Re: [patch] Fix ASAN failures on SPARC64/Linux

[Eric Botcazou <ebotcazou at adacore dot com>]

> Is the size of the virtual address space hole constant though (and will it
> remain constant)?

The kernel sources say that it's constant and with this position for SPARC-T4 
and later.  It's different (larger hole) for SPARC-T3 and earlier but I cannot 
really test.  I don't think that it will change for a given processor.

> E.g. on powerpc64 or aarch64 there are in each case like 4-5 different VA
> size configurations over the last 10+ years of kernel history and
> configuration options and fortunately all that is hidden inside of libasan,
> if you have older gcc and run into an unsupported VA configuration, all it
> takes is update libasan to one that supports it and binaries continue to
> work.

But a few targets have hardcoded VA size in TARGET_ASAN_SHADOW_OFFSET too.

> Could libasan initialization if it detects just PROT_NONE mmap from the end
> of hole to the start of the region it really supports (and fail if that
> fails), so that backward compatibility is ensured?

I'll investigate how targets supporting multiple VA size behave, but I don't 
have access to a large range of SPARC machines...

> Also, don't you need some corresponding libsanitizer changes?

Of course, just merged.

-- 
Eric Botcazou