Re: KASAN vs. boot-time switching between 4- and 5-level paging

[Kirill A. Shutemov]

On Mon, Jul 10, 2017 at 05:30:38PM -0700, Andy Lutomirski wrote:
> On Mon, Jul 10, 2017 at 2:24 PM, Kirill A. Shutemov
> <kirill@xxxxxxxxxxxxx> wrote:
> > On Mon, Jul 10, 2017 at 01:07:13PM -0700, Andy Lutomirski wrote:
> >> Can you give the disassembly of the backtrace lines?  Blaming the
> >> .endr doesn't make much sense to me.
> >
> > I don't have backtrace. It's before printk() is functional. I only see
> > triple fault and reboot.
> >
> > I had to rely on qemu tracing and gdb.
> 
> Can you ask GDB or objtool to disassemble around those addresses?  Can
> you also attach the big dump that QEMU throws out that shows register
> state?  In particular, CR2, CR3, and CR4 could be useful.

The last three execptions:

check_exception old: 0xffffffff new 0xe, cr2: 0xffffffff7ffffff8, rip: 0xffffffff84bb3036
RAX=00000000ffffffff RBX=ffffffff800000d8 RCX=ffffffff84be4021 RDX=dffffc0000000000
RSI=0000000000000006 RDI=ffffffff84c57000 RBP=ffffffff800000c8 RSP=ffffffff80000000
R8 =6d756e2032616476 R9 =2f7665642f3d746f R10=6f72203053797474 R11=3d656c6f736e6f63
R12=0000000000000006 R13=000000003fffb000 R14=ffffffff82a07ed8 R15=000000000140008e
RIP=ffffffff84bb3036 RFL=00000006 [-----P-] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 0000000000000000 00000000 00000000
CS =0010 0000000000000000 ffffffff 00af9b00 DPL=0 CS64 [-RA]
SS =0000 0000000000000000 ffffffff 00c09300 DPL=0 DS   [-WA]
DS =0000 0000000000000000 00000000 00000000
FS =0000 0000000000000000 00000000 00000000
GS =0000 ffffffff84b8f000 00000000 00000000
LDT=0000 0000000000000000 0000ffff 00008200 DPL=0 LDT
TR =0000 0000000000000000 0000ffff 00008b00 DPL=0 TSS64-busy
GDT=     ffffffff84ba1000 0000007f
IDT=     ffffffff84d92000 00000fff
CR0=80050033 CR2=ffffffff7ffffff8 CR3=0000000009c58000 CR4=000010a0
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000d01

check_exception old: 0xe new 0xe, cr2: 0xffffffff7ffffff8, rip: 0xffffffff84bb3141
RAX=00000000ffffffff RBX=ffffffff800000d8 RCX=ffffffff84be4021 RDX=dffffc0000000000
RSI=0000000000000006 RDI=ffffffff84c57000 RBP=ffffffff800000c8 RSP=ffffffff80000000
R8 =6d756e2032616476 R9 =2f7665642f3d746f R10=6f72203053797474 R11=3d656c6f736e6f63
R12=0000000000000006 R13=000000003fffb000 R14=ffffffff82a07ed8 R15=000000000140008e
RIP=ffffffff84bb3141 RFL=00000006 [-----P-] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 0000000000000000 00000000 00000000
CS =0010 0000000000000000 ffffffff 00af9b00 DPL=0 CS64 [-RA]
SS =0000 0000000000000000 ffffffff 00c09300 DPL=0 DS   [-WA]
DS =0000 0000000000000000 00000000 00000000
FS =0000 0000000000000000 00000000 00000000
GS =0000 ffffffff84b8f000 00000000 00000000
LDT=0000 0000000000000000 0000ffff 00008200 DPL=0 LDT
TR =0000 0000000000000000 0000ffff 00008b00 DPL=0 TSS64-busy
GDT=     ffffffff84ba1000 0000007f
IDT=     ffffffff84d92000 00000fff
CR0=80050033 CR2=ffffffff7ffffff8 CR3=0000000009c58000 CR4=000010a0
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000d01

