Re: QEMU on x64

[Christopher Caulfield]

Hi folks! Wanted to share some documentation if you all want to give QEMU a
try within WinDbg. This is something we've been invested in supporting.

   - Link to public project:
   https://github.com/microsoft/WinDbg-Samples/tree/master/Exdi/exdigdbsrv
   
<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fmicrosoft%2FWinDbg-Samples%2Ftree%2Fmaster%2FExdi%2Fexdigdbsrv=04%7C01%7CChristopher.Caulfield%40microsoft.com%7C7f9c66afb4f74e9cd61e08d9a625465a%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637723501320501730%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000=Bd%2Bvx2JaYtse35JmHigFtWLQzbXv1H9gZ1NseZB%2BF38%3D=0>
   - Link to external readme:  WinDbg-Samples/ExdiGdbSrv_readme.md at
   master · microsoft/WinDbg-Samples · GitHub
   
<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fmicrosoft%2FWinDbg-Samples%2Fblob%2Fmaster%2FExdi%2Fexdigdbsrv%2Fdoc%2FExdiGdbSrv_readme.md=04%7C01%7CChristopher.Caulfield%40microsoft.com%7C7f9c66afb4f74e9cd61e08d9a625465a%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637723501320511728%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000=kWn9Tlqtx1erYK8Pg0AHCSqNOLAYh171Cb9EmrR9cLg%3D=0>
   .

Anyone planning to add the missing x86-64 system registers to the QEMU
x86-64 GDb server?: QEMU registers support on x64 (#510) · Issues · QEMU /
QEMU · GitLab <https://gitlab.com/qemu-project/qemu/-/issues/510>? (I just
realized the title isn't great - O well...)

Thanks so much!
-Christopher

On Mon, Aug 2, 2021 at 6:34 PM Christopher Caulfield 
wrote:

> Thanks folks! I went ahead and made a feature/issue request based on
> Paolo's suggestion:
> QEMU registers support on x64 (#510) · Issues · QEMU / QEMU · GitLab
> <https://gitlab.com/qemu-project/qemu/-/issues/510>
>
> Please let me know if someone has the cycles to support this.
>
> -Christopher
>
> On Mon, Aug 2, 2021 at 10:37 AM Alex Bennée 
> wrote:
>
>>
>> Peter Maydell  writes:
>>
>> > On Fri, 30 Jul 2021 at 19:05, Christopher Caulfield
>> >  wrote:
>> >> This is Christopher from the debugging experiences team at Microsoft
>> focused on kernel debugging. I am reaching out with a few questions about
>> QEMU on x64.
>> >>
>> >> Is it possible for the QEMU-x86-64 GDB Server to send the full set
>> >> of x64 system registers (whether they are included in a separated
>> >> system xml file or as part of the core registers xml file)?
>> >
>> > Do you mean "is it possible for somebody to write code for
>> > QEMU to make it do that", or "does QEMU do it today if you pass
>> > it the right command line option" ? The answer to the former
>> > is "yes", to the latter "no". (If you want the debugger to
>> > be able to write to the system registers this might be a little
>> > trickier, mostly in terms of "auditing the code to make sure this
>> > can't confuse QEMU if you change some sysreg under its feet.".)
>> >
>> >> e.g. System registers missing from i386-64bit.xml file
>> >
>> >> DWORD64 IDTBase;
>> >> DWORD64 IDTLimit;
>> >> DWORD64 GDTBase;
>> >> DWORD64 GDTLimit;
>> >> DWORD SelLDT;
>> >> SEG64_DESC_INFO SegLDT;
>> >> DWORD SelTSS;
>> >> SEG64_DESC_INFO SegTSS;
>> >>
>> >> How can I access x64 MSR registers by using the QEMU-x86-64 GDB server?
>> >>
>> >> #define MSR_EFER 0xc080 // extended function enable register
>> >
>> > EFER is in the xml ("x64_efer") so should be already accessible.
>> > For anything else you're going to need to write some code to
>> > make it happen.
>> >
>> >>is there any plan to support reading/writing to MSRs via QEMU-x86-64
>> >GDB server?
>>
>> Not at the moment but I am keen to see any eventual solution try to be
>> generic rather than hardwired for one architecture. The ARM code
>> currently builds custom XML from it's register descriptors to expose
>> it's MSR registers to the gdbstub. Ideally architecture front ends
>> should register their registers with a new subsystem which can then do
>> the glue between gdbstub as well as other systems that also care about
>> register values (logging, HMP, TCG plugins).
>>
>> That said I'm not going to block any patches that just fix up the
>> current XML and target/i386/gdbstub code. I'm not familiar enough with
>> what the internal register representation state is for x86 w.r.t to TCG
>> and hypervisor based running modes.
>>
>> > Not that I know of. We'd be happy to review patches if you want to
>> > write them.
>> >
>> > thanks
>> > -- PMM
>>
>>
>> --
>> Alex Bennée
>>
>

