[Qemu-devel] [Bug 1812091] Re: gdbstub memory accesses performed with wrong attributes

[Peter Maydell]

Patch sent to list:

https://patchwork.ozlabs.org/patch/1026664/


** Changed in: qemu
       Status: New => In Progress

** Tags added: arm

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https://bugs.launchpad.net/bugs/1812091

Title:
  gdbstub memory accesses performed with wrong attributes

Status in QEMU:
  In Progress

Bug description:
  Qemu-commit: b2f7c27f56bf1116ebb7848c75914aa7c5d6a040

  
  The ARMv8-M architecture (with security extensions) contains a SAU, the 
Security Attribution Unit. After booting the mps2-an505 and immediately halting 
(`-S`), I attempt to read the SAU_TYPE register, located at 0xE000EDD4, using 
gdb (x 0xE000EDD4). The returned value is 0, while the expected value is 8 
(number of regions).

  On further investigation, it seems that `attrs.secure` is set to false
  (armv7m_nvic.c - nvic_readl, line 1167). Commenting out the check will
  return the correct value.

  As the CPU should be in 'secure' mode after reset, I think this
  behavior is wrong.

  Steps to reproduce:
  Example code that loads an endless loop into the beginning of secure memory: 
https://github.com/ajblane/armv8m-hello

  Commandline: qemu-system-arm -machine mps2-an505 -cpu cortex-m33 \
                            -m 4096 \
                            -nographic -serial mon:stdio \
                            -kernel $(IMAGE) -s -S

  Attach with arm-none-eabi-gdb, and run x 0xE000EDD4.

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