identify arm64 host in uname output?

[jeremyd2019]

I was recently thinking about how uname used to include -WOW64 for i686-on-x86_64 situations, and that it would be possible to use IsWow64Process2 to identify and report x86_64-on-ARM64 (and indeed i686-on-ARM64, if backported to 3.3) in a similar way. That might be useful for stats collection purposes (such as msys2/MSYS2-packages#2832).

I thought to bring this up on cygwin list, but I already have several outstanding messages there that have never been replied to, and I'd much rather my recent patch for hangs on ARM64 get attention, so I figured I'd memorialize the idea here.

[dscho]

This is a great idea! The only challenge I see is to decide what label to use... we clearly do not want to use aarch64 here lest there is confusion about an ARM64 runtime (which does not exist), and also -WOW64 is inappropriate because it's reserved for i686-on-x86_64, and not for x86_64-on-aarch64...

[jeremyd2019]

This is a great idea! The only challenge I see is to decide what label to use... we clearly do not want to use aarch64 here lest there is confusion about an ARM64 runtime (which does not exist), and also -WOW64 is inappropriate because it's reserved for i686-on-x86_64, and not for x86_64-on-aarch64...

Technically, there shouldn't be a confusion, because the arch the runtime is built for is in uname -m, while the -WOW64 tag was in uname -s:

# uname -s
MSYS_NT-10.0-19045-WOW64

# uname -m
i686

Of course, users are prone to confusion 😁

My first thought was appending -WOW64-arm64 (or -aarch64 - I'm not sold on one vs the other) to sysname.

prototype: https://gist.github.com/jeremyd2019/bb17f602da12e0f42aa4ff76848279e8

[lazka]

Isn't WOW64 separate? It's not used when emulating x64 on arm64 from what I understand.

[jeremyd2019]

I'm not sure - you find out using IsWow64Process2, but it does return IMAGE_FILE_MACHINE_UNKNOWN for the "process"/"emulated" value, which MSDN says means it is not a WOW64 process.

[lazka]

https://github.com/MicrosoftDocs/windows-dev-docs/blob/docs/landing/arm-docs/apps-on-arm-x86-emulation.md#how-emulation-works

I don't have a good idea for a name though. XOA64 :)

[jeremyd2019]

So you're proposing something more like https://gist.github.com/jeremyd2019/bb17f602da12e0f42aa4ff76848279e8/revisions#diff-b01848fbcc4d8de021593b1f35eb093d8721f33416483b366587de3b20eb187f ?

[jeremyd2019]

https://inbox.sourceware.org/cygwin/[email protected]/T/

[lazka]

msys2/msys2-devtools#10