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Re: [Qemu-arm] Regression tests for Assembly libraries for Cortex-M: Mor

From: Alex Bennée
Subject: Re: [Qemu-arm] Regression tests for Assembly libraries for Cortex-M: More recent qemu versions core-dump or fail with warnings
Date: Sat, 27 Apr 2019 23:16:20 +0100
User-agent: mu4e 1.3.1; emacs 26.1

"Björn Haase" <address@hidden> writes:

> Thank you peter for your helpful reply!
> Maybe I could make some effort of trying to boil down the testsuite code to 
> 16 MByte of memory and use a linker script for one of the larger Cortex-M3 
> sytems.
>>> Also I believe that semihosting will not be supported on any of the native 
>>> cortex-m machines? Any advice would be very appreciated.
>>All the cortex-m systems support semihosting. (Note
>>that the ABI for M-profile semihosting is not quite
>>the same as the A-profile ABI -- it uses a breakpoint
>>insn, rather than an SVC insn.) You need to enable
>>it with the -semihosting option, and you can't use
>>it from non-privileged code (this is the same as the
>>A-profile semihosting).
> You don't actually know whether someby has actually used this together with 
> the syscall implementations in newlib/libgloss? I somehow fear that my older 
> implementation
> only did work because it was using the SWI interface ...  However, I have 
> seen that libgloss seems to provide different versions of the "Angel" 
> interface. One of these
> also seems to use a breakpoint instruction.
> Do you know of any publicly available target project that actually
> uses semihosting on a Cortex-M? This might be a good starting point
> for analysis.

Well tests/tcg/arm/test-armv6m-undef.S does - it is nominally a microbit
with cortex-m0 but uses semihosting for reporting the test status to the

> Thanks again for your advice!
> Yours,
> Björn.

Alex Bennée

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