Re: [PATCH 1/2] Fix PR breakpoints/16889: gdb segfaults when printing ASM SDT arguments

Pedro Alves
2014-05-02T09:44:39Z

On 05/01/2014 10:52 PM, Sergio Durigan Junior wrote:

> gdb/testsuite/
> 2014-05-01 Sergio Durigan Junior <sergiodj@redhat.com>
>
> PR breakpoints/16889
> * gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.S: New file.
> * gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.exp: Likewise.

No "gdb/testsuite/" in the entries.

> ---

l-prefix.S b/gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.S
> new file mode 100644
> index 0000000..9c86f2d
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.S
> @@ -0,0 +1,29 @@
> +/* Copyright (C) 2014 Free Software Foundation, Inc.
> +
> + This file is part of GDB.
> +
> + 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/>. */
> +
> +#include <sys/sdt.h>
> + .file "amd64-stap-optional-prefix.S"

I think a line break after the include would read better.

> + .text
> + .globl main
> +main:

> + mov %rsp,%rbp
> + pushq $42
> + STAP_PROBE1(probe, foo, (%rsp))
> + STAP_PROBE1(probe, bar, -8(%rbp))

What controls whether the optional prefix is included? Could
we perhaps add two extra probes that probe the same values,
but use the optional prefix? Something to the effect of:

STAP_PROBE1(probe, foo, (%rsp))
STAP_PROBE1(probe, bar, -8(%rbp))
STAP_PROBE1(probe, foo_prefix, 8@(%rsp))
STAP_PROBE1(probe, bar_prefix, 8@-8(%rbp))

(but I'm clueless on how that is actually written.)

> + mov %rbp,%rsp
> + xor %rax,%rax
> + ret
> diff --git a/gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.exp b/gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.exp
> new file mode 100644
> index 0000000..9747dc8
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.exp
> @@ -0,0 +1,50 @@
> +# Copyright 2014 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/>.
> +
> +# This testcase is for PR breakpoints/16889
> +
> +if { ![istarget "x86_64-*-*"] } {
> + verbose "Skipping amd64-stap-special-operands.exp"
> + return
> +}
> +
> +standard_testfile ".S"

If you swap these, you can use $testfile:

standard_testfile ".S"

if { ![istarget "x86_64-*-*"] } {
verbose "Skipping $testfile.exp"
return
}

> +
> +if { [prepare_for_testing $testfile.exp $testfile $srcfile] } {
> + untested amd64-stap-optional-prefix.exp
> + return -1
> +}

Here too. But, prepare_for_testing already calls untested for
you, using the text passed as first argument. Write:

if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
return -1
}

> +
> +# Run to the first probe (foo).
> +
> +if { ![runto "-pstap foo"] } {
> + fail "run to probe foo"
> + return
> +}
> +
> +# Probe foo's first argument must me == $rsp

s/me/be ? I think you meant:

# Probe foo's first argument must be == ($rsp)

Might even make it easier to read to spell that out
in plain English.

Otherwise this looks good to me.

--
Pedro Alves