[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Xen-devel] [PATCH v5 04/16] arm: poison initmem when it is freed.
Hi Konrad,
On 21/09/16 18:32, Konrad Rzeszutek Wilk wrote:
The current byte sequence is '0xcc' which makes sense on x86,
but on ARM it is:
cccccccc stclgt 12, cr12, [ip], {204} ; 0xcc
Picking something more ARM applicable such as:
efefefef svc 0x00efefef
Creates a nice crash if one executes that code:
(XEN) CPU1: Unexpected Trap: Supervisor Call
But unfortunately that may not be a good choice either as in the future
we may want to implement support for it.
Julien suggested that we use a 4-byte insn instruction instead
of trying to work with one byte. To make sure nothing goes bad
we also require that the __init_[begin|end] be aligned properly.
As such on ARM 32 we use the udf instruction (see A8.8.247
in ARM DDI 0406C.c) and on ARM 64 use the AARCH64_BREAK_FAULT
instruction (aka brk instruction).
We don't have to worry about Thumb code so this instruction
is a safe to execute.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
Regards,
--
Julien Grall
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel
|
