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[0/3] tune-cortexa32: AArch32 Thumb-2/crypto fixes, plus a QEMU machine

Message ID 20260701-tune-a32-v1-0-a43f28b1d7a4@gmail.com
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Series tune-cortexa32: AArch32 Thumb-2/crypto fixes, plus a QEMU machine | expand

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Alex Kiernan July 1, 2026, 11:58 a.m. UTC 
Cortex-A32 is an AArch32-only ARMv8-A core - it has no AArch64 mode at
all. The current tune-cortexa32.inc lacks the thumb feature, and its
AArch32 crypto FPU selection and PACKAGE_EXTRA_ARCHS names are wrong for
a Thumb-2 build.

Patch 1 fixes the equivalent problem on the Rust side: rust-common's
target_is_armv7() doesn't recognise armv8a, so an AArch32 Thumb build
is missing both the +v8 and +thumb2 LLVM features, and the "arm-..."
RUST_TARGET_SYS triple doesn't parse as ARMv8 for inline-asm purposes
either. This has to land before patch 2, because once tune-cortexa32
enables the thumb feature, building rust for it fails without this fix.

Patch 2 is the tune-cortexa32.inc fix itself: add arm and thumb to
TUNE_FEATURES, fix PACKAGE_EXTRA_ARCHS to use the t2hf naming, and
append crypto-neon-fp-armv8 to TUNE_CCARGS_MFPU when both crypto and
neon are active, since on AArch32 the ARMv8 crypto extensions live in
the FPU rather than -march alone. Without this, GCC rejects the AES
intrinsics used by e.g. mbedtls' aesce.c with "target specific option
mismatch".

Patch 3 adds a qemuarmv8a32 machine so the above is actually
exercisable: QEMU has no Cortex-A32 model, so it boots the virt machine
with qemu-system-arm -cpu max instead, reusing the qemuarma15
linux-yocto BSP via KMACHINE. I'm really not sure if this is appropriate
for OE-Core - it's useful, but I suspect it really wants a proper U-Boot
and kernel config.

The real breakage I'm attempting to fix is mbedtls, which I need
(covered by #2), which then exposes the problems in libstd-rs (covered
by #1). #3 is really here so there's a way to show it which isn't the
board I'm building for.

AI-Generated: Claude Code (Claude Opus 4.8)
Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Signed-off-by: Alex Kiernan <alexk@a-squared-projects.uk>
---
Alex Kiernan (3):
      rust-target-config: armv8a AArch32 Thumb build fixes
      tune-cortexa32: enable Thumb-2 and fix AArch32 crypto FPU selection
      qemuarmv8a32: add QEMU machine for AArch32 ARMv8-A

 meta/classes-recipe/rust-target-config.bbclass     | 21 +++++++++++--
 .../machine/include/arm/armv8a/tune-cortexa32.inc  | 14 +++++++--
 meta/conf/machine/qemuarmv8a32.conf                | 36 ++++++++++++++++++++++
 meta/recipes-kernel/linux/linux-yocto_6.18.bb      |  2 +-
 4 files changed, 66 insertions(+), 7 deletions(-)
---
base-commit: 9780e392300549f69e11e2f3bcb9bff77b21d572
change-id: 20260701-tune-a32-78f0212484c9

Best regards,
--  
Alex Kiernan <alex.kiernan@gmail.com>