Re: QEMU on x64

[Christopher Caulfield]

Thanks folks! I went ahead and made a feature/issue request based on
Paolo's suggestion:
QEMU registers support on x64 (#510) · Issues · QEMU / QEMU · GitLab
<https://gitlab.com/qemu-project/qemu/-/issues/510>

Please let me know if someone has the cycles to support this.

-Christopher

On Mon, Aug 2, 2021 at 10:37 AM Alex Bennée  wrote:

>
> Peter Maydell  writes:
>
> > On Fri, 30 Jul 2021 at 19:05, Christopher Caulfield
> >  wrote:
> >> This is Christopher from the debugging experiences team at Microsoft
> focused on kernel debugging. I am reaching out with a few questions about
> QEMU on x64.
> >>
> >> Is it possible for the QEMU-x86-64 GDB Server to send the full set
> >> of x64 system registers (whether they are included in a separated
> >> system xml file or as part of the core registers xml file)?
> >
> > Do you mean "is it possible for somebody to write code for
> > QEMU to make it do that", or "does QEMU do it today if you pass
> > it the right command line option" ? The answer to the former
> > is "yes", to the latter "no". (If you want the debugger to
> > be able to write to the system registers this might be a little
> > trickier, mostly in terms of "auditing the code to make sure this
> > can't confuse QEMU if you change some sysreg under its feet.".)
> >
> >> e.g. System registers missing from i386-64bit.xml file
> >
> >> DWORD64 IDTBase;
> >> DWORD64 IDTLimit;
> >> DWORD64 GDTBase;
> >> DWORD64 GDTLimit;
> >> DWORD SelLDT;
> >> SEG64_DESC_INFO SegLDT;
> >> DWORD SelTSS;
> >> SEG64_DESC_INFO SegTSS;
> >>
> >> How can I access x64 MSR registers by using the QEMU-x86-64 GDB server?
> >>
> >> #define MSR_EFER 0xc080 // extended function enable register
> >
> > EFER is in the xml ("x64_efer") so should be already accessible.
> > For anything else you're going to need to write some code to
> > make it happen.
> >
> >>is there any plan to support reading/writing to MSRs via QEMU-x86-64
> >GDB server?
>
> Not at the moment but I am keen to see any eventual solution try to be
> generic rather than hardwired for one architecture. The ARM code
> currently builds custom XML from it's register descriptors to expose
> it's MSR registers to the gdbstub. Ideally architecture front ends
> should register their registers with a new subsystem which can then do
> the glue between gdbstub as well as other systems that also care about
> register values (logging, HMP, TCG plugins).
>
> That said I'm not going to block any patches that just fix up the
> current XML and target/i386/gdbstub code. I'm not familiar enough with
> what the internal register representation state is for x86 w.r.t to TCG
> and hypervisor based running modes.
>
> > Not that I know of. We'd be happy to review patches if you want to
> > write them.
> >
> > thanks
> > -- PMM
>
>
> --
> Alex Bennée
>

Re: QEMU on x64

[Alex Bennée]

Peter Maydell  writes:

> On Fri, 30 Jul 2021 at 19:05, Christopher Caulfield
>  wrote:
>> This is Christopher from the debugging experiences team at Microsoft focused 
>> on kernel debugging. I am reaching out with a few questions about QEMU on 
>> x64.
>>
>> Is it possible for the QEMU-x86-64 GDB Server to send the full set
>> of x64 system registers (whether they are included in a separated
>> system xml file or as part of the core registers xml file)?
>
> Do you mean "is it possible for somebody to write code for
> QEMU to make it do that", or "does QEMU do it today if you pass
> it the right command line option" ? The answer to the former
> is "yes", to the latter "no". (If you want the debugger to
> be able to write to the system registers this might be a little
> trickier, mostly in terms of "auditing the code to make sure this
> can't confuse QEMU if you change some sysreg under its feet.".)
>
>> e.g. System registers missing from i386-64bit.xml file
>
>> DWORD64 IDTBase;
>> DWORD64 IDTLimit;
>> DWORD64 GDTBase;
>> DWORD64 GDTLimit;
>> DWORD SelLDT;
>> SEG64_DESC_INFO SegLDT;
>> DWORD SelTSS;
>> SEG64_DESC_INFO SegTSS;
>>
>> How can I access x64 MSR registers by using the QEMU-x86-64 GDB server?
>>
>> #define MSR_EFER 0xc080 // extended function enable register
>
> EFER is in the xml ("x64_efer") so should be already accessible.
> For anything else you're going to need to write some code to
> make it happen.
>
>>is there any plan to support reading/writing to MSRs via QEMU-x86-64
>GDB server?

