old-cross-binutils/gdb/testsuite/gdb.base/valgrind-disp-step.exp
Pedro Alves 3fc8eb30a9 Disable displaced stepping if trying it fails
Running the testsuite with "maint set target-non-stop on" shows:

 (gdb) PASS: gdb.base/valgrind-infcall.exp: continue #98 (false warning)
 continue
 Continuing.
 dl_main (phdr=<optimized out>..., auxv=<optimized out>) at rtld.c:2302
 2302      LIBC_PROBE (init_complete, 2, LM_ID_BASE, r);
 Cannot access memory at address 0x400532
 (gdb) PASS: gdb.base/valgrind-infcall.exp: continue #99 (false warning)
 p gdb_test_infcall ()
 $1 = 1
 (gdb) FAIL: gdb.base/valgrind-infcall.exp: p gdb_test_infcall ()

Even though that was a native GNU/Linux test run, this test spawns
Valgrind and connects to it with "target remote".  The error above is
actually orthogonal to target-non-stop.  The real issue is that that
enables displaced stepping, and displaced stepping doesn't work with
Valgrind, because we can't write to the inferior memory (thus can't
copy the instruction to the scratch pad area).

I'm sure there will be other targets with the same issue, so trying to
identify Valgrind wouldn't be sufficient.  The fix is to try setting
up the displaced step anyway.  If we get a MEMORY_ERROR, we disable
displaced stepping for that inferior, and fall back to doing an
in-line step-over.  If "set displaced-stepping" is "on" (as opposed to
"auto), GDB warns displaced stepping failed ("on" is mainly useful for
the testsuite, not for users).

Tested on x86_64 Fedora 20.

gdb/ChangeLog:
2015-08-07  Pedro Alves  <palves@redhat.com>

	* inferior.h (struct inferior) <displaced_stepping_failed>: New
	field.
	* infrun.c (use_displaced_stepping_now_p): New parameter 'inf'.
	Return false if dispaced stepping failed before.
	(resume): Pass the current inferior to
	use_displaced_stepping_now_p.  Wrap displaced_step_prepare in
	TRY/CATCH.  If we get a MEMORY_ERROR, set the inferior's
	displaced_stepping_failed flag, and fall back to an in-line
	step-over.

gdb/testsuite/ChangeLog:
2015-08-07  Pedro Alves  <palves@redhat.com>

	* gdb.base/valgrind-disp-step.c: New file.
	* gdb.base/valgrind-disp-step.exp: New file.
2015-08-07 17:26:21 +01:00

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# Copyright 2012-2015 Free Software Foundation, Inc.
# 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/>.
# Step over breakpoints with displaced stepping on, against Valgrind.
# We can't really use displaced stepping with Valgrind, so what this
# really tests is that GDB falls back to in-line stepping
# automatically instead of getting stuck or crashing.
if [is_remote target] {
# The test always runs locally.
return 0
}
standard_testfile .c
if {[build_executable "failed to build" $testfile $srcfile {debug}] == -1} {
return -1
}
set test "spawn valgrind"
set cmd "valgrind --vgdb-error=0 $binfile"
set res [remote_spawn host $cmd]
if { $res < 0 || $res == "" } {
verbose -log "Spawning $cmd failed."
unsupported $test
return -1
}
pass $test
# Declare GDB now as running.
set gdb_spawn_id $res
# GDB started by vgdb stops already after the startup is executed, like with
# non-extended gdbserver. It is also not correct to run/attach the inferior.
set use_gdb_stub 1
set test "valgrind started"
# The trailing '.' differs for different memcheck versions.
gdb_test_multiple "" $test {
-re "Memcheck, a memory error detector\\.?\r\n" {
pass $test
}
-re "valgrind: failed to start tool 'memcheck' for platform '.*': No such file or directory" {
unsupported $test
return -1
}
-re "valgrind: wrong ELF executable class" {
unsupported $test
return -1
}
-re "command not found" {
# The spawn succeeded, but then valgrind was not found - e.g. if
# we spawned SSH to a remote system.
unsupported $test
return -1
}
-re "valgrind: Bad option.*--vgdb-error=0" {
# valgrind is not >= 3.7.0.
unsupported $test
return -1
}
}
set test "vgdb prompt"
# The trailing '.' differs for different memcheck versions.
gdb_test_multiple "" $test {
-re " (target remote | \[^\r\n\]*/vgdb \[^\r\n\]*)\r\n" {
set vgdbcmd $expect_out(1,string)
pass $test
}
}
# Do not kill valgrind.
set valgrind_pid [exp_pid -i [board_info host fileid]]
unset gdb_spawn_id
set board [host_info name]
unset_board_info fileid
clean_restart $testfile
# Make sure we're disconnected, in case we're testing with the
# native-extended-gdbserver board, where gdb_start/gdb_load spawn
# gdbserver and connect to it.
gdb_test "disconnect" ".*"
gdb_test "$vgdbcmd" " in \\.?_start .*" "target remote for vgdb"
gdb_test "monitor v.set gdb_output" "valgrind output will go to gdb.*"
gdb_test_no_output "set displaced-stepping off"
gdb_breakpoint "main" "breakpoint at main"
gdb_test "continue" " stop 0 .*" "continue to main"
delete_breakpoints
set curr_stop 0
foreach displaced { "off" "on" } {
with_test_prefix "displaced $displaced" {
gdb_test_no_output "set displaced-stepping $displaced"
foreach go { "once" "twice" } {
with_test_prefix $go {
gdb_test "break" "Breakpoint .* at .*" "set breakpoint"
# Whether we should see a warning.
set should_warn [expr {$go == "once" && $displaced == "on"}]
incr curr_stop
set msg "step over breakpoint"
set pattern " stop $curr_stop .*$gdb_prompt $"
gdb_test_multiple "next" $msg {
-re "warning: disabling displaced stepping.*$pattern" {
gdb_assert $should_warn $msg
}
-re "$pattern" {
gdb_assert !$should_warn $msg
}
}
}
}
}
}
# Only if valgrind got stuck.
remote_exec host "kill -9 ${valgrind_pid}"