qemu "info registers" doesn't match the one I saw from kgdb?

qemu "info registers" doesn't match the one I saw from kgdb?

[Neo Jia]

hi,

I am seeing something different between "info registers" from qemu
monitor window vs. kgdb. This is a 32-bit Linux guest running on
KVM-84.

When I just break into the guest kernel with kgdb, I tried the
follwoing commands:

(qemu) info registers
EAX=00010060 EBX=c0471e3c ECX=00000000 EDX=000002fd
ESI=000002fd EDI=c04c5d20 EBP=c0471ddc ESP=c0471ddc
EIP=c021129b EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =007b 00000000 ffffffff 00c0f300
CS =0060 00000000 ffffffff 00c09b00
SS =0068 00000000 ffffffff 00c09300
DS =007b 00000000 ffffffff 00c0f300
FS =0000 00000000 ffffffff 00000000
GS =0000 00000000 ffffffff 00000000
LDT=0000 00000000 ffffffff 00000000
TR =0000 00000000 0000ffff 00008b00
GDT=     c0407a80 000000ff
IDT=     c0464000 000007ff
CR0=80050033 CR2=00000000 CR3=004aa000 CR4=00000000
DR0=00000000 DR1=00000000 DR2=00000000 DR3=00000000
DR6=ffff0ff0 DR7=00000400
FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00000000
FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
XMM00=00000000000000000000000000000000 XMM01=00000000000000000000000000000000
XMM02=00000000000000000000000000000000 XMM03=00000000000000000000000000000000
XMM04=00000000000000000000000000000000 XMM05=00000000000000000000000000000000
XMM06=00000000000000000000000000000000 XMM07=00000000000000000000000000000000

But from Windbg, I got:

(gdb) info registers
eax            0x0      0x0
ecx            0xc      0xc
edx            0x0      0x0
ebx            0x0      0x0
esp            0xc0471f14       0xc0471f14
ebp            0xc0471fc0       0xc0471fc0
esi            0xc04ac07a       0xc04ac07a
edi            0xc04ad1f9       0xc04ad1f9
eip            0xc047a853       0xc047a853 <setup_arch+1036>
eflags         0x86     [ PF SF ]
cs             0x60     0x60
ss             0x68     0x68
ds             0xc049007b       0xc049007b
es             0x7b     0x7b
fs             0xffff   0xffff
gs             0xffff   0xffff

So, which one is correct? Do we still maintain the "info registers" on qemu?

Thanks,
Neo

-- 
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probably today we haven't the technology we are using!

Re: qemu "info registers" doesn't match the one I saw from kgdb?

[Jan Kiszka]

Neo Jia wrote:
> hi,
> 
> I am seeing something different between "info registers" from qemu
> monitor window vs. kgdb. This is a 32-bit Linux guest running on
> KVM-84.
> 
> When I just break into the guest kernel with kgdb, I tried the
> follwoing commands:
> 
> (qemu) info registers
> EAX=00010060 EBX=c0471e3c ECX=00000000 EDX=000002fd
> ESI=000002fd EDI=c04c5d20 EBP=c0471ddc ESP=c0471ddc
> EIP=c021129b EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
> ES =007b 00000000 ffffffff 00c0f300
> CS =0060 00000000 ffffffff 00c09b00
> SS =0068 00000000 ffffffff 00c09300
> DS =007b 00000000 ffffffff 00c0f300
> FS =0000 00000000 ffffffff 00000000
> GS =0000 00000000 ffffffff 00000000
> LDT=0000 00000000 ffffffff 00000000
> TR =0000 00000000 0000ffff 00008b00
> GDT=     c0407a80 000000ff
> IDT=     c0464000 000007ff
> CR0=80050033 CR2=00000000 CR3=004aa000 CR4=00000000
> DR0=00000000 DR1=00000000 DR2=00000000 DR3=00000000
> DR6=ffff0ff0 DR7=00000400
> FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00000000
> FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
> FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
> FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
> FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
> XMM00=00000000000000000000000000000000 XMM01=00000000000000000000000000000000
> XMM02=00000000000000000000000000000000 XMM03=00000000000000000000000000000000
> XMM04=00000000000000000000000000000000 XMM05=00000000000000000000000000000000
> XMM06=00000000000000000000000000000000 XMM07=00000000000000000000000000000000
> 
> But from Windbg, I got:
> 
> (gdb) info registers
> eax            0x0      0x0
> ecx            0xc      0xc
> edx            0x0      0x0
> ebx            0x0      0x0
> esp            0xc0471f14       0xc0471f14
> ebp            0xc0471fc0       0xc0471fc0
> esi            0xc04ac07a       0xc04ac07a
> edi            0xc04ad1f9       0xc04ad1f9
> eip            0xc047a853       0xc047a853 <setup_arch+1036>
> eflags         0x86     [ PF SF ]
> cs             0x60     0x60
> ss             0x68     0x68
> ds             0xc049007b       0xc049007b
> es             0x7b     0x7b
> fs             0xffff   0xffff
> gs             0xffff   0xffff
> 
> So, which one is correct? Do we still maintain the "info registers" on qemu?

Yes, we do maintain them (for now only in the kvm tree, upstream is yet
lacking a few patches). But you have to keep in mind that, when you take
a snapshot of the guest running inside Windbg via "info registers" (or
via the built-in gdbstub), you actually debug Windbg itself, no longer
the guest kernel code Windbg is interrupting. That's why you see
different EIP values...

Jan

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