Not at the moment but I am keen to see any eventual solution try to be
generic rather than hardwired for one architecture. The ARM code
currently builds custom XML from it's register descriptors to expose
it's MSR registers to the gdbstub. Ideally architecture front ends
should register their registers with a new subsystem which can then do
the glue between gdbstub as well as other systems that also care about
register values (logging, HMP, TCG plugins).

That said I'm not going to block any patches that just fix up the
current XML and target/i386/gdbstub code. I'm not familiar enough with
what the internal register representation state is for x86 w.r.t to TCG
and hypervisor based running modes.

> Not that I know of. We'd be happy to review patches if you want to
> write them.
>
> thanks
> -- PMM


-- 
Alex Bennée

Re: QEMU on x64

[Paolo Bonzini]

On 30/07/21 19:36, Christopher Caulfield wrote:

Hi QEMU community,

This is Christopher from the debugging experiences team at Microsoft 
focused on kernel debugging. I am reaching out with a few questions 
about QEMU on x64.


 1. Is it possible for the QEMU-x86-64 GDB Server to send the full set
of x64 system registers (whether they are included in a separated
system xml file or as part of the core registers xml file)?
  * e.g. System registers missing from i386-64bit.xml file

DWORD64 IDTBase;
DWORD64 IDTLimit;
DWORD64 GDTBase;
DWORD64 GDTLimit;
DWORD SelLDT;
SEG64_DESC_INFO SegLDT;
DWORD SelTSS;
SEG64_DESC_INFO SegTSS;


Yes, that is possible.


 2. How can I access x64 MSR registers by using the QEMU-x86-64 GDB server?
  * #define MSR_EFER 0xc080 // extended function enable register
#define MSR_STAR 0xc081 // system call selectors
#define MSR_LSTAR 0xc082 // system call 64-bit entry
#define MSR_CSTAR 0xc083 // system call 32-bit entry
 3. Going off of #2 - can you access it via reading GDB memory command?
if not - is there any plan to support reading/writing to MSRs via
QEMU-x86-64 GDB server?


Right now it's not possible, but for specific MSRs it's possible to add 
them to the XML and export them.


Can you create an issue on https://gitlab.com/qemu-project/qemu/-/issues 
please?


Paolo

Re: QEMU on x64

[Peter Maydell]

On Fri, 30 Jul 2021 at 19:05, Christopher Caulfield
 wrote:
> This is Christopher from the debugging experiences team at Microsoft focused 
> on kernel debugging. I am reaching out with a few questions about QEMU on x64.
>
> Is it possible for the QEMU-x86-64 GDB Server to send the full set of x64 
> system registers (whether they are included in a separated system xml file or 
> as part of the core registers xml file)?

Do you mean "is it possible for somebody to write code for
QEMU to make it do that", or "does QEMU do it today if you pass
it the right command line option" ? The answer to the former
is "yes", to the latter "no". (If you want the debugger to
be able to write to the system registers this might be a little
trickier, mostly in terms of "auditing the code to make sure this
can't confuse QEMU if you change some sysreg under its feet.".)

> e.g. System registers missing from i386-64bit.xml file

> DWORD64 IDTBase;
> DWORD64 IDTLimit;
> DWORD64 GDTBase;
> DWORD64 GDTLimit;
> DWORD SelLDT;
> SEG64_DESC_INFO SegLDT;
> DWORD SelTSS;
> SEG64_DESC_INFO SegTSS;
>
> How can I access x64 MSR registers by using the QEMU-x86-64 GDB server?
>
> #define MSR_EFER 0xc080 // extended function enable register

EFER is in the xml ("x64_efer") so should be already accessible.
For anything else you're going to need to write some code to
make it happen.

