Re: [PATCH 1/2] watchpoint-reuse-slot.exp: skip some tests on targets have different wp and bp registers

[Yao Qi <qiyaoltc@gmail.com>]

Pedro Alves <palves@redhat.com> writes:

> Hmm, is this just to save test time?  If so, I'd prefer not skipping,
> as it may always catch other bugs, in the target backends or
> the kernel.

No, watchpoint-reuse-slot.exp sets some HW breakpoint/watchpoint on some
address doesn't meet the alignment requirements by kernel, kernel
will reject the ptrace (PTRACE_SETHBPREGS) call, and some fails are
caused, for example:

(gdb) PASS: gdb.base/watchpoint-reuse-slot.exp: always-inserted off: watch x hbreak: : width 1, iter 0: base + 0: delete $bpnum
hbreak *(buf.byte + 0 + 1)^M
Hardware assisted breakpoint 80 at 0x410a61^M
(gdb) PASS: gdb.base/watchpoint-reuse-slot.exp: always-inserted off: watch x hbreak: : width 1, iter 0: base + 1: hbreak *(buf.byte + 0 + 1)
stepi^M
Warning:^M
Cannot insert hardware breakpoint 80.^M
Could not insert hardware breakpoints:^M
You may have requested too many hardware breakpoints/watchpoints.^M
^M
(gdb) FAIL: gdb.base/watchpoint-reuse-slot.exp: always-inserted off: watch x hbreak: : width 1, iter 0: base + 1: stepi advanced

hbreak *(buf.byte + 0 + 1)^M
Hardware assisted breakpoint 440 at 0x410a61^M
Warning:^M
Cannot insert hardware breakpoint 440.^M
Could not insert hardware breakpoints:^M
You may have requested too many hardware breakpoints/watchpoints.^M
^M
(gdb) FAIL: gdb.base/watchpoint-reuse-slot.exp: always-inserted on: watch x hbreak: : width 1, iter 0: base + 1: hbreak *(buf.byte + 0 + 1)

Do you suggest that we don't skip these tests even requested
breakpoint/watchpoint don't go in the same slot (debugging register)? so
that the test can cover more.  If the requested address of HW
breakpoint/watchpoint doesn't meet the arch/kernel requirements, we can
skip it, is it OK?

The inner loop of test has two parts, "base + 0" and "base + 1",

		    append prefix "$cmd1 x $cmd2: "
		    with_test_prefix "$prefix: width $width, iter $x" {
			with_test_prefix "base + 0" {
			    watch_command $cmd1 $x 0 $width
			    stepi
			    gdb_test_no_output "delete \$bpnum"
			}
			with_test_prefix "base + 1" {
			    watch_command $cmd2 $x 1 $width
			    stepi
			    gdb_test_no_output "delete \$bpnum"
			}
		    }

if we skip "base + 1" part, do we skip "base + 0" too? if not, prefix in
test summary "$cmd1 x $cmd2: " doesn't reflect the fact.

>
> Despite the test's file name, the test doesn't actually create two
> breakpoints/watchpoints at the same time, as mentioned at the top
> of the file.

Yes, only one breakpoint/watchpoint is inserted at a time.

-- 
Yao (齐尧)