Am 17.02.2014 16:18, schrieb Peter Maydell: > On 17 February 2014 14:52, Andreas Galauner <andr...@galauner.de> wrote: >> I'm currently trying to emulate an ARM Cortex-M3 and I need to debug the >> system using GDB and IDA Pro. The platform is an STM32 and I'm using a >> port from github [1] based on qemu 1.5.1 for that. I ported the custom >> STM32 code to qemu 1.7.0 to have a more recent version to work with. >> >> During a debug session, I'm experiencing segfaults in armv7m_nvic.c when >> reading the CPUID and Vector base registers (lines 176 and 212), because >> ARM_CPU(current_cpu) returns a NULL-pointer. IDA seems to do that quite >> regularly. Debugging with GDB works until you try to read the mentioned >> registers by hand like this: >> >>> (gdb) target remote :1234 >>> Remote debugging using :1234 >>> 0x08005d1c in ?? () >>> (gdb) x/x *0xE000ED00 >>> Remote connection closed [...] > The crash you're running into is caused by the device code assuming > that it's only ever accessed by a CPU, not by some other thing like > a debugger or DMA access. For the NVIC code in armv7m_nvic.c we > know that a v7M CPU has only one core, so you should just be able > to replace the uses of "current_cpu" with "first_cpu". Other > places which use current_cpu (such as the GIC proper) might be > shared with configurations which do have multiple cores and so > really do need current_cpu.
While first_cpu may help Andreas in his local copy for STM32, that assumption is not okay in general. The Vybrid VF6 has both a GIC and an NVIC, so our NVIC code should not make assumptions which CPU it can access. I assume we would shield both using CPU address spaces, but I wonder if either of you two has already thought about how those will interact for gdbstub? I remember there being two CPU variables in gdbstub, maybe Andreas can use them to temporarily set current_cpu? Regards, Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
