[Qemu-devel] [Bug 1699867] [NEW] x86_64 qemu crashes at far call into long-mode

[Qemu-devel] [Bug 1699867] [NEW] x86_64 qemu crashes at far call into long-mode

[Anatol Pomozov]

Public bug reported:

I am experimenting with this OS https://github.com/phil-opp/blog_os and
spotted a weird behavior with qemu.

I am looking at code that does transition from 32bit mode to 64bit mode.
Right now it does 'jmp $SELECTOR,64bitfunction'. https://github.com
/phil-
opp/blog_os/blob/557c6a58ea11e31685b9d014d307002d64df5c22/src/arch/x86_64/boot.asm#L32

This code works fine with qemu/kvm/vmware.

To transition from 32 to 64 bit code it is possible to use 'call'
operation. So I am trying to replace that code with 'call
$SELECTOR,64bitfunction'. It works fine with kvm and wmware. But it
fails with Qemu emulation. See the interrup debug log attached. qemu
crashes at 10302c (far call mnemonic).


  103016:       e8 18 00 00 00          callq  103033 <set_up_page_tables>
  10301b:       e8 5c 00 00 00          callq  10307c <enable_paging>
  103020:       e8 ec 00 00 00          callq  103111 <set_up_SSE>
  103025:       0f 01 15 28 00 10 00    lgdt   0x100028(%rip)        # 203054 <GCC_except_table2+0xdb5f8>
  10302c:       9a                      (bad)  
  10302d:       40 31 10                rex xor %edx,(%rax)
  103030:       00 08                   add    %cl,(%rax)


As the code works at hardware I expect it to work with qemu. Thus current qemu behavior looks like a bug.

** Affects: qemu
     Importance: Undecided
         Status: New

** Attachment added: "Debug log for qemu crash at far call"
   https://bugs.launchpad.net/bugs/1699867/+attachment/4901095/+files/debug.log

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Title:
  x86_64 qemu crashes at far call into long-mode

Status in QEMU:
  New

Bug description:
  I am experimenting with this OS https://github.com/phil-opp/blog_os
  and spotted a weird behavior with qemu.

  I am looking at code that does transition from 32bit mode to 64bit
  mode. Right now it does 'jmp $SELECTOR,64bitfunction'.
  https://github.com/phil-
  opp/blog_os/blob/557c6a58ea11e31685b9d014d307002d64df5c22/src/arch/x86_64/boot.asm#L32

  This code works fine with qemu/kvm/vmware.

  To transition from 32 to 64 bit code it is possible to use 'call'
  operation. So I am trying to replace that code with 'call
  $SELECTOR,64bitfunction'. It works fine with kvm and wmware. But it
  fails with Qemu emulation. See the interrup debug log attached. qemu
  crashes at 10302c (far call mnemonic).

  
    103016:       e8 18 00 00 00          callq  103033 <set_up_page_tables>
    10301b:       e8 5c 00 00 00          callq  10307c <enable_paging>
    103020:       e8 ec 00 00 00          callq  103111 <set_up_SSE>
    103025:       0f 01 15 28 00 10 00    lgdt   0x100028(%rip)        # 203054 <GCC_except_table2+0xdb5f8>
    10302c:       9a                      (bad)  
    10302d:       40 31 10                rex xor %edx,(%rax)
    103030:       00 08                   add    %cl,(%rax)

  
  As the code works at hardware I expect it to work with qemu. Thus current qemu behavior looks like a bug.

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[Bug 1699867] Re: x86_64 qemu crashes at far call into long-mode

[Thomas Huth]

The QEMU project is currently considering to move its bug tracking to another system. For this we need to know which bugs are still valid and which could be closed already. Thus we are setting older bugs to "Incomplete" now.
If you still think this bug report here is valid, then please switch the state back to "New" within the next 60 days, otherwise this report will be marked as "Expired". Or mark it as "Fix Released" if the problem has been solved with a newer version of QEMU already. Thank you and sorry for the inconvenience.

** Changed in: qemu
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1699867

Title:
  x86_64 qemu crashes at far call into long-mode

Status in QEMU:
  Incomplete

Bug description:
  I am experimenting with this OS https://github.com/phil-opp/blog_os
  and spotted a weird behavior with qemu.

  I am looking at code that does transition from 32bit mode to 64bit
  mode. Right now it does 'jmp $SELECTOR,64bitfunction'.
  https://github.com/phil-
  opp/blog_os/blob/557c6a58ea11e31685b9d014d307002d64df5c22/src/arch/x86_64/boot.asm#L32

  This code works fine with qemu/kvm/vmware.

  To transition from 32 to 64 bit code it is possible to use 'call'
  operation. So I am trying to replace that code with 'call
  $SELECTOR,64bitfunction'. It works fine with kvm and wmware. But it
  fails with Qemu emulation. See the interrup debug log attached. qemu
  crashes at 10302c (far call mnemonic).

  
    103016:       e8 18 00 00 00          callq  103033 <set_up_page_tables>
    10301b:       e8 5c 00 00 00          callq  10307c <enable_paging>
    103020:       e8 ec 00 00 00          callq  103111 <set_up_SSE>
    103025:       0f 01 15 28 00 10 00    lgdt   0x100028(%rip)        # 203054 <GCC_except_table2+0xdb5f8>
    10302c:       9a                      (bad)  
    10302d:       40 31 10                rex xor %edx,(%rax)
    103030:       00 08                   add    %cl,(%rax)

  
  As the code works at hardware I expect it to work with qemu. Thus current qemu behavior looks like a bug.

To manage notifications about this bug go to:
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[Bug 1699867] Re: x86_64 qemu crashes at far call into long-mode

[Launchpad Bug Tracker]

[Expired for QEMU because there has been no activity for 60 days.]

** Changed in: qemu
       Status: Incomplete => Expired

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You received this bug notification because you are a member of qemu-
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https://bugs.launchpad.net/bugs/1699867

Title:
  x86_64 qemu crashes at far call into long-mode

Status in QEMU:
  Expired

Bug description:
  I am experimenting with this OS https://github.com/phil-opp/blog_os
  and spotted a weird behavior with qemu.

  I am looking at code that does transition from 32bit mode to 64bit
  mode. Right now it does 'jmp $SELECTOR,64bitfunction'.
  https://github.com/phil-
  opp/blog_os/blob/557c6a58ea11e31685b9d014d307002d64df5c22/src/arch/x86_64/boot.asm#L32

  This code works fine with qemu/kvm/vmware.

  To transition from 32 to 64 bit code it is possible to use 'call'
  operation. So I am trying to replace that code with 'call
  $SELECTOR,64bitfunction'. It works fine with kvm and wmware. But it
  fails with Qemu emulation. See the interrup debug log attached. qemu
  crashes at 10302c (far call mnemonic).

  
    103016:       e8 18 00 00 00          callq  103033 <set_up_page_tables>
    10301b:       e8 5c 00 00 00          callq  10307c <enable_paging>
    103020:       e8 ec 00 00 00          callq  103111 <set_up_SSE>
    103025:       0f 01 15 28 00 10 00    lgdt   0x100028(%rip)        # 203054 <GCC_except_table2+0xdb5f8>
    10302c:       9a                      (bad)  
    10302d:       40 31 10                rex xor %edx,(%rax)
    103030:       00 08                   add    %cl,(%rax)

  
  As the code works at hardware I expect it to work with qemu. Thus current qemu behavior looks like a bug.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1699867/+subscriptions