Add armv8l virtualized 32-bit ARM core detection

[ayakael]

Expected behavior

Runtime should be able to build within 32-bit userspace on 64-bit ARM cores.

Actual behavior

Per dotnet/source-build#2781, runtime does not know to parse as arm when output of uname -m is armv8l.

Proposed modifications

This pull request modifies existing logics to parse armv8l in the same way as armv7l.

Varia

Parallel merge request on Alpine's side
Arm support on source-build at dotnet/installer#13378

Made as part of Alpine Linux dotnet6 packaging project, see dotnet/source-build#2782

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Issue Details

---

Expected behavior

Runtime should be able to build within 32-bit userspace on 64-bit ARM cores.

Actual behavior

Per dotnet/source-build#2781, runtime does not know to parse as arm when output of uname -m is armv8l.

Proposed modifications

This pull request modifies existing logics to parse armv8l in the same way as armv7l.

Varia

Parallel merge request on Alpine's side
Arm support on source-build at dotnet/installer#13378

Made as part of Alpine Linux dotnet6 packaging project, see dotnet/source-build#2782

Author:	ayakael
Assignees:	-
Labels:	area-Infrastructure, community-contribution
Milestone:	-

[jkoritzinsky]

This looks okay to me. My only concern is that someone could build on an ARMv8 system and it would fail to run on an ARMv7 system. Is that something that can occur with this change?

[directhex]

@jkoritzinsky I don't believe that can occur here. As it happens I already filed an issue similar to this in 2019. dotnet/arcade#4527

[jkoritzinsky]

@directhex has more experience in this area and says there's no issue, so I'm okay with the change

[ayakael]

@directhex Should I change the logics to cover arm*vl like in your PR?

[akoeplinger]

Yeah I think that makes sense so we're ready for armv9l 😄
There's also another check here that needs updating:

runtime/eng/native/configuretools.cmake

Line 56 in 458524a

CMAKE_SYSTEM_PROCESSOR MATCHES "^(armv7l|armv6l|aarch64|arm|s390x)$")

[ayakael]

Yeah I think that makes sense so we're ready for armv9l smile There's also another check here that needs updating:

runtime/eng/native/configuretools.cmake

Line 56 in 458524a

CMAKE_SYSTEM_PROCESSOR MATCHES "^(armv7l|armv6l|aarch64|arm|s390x)$")

I'm ignorant of proper syntax, does CMAKE_SYSTEM_PROCESSOR MATCHES "^(armv*l|aarch64|arm|s390x)$") and elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL armv*l) work?

[akoeplinger]

It's a regex so it'd need to be .*, but I wonder if we shouldn't just use the explicit names in this case and update it once/if armv9l becomes a thing.

[ayakael]

It's a regex so it'd need to be .*, but I wonder if we shouldn't just use the explicit names in this case and update it once/if armv9l becomes a thing.

That might be more prudent, indeed.