u-boot.git/arch/arm/lib/semihosting.S, branch main

arm: Add ARMv8-M aarch32 support

2026-04-13T23:34:02Z

Add configuration for ARMv8-M aarch32 core, which are currently Cortex-M23/M33 cores. These cores are treated similar to ARMv7-M cores, except the code has to be compiled with matching compiler -march=armv8-m.main flag . These cores have no MMU, they have MPU, which is currently not configured. Unlike ARMv7-M, these cores have 512 interrupt vectors. While the SYS_ARM_ARCH should be set to 8, it is set to 7 because all of the initialization code is built from arch/arm/cpu/armv7m and not armv8. Furthermore, CONFIG_ARM64 must be disabled, although DTs for devices using these cores do come from arch/arm64/boot/dts. To avoid excess duplication in Makefiles, introduce one new Kconfig symbol, CPU_V7M_V8M. The CPU_V7M_V8M cover both ARMv7-M and ARMv8-M cores. Signed-off-by: Marek Vasut Acked-by: Udit Kumar

arm: semihosting: Fix returning from traps on ARMv6 and lower

2023-11-10T17:52:28Z

U-Boot runs in supervisor mode. On ARMv6 and lower, software interrupts are taken in supervisor mode. When entering an interrupt, the link register is set to the address of the next instruction. However, if we are already in supervisor mode, this clobbers the link register. The debugger can't help us, since by the time it notices we've taken a software interrupt, the link register is already gone. Work around this by moving the return address to another register. Signed-off-by: Sean Anderson

arm: semihosting: replace inline assembly with assembly file

2023-03-06T22:06:17Z

So far we used inline assembly to inject the actual instruction that triggers the semihosting service. While this sounds elegant, as it's really only about one instruction, it has some serious downsides: - We need some barriers in place to force the compiler to issue writes to a data structure before issuing the trap instruction. - We need to convince the compiler to actually fill the structures that we use pointers to. - We need a memory clobber to avoid the compiler caching the data in those structures, when semihosting writes data back. - We need register arguments to make sure the function ID and the pointer land in the right registers. This is all doable, but fragile and somewhat cumbersome. Since we now have a separate function in an extra file anyway, we can do away with all the magic and just write that in an actual assembly file. This is much more readable and robust. Signed-off-by: Andre Przywara Reviewed-by: Sean Anderson