check_exception old: 0x8 new 0xe, cr2: 0xffffffff7ffffff8, rip: 0xffffffff84bb3141
RAX=00000000ffffffff RBX=ffffffff800000d8 RCX=ffffffff84be4021 RDX=dffffc0000000000
RSI=0000000000000006 RDI=ffffffff84c57000 RBP=ffffffff800000c8 RSP=ffffffff80000000
R8 =6d756e2032616476 R9 =2f7665642f3d746f R10=6f72203053797474 R11=3d656c6f736e6f63
R12=0000000000000006 R13=000000003fffb000 R14=ffffffff82a07ed8 R15=000000000140008e
RIP=ffffffff84bb3141 RFL=00000006 [-----P-] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 0000000000000000 00000000 00000000
CS =0010 0000000000000000 ffffffff 00af9b00 DPL=0 CS64 [-RA]
SS =0000 0000000000000000 ffffffff 00c09300 DPL=0 DS   [-WA]
DS =0000 0000000000000000 00000000 00000000
FS =0000 0000000000000000 00000000 00000000
GS =0000 ffffffff84b8f000 00000000 00000000
LDT=0000 0000000000000000 0000ffff 00008200 DPL=0 LDT
TR =0000 0000000000000000 0000ffff 00008b00 DPL=0 TSS64-busy
GDT=     ffffffff84ba1000 0000007f
IDT=     ffffffff84d92000 00000fff
CR0=80050033 CR2=ffffffff7ffffff8 CR3=0000000009c58000 CR4=000010a0
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000d01
Triple fault

Dump of assembler code for function early_idt_handler_array:
   0xffffffff84bb3000 <+0>:     pushq  $0x0
   0xffffffff84bb3002 <+2>:     pushq  $0x0
   0xffffffff84bb3004 <+4>:     jmpq   0xffffffff84bb3120 <early_idt_handler_common>
   0xffffffff84bb3009 <+9>:     pushq  $0x0
   0xffffffff84bb300b <+11>:    pushq  $0x1
   0xffffffff84bb300d <+13>:    jmpq   0xffffffff84bb3120 <early_idt_handler_common>
   0xffffffff84bb3012 <+18>:    pushq  $0x0
   0xffffffff84bb3014 <+20>:    pushq  $0x2
   0xffffffff84bb3016 <+22>:    jmpq   0xffffffff84bb3120 <early_idt_handler_common>
   0xffffffff84bb301b <+27>:    pushq  $0x0
   0xffffffff84bb301d <+29>:    pushq  $0x3
   0xffffffff84bb301f <+31>:    jmpq   0xffffffff84bb3120 <early_idt_handler_common>
   0xffffffff84bb3024 <+36>:    pushq  $0x0
   0xffffffff84bb3026 <+38>:    pushq  $0x4
   0xffffffff84bb3028 <+40>:    jmpq   0xffffffff84bb3120 <early_idt_handler_common>
   0xffffffff84bb302d <+45>:    pushq  $0x0
   0xffffffff84bb302f <+47>:    pushq  $0x5
   0xffffffff84bb3031 <+49>:    jmpq   0xffffffff84bb3120 <early_idt_handler_common>
=> 0xffffffff84bb3036 <+54>:    pushq  $0x0
   0xffffffff84bb3038 <+56>:    pushq  $0x6
   0xffffffff84bb303a <+58>:    jmpq   0xffffffff84bb3120 <early_idt_handler_common>
   0xffffffff84bb303f <+63>:    pushq  $0x0
   0xffffffff84bb3041 <+65>:    pushq  $0x7
   0xffffffff84bb3043 <+67>:    jmpq   0xffffffff84bb3120 <early_idt_handler_common>
   0xffffffff84bb3048 <+72>:    pushq  $0x8
   0xffffffff84bb304a <+74>:    jmpq   0xffffffff84bb3120 <early_idt_handler_common>
   0xffffffff84bb304f <+79>:    int3
   0xffffffff84bb3050 <+80>:    int3
...

-- 
 Kirill A. Shutemov