[Qemu-devel] [Bug 1838475] [NEW] qemu-system-arm exits when cortex-m4 floating point used and irq occurs

[KD]

Public bug reported:

qemu-system-arm exits with

"...Secure UsageFault with CFSR.NOCP because NSACR.CP10 prevents stacking FP 
regs
...taking pending nonsecure exception 3
Taking exception 7 [Breakpoint]
qemu: fatal: Lockup: can't escalate 3 to HardFault (current priority -1)" 

when emulating Cortex-m4, executing at least 1 floating point
instruction, and then an irq (e.g. sys tick) occurring.

CPACR.CP10 and CPACR.CP11 are set to 0x3 respectively prior to executing
the fp instructions.

NOTE: NSACR does not appear to be a cortex m4 register.

Attached is a simplified elf to repro the issue.

The qemu command line is: "qemu-system-arm --gdb tcp::1234 -cpu
cortex-m4 -machine lm3s6965evb -nographic -semihosting-config
enable=on,target=native -kernel QemuExitWhenUsingFPAndIRQOccurs.elf -d
int"

** Affects: qemu
     Importance: Undecided
         Status: New

** Attachment added: "QemuExitWhenUsingFPAndIRQOccurs.elf"
   
https://bugs.launchpad.net/bugs/1838475/+attachment/5280090/+files/QemuExitWhenUsingFPAndIRQOccurs.elf

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https://bugs.launchpad.net/bugs/1838475

Title:
  qemu-system-arm exits when cortex-m4 floating point used and irq
  occurs

Status in QEMU:
  New

Bug description:
  qemu-system-arm exits with

  "...Secure UsageFault with CFSR.NOCP because NSACR.CP10 prevents stacking FP 
regs
  ...taking pending nonsecure exception 3
  Taking exception 7 [Breakpoint]
  qemu: fatal: Lockup: can't escalate 3 to HardFault (current priority -1)" 

  when emulating Cortex-m4, executing at least 1 floating point
  instruction, and then an irq (e.g. sys tick) occurring.

  CPACR.CP10 and CPACR.CP11 are set to 0x3 respectively prior to
  executing the fp instructions.

  NOTE: NSACR does not appear to be a cortex m4 register.

  Attached is a simplified elf to repro the issue.

  The qemu command line is: "qemu-system-arm --gdb tcp::1234 -cpu
  cortex-m4 -machine lm3s6965evb -nographic -semihosting-config
  enable=on,target=native -kernel QemuExitWhenUsingFPAndIRQOccurs.elf -d
  int"

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