Re: [PATCH] Tighten gdb.base/disp-step-syscall.exp

["Breazeal, Don" <donb at codesourcery dot com>]

On 3/2/2015 12:18 PM, Pedro Alves wrote:
> On 02/27/2015 12:46 AM, Don Breazeal wrote:
>>  - There are a couple of tests that show new failures that actually
>>    fail in the current mainline.  Details of these are as follows:
>>
>>    * when vfork events are enabled, gdb.base/disp-step-syscall.exp
>>      shows PASS => FAIL in .sum diffs.  The test actually always
>>      fails.  With native/master, we see
>>
>>       stepi^M
>>       FAIL: gdb.base/disp-step-syscall.exp: vfork: stepi vfork insn
>> (timeout)
>>
> 
> Hmm, I don't see that here.  I get a full pass on x86_64 Fedora 20.
> Can you try "set debug infrun 1" / "set debug lin-lwp 1" / "set debug displaced 1"
> to check if there's a gdb or kernel bug here?
> 
>>      With remote and extended-remote/master, we see a bogus PASS result:
>>       stepi^M
>>       [Inferior 1 (process 9399) exited normally]^M
>>       (gdb) PASS: gdb.base/disp-step-syscall.exp: vfork: stepi vfork insn
>>
>>     The criteria to pass that test are pretty lax:
>>       gdb_test "stepi" ".*" "stepi $syscall insn"
> 
> Yeah.  I see several other problems.  Here's a patch to improve it.
> 
> Comments?

Hi Pedro,
This patch makes sense to me, and it has been working great for me while
debugging my updates to the follow-fork patchset.  We will need to
update this once the remote follow patches are committed, I guess,
since presumably the kfail 13796 will be resolved then.

> 
> Unfortunately, with your full series applied, I get this:
> 
>  (gdb) PASS: gdb.base/disp-step-syscall.exp: vfork: get hexadecimal valueof "$pc"
>  stepi
>  Detaching from process 29944
>  Killing process(es): 29942 29944
>  /home/pedro/gdb/mygit/src/gdb/gdbserver/linux-low.c:998: A problem internal to GDBserver has been detected.
>  kill_wait_lwp: Assertion `res > 0' failed.
>  /home/pedro/gdb/mygit/src/gdb/thread.c:1182: internal-error: switch_to_thread: Assertion `inf != NULL' failed.
>  A problem internal to GDB has been detected,
>  further debugging may prove unreliable.
>  Quit this debugging session? (y or n) FAIL: gdb.base/disp-step-syscall.exp: vfork: stepi vfork insn (GDB internal error)
>  Resyncing due to internal error.
>  n

The updated patchset just posted should address this issue.
https://sourceware.org/ml/gdb-patches/2015-03/msg00503.html