>is there any plan to support reading/writing to MSRs via QEMU-x86-64 GDB 
>server?

Not that I know of. We'd be happy to review patches if you want to
write them.

thanks
-- PMM

QEMU on x64

[Christopher Caulfield]

Hi QEMU community,

This is Christopher from the debugging experiences team at Microsoft
focused on kernel debugging. I am reaching out with a few questions about
QEMU on x64.


   1. Is it possible for the QEMU-x86-64 GDB Server to send the full set of
   x64 system registers (whether they are included in a separated system xml
   file or as part of the core registers xml file)?
  - e.g. System registers missing from i386-64bit.xml file

  DWORD64 IDTBase;
  DWORD64 IDTLimit;
  DWORD64 GDTBase;
  DWORD64 GDTLimit;
  DWORD SelLDT;
  SEG64_DESC_INFO SegLDT;
  DWORD SelTSS;
  SEG64_DESC_INFO SegTSS;
  2. How can I access x64 MSR registers by using the QEMU-x86-64 GDB
   server?
  - #define MSR_EFER 0xc080 // extended function enable register
  #define MSR_STAR 0xc081 // system call selectors
  #define MSR_LSTAR 0xc082 // system call 64-bit entry
  #define MSR_CSTAR 0xc083 // system call 32-bit entry
   3. Going off of #2 - can you access it via reading GDB memory command?
   if not - is there any plan to support reading/writing to MSRs via
   QEMU-x86-64 GDB server?


Thank you for taking time to answer our questions! :)

-Christopher
LinkedIn <https://www.linkedin.com/in/ctcaulfield/> | Twitter
<https://twitter.com/ctcaulfield>

Re: [Qemu-devel] run qemu on x64 system ( ARCH=i386 or ARCH=x86-64) and on x86 system

[Marwa Hamza]

it shows:
-rwxr-xr-x 1 root root 265848 يول 18  2014 /sbin/init

2016-04-03 21:13 GMT+01:00 Marwa Hamza :

> it shows:
> -rwxr-xr-x 1 root root 265848 يول 18  2014 /sbin/init
>
>
> 2016-04-03 20:49 GMT+01:00 Marwa Hamza :
>
>> the output of this command  > ./i386-softmmu/qemu-system-i386 -M pc
>> -kernel
>> >
>> /home/marwa/Bureau/lauterbach/i386_qemu/linux-4.1.18/arch/i386/boot/bzImage
>> > -initrd
>> /home/marwa/Bureau/lauterbach/i386_qemu/busybox-1.21.0/rootfs.img.gz
>> > -append “root=/dev/ram rdinit=/sbin/init”
>> >
>> starting init :/sbin/init exists but couldn't execute it (error -8)
>> starting init : /bin/sh exists but couldn't execute it (error -8)
>> kernel panic not syncing : no working init found , try passing init=
>> option to kernel
>>
>> 2016-04-03 19:38 GMT+01:00 Pranith Kumar :
>>
>>> On Sun, Apr 3, 2016 at 9:50 AM, Marwa Hamza 
>>> wrote:
>>>
>>> > ./i386-softmmu/qemu-system-i386 -M pc -kernel
>>> >
>>> /home/marwa/Bureau/lauterbach/i386_qemu/linux-4.1.18/arch/i386/boot/bzImage
>>> > -initrd
>>> /home/marwa/Bureau/lauterbach/i386_qemu/busybox-1.21.0/rootfs.img.gz
>>> > -append “root=/dev/ram rdinit=/sbin/init”
>>> >
>>>
>>> Can you post the output when you run this command? In particular, does
>>> the /sbin/init exist in the rootfs?
>>>
>>> --
>>> Pranith
>>>
>>
>>
>

Re: [Qemu-devel] run qemu on x64 system ( ARCH=i386 or ARCH=x86-64) and on x86 system

[Marwa Hamza]

it shows:
-rwxr-xr-x 1 root root 265848 يول 18  2014 /sbin/init


2016-04-03 20:49 GMT+01:00 Marwa Hamza :

