qemu-devel
[Top][All Lists]
Advanced
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Bug with Windows tap network when running qemu-system-ppc with Mac O

From: BALATON Zoltan
Subject: Re: Bug with Windows tap network when running qemu-system-ppc with Mac OS 9 guest
Date: Fri, 26 Mar 2021 20:54:55 +0100 (CET) 
On Fri, 26 Mar 2021, Howard Spoelstra wrote:

On Fri, Mar 26, 2021 at 10:00 AM Bin Meng <bmeng.cn@gmail.com> wrote:


On Fri, Mar 26, 2021 at 4:49 PM Jason Wang <jasowang@redhat.com> wrote:



在 2021/3/26 下午4:21, BALATON Zoltan 写道:

On Fri, 26 Mar 2021, Howard Spoelstra wrote:

On Fri, Mar 26, 2021 at 2:50 AM Bin Meng <bmeng.cn@gmail.com> wrote:


Hi Howard,

On Fri, Mar 26, 2021 at 1:35 AM Peter Maydell
<peter.maydell@linaro.org> wrote:


(adding the relevant people to the cc list)

On Thu, 25 Mar 2021 at 17:26, Howard Spoelstra <hsp.cat7@gmail.com>
wrote:


Hi,

When running qemu-system-ppc with Mac OS guest, the guest crashes
when
using a tap network connection. Openvpn 2.4.9-I601-win10 is installed
with TAP-Windows 9.24.2. A tap connection called TapQemu is bridged
with the default ethernet connection. It gets activated when I start
qemu.

To reproduce, compile qemu-system-ppc from current source and run:

qemu-system-ppc.exe ^
-L pc-bios ^
-M mac99 ^
-m 128 ^
-sdl -serial stdio ^
-boot c ^
-drive file=C:\Mac-disks\9.2.img,format=raw,media=disk ^
-device sungem,netdev=network01 -netdev
tap,ifname=TapQemu,id=network01

I bisected to the commit below. Thanks for looking into this.


Thanks for reporting.

Can you please provide some further information:

1. Does "-net user" work on Windows?
2. If running QEMU under Linux, does "-net tap" or "-net user" work?

Regards,
Bin


Hello Bin,

Thanks for getting back to me. I forgot to mention that reverting the
above patch restores functionality. And that other applications using
the same tap device work correctly.
In answer to your questions:

1. Yes, slirp works on Windows 10 with this setup.
2. Yes, in Linux both tap and slirp work.

My Windows build is done with a fully up to date msys2 installation.

I tried to debug in Windows:
(gdb) run
Starting program: c:\qemu-master-msys2\qemu-system-ppc.exe -L pc-bios
-M mac99 -m 128 -sdl -serial stdio -boot c -drive
"file=C:\Mac-disks\9.2-usb-pci-ddk.img,format=raw,media=disk" -device
"sungem,netdev=network01" -netdev "tap,ifname=TapQemu,id=network01" -S
[New Thread 13304.0x1f00]
[New Thread 13304.0x2f84]
[New Thread 13304.0x3524]
[New Thread 13304.0x2b8c]
[New Thread 13304.0x368c]
[New Thread 13304.0x3668]
[New Thread 13304.0xf4c]
[New Thread 13304.0x49c]
[New Thread 13304.0x1d4c]
[New Thread 13304.0x7fc]
[Thread 13304.0x7fc exited with code 0]
[New Thread 13304.0x357c]
[New Thread 13304.0x7c0]
[New Thread 13304.0x3564]
[New Thread 13304.0x26f4]
[New Thread 13304.0x2f68]

Program received signal SIGSEGV, Segmentation fault.
0x00007ffb9edea991 in ?? () from c:\qemu-master-msys2\libglib-2.0-0.dll
(gdb) bt
#0  0x00007ffb9edea991 in ?? () from
c:\qemu-master-msys2\libglib-2.0-0.dll
#1  0x000800000480bf50 in ?? ()
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
(gdb)

Even before I could attach to the process.


If you run QEMU under gdb you don't have to attach to it but to get a
meaningful backtrace you should configure and compile QEMU with
--enable-debug (this will make it run slower so not recommended
normally but for debugging that would be needed). If the stack is
really corrupted then you may not get a useful backtrace or it may be
a problem with gdb on Windows. I've found that gdb on Windows works
for simple things but could give bad results for more complex stuff.
WinDbg may be better but it's harder to use (needs some registry
change I think to enable core dumps then you could open and analyze
core dumps with it or it should be able to run command directly but I
don't know how that works).

Another idea: maybe you could check other threads in gdb. Not sure if
that would reveal anything but may worth a try. I think the commands
you need are "info threads" and "apply all bt" or something similar.

Regards,
BALATON Zoltan



It looks to me the patch tires to recycle a temporary buffer to tap thread.

Please try to attached fix to see it if works.


Yep, good catch, thanks! This patch looks correct to me.

Regards,
Bin


Hi,

While the patch applies, it will not compile:

../net/tap-win32.c: In function 'tap_win32_send':
../net/tap-win32.c:697:18: error: assignment to 'uint8_t' {aka
'unsigned char'} from 'uint8_t *' {aka 'unsigned char *'} makes
integer from pointer without a cast [-Werror=int-conversion]
 697 |         orig_buf = buf;
     |                  ^
../net/tap-win32.c:707:42: error: passing argument 2 of
'tap_win32_free_buffer' makes pointer from integer without a cast
[-Werror=int-conversion]
 707 |         tap_win32_free_buffer(s->handle, orig_buf);
     |                                          ^~~~~~~~
     |                                          |
     |                                          uint8_t {aka unsigned char}
../net/tap-win32.c:590:44: note: expected 'uint8_t *' {aka 'unsigned
char *'} but argument is of type 'uint8_t' {aka 'unsigned char'}
 590 |                                   uint8_t *pbuf)
     |                                   ~~~~~~~~~^~~~


Patch missing a * from this line:

+    uint8_t *buf, orig_buf;

should be

+    uint8_t *buf, *orig_buf;

Regards,
BALATON Zoltan
reply via email to
[Prev in Thread] Current Thread [Next in Thread]