Fix for PR gdb/17235: possible bug extracting systemtap probe operand

This patch is a fix to PR gdb/17235.  The bug is about an unused
variable that got declared and set during one of the parsing phases of
an SDT probe's argument.  I took the opportunity to rewrite some of the
code to improve the parsing.  The bug was actually a thinko, because
what I wanted to do in the code was to discard the number on the string
being parsed.

During this portion, the code identifies that it is dealing with an
expression that begins with a sign ('+', '-' or '~').  This means that
the expression could be:

- a numeric literal (e.g., '+5')
- a register displacement (e.g., '-4(%rsp)')
- a subexpression (e.g., '-(2*3)')

So, after saving the sign and moving forward 1 char, now the code needs
to know if there is a digit followed by a register displacement prefix
operand (e.g., '(' on x86_64).  If yes, then it is a register
operation.  If not, then it will be handled recursively, and the code
will later apply the requested operation on the result (either a '+', a
'-' or a '~').

With the bug, the code was correctly discarding the digit (though using
strtol unnecessarily), but it wasn't properly dealing with
subexpressions when the register indirection prefix was '(', like on
x86_64.  This patch also fixes this bug, and includes a testcase.  It
passes on x86_64 Fedora 20.
This commit is contained in:
Sergio Durigan Junior 2014-09-05 15:21:44 -04:00
parent 514104634d
commit 474ca4f687
5 changed files with 103 additions and 18 deletions

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@ -1,3 +1,10 @@
2014-09-05 Sergio Durigan Junior <sergiodj@redhat.com>
PR gdb/17235
* stap-probe.c (stap_parse_single_operand): Delete unused variable
'number'. New variable 'has_digit'. Rewrite code to deal with
subexpressions on SDT probes.
2014-09-04 Pedro Alves <palves@redhat.com>
* c-exp.y (parse_number): Skip handling base-switching prefixes if

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@ -753,9 +753,9 @@ stap_parse_single_operand (struct stap_parse_info *p)
if (*p->arg == '-' || *p->arg == '~' || *p->arg == '+')
{
char c = *p->arg;
int number;
/* We use this variable to do a lookahead. */
const char *tmp = p->arg;
int has_digit = 0;
/* Skipping signal. */
++tmp;
@ -772,26 +772,19 @@ stap_parse_single_operand (struct stap_parse_info *p)
if (p->inside_paren_p)
tmp = skip_spaces_const (tmp);
if (isdigit (*tmp))
while (isdigit (*tmp))
{
char *endp;
number = strtol (tmp, &endp, 10);
tmp = endp;
/* We skip the digit here because we are only interested in
knowing what kind of unary operation this is. The digit
will be handled by one of the functions that will be
called below ('stap_parse_argument_conditionally' or
'stap_parse_register_operand'). */
++tmp;
has_digit = 1;
}
if (!stap_is_register_indirection_prefix (gdbarch, tmp, NULL))
{
/* This is not a displacement. We skip the operator, and deal
with it later. */
++p->arg;
stap_parse_argument_conditionally (p);
if (c == '-')
write_exp_elt_opcode (&p->pstate, UNOP_NEG);
else if (c == '~')
write_exp_elt_opcode (&p->pstate, UNOP_COMPLEMENT);
}
else
if (has_digit && stap_is_register_indirection_prefix (gdbarch, tmp,
NULL))
{
/* If we are here, it means it is a displacement. The only
operations allowed here are `-' and `+'. */
@ -801,6 +794,17 @@ stap_parse_single_operand (struct stap_parse_info *p)
stap_parse_register_operand (p);
}
else
{
/* This is not a displacement. We skip the operator, and
deal with it when the recursion returns. */
++p->arg;
stap_parse_argument_conditionally (p);
if (c == '-')
write_exp_elt_opcode (&p->pstate, UNOP_NEG);
else if (c == '~')
write_exp_elt_opcode (&p->pstate, UNOP_COMPLEMENT);
}
}
else if (isdigit (*p->arg))
{

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@ -1,3 +1,9 @@
2014-09-05 Sergio Durigan Junior <sergiodj@redhat.com>
PR gdb/17235
* gdb.arch/amd64-stap-wrong-subexp.exp: New file.
* gdb.arch/amd64-stap-wrong-subexp.S: Likewise.
2014-09-04 Sergio Durigan Junior <sergiodj@redhat.com>
PR fortran/17237

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@ -0,0 +1,27 @@
/* 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-wrong-subexp.S"
.text
.globl main
main:
STAP_PROBE1(probe, foo, -4@$-3($4+$3))
STAP_PROBE2(probe, bar, -4@-($4), -4@$-3+($22/$2)-$16)
xor %rax,%rax
ret

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@ -0,0 +1,41 @@
# 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/>.
if { ![istarget "x86_64-*-*"] || ![is_lp64_target] } {
verbose "Skipping amd64-stap-wrong-subexp.exp"
return
}
standard_testfile amd64-stap-wrong-subexp.S
if { [prepare_for_testing $testfile.exp $testfile $srcfile] } {
untested amd64-stap-wrong-subexp.exp
return -1
}
proc goto_probe { probe_name } {
if { ![runto "-pstap $probe_name"] } {
fail "run to probe $probe_name"
return
}
}
goto_probe foo
gdb_test "print \$_probe_arg0" "Invalid operator `\\\(' on expression .*" \
"print probe foo arg0"
goto_probe bar
gdb_test "print \$_probe_arg0" " = -4" "print probe bar arg0"
gdb_test "print \$_probe_arg1" " = -8" "print probe bar arg1"