SEGFAULT caused by modifying the CPSR register

[LG]

IIf the CPSR register (qemu-system-arm) is set to an invalid mode, qemu will segfault, because it tries to access a NULL-Pointer "env" in translate.c:9286. Either way, qemu will abort in exec.c:1863.

[LG (lauragwd)]

Here is a part of the gdb backtrace:

#2 0x000000000051a2bb in bank_number (env=<value optimized out>
#4 0x000000000051a584 in cpsr_write ((env=0x110a9d0

If I build qemu with debug flags, the env value won't be optimized out, but will remain 0.

[Peter Maydell (pmaydell)]

The missing detail in this bug report is that you only get the segfault if the CPSR register is being changed via the gdb stub interface. This happens because we try to use cpu_single_env as the env to pass to cpu_abort(), and if you've got to bank_number() via the gdb stub then cpu_single_env is NULL. I'm going to submit some patches which (a) fix this and (b) change behaviour to ignore bogus mode setting attempts rather than aborting.

[Peter Maydell (pmaydell)]

The patches that fix this bug are in QEMU 1.1.