binutils-gdb/gdb/testsuite/gdb.base/watch-bitfields.exp

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# Copyright 2014-2017 Free Software Foundation, Inc.
Fix PR12526: -location watchpoints for bitfield arguments PR 12526 reports that -location watchpoints against bitfield arguments trigger false positives when bits around the bitfield, but not the bitfield itself, are modified. This happens because -location watchpoints naturally operate at the byte level, not at the bit level. When the address of a bitfield lvalue is taken, information about the bitfield (i.e. its offset and size) is lost in the process. This information must first be retained throughout the lifetime of the -location watchpoint. This patch achieves this by adding two new fields to the watchpoint struct: val_bitpos and val_bitsize. These fields are set when a watchpoint is first defined in watch_command_1. They are both equal to zero if the watchpoint is not a -location watchpoint or if the argument is not a bitfield. Then these bitfield parameters are used inside update_watchpoint and watchpoint_check to extract the actual value of the bitfield from the watchpoint address, with the help of a local helper function extract_bitfield_from_watchpoint_value. Finally when creating a HW breakpoint pointing to a bitfield, we optimize the address and length of the breakpoint. By skipping over the bytes that don't cover the bitfield, this step reduces the frequency at which a read watchpoint for the bitfield is triggered. It also reduces the number of times a false-positive call to check_watchpoint is triggered for a write watchpoint. gdb/ PR breakpoints/12526 * breakpoint.h (struct watchpoint): New fields val_bitpos and val_bitsize. * breakpoint.c (watch_command_1): Use these fields to retain bitfield information. (extract_bitfield_from_watchpoint_value): New function. (watchpoint_check): Use it. (update_watchpoint): Use it. Optimize the address and length of a HW watchpoint pointing to a bitfield. * value.h (unpack_value_bitfield): New prototype. * value.c (unpack_value_bitfield): Make extern. gdb/testsuite/ PR breakpoints/12526 * gdb.base/watch-bitfields.exp: New file. * gdb.base/watch-bitfields.c: New file.
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# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# This file is part of the gdb testsuite
standard_testfile
if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
Fix PR12526: -location watchpoints for bitfield arguments PR 12526 reports that -location watchpoints against bitfield arguments trigger false positives when bits around the bitfield, but not the bitfield itself, are modified. This happens because -location watchpoints naturally operate at the byte level, not at the bit level. When the address of a bitfield lvalue is taken, information about the bitfield (i.e. its offset and size) is lost in the process. This information must first be retained throughout the lifetime of the -location watchpoint. This patch achieves this by adding two new fields to the watchpoint struct: val_bitpos and val_bitsize. These fields are set when a watchpoint is first defined in watch_command_1. They are both equal to zero if the watchpoint is not a -location watchpoint or if the argument is not a bitfield. Then these bitfield parameters are used inside update_watchpoint and watchpoint_check to extract the actual value of the bitfield from the watchpoint address, with the help of a local helper function extract_bitfield_from_watchpoint_value. Finally when creating a HW breakpoint pointing to a bitfield, we optimize the address and length of the breakpoint. By skipping over the bytes that don't cover the bitfield, this step reduces the frequency at which a read watchpoint for the bitfield is triggered. It also reduces the number of times a false-positive call to check_watchpoint is triggered for a write watchpoint. gdb/ PR breakpoints/12526 * breakpoint.h (struct watchpoint): New fields val_bitpos and val_bitsize. * breakpoint.c (watch_command_1): Use these fields to retain bitfield information. (extract_bitfield_from_watchpoint_value): New function. (watchpoint_check): Use it. (update_watchpoint): Use it. Optimize the address and length of a HW watchpoint pointing to a bitfield. * value.h (unpack_value_bitfield): New prototype. * value.c (unpack_value_bitfield): Make extern. gdb/testsuite/ PR breakpoints/12526 * gdb.base/watch-bitfields.exp: New file. * gdb.base/watch-bitfields.c: New file.
