On Mon, 27 Mar 2017 23:07:53 +0200, Jan Kratochvil wrote:
Hi,

obsoletes:
	[patch] aarch64: PR 19806: watchpoints: false negatives -> false positives
	https://sourceware.org/ml/gdb-patches/2016-06/msg00078.html
	Message-ID: <20160606075945.GA19395@host1.jankratochvil.net>

Therefore on old kernels (see below) it will now rather report watchpoint
which was hit only next to it (for rwatch/awatch).  But it will never miss
a watchpoint.

Additionally it now supports any watchpoint masks as described in:
	kernel RFE: aarch64: ptrace: BAS: Support any contiguous range (edit) 
	https://sourceware.org/bugzilla/show_bug.cgi?id=20207
which is already fixed in recent Linux kernels.

Tested on RHEL-7.{3,4} for no regressions on:
	kernel-4.10.0-6.el7.aarch64 (contiguous watchpoints supported)
	kernel-4.5.0-15.el7.aarch64 (contiguous watchpoints unsupported)
I have seen (not investigated):
	-FAIL: gdb.threads/thread-specific-bp.exp: non-stop: thread-specific breakpoint was deleted (timeout)
	+PASS: gdb.threads/thread-specific-bp.exp: non-stop: thread-specific breakpoint was deleted

There may be a regresion that it now less merges watchpoints so that with
multiple overlapping watchpoints it may run out of the 4 hardware watchpoint
registers.  But as discussed in the original thread GDB needs some generic
watchpoints merging framework to be used by all the target specific code.
Even current FSF GDB code does not merge it perfectly.  Also with the more
precise watchpoints one can technically merge them less.  And I do not think
it matters too much to improve mergeability only for old kernels.
Still even on new kernels some better merging logic would make sense.

OK for check-in?


Thanks,
Jan