[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH] x86/debug: fix page-overflow bug in dbg_rw_guest_mem

On 30.01.2021 03:59, Andrew Cooper wrote:
> On 30/01/2021 01:59, Tamas K Lengyel wrote:
>> When using gdbsx dbg_rw_guest_mem is used to read/write guest memory. When 
>> the
>> buffer being accessed is on a page-boundary, the next page needs to be 
>> grabbed
>> to access the correct memory for the buffer's overflown parts. While
>> dbg_rw_guest_mem has logic to handle that, it broke with 229492e210a. Instead
>> of grabbing the next page the code right now is looping back to the
>> start of the first page. This results in errors like the following while 
>> trying
>> to use gdb with Linux' lx-dmesg:
>> [    0.114457] PM: hibernation: Registered nosave memory: [mem
>> 0xfdfff000-0xffffffff]
>> [    0.114460] [mem 0x90000000-0xfbffffff] available for PCI demem 0
>> [    0.114462] f]f]
>> Python Exception <class 'ValueError'> embedded null character:
>> Error occurred in Python: embedded null character
>> Fixing this bug by taking the variable assignment outside the loop.
>> Signed-off-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

I have to admit that I'm irritated: On January 14th I did submit
a patch ('x86/gdbsx: convert "user" to "guest" accesses') fixing this
as a side effect. I understand that one was taking care of more
issues here, but shouldn't that be preferred? Re-basing isn't going
to be overly difficult, but anyway.




Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.