rombios triple fault with -fcf-protection

[Jason Andryuk <jandryuk@xxxxxxxxx>]

This is the output from a failed rombios boot:

(d11) Invoking ROMBIOS ...
(XEN) stdvga.c:173:d11v0 entering stdvga mode
(d11) VGABios $Id: vgabios.c,v 1.67 2008/01/27 09:44:12 vruppert Exp $
(d11) Bochs BIOS - build: 06/23/99
(d11) $Revision: 1.221 $ $Date: 2008/12/07 17:32:29 $
(d11) Options: apmbios pcibios eltorito PMM
(d11)
(d11) ata0 master: QEMU HARDDISK ATA-7 Hard-Disk ( 112 MBytes)
(d11)
(XEN) MMIO emulation failed (1): d11v0 32bit @ 0008:ffffffff ->
(XEN) d11v0 Triple fault - invoking HVM shutdown action 1
(XEN) *** Dumping Dom11 vcpu#0 state: ***
(XEN) ----[ Xen-4.14-unstable  x86_64  debug=y   Not tainted ]----
(XEN) CPU:    1
(XEN) RIP:    0008:[<00000000ffffffff>]
(XEN) RFLAGS: 0000000000010086   CONTEXT: hvm guest (d11v0)
(XEN) rax: 0000000043001000   rbx: 000000000009c30e   rcx: 0000000000000000
(XEN) rdx: 0000000000000000   rsi: 000000000000031e   rdi: 0000000000000020
(XEN) rbp: 00000000000002de   rsp: 000000000009ef48   r8:  0000000000000000
(XEN) r9:  0000000000000000   r10: 0000000000000000   r11: 0000000000000000
(XEN) r12: 0000000000000000   r13: 0000000000000000   r14: 0000000000000000
(XEN) r15: 0000000000000000   cr0: 0000000000000011   cr4: 0000000000000000
(XEN) cr3: 0000000000400000   cr2: 0000000000000000
(XEN) fsb: 0000000000000000   gsb: 00000000000c9000   gss: 0000000000000002
(XEN) ds: 0018   es: 0018   fs: 0000   gs: c900   ss: 0018   cs: 0008

For a traditional stubdom with sdl enabled, I also see the init_message of iPXE
iPXE (http://ipxe.org) 00:04.0 C900 PCI2.10 PMM_

The underscore might be the cursor?

The VM reboots.  If I set on_reboot="preserve" and use gdbsx:

(gdb) target remote :1234
Remote debugging using :1234
0xdeadf00d in ?? ()
(gdb) bt
#0  0xdeadf00d in ?? ()
(gdb) i r
eax            0x0                 0
ecx            0x0                 0
edx            0xe5a08016          -442466282
ebx            0x87                135
esp            0x23aa              0x23aa <memset+22>
ebp            0x0                 0x0
esi            0x0                 0
edi            0x0                 0
eip            0xdeadf00d          0xdeadf00d
eflags         0xdeadbeef          [ CF PF ZF SF IF DF OF RF AC VIF ID ]
cs             0xdeadf00d          -559026163
ss             0xdeadbeef          -559038737
ds             0x5ef890            6224016
es             0x0                 0
fs             0x5ef868            6223976
gs             0x0                 0