Re: [Qemu-devel] [PATCH] Revert "armv7m: Guard against no -kernel argument"

[Philippe Mathieu-Daudé]

On 4/25/19 8:07 PM, Philippe Mathieu-Daudé wrote:
> Hi Peter, Stefan,
> 
> On 1/4/19 4:16 PM, Peter Maydell wrote:
>> On Thu, 3 Jan 2019 at 14:41, Stefan Hajnoczi <address@hidden> wrote:
>>>
>>> This reverts commit 01fd41ab3fb69971c24a69ed49cde96086d81278.
>>>
>>> The generic loader device (-device loader,file=kernel.bin) can be used
>>> to load a kernel instead of the -kernel option.  Some boards have flash
>>> memory (pflash) that is set via the -pflash or -drive options.
>>>
>>> Allow starting QEMU without the -kernel option to accommodate these
>>> scenarios.
>>>
>>> Suggested-by: Peter Maydell <address@hidden>
>>> Signed-off-by: Stefan Hajnoczi <address@hidden>
> 
> Previous to this commit (v3.1), we have:
> 
> $ qemu-system-aarch64 -M netduino2
> qemu-system-aarch64: Guest image must be specified (using -kernel)
> 
> Now (v4.0) we get:
> 
> $ qemu-system-aarch64 -M netduino2
> qemu: fatal: Lockup: can't escalate 3 to HardFault (current priority -1)
> 
> R00=00000000 R01=00000000 R02=00000000 R03=00000000
> R04=00000000 R05=00000000 R06=00000000 R07=00000000
> R08=00000000 R09=00000000 R10=00000000 R11=00000000
> R12=00000000 R13=ffffffe0 R14=fffffff9 R15=00000000
> XPSR=40000003 -Z-- A handler
> FPSCR: 00000000
> Aborted (core dumped)

(gdb) bt
#0  0x00007fd14f39457f in raise () at /lib64/libc.so.6
#1  0x00007fd14f37e895 in abort () at /lib64/libc.so.6
#2  0x000056286da2695c in cpu_abort (cpu=0x5628705c43c0,
fmt=0x56286dfdc450 "Lockup: can't escalate %d to HardFault (current
priority %d)\n") at /source/qemu/exec.c:1282
#3  0x000056286dada4ea in do_armv7m_nvic_set_pending
(opaque=0x5628705a5030, irq=3, secure=false, derived=false) at
/source/qemu/hw/intc/armv7m_nvic.c:632
#4  0x000056286dada568 in armv7m_nvic_set_pending
(opaque=0x5628705a5030, irq=6, secure=false) at
/source/qemu/hw/intc/armv7m_nvic.c:650
#5  0x000056286db3ae1b in arm_v7m_cpu_do_interrupt (cs=0x5628705c43c0)
at /source/qemu/target/arm/helper.c:8822
#6  0x000056286dad2e9e in cpu_handle_exception (cpu=0x5628705c43c0,
ret=0x7fd13d9fbe2c) at /source/qemu/accel/tcg/cpu-exec.c:504
#7  0x000056286dad350a in cpu_exec (cpu=0x5628705c43c0) at
/source/qemu/accel/tcg/cpu-exec.c:709
#8  0x000056286da77497 in tcg_cpu_exec (cpu=0x5628705c43c0) at
/source/qemu/cpus.c:1431
#9  0x000056286da77caf in qemu_tcg_cpu_thread_fn (arg=0x5628705c43c0) at
/source/qemu/cpus.c:1735
#10 0x000056286deb5dce in qemu_thread_start (args=0x5628705ea850) at
/source/qemu/util/qemu-thread-posix.c:502
#11 0x00007fd14f52a58e in start_thread () at /lib64/libpthread.so.0
#12 0x00007fd14f459683 in clone () at /lib64/libc.so.6

Running with -d in_asm,int:
----------------
IN:
0x00000000:  00000000  andeq    r0, r0, r0

Taking exception 18 [v7M INVSTATE UsageFault]
...BusFault with BFSR.STKERR
...taking pending nonsecure exception 3
----------------
IN:
0x00000000:  00000000  andeq    r0, r0, r0

Taking exception 18 [v7M INVSTATE UsageFault]
qemu: fatal: Lockup: can't escalate 3 to HardFault (current priority -1)

Since I didn't provided anything to bootstrap the guest, the bootvector
in flash is obviously empty.

> 
> This is confusing.
> 
> (same happens with emcraft-sf2, microbit, musca-*)
> 
> Regards,
> 
> Phil.
>