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According to the SystemTap documentation on user-space probes[0], stap probe points without semaphores are denoted by setting the semaphore address in the probe's note to zero. At present the code does do a comparison of the semaphore address against zero, but only after it's been relocated; as such it will (almost?) always fail, commonly resulting in GDB trying to overwrite the ELF magic located at the image's base address. This commit tests the address as specified in the SDT note rather than the relocated value in order to correctly detect absent probe semaphores. [0]: https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation gdb/Changelog: 2020-01-11 George Barrett <bob@bob131.so> * stap-probe.c (stap_modify_semaphore): Don't check for null semaphores. (stap_probe::set_semaphore, stap_probe::clear_semaphore): Check for null semaphores. gdb/testsuite/ChangeLog: 2020-01-11 George Barrett <bob@bob131.so> * gdb.base/stap-probe.c (relocation_marker): Add dummy variable to help in finding the image relocation offset. * gdb.base/stap-probe.exp (stap_test): Accept arbitrary compile options in arguments. (stap_test_no_debuginfo): Likewise. (stap-probe-nosem-noopt-pie, stap-probe-nosem-noopt-nopie): Add test variants. (stap_test): Add null semaphore relocation test.
208 lines
6.5 KiB
Plaintext
208 lines
6.5 KiB
Plaintext
# Copyright (C) 2012-2020 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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standard_testfile
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# Run the tests. We run the tests two different ways: once with a
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# plain probe, and once with a probe that has an associated semaphore.
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# This returns -1 on failure to compile or start, 0 otherwise.
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proc stap_test {exec_name {args ""}} {
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global testfile hex srcfile
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if {[prepare_for_testing "failed to prepare" ${exec_name} $srcfile \
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[concat $args debug]]} {
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return -1
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}
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set semaphore_addr_var ""
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if {[string first "-DUSE_SEMAPHORES" $args] == -1} {
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gdb_test_no_output "set breakpoint always-inserted on"
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set semaphore_addr_var [get_hexadecimal_valueof "&relocation_marker" "0"]
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}
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if ![runto_main] {
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return -1
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}
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gdb_test "print \$_probe_argc" "No probe at PC $hex" \
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"check argument not at probe point"
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if {[string first "-DUSE_SEMAPHORES" $args] != -1} {
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gdb_test "info probes stap" \
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"test *user *$hex *$hex .*"
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} else {
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gdb_test "info probes stap" \
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"test *user *$hex .*"
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}
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if {[runto "-pstap test:user"]} {
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pass "run to -pstap test:user"
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} else {
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fail "run to -pstap test:user"
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}
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if {[string first "-DUSE_SEMAPHORES" $args] == -1} {
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set relocation_base \
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[expr [get_hexadecimal_valueof "&relocation_marker" "0"] - $semaphore_addr_var]
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if {$relocation_base != 0} {
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# Checks that GDB doesn't mistakenly relocate and write to null
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# semaphore addresses. If it were to relocate a zero-valued
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# semaphore address and increment the value at that address, we
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# would expect to see "\200ELF" here instead.
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gdb_test "p (*(char*) $relocation_base)@4" \
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" = \"\\\\177ELF\"" \
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"null semaphore relocation"
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}
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}
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# Test probe arguments.
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gdb_test "print \$_probe_argc" " = 1" \
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"print \$_probe_argc for probe user"
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gdb_test "print \$_probe_arg0 == x" " = 1" \
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"check \$_probe_arg0 for probe user"
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gdb_test "print \$_probe_arg1" \
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"Invalid probe argument 1 -- probe has 1 arguments available" \
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"check \$_probe_arg1 for probe user"
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# Set a breakpoint with multiple probe locations.
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gdb_test "break -pstap test:two" \
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"Breakpoint \[0-9\]+ at $hex.*2 locations.*" \
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"set multi-location probe breakpoint (probe two)"
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# Reinit GDB, set a breakpoint on probe m4.
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delete_breakpoints
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if {[runto "-pstap test:m4"]} {
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pass "run to -pstap test:m4"
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} else {
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fail "run to -pstap test:m4"
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}
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# Testing probe arguments.