> the output of this command  > ./i386-softmmu/qemu-system-i386 -M pc
> -kernel
> >
> /home/marwa/Bureau/lauterbach/i386_qemu/linux-4.1.18/arch/i386/boot/bzImage
> > -initrd
> /home/marwa/Bureau/lauterbach/i386_qemu/busybox-1.21.0/rootfs.img.gz
> > -append “root=/dev/ram rdinit=/sbin/init”
> >
> starting init :/sbin/init exists but couldn't execute it (error -8)
> starting init : /bin/sh exists but couldn't execute it (error -8)
> kernel panic not syncing : no working init found , try passing init=
> option to kernel
>
> 2016-04-03 19:38 GMT+01:00 Pranith Kumar :
>
>> On Sun, Apr 3, 2016 at 9:50 AM, Marwa Hamza 
>> wrote:
>>
>> > ./i386-softmmu/qemu-system-i386 -M pc -kernel
>> >
>> /home/marwa/Bureau/lauterbach/i386_qemu/linux-4.1.18/arch/i386/boot/bzImage
>> > -initrd
>> /home/marwa/Bureau/lauterbach/i386_qemu/busybox-1.21.0/rootfs.img.gz
>> > -append “root=/dev/ram rdinit=/sbin/init”
>> >
>>
>> Can you post the output when you run this command? In particular, does
>> the /sbin/init exist in the rootfs?
>>
>> --
>> Pranith
>>
>
>

Re: [Qemu-devel] run qemu on x64 system ( ARCH=i386 or ARCH=x86-64) and on x86 system

[Pranith Kumar]

On Sun, Apr 3, 2016 at 3:49 PM, Marwa Hamza  wrote:
> the output of this command  > ./i386-softmmu/qemu-system-i386 -M pc -kernel
>>
>> /home/marwa/Bureau/lauterbach/i386_qemu/linux-4.1.18/arch/i386/boot/bzImage
>> -initrd
>> /home/marwa/Bureau/lauterbach/i386_qemu/busybox-1.21.0/rootfs.img.gz
>> -append “root=/dev/ram rdinit=/sbin/init”
>>
> starting init :/sbin/init exists but couldn't execute it (error -8)
> starting init : /bin/sh exists but couldn't execute it (error -8)
> kernel panic not syncing : no working init found , try passing init= option
> to kernel
>

I don't think this is a qemu problem. From the error message it looks
like init in your busybox root image is not configured properly. I
would focus on finding why the init file is not able to
run(permissions, maybe?).


-- 
Pranith

Re: [Qemu-devel] run qemu on x64 system ( ARCH=i386 or ARCH=x86-64) and on x86 system

[Marwa Hamza]

the output of this command  > ./i386-softmmu/qemu-system-i386 -M pc -kernel
>
/home/marwa/Bureau/lauterbach/i386_qemu/linux-4.1.18/arch/i386/boot/bzImage
> -initrd
/home/marwa/Bureau/lauterbach/i386_qemu/busybox-1.21.0/rootfs.img.gz
> -append “root=/dev/ram rdinit=/sbin/init”
>
starting init :/sbin/init exists but couldn't execute it (error -8)
starting init : /bin/sh exists but couldn't execute it (error -8)
kernel panic not syncing : no working init found , try passing init= option
to kernel

2016-04-03 19:38 GMT+01:00 Pranith Kumar :

> On Sun, Apr 3, 2016 at 9:50 AM, Marwa Hamza 
> wrote:
>
> > ./i386-softmmu/qemu-system-i386 -M pc -kernel
> >
> /home/marwa/Bureau/lauterbach/i386_qemu/linux-4.1.18/arch/i386/boot/bzImage
> > -initrd
> /home/marwa/Bureau/lauterbach/i386_qemu/busybox-1.21.0/rootfs.img.gz
> > -append “root=/dev/ram rdinit=/sbin/init”
> >
>
> Can you post the output when you run this command? In particular, does
> the /sbin/init exist in the rootfs?
>
> --
> Pranith
>

Re: [Qemu-devel] run qemu on x64 system ( ARCH=i386 or ARCH=x86-64) and on x86 system

[Pranith Kumar]

On Sun, Apr 3, 2016 at 9:50 AM, Marwa Hamza  wrote:

> ./i386-softmmu/qemu-system-i386 -M pc -kernel
> /home/marwa/Bureau/lauterbach/i386_qemu/linux-4.1.18/arch/i386/boot/bzImage
> -initrd /home/marwa/Bureau/lauterbach/i386_qemu/busybox-1.21.0/rootfs.img.gz
> -append “root=/dev/ram rdinit=/sbin/init”
>

Can you post the output when you run this command? In particular, does
the /sbin/init exist in the rootfs?

