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Step over fork/vfork syscall insn in gdbserver

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We can also extend disp-step-syscall.exp to test GDBserver step over
breakpoint on syscall instruction.  That is, we set a breakpoint
with a false condition on syscall instruction, so that GDBserver will
step over it.

This test triggers a GDBserver internal error, which can be fixed by
this series.

(gdb) PASS: gdb.base/disp-step-syscall.exp: fork: break cond on target: break on syscall insns
continue^M
Continuing.^M
Remote connection closed^M
(gdb) FAIL: gdb.base/disp-step-syscall.exp: fork: break cond on target: continue to fork again

In GDBserver, there is an internal error,

/home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/linux-low.c:1922: A problem internal to GDBserver has been detected.
unsuspend LWP 25554, suspended=-1

the simplified reproducer is like,

$ ./gdb ./testsuite/outputs/gdb.base/disp-step-syscall/disp-step-fork
(gdb) b main
(gdb) c
(gdb) disassemble fork // in order to find the address of insn 'syscall'
....
   0x00007ffff7ad6023 <+179>:	syscall
(gdb) b *0x00007ffff7ad6023 if main == 0
(gdb) c

gdb/testsuite:

2016-03-03  Yao Qi  <yao.qi@linaro.org>

	* gdb.base/disp-step-syscall.exp (break_cond_on_syscall): New.
	If target supports condition evaluation on target, invoke
	break_cond_on_syscall for fork and vfork.
This commit is contained in:
Yao Qi 2016-03-03 09:17:44 +00:00
parent e197ad3c87
commit 92fa70b0bd
2 changed files with 63 additions and 0 deletions
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6
gdb/testsuite/ChangeLog
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@ -1,3 +1,9 @@
2016-03-03 Yao Qi <yao.qi@linaro.org>
* gdb.base/disp-step-syscall.exp (break_cond_on_syscall): New.
If target supports condition evaluation on target, invoke
break_cond_on_syscall for fork and vfork.
2016-03-03 Yao Qi <yao.qi@linaro.org>
* gdb.base/disp-step-syscall.exp: Don't invoke

57
gdb/testsuite/gdb.base/disp-step-syscall.exp
View File

@ -168,5 +168,62 @@ proc disp_step_cross_syscall { syscall } {
}
}
# Set a breakpoint with a condition that evals false on syscall
# instruction. In fact, it tests GDBserver steps over syscall
# instruction.
proc break_cond_on_syscall { syscall } {
with_test_prefix "break cond on target : $syscall" {
set testfile "disp-step-$syscall"
set ret [setup $syscall]
set syscall_insn_addr [lindex $ret 0]
set syscall_insn_next_addr [lindex $ret 1]
if { $syscall_insn_addr == -1 } {
return -1
}
gdb_test "continue" "Continuing\\..*Breakpoint \[0-9\]+, (.* in |__libc_|)$syscall \\(\\).*" \
"continue to $syscall"
# Delete breakpoint syscall insns to avoid interference with other syscalls.
delete_breakpoints
# Create a breakpoint with a condition that evals false.
gdb_test "break \*$syscall_insn_addr if main == 0" \
"Breakpoint \[0-9\]* at .*"
gdb_test "break marker" "Breakpoint.*at.* file .*${testfile}.c, line.*"
gdb_test "continue" "Continuing\\..*Breakpoint \[0-9\]+, marker \\(\\) at.*" \
"continue to marker ($syscall)"
}
}
disp_step_cross_syscall "fork"
disp_step_cross_syscall "vfork"
set testfile "disp-step-fork"
clean_restart $testfile
if { ![runto main] } then {
fail "run to main"
return -1
}
set cond_bp_target 1
set test "set breakpoint condition-evaluation target"
gdb_test_multiple $test $test {
-re "warning: Target does not support breakpoint condition evaluation.\r\nUsing host evaluation mode instead.\r\n$gdb_prompt $" {
# Target doesn't support breakpoint condition
# evaluation on its side.
set cond_bp_target 0
}
-re "^$test\r\n$gdb_prompt $" {
}
}
if { $cond_bp_target } {
break_cond_on_syscall "fork"
break_cond_on_syscall "vfork"
}