1# This testcase is part of GDB, the GNU debugger.
2
3# Copyright 2014-2020 Free Software Foundation, Inc.
4
5# This program is free software; you can redistribute it and/or modify
6# it under the terms of the GNU General Public License as published by
7# the Free Software Foundation; either version 3 of the License, or
8# (at your option) any later version.
9#
10# This program is distributed in the hope that it will be useful,
11# but WITHOUT ANY WARRANTY; without even the implied warranty of
12# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13# GNU General Public License for more details.
14#
15# You should have received a copy of the GNU General Public License
16# along with this program.  If not, see <http://www.gnu.org/licenses/>.
17
18# This file is part of the gdb testsuite.
19
20# Test that GDB presents a hardware watchpoint stop at the first
21# instruction right after the instruction that changes memory.
22#
23# Some targets trigger a hardware watchpoint after the instruction
24# that wrote memory executes, thus with the memory already changed and
25# the PC pointing to the instruction after the instruction that wrote
26# to memory.  These targets are said to have "continuable"
27# watchpoints, referring to the fact that to make progress after the
28# watchpoint triggers, GDB just needs to continue the target.
29#
30# Other targets trigger a hardware watchpoint at the instruction which
31# has attempted to write to the piece of memory under control of the
32# watchpoint, with the instruction actually not executed yet.  To be
33# able to check whether the watched value changed, GDB needs to
34# complete the memory write, single-stepping the target once.  These
35# targets are said to have "non-continuable" watchpoints.
36#
37# This test makes sure that GDB knows which kind of watchpoint the
38# target has, using this sequence of steps:
39#
40# 1 - run to main
41#
42# 2 - set a software watchpoint
43#
44# 3 - continue until watchpoint triggers
45#
46# 4 - the PC now points to the instruction right after the instruction
47#     that actually caused the memory write.  So this is the address a
48#     hardware watchpoint should present the stop to the user too.
49#     Store the PC address.
50#
51# 5 - replace the software watchpoint by a hardware watchpoint
52#
53# 6 - continue until hardware watchpoint triggers
54#
55# 7 - the PC must point to the same address the software watchpoint
56#     triggered at.
57#
58# If the target has continuable watchpoints, but GDB thinks it has
59# non-continuable watchpoints, GDB will stop the inferior two
60# instructions after the watched value change, rather than at the next
61# instruction.
62#
63# If the target has non-continuable watchpoints, while GDB thinks it
64# has continuable watchpoints, GDB will see a watchpoint trigger,
65# notice no value changed, and immediatly continue the target.  Now,
66# either the target manages to step-over the watchpoint transparently,
67# and GDB thus fails to present to value change to the user, or, the
68# watchpoint will keep re-triggering, with the program never making
69# any progress.
70
71standard_testfile
72
73# No use testing this if we can't use hardware watchpoints.
74if {[target_info exists gdb,no_hardware_watchpoints]} {
75    return -1
76}
77
78if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
79    return -1
80}
81
82if { ![runto main] } then {
83    fail "run to main"
84    return
85}
86
87# Get the current PC.  TEST is used as test prefix.
88
89proc get_pc {test} {
90    global hex gdb_prompt
91
92    set addr ""
93    gdb_test_multiple "p /x \$pc" "$test" {
94	-re " = ($hex).*$gdb_prompt $" {
95	    set addr $expect_out(1,string)
96	    pass "$test"
97	}
98    }
99
100    return $addr
101}
102
103# So we get an immediate warning/error if the target doesn't support a
104# given watchpoint type.
105gdb_test_no_output "set breakpoint always-inserted on"
106
107set hw_watchpoints_supported 0
108
109set test "set probe hw watchpoint"
110gdb_test_multiple "watch global" $test {
111    -re "You may have requested too many.*$gdb_prompt $" {
112	pass $test
113    }
114    -re "Target does not support.*$gdb_prompt $" {
115	pass $test
116    }
117    -re "$gdb_prompt $" {
118	pass $test
119	set hw_watchpoints_supported 1
120    }
121}
122
123if {!$hw_watchpoints_supported} {
124    unsupported "no hw watchpoints support"
125    return
126}
127
128delete_breakpoints
129
130proc test {always_inserted} {
131    global srcfile binfile
132
133    with_test_prefix "always-inserted $always_inserted" {
134
135	clean_restart $binfile
136
137	if { ![runto main] } then {
138	    fail "run to main"
139	    return
140	}
141
142	# Force use of software watchpoints.
143	gdb_test_no_output "set can-use-hw-watchpoints 0"
144
145	gdb_test "watch global" \
146	    "Watchpoint .*: global" \
147	    "set software watchpoint on global variable"
148
149	gdb_test "continue" \
150	    "Watchpoint .*: global.*Old value = 0.*New value = 1.*set_global \\(val=1\\).*$srcfile.*" \
151	    "software watchpoint triggers"
152
153	set sw_watch_pc [get_pc "get sw watchpoint PC"]
154
155	delete_breakpoints
156
157	# Allow hardware watchpoints again.
158	gdb_test_no_output "set can-use-hw-watchpoints 1"
159
160	gdb_test "watch global" \
161	    "Hardware watchpoint .*: global" \
162	    "set hardware watchpoint on global variable"
163
164	gdb_test "continue" \
165	    "Hardware watchpoint .*: global.*Old value = 1.*New value = 2.*set_global \\(val=2\\).*$srcfile.*" \
166	    "hardware watchpoint triggers"
167
168	set hw_watch_pc [get_pc "get hw watchpoint PC"]
169
170	gdb_assert {$sw_watch_pc == $hw_watch_pc} "hw watchpoint stops at right instruction"
171    }
172}
173
174foreach always_inserted {"off" "on" } {
175    test $always_inserted
176}
177