absolute firmware path made relocatable in qemu 5.2.0

absolute firmware path made relocatable in qemu 5.2.0

[Dave]

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Hi,

Is seem that absolute firmwarepath compilation option is converted  to 
relocatable in 5.2.0 qemu.

# QEMU configure log Tue 12 Jan 14:46:41 GST 2021
# Configured with: '../configure' '--prefix=/usr' 
'--sysconfdir=/etc/qemu' '--disable-bochs'  
'*--firmwarepath=/usr/share/qemu:/usr/share/qemu-firmware*'
#

And trying to run the executable

    bash-5.1# ./qemu-system-x86_64
    qemu: could not load PC BIOS 'bios-256k.bin'

If i print out the resultant binary paths

    bash-5.1# ./qemu-system-x86_64 -L help
    /root/qemu/../share/qemu
    /root/qemu/../share/qemu-firmware

So there is no way to have a absolute path for firmware /bios and all 
qemu's that we test need to be at the right directory nesting to find 
firmware, bios etc or else they all need their own duplicate firmware 
files. Firmware path needs to honor the absolute paths i believe.

Comments ?

Dave


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Re: absolute firmware path made relocatable in qemu 5.2.0

[Paolo Bonzini]

On 12/01/21 15:05, Dave wrote:
> Is seem that absolute firmwarepath compilation option is converted  to 
> relocatable in 5.2.0 qemu.
> 
> # QEMU configure log Tue 12 Jan 14:46:41 GST 2021
> # Configured with: '../configure' '--prefix=/usr' 
> '--sysconfdir=/etc/qemu' '--disable-bochs'  
> '*--firmwarepath=/usr/share/qemu:/usr/share/qemu-firmware*'
> #

Yes, all paths within the prefix are relocated.  The workaround is 
simply to configure the intended prefix with configure:

./configure --prefix=/root/qemu ...

or if you don't know the prefix:

./configure --prefix=/nonexistent ...

Because /usr/share/qemu and /usr/share/qemu-firmware are outside /usr, 
they will be treated as absolute just like /etc/qemu.

Thanks,

Paolo

> And trying to run the executable
> 
>     bash-5.1# ./qemu-system-x86_64
>     qemu: could not load PC BIOS 'bios-256k.bin'
> 
> If i print out the resultant binary paths
> 
>     bash-5.1# ./qemu-system-x86_64 -L help
>     /root/qemu/../share/qemu
>     /root/qemu/../share/qemu-firmware
> 
> So there is no way to have a absolute path for firmware /bios and all 
> qemu's that we test need to be at the right directory nesting to find 
> firmware, bios etc or else they all need their own duplicate firmware 
> files. Firmware path needs to honor the absolute paths i believe.
> 

Re: absolute firmware path made relocatable in qemu 5.2.0

[Dave]

Hi Paolo,

While this (option 2) partially works, it will still search for 
/nonexistent/libexec/qemu-bridge-helper for example so seems that some 
paths are still absolute and some relative.

To explain, what we are expecting that we compile one binary with the 
relevant options, test that and then it goes into production. If we 
compile with --prefix=/usr (it's final resting place will be /usr/bin) 
then everything works as expected once it is in production (since 
/usr/share/qemu, /usr/libexec, /etc/qemu exists as expected).  However 
when we are testing the binary in a directory /root/qemu/5.2.0 with 
--prefix=/usr it breaks since it converts the firmware and bios paths to 
/root/qemu/5.2.0/../share/qemu. This means we need to recompile twice 
with relevant prefixes since if i use --prefix=/nonexistent then we 
can't find the qemu-bridge-helper when the binary goes into production.

It would be nicer with the relocatable binary took some fixed paths from 
/etc/qemu.conf for the bridge-helper, firmware, bios, qemu-ifup/down.

thanks
Dave


On 12/01/2021 18:48, Paolo Bonzini wrote:
> On 12/01/21 15:05, Dave wrote:
>> Is seem that absolute firmwarepath compilation option is converted  to 
>> relocatable in 5.2.0 qemu.
>>
>> # QEMU configure log Tue 12 Jan 14:46:41 GST 2021
>> # Configured with: '../configure' '--prefix=/usr' 
>> '--sysconfdir=/etc/qemu' '--disable-bochs' 
>> '*--firmwarepath=/usr/share/qemu:/usr/share/qemu-firmware*'
>> #
> 
> Yes, all paths within the prefix are relocated.  The workaround is 
> simply to configure the intended prefix with configure:
> 
> ./configure --prefix=/root/qemu ...
> 
> or if you don't know the prefix:
> 
> ./configure --prefix=/nonexistent ...
> 
> Because /usr/share/qemu and /usr/share/qemu-firmware are outside /usr, 
> they will be treated as absolute just like /etc/qemu.
> 
> Thanks,
> 
> Paolo
> 
>> And trying to run the executable
>>
>>     bash-5.1# ./qemu-system-x86_64
>>     qemu: could not load PC BIOS 'bios-256k.bin'
>>
>> If i print out the resultant binary paths
>>
>>     bash-5.1# ./qemu-system-x86_64 -L help
>>     /root/qemu/../share/qemu
>>     /root/qemu/../share/qemu-firmware
>>
>> So there is no way to have a absolute path for firmware /bios and all 
>> qemu's that we test need to be at the right directory nesting to find 
>> firmware, bios etc or else they all need their own duplicate firmware 
>> files. Firmware path needs to honor the absolute paths i believe.
>>
> 