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return -1
}
# Set a watchpoint watching EXPR.
proc watch { expr } {
global decimal
set expr_re [string_to_regexp $expr]
gdb_test "watch $expr" \
"\(Hardware \)?\[Ww\]atchpoint $decimal: $expr_re"
Fix PR12526: -location watchpoints for bitfield arguments PR 12526 reports that -location watchpoints against bitfield arguments trigger false positives when bits around the bitfield, but not the bitfield itself, are modified. This happens because -location watchpoints naturally operate at the byte level, not at the bit level. When the address of a bitfield lvalue is taken, information about the bitfield (i.e. its offset and size) is lost in the process. This information must first be retained throughout the lifetime of the -location watchpoint. This patch achieves this by adding two new fields to the watchpoint struct: val_bitpos and val_bitsize. These fields are set when a watchpoint is first defined in watch_command_1. They are both equal to zero if the watchpoint is not a -location watchpoint or if the argument is not a bitfield. Then these bitfield parameters are used inside update_watchpoint and watchpoint_check to extract the actual value of the bitfield from the watchpoint address, with the help of a local helper function extract_bitfield_from_watchpoint_value. Finally when creating a HW breakpoint pointing to a bitfield, we optimize the address and length of the breakpoint. By skipping over the bytes that don't cover the bitfield, this step reduces the frequency at which a read watchpoint for the bitfield is triggered. It also reduces the number of times a false-positive call to check_watchpoint is triggered for a write watchpoint. gdb/ PR breakpoints/12526 * breakpoint.h (struct watchpoint): New fields val_bitpos and val_bitsize. * breakpoint.c (watch_command_1): Use these fields to retain bitfield information. (extract_bitfield_from_watchpoint_value): New function. (watchpoint_check): Use it. (update_watchpoint): Use it. Optimize the address and length of a HW watchpoint pointing to a bitfield. * value.h (unpack_value_bitfield): New prototype. * value.c (unpack_value_bitfield): Make extern. gdb/testsuite/ PR breakpoints/12526 * gdb.base/watch-bitfields.exp: New file. * gdb.base/watch-bitfields.c: New file.
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}
# Continue inferior execution, expecting the watchpoint EXPR to be triggered
# having old value OLD and new value NEW.
proc expect_watchpoint { expr old new } {
with_test_prefix "$expr: $old->$new" {
set expr_re [string_to_regexp $expr]
gdb_test "print $expr" "\\$\\d+ = $old\\s" "print expression before"
gdb_test "continue" "$expr_re\\s.*Old value = $old\\s+New value = $new\\s.*"
gdb_test "print $expr" "\\$\\d+ = $new\\s" "print expression after"
}
Fix PR12526: -location watchpoints for bitfield arguments PR 12526 reports that -location watchpoints against bitfield arguments trigger false positives when bits around the bitfield, but not the bitfield itself, are modified. This happens because -location watchpoints naturally operate at the byte level, not at the bit level. When the address of a bitfield lvalue is taken, information about the bitfield (i.e. its offset and size) is lost in the process. This information must first be retained throughout the lifetime of the -location watchpoint. This patch achieves this by adding two new fields to the watchpoint struct: val_bitpos and val_bitsize. These fields are set when a watchpoint is first defined in watch_command_1. They are both equal to zero if the watchpoint is not a -location watchpoint or if the argument is not a bitfield. Then these bitfield parameters are used inside update_watchpoint and watchpoint_check to extract the actual value of the bitfield from the watchpoint address, with the help of a local helper function extract_bitfield_from_watchpoint_value. Finally when creating a HW breakpoint pointing to a bitfield, we optimize the address and length of the breakpoint. By skipping over the bytes that don't cover the bitfield, this step reduces the frequency at which a read watchpoint for the bitfield is triggered. It also reduces the number of times a false-positive call to check_watchpoint is triggered for a write watchpoint. gdb/ PR breakpoints/12526 * breakpoint.h (struct watchpoint): New fields val_bitpos and val_bitsize. * breakpoint.c (watch_command_1): Use these fields to retain bitfield information. (extract_bitfield_from_watchpoint_value): New function. (watchpoint_check): Use it. (update_watchpoint): Use it. Optimize the address and length of a HW watchpoint pointing to a bitfield. * value.h (unpack_value_bitfield): New prototype. * value.c (unpack_value_bitfield): Make extern. gdb/testsuite/ PR breakpoints/12526 * gdb.base/watch-bitfields.exp: New file. * gdb.base/watch-bitfields.c: New file.
