[Qemu-devel] [Bug 1840922] Re: qemu-arm for cortex-m33 aborts with unhandled CPU exception 0x8

[Peter Maydell]

The test for v8m magic return addresses is not too loose -- see the v8M
pseudocode IsReturn(). Architecturally the whole range of these values
is special, even though in fact the exception return address encoding
currently doesn't use all the bits that are reserved in this manner.

I would prefer not to unset ARM_FEATURE_M_SECURITY if we can avoid it.

We should definitely not allow guest code to be loaded at weird
addresses in linux-user mode, I agree.

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https://bugs.launchpad.net/bugs/1840922

Title:
  qemu-arm for cortex-m33 aborts with unhandled CPU exception 0x8

Status in QEMU:
  Confirmed

Bug description:
  Hi,

  While experimenting with running the GCC testsuite with cortex-m33 as target 
(to exercise v8-m code), I came across this failure:
  qemu: unhandled CPU exception 0x8 - aborting
  R00=fffeaf58 R01=fffeaf58 R02=00000000 R03=fffeaf5d
  R04=fffeaf5c R05=fffeaf9c R06=00000000 R07=fffeaf80
  R08=00000000 R09=00000000 R10=00019dbc R11=00000000
  R12=000000f0 R13=fffeaf58 R14=000081f3 R15=fffeaf5c
  XPSR=61000000 -ZC- T NS priv-thread
  qemu:handle_cpu_signal received signal outside vCPU context @ pc=0x6033c908

  I'm using arm-eabi-gcc, so it targets bare-metal, not linux.

  The testcase is GCC's
  gcc/testsuite/gcc.c-torture/execute/20000822-1.c; it works when
  compiled at -O2, but crashes when compiled at -Os. The test uses
  nested functions, so it creates a trampoline on the stack, whose
  address may be a problem. But since the stack address seems to be in
  the same range in the O2 and Os cases, it's not that clear.

  I'm attaching the C source, asm, binary executables and qemu traces
  with in_asm,cpu.

  I execute the binaries with:
  qemu-arm --cpu cortex-m33  ./20000822-1.exe.Os

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