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gdb_test "print \$_probe_argc" " = 3" \
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"print \$_probe_argc for probe m4"
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gdb_test "print \$_probe_arg0" " = 42" \
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"check \$_probe_arg0 for probe m4"
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gdb_test "print (const char *) \$_probe_arg1" \
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" = $hex .This is a test message.*" \
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"check \$_probe_arg1 for probe m4"
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gdb_test "print \$_probe_arg2 == v" " = 1" \
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"check \$_probe_arg2 for probe m4"
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# Reinit GDB, set a breakpoint on probe ps.
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delete_breakpoints
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if {[runto "-pstap test:ps"]} {
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pass "run to -pstap test:m4"
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} else {
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fail "run to -pstap test:m4"
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}
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gdb_test "print \$_probe_argc" " = 3" \
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"print \$_probe_argc for probe ps"
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gdb_test "print (const char *) \$_probe_arg1" \
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" = $hex .This is another test message.*" \
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"print \$_probe_arg1 for probe ps"
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return 0
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}
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proc stap_test_no_debuginfo {exec_name {args ""}} {
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global testfile hex
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if {[prepare_for_testing "failed to prepare" ${exec_name} ${testfile}.c \
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[concat $args nodebug optimize=-O2]]} {
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return -1
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}
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if {[runto "-pstap test:user"]} {
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pass "run to -pstap test:user"
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} else {
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fail "run to -pstap test:user"
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}
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# Test probe arguments.
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gdb_test "print \$_probe_argc" " = 1" \
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"print \$_probe_argc for probe user"
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gdb_test "print \$_probe_arg0 == 23" " = 1" \
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"check \$_probe_arg0 for probe user"
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gdb_test "print \$_probe_arg1" \
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"Invalid probe argument 1 -- probe has 1 arguments available" \
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"check \$_probe_arg1 for probe user"
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# Set a breakpoint with multiple probe locations.
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# In this scenario, we may expect more than 2 locations because of
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# the optimizations (inlining, loop unrolling, etc).
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gdb_test "break -pstap test:two" \
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"Breakpoint .* at $hex.*\[0-9\]+ locations.*" \
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"set multi-location probe breakpoint (probe two)"
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# Reinit GDB, set a breakpoint on probe m4.
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delete_breakpoints
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if {[runto "-pstap test:m4"]} {
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pass "run to -pstap test:m4"
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} else {
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fail "run to -pstap test:m4"
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}
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# Testing probe arguments.
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gdb_test "print \$_probe_argc" " = 3" \
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"print \$_probe_argc for probe m4"
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gdb_test "print \$_probe_arg0" " = 42" \
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"check \$_probe_arg0 for probe m4"
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gdb_test "print (const char *) \$_probe_arg1" \
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" = $hex .This is a test message.*" \
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"check \$_probe_arg1 for probe m4"
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gdb_test "print \$_probe_arg2 == 0" " = 1" \
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"check \$_probe_arg2 for probe m4"
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# Reinit GDB, set a breakpoint on probe ps.
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delete_breakpoints
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if {[runto "-pstap test:ps"]} {
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pass "run to -pstap test:m4"
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} else {
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fail "run to -pstap test:m4"
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}
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gdb_test "print \$_probe_argc" " = 3" \
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"print \$_probe_argc for probe ps"
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gdb_test "print (const char *) \$_probe_arg1" \
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" = $hex .This is another test message.*" \
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"print \$_probe_arg1 for probe ps"
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return 0
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}
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with_test_prefix "without semaphore, not optimized" {
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if {[stap_test "stap-probe-nosem-noopt"] == -1} {
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untested "stap probe test failed"
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return -1
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}
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foreach_with_prefix pie { "nopie" "pie" } {
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stap_test "stap-probe-nosem-noopt-$pie" $pie
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}
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}
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with_test_prefix "with semaphore, not optimized" {
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stap_test "stap-probe-sem-noopt" additional_flags=-DUSE_SEMAPHORES
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}
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with_test_prefix "without semaphore, optimized" {
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stap_test_no_debuginfo "stap-probe-nosem-opt"
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}
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with_test_prefix "with semaphore, optimized" {
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stap_test_no_debuginfo "stap-probe-sem-opt" additional_flags=-DUSE_SEMAPHORES
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}
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