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}
# Check that -location watchpoints against bitfields trigger properly.
proc test_watch_location {} {
with_test_prefix "-location watch against bitfields" {
if {![runto_main]} {
return -1
}
watch "-location q.a"
watch "-location q.e"
expect_watchpoint "q.a" 0 1
expect_watchpoint "q.e" 0 5
expect_watchpoint "q.a" 1 0
expect_watchpoint "q.e" 5 4
# It'll execute a large amount of code with software watchpoint
# enabled, which means GDB will single stepping all the way
# through til the inferior exits. Increase the timeout by a
# factor of 4.
with_timeout_factor 4 {
gdb_continue_to_end
}
}
}
# Check that regular watchpoints against expressions involving
# bitfields trigger properly.
proc test_regular_watch {} {
with_test_prefix "regular watch against bitfields" {
if {![runto_main]} {
return -1
}
watch "q.d + q.f + q.g"
expect_watchpoint "q.d + q.f + q.g" 0 4
expect_watchpoint "q.d + q.f + q.g" 4 10
expect_watchpoint "q.d + q.f + q.g" 10 3
expect_watchpoint "q.d + q.f + q.g" 3 2
expect_watchpoint "q.d + q.f + q.g" 2 1
expect_watchpoint "q.d + q.f + q.g" 1 0
# It'll execute a large amount of code with software watchpoint
# enabled, which means GDB will single stepping all the way
# through til the inferior exits. Increase the timeout by a
# factor of 4.
with_timeout_factor 4 {
gdb_continue_to_end
}
}
}
Use software watchpoints if hardware watchpoints are not available when testing gdb.base/watch-bitfields.exp There are targets GDB thinks support hardware watchpoints, but in reality they don't. Though it may seem that hardware watchpoint creation was successful, the actual insertion of such watchpoint will fail when GDB moves the inferior. (gdb) watch -location q.a^M Hardware watchpoint 2: -location q.a^M (gdb) PASS: gdb.base/watch-bitfields.exp: -location watch against bitfields: watch -location q.a watch -location q.e^M Hardware watchpoint 3: -location q.e^M (gdb) PASS: gdb.base/watch-bitfields.exp: -location watch against bitfields: watch -location q.e print q.a^M $1 = 0^M (gdb) PASS: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.a: 0->1: print expression before continue^M Continuing.^M Warning:^M Could not insert hardware watchpoint 2.^M Could not insert hardware watchpoint 3.^M Could not insert hardware breakpoints:^M You may have requested too many hardware breakpoints/watchpoints.^M ^M (gdb) FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.a: 0->1: continue This leads to a number of FAILs: FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.a: 0->1: continue FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.a: 0->1: print expression after FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.e: 0->5: continue FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.e: 0->5: print expression after FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.a: 1->0: print expression before FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.a: 1->0: continue FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.e: 5->4: print expression before FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.e: 5->4: continue FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: q.e: 5->4: print expression after FAIL: gdb.base/watch-bitfields.exp: -location watch against bitfields: continue until exit FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 0->4: continue FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 0->4: print expression after FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 4->10: print expression before FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 4->10: continue FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 4->10: print expression after FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 10->3: print expression before FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 10->3: continue FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 10->3: print expression after FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 3->2: print expression before FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 3->2: continue FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 3->2: print expression after FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 2->1: print expression before FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 2->1: continue FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 2->1: print expression after FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 1->0: print expression before FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: q.d + q.f + q.g: 1->0: continue FAIL: gdb.base/watch-bitfields.exp: regular watch against bitfields: continue until exit We can avoid these errors/FAILs by checking the board data and switching to software watchpoints if the board does not support hardware watchpoints. gdb/testsuite/ChangeLog: 2015-04-29 Luis Machado <lgustavo@codesourcery.com> * gdb.base/watch-bitfields.exp: Switch to software watchpoints if the target does not support hardware watchpoints.
2015-04-29 17:22:24 +02:00
# Disable hardware watchpoints if the target does not support them.
if [target_info exists gdb,no_hardware_watchpoints] {
gdb_test_no_output "set can-use-hw-watchpoints 0"
}
test_watch_location
test_regular_watch