This patch adds support for the length argument to the xscale implementation of
the wp command. Per discussion with David, the length argument specifies the
range of addresses over which a memory access should generate a debug exception.
This patch utilizes the "mask" feature of the xscale debug hardware to implement
the correct functionality of the length argument. Some limitations imposed by
the hardware are:
- The length must be a power of two, with a minumum of 4.
- Two data breakpoint registers are available, allowing for two watchpoints.
However, if the length of a watchpoint is greater than four, both registers
are used (the second for a mask value), limiting the number of watchpoints
to one.
This patch also removes a useless call to xscale_get_reg(dbcon) in
xscale_set_watchpoint() (value had already been read from the register cache,
and the same previously read value is then modified and written back).
I have been using and testing this patch for a couple days.
Questions, corrections, criticisms of course gratefully received.
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