1 # This testcase is part of GDB, the GNU debugger.
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18 # This file is part of the gdb testsuite.
20 # Test that GDB presents a hardware watchpoint stop at the first
21 # instruction right after the instruction that changes memory.
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.
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.
37 # This test makes sure that GDB knows which kind of watchpoint the
38 # target has, using this sequence of steps:
42 # 2 - set a software watchpoint
44 # 3 - continue until watchpoint triggers
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.
51 # 5 - replace the software watchpoint by a hardware watchpoint
53 # 6 - continue until hardware watchpoint triggers
55 # 7 - the PC must point to the same address the software watchpoint
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
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
73 # No use testing this if we can't use hardware watchpoints.
74 require allow_hw_watchpoint_tests
76 if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
84 # Get the current PC. TEST is used as test prefix.
90 gdb_test_multiple "p /x \$pc" "$test" {
91 -re " = ($hex).*$gdb_prompt $" {
92 set addr $expect_out(1,string)
100 # So we get an immediate warning/error if the target doesn't support a
101 # given watchpoint type.
102 gdb_test_no_output "set breakpoint always-inserted on"
104 set hw_watchpoints_supported 0
106 set test "set probe hw watchpoint"
107 gdb_test_multiple "watch global" $test {
108 -re "You may have requested too many.*$gdb_prompt $" {
111 -re "Target does not support.*$gdb_prompt $" {
114 -re "$gdb_prompt $" {
116 set hw_watchpoints_supported 1
120 if {!$hw_watchpoints_supported} {
121 unsupported "no hw watchpoints support"
127 proc test {always_inserted} {
128 global srcfile binfile
130 with_test_prefix "always-inserted $always_inserted" {
132 clean_restart $binfile
138 # Force use of software watchpoints.
139 gdb_test_no_output "set can-use-hw-watchpoints 0"
141 gdb_test "watch global" \
142 "Watchpoint .*: global" \
143 "set software watchpoint on global variable"
145 gdb_test "continue" \
146 "Watchpoint .*: global.*Old value = 0.*New value = 1.*set_global \\(val=1\\).*$srcfile.*" \
147 "software watchpoint triggers"
149 set sw_watch_pc [get_pc "get sw watchpoint PC"]
153 # Allow hardware watchpoints again.
154 gdb_test_no_output "set can-use-hw-watchpoints 1"
156 gdb_test "watch global" \
157 "Hardware watchpoint .*: global" \
158 "set hardware watchpoint on global variable"
160 gdb_test "continue" \
161 "Hardware watchpoint .*: global.*Old value = 1.*New value = 2.*set_global \\(val=2\\).*$srcfile.*" \
162 "hardware watchpoint triggers"
164 set hw_watch_pc [get_pc "get hw watchpoint PC"]
166 gdb_assert {$sw_watch_pc == $hw_watch_pc} "hw watchpoint stops at right instruction"
170 foreach always_inserted {"off" "on" } {
171 test $always_inserted