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broken on 32-bit kernels #33

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chrf01 opened this issue May 3, 2024 · 4 comments
Open

broken on 32-bit kernels #33

chrf01 opened this issue May 3, 2024 · 4 comments

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@chrf01
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chrf01 commented May 3, 2024 •
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broken on 32-bit x86 kernel

pwndbg> pt
Cannot get qemu-system pid Unknown arch. Message: The target architecture is set to "auto" (currently "i386").
@martinradev
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Thanks for the report

Can you please share this info:

qemu version
launch command
kernel version

@chrf01
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chrf01 commented May 3, 2024

Oh yeah sorry:

kernel version: 4.4.195
qemu version: 9.0.0
Launch command: qemu-system-i386 -kernel images/vmlinuz-4.4.195-i386 -initrd build/initramfs-x86.cpio.gz -nographic -append "console=ttyS0" -enable-kvm -s -S

but i guess it should fail on all kernels running with qemu-system-i386 because we dont check for "i386" in show architecture command

martinradev added a commit that referenced this issue May 4, 2024
@martinradev
x86: fix failure to determine arch
f79d126 
This patch fixes the failure to discover the arch type
when the VM is started via qemu-system-i386.

Two issues are fixed:
- The patch adds a check for the string "i386" in the qemu arch
  string to determine if this is an x86 machine. The x86 backend
  further determines what x86 mode is enabled by reading MSRs.
- The patch updates the code for determining if long mode is
  enabled to expect that reading the EFER MSR may fail. This failure
  can happen when the VM machine type is 32-bit - e.g. qemu-system-i386
  is used.

Issue #33
martinradev added a commit that referenced this issue May 4, 2024
@martinradev
x86: add regression test for issue 33
29ade5b 
This patch adds an "i386" backend that allows launching
an x86-32 VM via the qemu-system-i386 program. This is
test necessary to ensure that gdb-pt-dump correctly
determines that the VM is an x86 VM if the target arch
is i386.

For the kernel, the kolibri image is used.

Issue #33
@martinradev
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@chrf01

Could you please check if #34 works for you?

I tried it locally with an x86 kolibri image.

@chrf01
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chrf01 commented May 5, 2024

@chrf01

Could you please check if #34 works for you?

I tried it locally with an x86 kolibri image.

fails at PML4_Entry.__init__() now.
TypeError: PML4_Entry.__init__() missing 1 required positional argument: 'index'

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@martinradev @chrf01