[Bug 218339] kernel goes unresponsive if single-stepping over an instruction which writes to an address for which a hardware read/write watchpoint has been set

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=218339

Yao Yuan (yaoyuan0329@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yaoyuan0329@gmail.com

--- Comment #3 from Yao Yuan (yaoyuan0329@gmail.com) ---
Hi,

I tried on my side but can't reproducce it, logs below. Any steps I missed ?

(gdb) b *0x00007ffff7fe4048                                                     
Breakpoint 1 at 0x7ffff7fe4048: file ./elf/rtld.c, line 527.                    
(gdb) c                                                                         
Continuing.                                                                     

Breakpoint 1, 0x00007ffff7fe4048 in _dl_start (arg=0x7fffffffe510) at
./elf/rtld.c:527                                                                
527     in ./elf/rtld.c                                                         
(gdb) disassemble                                                               
Dump of assembler code for function _dl_start:                                  
   0x00007ffff7fe4030 <+0>:     endbr64                                         
   0x00007ffff7fe4034 <+4>:     push   %rbp                                     
   0x00007ffff7fe4035 <+5>:     mov    %rsp,%rbp                                
   0x00007ffff7fe4038 <+8>:     push   %r15                                     
   0x00007ffff7fe403a <+10>:    push   %r14                                     
   0x00007ffff7fe403c <+12>:    push   %r13                                     
   0x00007ffff7fe403e <+14>:    push   %r12                                     
   0x00007ffff7fe4040 <+16>:    push   %rbx                                     
   0x00007ffff7fe4041 <+17>:    sub    $0x88,%rsp                               
=> 0x00007ffff7fe4048 <+24>:    mov    %rdi,-0x78(%rbp)                         
   0x00007ffff7fe404c <+28>:    rdtsc                                           
(gdb) x/16xb $rbp-0x78                                                          
0x7fffffffe488: 0x00    0x00    0x00    0x00    0x00    0x00    0x00    0x00    
0x7fffffffe490: 0x00    0x00    0x00    0x00    0x00    0x00    0x00    0x00    
(gdb) awatch *0x7fffffffe488                                                    
Hardware access (read/write) watchpoint 2: *0x7fffffffe488                      
(gdb) stepi                                                                     

Hardware access (read/write) watchpoint 2: *0x7fffffffe488                      

Old value = 0                                                                   
New value = -6896                                                               
0x00007ffff7fe404c in rtld_timer_start (var=0x7ffff7ffcaa0 <start_time>) at
./elf/rtld.c:85                                                                 
85      in ./elf/rtld.c     


the guest kernel runs properly after above steps inside guest.

My configure:
Host: stable kernel v6.6.8 commit 4c9646a796d66a2d81871a694e88e19a38b115a7
QEMU: v8.1.1 commit 6bb4a8a47a43f35a345f107227fcd6abed59e62c
Guest kernel: kvm tree tags/kvm-6.8-1 commit
1c6d984f523f67ecfad1083bb04c55d91977bb15

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