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Date:      Thu, 18 Jan 2024 20:57:26 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 276426] amd64: microcode update caused a page fault trying to send data to the logger
Message-ID:  <bug-276426-227-xVfqNVNePm@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-276426-227@https.bugs.freebsd.org/bugzilla/>
References:  <bug-276426-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D276426

--- Comment #6 from John F. Carr <jfc@mit.edu> ---
The first crash is from AMD Excavator (Family 0x15) running 12.4.  That
processor is from 2015 and may not have SMAP.

The second crash is from AMD Zen 2 (Family 0x17) running 13.2.  That proces=
sor
is from 2020 and has SMAP before microcode is loaded.  Features do not chan=
ge
when microcode is loaded.

In the code below the marked mov %rdx,(%rdi) at 0xffffffff81088c43 is the
faulting instruction.  The fault address is at the start of a page in the u=
ser
address space and is the same as uio->uio_iov[0].iov_base, i.e. the first w=
ord
to be written.  The value of td->td_md.md_pcb.pcb_onfault is 0 in the dump
image.  I can't tell what it was while copyout was running.  A comment says=
 it
should be non-null.

   0xffffffff81088c1c <copyout_smap_std+60>:    mov    %rsi,%rdi
   0xffffffff81088c1f <copyout_smap_std+63>:    mov    %r8,%rsi
   0xffffffff81088c22 <copyout_smap_std+66>:    mov    %rdx,%rcx
   0xffffffff81088c25 <copyout_smap_std+69>:    stac
   0xffffffff81088c28 <copyout_smap_std+72>:    cmp    $0x20,%rcx
   0xffffffff81088c2c <copyout_smap_std+76>:    jbe    0xffffffff81088c90
<copyout_smap_std+176>
   0xffffffff81088c2e <copyout_smap_std+78>:    cmp    $0x100,%rcx
   0xffffffff81088c35 <copyout_smap_std+85>:    ja     0xffffffff81088d70
<copyout_smap_std+400>
   0xffffffff81088c3b <copyout_smap_std+91>:    nopl   0x0(%rax,%rax,1)
   0xffffffff81088c40 <copyout_smap_std+96>:    mov    (%rsi),%rdx
*  0xffffffff81088c43 <copyout_smap_std+99>:    mov    %rdx,(%rdi)
   0xffffffff81088c46 <copyout_smap_std+102>:   mov    0x8(%rsi),%rdx
   0xffffffff81088c4a <copyout_smap_std+106>:   mov    %rdx,0x8(%rdi)
   0xffffffff81088c4e <copyout_smap_std+110>:   mov    0x10(%rsi),%rdx
   0xffffffff81088c52 <copyout_smap_std+114>:   mov    %rdx,0x10(%rdi)
   0xffffffff81088c56 <copyout_smap_std+118>:   mov    0x18(%rsi),%rdx
   0xffffffff81088c5a <copyout_smap_std+122>:   mov    %rdx,0x18(%rdi)
   0xffffffff81088c5e <copyout_smap_std+126>:   lea    0x20(%rsi),%rsi
   0xffffffff81088c62 <copyout_smap_std+130>:   lea    0x20(%rdi),%rdi
   0xffffffff81088c66 <copyout_smap_std+134>:   sub    $0x20,%rcx

--=20
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