Thanks,
--Don

> 
> Note, you'll need this one:
> 
>  https://sourceware.org/ml/gdb-patches/2015-03/msg00045.html
> 
> for that internal error to result in a quick bail...
> 
> ----------
> From 1f825812d3f17a2940065d0de38592700e7437bc Mon Sep 17 00:00:00 2001
> From: Pedro Alves <palves@redhat.com>
> Date: Mon, 2 Mar 2015 20:16:23 +0000
> Subject: [PATCH] Tighten gdb.base/disp-step-syscall.exp
> 
> This fixes several problems with this test.
> 
> E.g,. with --target_board=native-extended-gdbserver on
> x86_64 Fedora 20, I get:
> 
>  Running /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.base/disp-step-syscall.exp ...
>  FAIL: gdb.base/disp-step-syscall.exp: vfork: get hexadecimal valueof "$pc" (timeout)
>  FAIL: gdb.base/disp-step-syscall.exp: vfork: single step over vfork final pc
>  FAIL: gdb.base/disp-step-syscall.exp: vfork: delete break vfork insn
>  FAIL: gdb.base/disp-step-syscall.exp: vfork: continue to marker (vfork) (the program is no longer running)
> 
> And with --target=native-gdbserver, I get:
> 
>  Running /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.base/disp-step-syscall.exp ...
>  KPASS: gdb.base/disp-step-syscall.exp: vfork: single step over vfork (PRMS server/13796)
>  FAIL: gdb.base/disp-step-syscall.exp: vfork: get hexadecimal valueof "$pc" (timeout)
>  FAIL: gdb.base/disp-step-syscall.exp: vfork: single step over vfork final pc
>  FAIL: gdb.base/disp-step-syscall.exp: vfork: delete break vfork insn
>  FAIL: gdb.base/disp-step-syscall.exp: vfork: continue to marker (vfork) (the program is no longer running)
> 
> First, the lack of fork support on remote targets is supposed to be
> kfailed, so the KPASS is obviously bogus.  The extended-remote board
> should have KFAILed too.
> 
> The problem is that the test is using "is_remote" instead of
> gdb_is_target_remote.
> 
> And then, I get:
> 
>  (gdb) PASS: gdb.base/disp-step-syscall.exp: vfork: set displaced-stepping on
>  stepi
> 
>  Program terminated with signal SIGSEGV, Segmentation fault.
>  The program no longer exists.
>  (gdb) PASS: gdb.base/disp-step-syscall.exp: vfork: single step over vfork
> 
> Obviously, that should be a FAIL.  The problem is that the test only
> expects SIGILL, not SIGSEGV.  It also doesn't bail correctly if an
> internal error or some other pattern caught by gdb_test_multiple
> matches.  The test doesn't really need to match specific exits/crashes
> patterns, if the PASS regex is improved, like in ...
> 
> ... this and the other "stepi" tests are a bit too lax, passing on
> ".*".  This tightens those up to expect "x/i" and the "=>" current PC
> indicator, like in:
> 
>  1: x/i $pc
>  => 0x3b36abc9e2 <vfork+34>:     syscall
> 
> On x86_64 Fedora 20, I now get a quick KFAIL instead of timeouts with
> both the native-extended-gdbserver and native-gdbserver boards:
> 
>  PASS: gdb.base/disp-step-syscall.exp: vfork: delete break vfork
>  PASS: gdb.base/disp-step-syscall.exp: vfork: continue to syscall insn vfork
>  PASS: gdb.base/disp-step-syscall.exp: vfork: set displaced-stepping on
>  KFAIL: gdb.base/disp-step-syscall.exp: vfork: single step over vfork (PRMS: server/13796)
> 
> and a full pass with native testing.
> 
> gdb/testsuite/
> 2015-03-02  Pedro Alves  <palves@redhat.com>
> 
> 	* gdb.base/disp-step-syscall.exp (disp_step_cross_syscall.exp):
> 	Use gdb_is_target_remote instead of is_remote.  Use
> 	gdb_test_multiple instead of gdb_expect.  Exit early if
> 	gdb_test_multiple hits its internal matches.  Tighten stepi tests
> 	expected output.  Fail on exit with any signal, instead of just
> 	SIGILL.
> ---
>  gdb/testsuite/gdb.base/disp-step-syscall.exp | 53 ++++++++++++++--------------
>  1 file changed, 26 insertions(+), 27 deletions(-)
> 
> diff --git a/gdb/testsuite/gdb.base/disp-step-syscall.exp b/gdb/testsuite/gdb.base/disp-step-syscall.exp
> index ff66f83..b13dce4 100644
> --- a/gdb/testsuite/gdb.base/disp-step-syscall.exp
> +++ b/gdb/testsuite/gdb.base/disp-step-syscall.exp
> @@ -49,6 +49,8 @@ proc disp_step_cross_syscall { syscall } {
>  	    return
>  	}
>  
> +	set is_target_remote [gdb_is_target_remote]
> +
>  	# Delete the breakpoint on main.
>  	gdb_test_no_output "delete break 1"
>  
> @@ -77,27 +79,34 @@ proc disp_step_cross_syscall { syscall } {
>  	gdb_test "display/i \$pc" ".*"
>  
>  
> -	# Single step until we see sysall insn or we reach the upper bound of loop
> -	# iterations.
> -	set see_syscall_insn 0
> -
> -	for {set i 0} {$i < 1000 && $see_syscall_insn == 0} {incr i} {
> -	    send_gdb "stepi\n"
> -	    gdb_expect {
> -		-re ".*$syscall_insn.*$gdb_prompt $" {
> -		    set see_syscall_insn 1
> +	# Single step until we see a syscall insn or we reach the
> +	# upper bound of loop iterations.
> +	set msg "find syscall insn in $syscall"
> +	set steps 0
> +	set max_steps 1000
> +	gdb_test_multiple "stepi" $msg {
> +	    -re ".*$syscall_insn.*$gdb_prompt $" {
> +		pass $msg
> +	    }
> +	    -re "x/i .*=>.*\r\n$gdb_prompt $" {
> +		incr steps
> +		if {$steps == $max_steps} {
> +		    fail $msg
> +		} else {
> +		    send_gdb "stepi\n"
> +		    exp_continue
>  		}
> -		-re ".*$gdb_prompt $" {}
>  	    }
>  	}
>  
> -	if {$see_syscall_insn == 0} then {
> -	    fail "find syscall insn in $syscall"
> +	if {$steps == $max_steps} {
>  	    return -1
>  	}
>  
>  	set syscall_insn_addr [get_hexadecimal_valueof "\$pc" "0"]
> -	gdb_test "stepi" ".*" "stepi $syscall insn"
> +	if {[gdb_test "stepi" "x/i .*=>.*" "stepi $syscall insn"] != 0} {
> +	    return -1
> +	}
>  	set syscall_insn_next_addr [get_hexadecimal_valueof "\$pc" "0"]
>  
>  	gdb_test "continue" "Continuing\\..*Breakpoint \[0-9\]+, (.* in |__libc_|)$syscall \\(\\).*" \
> @@ -121,22 +130,12 @@ proc disp_step_cross_syscall { syscall } {
>  	gdb_test_no_output "set displaced-stepping on"
>  
>  	# Check the address of next instruction of syscall.
> -	if {$syscall == "vfork" && [is_remote target]} {
> +	if {$syscall == "vfork" && $is_target_remote} {
>  	    setup_kfail server/13796 "*-*-*"
>  	}
> -	set test "single step over $syscall"
> -	gdb_test_multiple "stepi" $test {
> -	    -re "Program terminated with signal SIGILL,.*\r\n$gdb_prompt $" {
> -		fail $test
> -		return
> -	    }
> -	    -re "\\\[Inferior .* exited normally\\\].*\r\n$gdb_prompt $" {
> -		fail $test
> -		return
> -	    }
> -	    -re "\r\n$gdb_prompt $" {
> -		pass $test
> -	    }
> +
> +	if {[gdb_test "stepi" "x/i .*=>.*" "single step over $syscall"] != 0} {
> +	    return -1
>  	}
>  
>  	set syscall_insn_next_addr_found [get_hexadecimal_valueof "\$pc" "0"]
>