[PATCH] Add Safe-Linking to fastbins and tcache

[Wilco Dijkstra]

Hi Eyal,

> I went over the patch and fixed it to conform to the coding standards.
> I'm also added it as an attachment, hoping that this way lines won't
> break during the transmission of the email.

Thanks, it now applied fine. There are still a few long lines over 80 chars:

+          if (__glibc_unlikely (!aligned_OK (p)))
+            malloc_printerr ("do_check_malloc_state(): un-aligned fastbin chunk detected");

There is a build issue in that PAGE_SHIFT is not defined. I'm not sure whether
this should come from a Linux header, but it only seems to be set by a few
targets with no generic default defined.

> Regarding the benchmarks, I've just ran them on a simple GCP instance
> (1 vCPU) before and after the patch. As you can see below, the change
> isn't measurable in the "malloc-simple" tests. Sometimes the vanilla
> version is faster (as it should be), but sometimes the patched version
> is faster, which usually means that the change is lower than the noise
> level on the testing server.

Yes, ideally you need an unshared machine with turbo turned off if.
I tried it on a Neoverse N1 and the results look pretty much identical.
The perf profile shows it doesn't affect the hottest paths and only adds a
few extra instructions. So from a performance viewpoint it looks good.

Cheers,
Wilco