Re: absolute firmware path made relocatable in qemu 5.2.0

[Paolo Bonzini]

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Il mar 12 gen 2021, 17:48 Dave <dave@0bits.com> ha scritto:

> Hi Paolo,
>
> While this (option 2) partially works, it will still search for
> /nonexistent/libexec/qemu-bridge-helper for example so seems that some
> paths are still absolute and some relative.
>

Ok, that's a bug that can be fixed in 5.2.1. Are there other instances?


> To explain, what we are expecting that we compile one binary with the
> relevant options, test that and then it goes into production. If we
> compile with --prefix=/usr (it's final resting place will be /usr/bin)
> then everything works as expected once it is in production (since
> /usr/share/qemu, /usr/libexec, /etc/qemu exists as expected).  However
> when we are testing the binary in a directory /root/qemu/5.2.0 with
> --prefix=/usr it breaks since it converts the firmware and bios paths to
> /root/qemu/5.2.0/../share/qemu. This means we need to recompile twice
> with relevant prefixes since if i use --prefix=/nonexistent then we
> can't find the qemu-bridge-helper when the binary goes into production.
>
> It would be nicer with the relocatable binary took some fixed paths from
> /etc/qemu.conf for the bridge-helper, firmware, bios, qemu-ifup/down.
>
> thanks
> Dave
>
>
> On 12/01/2021 18:48, Paolo Bonzini wrote:
> > On 12/01/21 15:05, Dave wrote:
> >> Is seem that absolute firmwarepath compilation option is converted  to
> >> relocatable in 5.2.0 qemu.
> >>
> >> # QEMU configure log Tue 12 Jan 14:46:41 GST 2021
> >> # Configured with: '../configure' '--prefix=/usr'
> >> '--sysconfdir=/etc/qemu' '--disable-bochs'
> >> '*--firmwarepath=/usr/share/qemu:/usr/share/qemu-firmware*'
> >> #
> >
> > Yes, all paths within the prefix are relocated.  The workaround is
> > simply to configure the intended prefix with configure:
> >
> > ./configure --prefix=/root/qemu ...
> >
> > or if you don't know the prefix:
> >
> > ./configure --prefix=/nonexistent ...
> >
> > Because /usr/share/qemu and /usr/share/qemu-firmware are outside /usr,
> > they will be treated as absolute just like /etc/qemu.
> >
> > Thanks,
> >
> > Paolo
> >
> >> And trying to run the executable
> >>
> >>     bash-5.1# ./qemu-system-x86_64
> >>     qemu: could not load PC BIOS 'bios-256k.bin'
> >>
> >> If i print out the resultant binary paths
> >>
> >>     bash-5.1# ./qemu-system-x86_64 -L help
> >>     /root/qemu/../share/qemu
> >>     /root/qemu/../share/qemu-firmware
> >>
> >> So there is no way to have a absolute path for firmware /bios and all
> >> qemu's that we test need to be at the right directory nesting to find
> >> firmware, bios etc or else they all need their own duplicate firmware
> >> files. Firmware path needs to honor the absolute paths i believe.
> >>
> >
>
>

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Re: absolute firmware path made relocatable in qemu 5.2.0

[Dave]

Thanks Paola,

We are still in testing and that's the only thing we've uncovered so far 
with the new 5.2.0. I will post if the ops guys find anything else.

