commit c7c77ebc3aad10cbf7be91e09de839bccdbf06ca Author: Sergio Durigan Junior Date: Thu May 1 18:20:05 2014 -0300 Fix PR breakpoints/16889: gdb segfaults when printing ASM SDT arguments This commit fixes PR breakpoints/16889, which is about a bug that triggers when GDB tries to parse probes whose arguments do not contain the initial (and optional) "N@" part. For reference sake, the de facto format is described here: Anyway, this PR actually uncovered two bugs (related) that were happening while parsing the arguments. The first one was that the parser *was* catching *some* arguments that were missing the "N@" part, but it wasn't correctly setting the argument's type. This was causing a NULL pointer being dereferenced, ouch... The second bug uncovered was that the parser was not catching all of the cases for a probe which did not provide the "N@" part. The fix for that was to simplify the check that the code was making to identify non-prefixed probes. The code is simpler and easier to read now. I am also providing a testcase for this bug, only for x86_64 architectures. gdb/ 2014-05-01 Sergio Durigan Junior PR breakpoints/16889 * stap-probe.c (stap_parse_probe_arguments): Simplify check for non-prefixed probes (i.e., probes whose arguments do not start with "N@"). Always set the argument type to a sane value. gdb/testsuite/ 2014-05-01 Sergio Durigan Junior PR breakpoints/16889 * gdb.arch/amd64-stap-optional-prefix.S: New file. * gdb.arch/amd64-stap-optional-prefix.exp: Likewise. diff --git a/gdb/stap-probe.c b/gdb/stap-probe.c index dbe9f31..ef45495 100644 --- a/gdb/stap-probe.c +++ b/gdb/stap-probe.c @@ -1098,10 +1098,8 @@ stap_parse_probe_arguments (struct stap_probe *probe, struct gdbarch *gdbarch) Where `N' can be [+,-][4,8]. This is not mandatory, so we check it here. If we don't find it, go to the next state. */ - if ((*cur == '-' && cur[1] != '\0' && cur[2] != '@') - && cur[1] != '@') - arg.bitness = STAP_ARG_BITNESS_UNDEFINED; - else + if ((cur[0] == '-' && isdigit (cur[1]) && cur[2] == '@') + || (isdigit (cur[0]) && cur[1] == '@')) { if (*cur == '-') { @@ -1127,11 +1125,14 @@ stap_parse_probe_arguments (struct stap_probe *probe, struct gdbarch *gdbarch) } arg.bitness = b; - arg.atype = stap_get_expected_argument_type (gdbarch, b); /* Discard the number and the `@' sign. */ cur += 2; } + else + arg.bitness = STAP_ARG_BITNESS_UNDEFINED; + + arg.atype = stap_get_expected_argument_type (gdbarch, arg.bitness); expr = stap_parse_argument (&cur, arg.atype, gdbarch); diff --git a/gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.S b/gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.S new file mode 100644 index 0000000..66689cb --- /dev/null +++ b/gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.S @@ -0,0 +1,32 @@ +/* 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 . */ + +#include + + .file "amd64-stap-optional-prefix.S" + .text + .globl main +main: + mov %rsp,%rbp + pushq $42 + 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)) + 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..c69e54c --- /dev/null +++ b/gdb/testsuite/gdb.arch/amd64-stap-optional-prefix.exp @@ -0,0 +1,68 @@ +# 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 . + +# This testcase is for PR breakpoints/16889 + +standard_testfile ".S" + +if { ![istarget "x86_64-*-*"] } { + verbose "Skipping $testfile.exp" + return +} + +if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } { + return -1 +} + +# Helper procedure to go to probe NAME + +proc goto_probe { name } { + global decimal hex + + gdb_test "break -pstap $name" "Breakpoint $decimal at $hex" + gdb_test "continue" "Breakpoint $decimal, main \\(\\) at .*\r\n.*STAP_PROBE1.*${name},.*\\)" +} + +# Helper procedure to test the probe's argument + +proc test_probe_value { value reg_val } { + gdb_test "print \$_probe_argc" "= 1" + gdb_test "print \$_probe_arg0" "= $value" + gdb_test "print \$_probe_arg0 == *((unsigned int *) (${reg_val}))" "= 1" +} + +# Run to the first probe (foo). + +if { ![runto "-pstap foo"] } { + fail "run to probe foo" + return +} + +# Probe foo's first argument must be $rsp + +test_probe_value "42" "\$rsp" + +# Continuing to the second probe (bar) + +goto_probe "bar" +test_probe_value "42" "\$rbp - 8" + +# Now, testing the prefixed probes + +goto_probe "foo_prefix" +test_probe_value "42" "\$rsp" + +goto_probe "bar_prefix" +test_probe_value "42" "\$rbp - 8"