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