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Re: [Xen-devel] guest attempted write to read-only memory page.

Tian, Kevin wrote:
From: Tian, Kevin
Sent: Monday, December 22, 2008 9:11 PM
Possibly we should silence the shadow code too, at least perhaps while in
real mode or for a certain EIP range.

I'm not sure that's the right fix. Why is write access to rom disabled
before rom scan when etherboot is known to have write requirement?

 call _enable_rom_write_access
 call _clobber_entry_point
 call _copy_e820_table
 call smbios_init
 call _disable_rom_write_access

 call _init_boot_vectors

 mov  cx, #0xc800  ;; init option roms
 mov  ax, #0xe000
 call rom_scan

Should we move disable action to post rom_scan? If shadow warning
is simply silenced for such case, it seems breaking the purpose of

I make a quick test, that warning disappears after moving disable
action post rom_scan. But I haven't found the place triggering such
write violation, as in previous revision write access is also disabled
before rom_scan. It could come from recent bochs update on expansion rom part by 18931.

Sorry for my late response.
That's a bug of mine.

Some option ROMs would do write accesses.
So rombios need to enable write acess before rom_scan.
I'll post a patch to fix.

Best Regards,

Akio Takebe

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