. Lu via Libc-alpha wrote:
>> On Mon, Nov 23, 2020 at 7:44 AM Richard Earnshaw via Libc-alpha
>> <libc-alpha@sourceware.org> wrote:
>>>
>>>
>>> Add a new glibc tunable: mtag.enable, bound to the environment variable
>>> _MTAG_ENABLE.  This is a decimal constant in the range 0-255 but used
>>
>> Do we really need LD_MTAG_ENABLE?
>>
> 
> Ahh, thanks for pointing that out, I missed that.  The env aliases are
> really just for compatibility and newer tunables should not add them.
> 
> Siddhesh

Well,
1) We already have MALLOC_CHECK_; this is just similar but with a wider
scope because ...
2) Turning on MTE enables the feature beyond just GLIBC, since it
activates the prctl call in the kernel to permit calls to mmap to
request tagged memory.  So I think this is beyond the level of a real
tunable (though having a tunable does make things easier in the internal
logic of glibc).

R.