Linux 5.14 ARM64 Preps For When Not All The CPU Cores Support 32-bit Execution

[phoronix]

Phoronix: Linux 5.14 ARM64 Preps For When Not All The CPU Cores Support 32-bit Execution

The 64-bit ARM architecture changes were submitted this week for the ongoing Linux 5.14...

https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.14-ARM64

[uid313]

Good!

I think Apple already has 64-bit only chips that don't support 32-bit.

[pinguinpc]

new arm cores X2 and A510 dont support 32bit but curiously A710 support 32bit

https://www.anandtech.com/show/16693/arm-announces-mobile-armv9-cpu-microarchitectures-cortexx2-cortexa710-cortexa510

[CommunityMember]

new arm cores X2 and A510 dont support 32bit but curiously A710 support 32bit

Toleration/transition support is often needed, even if hardware designers would like to use that silicon and power budget for other things. Give it another generation or so before future A9 designs completely kill off 32bit.

[zamadatix]

Before the comments get filled with discussions about systems which are ARM64 only it's important to note that's not what this patch is about. This patch is actually about individual systems with which have a mix both 64 bit only and 64/32 bit capable cores at the same time https://lore.kernel.org/patchwork/patch/1436130/

When confronted with a mixture of CPUs, some of which support 32-bit applications and others which don't, we quite sensibly treat the system as 64-bit only for userspace and prevent execve() of 32-bit binaries. Unfortunately, some crazy folks have decided to build systems like this with the intention of running 32-bit applications, so relax our sanitisation logic to continue to advertise 32-bit support to userspace on these systems and track the real 32-bit capable cores in a cpumask instead. For now, the default behaviour remains but will be tied to a command-line option in a later patch.