gdb/testsuite/gdb.base/watchpoint-stops-at-right-insn.exp

   1 # This testcase is part of GDB, the GNU debugger.
   2
   3 # Copyright 2014-2022 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
  71 standard_testfile
  72
  73 # No use testing this if we can't use hardware watchpoints.
  74 if {[target_info exists gdb,no_hardware_watchpoints]} {
  75     return -1
  76 }
  77
  78 if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
  79     return -1
  80 }
  81
  82 if { ![runto_main] } then {
  83     fail "run to main"
  84     return
  85 }
  86
  87 # Get the current PC.  TEST is used as test prefix.
  88
  89 proc get_pc {test} {
  90     global hex gdb_prompt
  91
  92     set addr ""
  93     gdb_test_multiple "p /x \$pc" "$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.
 105 gdb_test_no_output "set breakpoint always-inserted on"
 106
 107 set hw_watchpoints_supported 0
 108
 109 set test "set probe hw watchpoint"
 110 gdb_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 $test
 119         set hw_watchpoints_supported 1
 120     }
 121 }
 122
 123 if {!$hw_watchpoints_supported} {
 124     unsupported "no hw watchpoints support"
 125     return
 126 }
 127
 128 delete_breakpoints
 129
 130 proc 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
 174 foreach always_inserted {"off" "on" } {
 175     test $always_inserted
 176 }