Dave

On 12/01/2021 20:53, Paolo Bonzini wrote:
> 
> 
> Il mar 12 gen 2021, 17:48 Dave <dave@0bits.com <mailto:dave@0bits.com>> 
> ha scritto:
> 
>     Hi Paolo,
> 
>     While this (option 2) partially works, it will still search for
>     /nonexistent/libexec/qemu-bridge-helper for example so seems that some
>     paths are still absolute and some relative.
> 
> 
> Ok, that's a bug that can be fixed in 5.2.1. Are there other instances?
> 
> 
>     To explain, what we are expecting that we compile one binary with the
>     relevant options, test that and then it goes into production. If we
>     compile with --prefix=/usr (it's final resting place will be /usr/bin)
>     then everything works as expected once it is in production (since
>     /usr/share/qemu, /usr/libexec, /etc/qemu exists as expected).  However
>     when we are testing the binary in a directory /root/qemu/5.2.0 with
>     --prefix=/usr it breaks since it converts the firmware and bios
>     paths to
>     /root/qemu/5.2.0/../share/qemu. This means we need to recompile twice
>     with relevant prefixes since if i use --prefix=/nonexistent then we
>     can't find the qemu-bridge-helper when the binary goes into production.
> 
>     It would be nicer with the relocatable binary took some fixed paths
>     from
>     /etc/qemu.conf for the bridge-helper, firmware, bios, qemu-ifup/down.
> 
>     thanks
>     Dave
> 
> 
>     On 12/01/2021 18:48, Paolo Bonzini wrote:
>      > On 12/01/21 15:05, Dave wrote:
>      >> Is seem that absolute firmwarepath compilation option is
>     converted  to
>      >> relocatable in 5.2.0 qemu.
>      >>
>      >> # QEMU configure log Tue 12 Jan 14:46:41 GST 2021
>      >> # Configured with: '../configure' '--prefix=/usr'
>      >> '--sysconfdir=/etc/qemu' '--disable-bochs'
>      >> '*--firmwarepath=/usr/share/qemu:/usr/share/qemu-firmware*'
>      >> #
>      >
>      > Yes, all paths within the prefix are relocated.  The workaround is
>      > simply to configure the intended prefix with configure:
>      >
>      > ./configure --prefix=/root/qemu ...
>      >
>      > or if you don't know the prefix:
>      >
>      > ./configure --prefix=/nonexistent ...
>      >
>      > Because /usr/share/qemu and /usr/share/qemu-firmware are outside
>     /usr,
>      > they will be treated as absolute just like /etc/qemu.
>      >
>      > Thanks,
>      >
>      > Paolo
>      >
>      >> And trying to run the executable
>      >>
>      >>     bash-5.1# ./qemu-system-x86_64
>      >>     qemu: could not load PC BIOS 'bios-256k.bin'
>      >>
>      >> If i print out the resultant binary paths
>      >>
>      >>     bash-5.1# ./qemu-system-x86_64 -L help
>      >>     /root/qemu/../share/qemu
>      >>     /root/qemu/../share/qemu-firmware
>      >>
>      >> So there is no way to have a absolute path for firmware /bios
>     and all
>      >> qemu's that we test need to be at the right directory nesting to
>     find
>      >> firmware, bios etc or else they all need their own duplicate
>     firmware
>      >> files. Firmware path needs to honor the absolute paths i believe.
>      >>
>      >
> 

Re: absolute firmware path made relocatable in qemu 5.2.0

[Paolo Bonzini]

On 12/01/21 18:04, Dave wrote:
> Thanks Paola,
> 
> We are still in testing and that's the only thing we've uncovered so far 
> with the new 5.2.0. I will post if the ops guys find anything else.

Hmm, that's weird though.  The path to the default bridge helper is 
relocated:

net/tap.c:        helper = default_helper = 
get_relocated_path(DEFAULT_BRIDGE_HELPER);

Paolo

Re: absolute firmware path made relocatable in qemu 5.2.0

[Dave]

This is my qemu binary compiled with --prefix=/nonexistent


bash-5.1# ./qemu-system-x86_64 -L help
/usr/share/qemu
/usr/share/qemu-firmware
/usr/src/sources/qemu-5.2.0/build/pc-bios

bash-5.1# ./qemu-system-x86_64 --help|grep helper
 
[,br=bridge][,helper=helper][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off]
                 use network helper 'helper' 
(default=/nonexistent/libexec/qemu-bridge-helper) to
-netdev bridge,id=str[,br=bridge][,helper=helper]
                 using the program 'helper 
(default=/nonexistent/libexec/qemu-bridge-helper)

See that it will call /nonexistent/libexec/qemu-bridge-helper by default.

Dave

On 12/01/2021 23:53, Paolo Bonzini wrote:
> On 12/01/21 18:04, Dave wrote:
>> Thanks Paola,
>>
>> We are still in testing and that's the only thing we've uncovered so 
>> far with the new 5.2.0. I will post if the ops guys find anything else.
> 
> Hmm, that's weird though.  The path to the default bridge helper is 
> relocated:
> 
> net/tap.c:        helper = default_helper = 
> get_relocated_path(DEFAULT_BRIDGE_HELPER);
> 
> Paolo
> 

Re: absolute firmware path made relocatable in qemu 5.2.0

[Paolo Bonzini]

On 13/01/21 08:51, Dave wrote:
> 
> [,br=bridge][,helper=helper][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off] 
> 
>                  use network helper 'helper' 
> (default=/nonexistent/libexec/qemu-bridge-helper) to
> -netdev bridge,id=str[,br=bridge][,helper=helper]
>                  using the program 'helper 
> (default=/nonexistent/libexec/qemu-bridge-helper)
> 
> See that it will call /nonexistent/libexec/qemu-bridge-helper by default.

Nice catch; fortunately, only the help is wrong.  That's not easy to fix 
but I'll see what I can do.

Paolo