-- 
Pranith

Re: [Qemu-devel] run qemu on x64 system ( ARCH=i386 or ARCH=x86-64) and on x86 system

[Marwa Hamza]

but i tried the same thing with arm arch ( file system made by busybox) and
i used sh shell and it worked well

2016-04-03 20:20 GMT+02:00 Pranith Kumar <bobby.pr...@gmail.com>:

> On Sun, Apr 3, 2016 at 9:50 AM, Marwa Hamza <marwahamz...@gmail.com>
> wrote:
> > hello , i tried to run qemu on x64 system ,
> >
> > those are steps that i followed
> > i compile the kernel 4.4.1 with arch =i386
> > i download busybox 1.21.0
> > make ARCH=i386 menuconfig
> > I checked the option to compile Busybox as a static executable
> > make ARCH=i386 install
> > cd _install
> > mkdir proc sys dev lib etc etc/init.d
> > gedit etc/inittab
> > ::sysinit:/etc/init.d/rcS
> > sudo chmod +x etc/inittab
> > sudo gedit etc/init.d/rcS
> > #!/bin/sh
>
> Can you try changing this line to: "#!/sbin/ash"?
>
> I am not sure busybox has sh shell installed or configured properly.
> That is what your error message is pointing to atleast.
>
>
> > starting init :/bin/sh exists but couldn’t execute it
> > kernel panic – not syncing no working init found
>
>
> Thanks!
> --
> Pranith
>

Re: [Qemu-devel] run qemu on x64 system ( ARCH=i386 or ARCH=x86-64) and on x86 system

[Pranith Kumar]

On Sun, Apr 3, 2016 at 9:50 AM, Marwa Hamza <marwahamz...@gmail.com> wrote:
> hello , i tried to run qemu on x64 system ,
>
> those are steps that i followed
> i compile the kernel 4.4.1 with arch =i386
> i download busybox 1.21.0
> make ARCH=i386 menuconfig
> I checked the option to compile Busybox as a static executable
> make ARCH=i386 install
> cd _install
> mkdir proc sys dev lib etc etc/init.d
> gedit etc/inittab
> ::sysinit:/etc/init.d/rcS
> sudo chmod +x etc/inittab
> sudo gedit etc/init.d/rcS
> #!/bin/sh

Can you try changing this line to: "#!/sbin/ash"?

I am not sure busybox has sh shell installed or configured properly.
That is what your error message is pointing to atleast.


> starting init :/bin/sh exists but couldn’t execute it
> kernel panic – not syncing no working init found


Thanks!
-- 
Pranith

[Qemu-devel] run qemu on x64 system ( ARCH=i386 or ARCH=x86-64) and on x86 system

[Marwa Hamza]

hello , i tried to run qemu on x64 system ,

those are steps that i followed
i compile the kernel 4.4.1 with arch =i386
i download busybox 1.21.0
make ARCH=i386 menuconfig
I checked the option to compile Busybox as a static executable
make ARCH=i386 install
cd _install
mkdir proc sys dev lib etc etc/init.d
gedit etc/inittab
::sysinit:/etc/init.d/rcS
sudo chmod +x etc/inittab
sudo gedit etc/init.d/rcS
#!/bin/sh
echo “hello” // hello display when starting the qemu
mount -t proc none /proc
mount -t sysfs none /sys
/sbin/mdev -s
sudo chmod +x _install/etc/init.d/rcS
find . | cpio -o –format=newc > ../rootfs.img
cd ..
gzip -c rootfs.img > rootfs.img.gz
./i386-softmmu/qemu-system-i386 -M pc -kernel
/home/marwa/Bureau/lauterbach/i386_qemu/linux-4.1.18/arch/i386/boot/bzImage
-initrd /home/marwa/Bureau/lauterbach/i386_qemu/busybox-1.21.0/rootfs.img.gz
-append “root=/dev/ram rdinit=/sbin/init”

i have tried this command too

./i386-softmmu/qemu-system-i386 -M pc -kernel
/home/marwa/Bureau/lauterbach/i386_qemu/linux-4.1.18/arch/i386/boot/bzImage
-initrd /home/marwa/Bureau/lauterbach/i386_qemu/busybox-1.21.0/rootfs.img.gz
-append “root=/dev/ram rdinit=/bin/sh”
but i got this msg in qemu ‘shell
starting init :/bin/sh exists but couldn’t execute it
kernel panic – not syncing no working init found

should i work with another file system ? or create a new one , I got the
same error with x86 , , any one please can help me to get qemu working
perfectly
thanks