Re: md-raid 6.11.8 page fault oops

[Genes Lists <lists@xxxxxxxxxxxx>]

On Tue, 2024-11-19 at 17:04 +0530, Ojaswin Mujoo wrote:

...

 (gdb) list *(rb_first+0x13)

  0xffffffff81de1af3 is in rb_first (lib/rbtree.c:473).

  468       struct rb_node  *n;

  469

  470       n = root->rb_node;

  471       if (!n)

  472           return NULL;

  473       while (n->rb_left)

Now this looks strange, we already make sure n is not NULL and then

somehow this line ends up in

 BUG: unable to handle page fault for address: 0000000000200010

Now, decoding the code with an x86 vmlinux, I see the fauling opcode

faulting:

Code starting with the faulting instruction

===========================================

   0:   0f 1f 80 00 00 00 00    nopl   0x0(%rax)

   7:   90                      nop

   8:   90                      nop

   9:   90                      nop

   a:   90                      nop

   b:   90                      nop

   c:   90                      nop

   d:   90                      nop

   e:   90                      nop

   f:   90                      nop

Now RAX is 0x200000 but I don't think the nopl instruction should have resulted

in a mem access AFA my limited understanding of x86 ISA goes.

I also don't see nopl in my vmlinux in rb_first, my binary being compiled with

gcc 8.5. Are you by chance using clang or higher version or higher optimization in gcc.

Regards,

ojaswin

I am using Arch toolchain with 

   gcc 14.2.1+r134+gab884fffe3fc-1

I do not set CFLAGS_KERNEL  so compile options are the default.

thanks

gene

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