[PATCH v5 5/5] Implement proper "startup-with-shell" support on gdbserver

Sergio Durigan Junior
2017-03-30T01:55:12Z

This patch implements the proper support for the "startup-with-shell"
feature on gdbserver. A new packet is added, QStartupWithShell, and
it is sent on initialization. If the host sends a
"QStartupWithShell:1", it means the inferior shall be started using a
shell. If the host sends a "QStartupWithShell:0", it means the
inferior shall be started without using a shell. Any other value is
considered an error.

There is no way to remotely set the shell that will be used by the
target to start the inferior. In order to do that, the user must
start gdbserver while providing a shell via the $SHELL environment
variable. The same is true for the host side.

The "set startup-with-shell" setting from the host side is used to
decide whether to start the remote inferior using a shell. This same
setting is also used to decide whether to use a shell to start the
host inferior; this means that it is not really possible to start the
inferior using different mechanisms on target and host.

A documentation patch is included, along with a new testcase for the
feature.

gdb/ChangeLog:
yyyy-mm-dd Sergio Durigan Junior <sergiodj@redhat.com>

* NEWS (Changes since GDB 7.12): Announce that GDBserver is now
able to start inferiors using a shell.
(New remote packets): Announce new packet "QStartupWithShell".
* remote.c: Add PACKET_QStartupWithShell.
(extended_remote_create_inferior): Handle new
PACKET_QStartupWithShell.
(remote_protocol_features) <QStartupWithShell>: New entry for
PACKET_QStartupWithShell.
(_initialize_remote): Call "add_packet_config_cmd" for
QStartupShell.

gdb/gdbserver/ChangeLog:
yyyy-mm-dd Sergio Durigan Junior <sergiodj@redhat.com>

* server.c (handle_general_set): Handle new packet
"QStartupWithShell".
(handle_query): Add "QStartupWithShell" to the list of supported
packets.
(gdbserver_usage): Add help text explaining the
new "--startup-with-shell" and "--no-startup-with-shell" CLI
options.
(captured_main): Recognize and act upon the presence of the new
CLI options.

gdb/testsuite/ChangeLog:
yyyy-mm-dd Sergio Durigan Junior <sergiodj@redhat.com>

* gdb.base/startup-with-shell.c: New file.
* gdb.base/startup-with-shell.exp: Likewise.

gdb/doc/ChangeLog:
yyyy-mm-dd Sergio Durigan Junior <sergiodj@redhat.com>

* gdb.texinfo (Starting) <startup-with-shell>: Add @anchor.
(Connecting) <Remote Packet>: Add "startup-with-shell"
and "QStartupWithShell" to the table.
(Remote Protocol) <QStartupWithShell>: New item, explaining the
packet.
---
gdb/NEWS | 12 ++++
gdb/doc/gdb.texinfo | 39 +++++++++++++
gdb/gdbserver/server.c | 38 ++++++++++++-
gdb/remote.c | 20 +++++++
gdb/testsuite/gdb.base/startup-with-shell.c | 29 ++++++++++
gdb/testsuite/gdb.base/startup-with-shell.exp | 79 +++++++++++++++++++++++++++
6 files changed, 216 insertions(+), 1 deletion(-)
create mode 100644 gdb/testsuite/gdb.base/startup-with-shell.c
create mode 100644 gdb/testsuite/gdb.base/startup-with-shell.exp

diff --git a/gdb/NEWS b/gdb/NEWS
index 29ae40c..485b9dd 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,15 @@

*** Changes since GDB 7.12

+* On Unix systems, GDBserver now does globbing expansion and variable
+ substitution in inferior command line arguments.
+
+ This is done by starting inferiors using a shell, like GDB does.
+ See "set startup-with-shell" in the user manual for how to disable
+ this from GDB when using "target extended-remote". When using
+ "target remote", you can disable the startup with shell by using the
+ new "--no-startup-with-shell" GDBserver command line option.
+
* GDB now supports access to the PKU register on GNU/Linux. The register is
added by the Memory Protection Keys for Userspace feature which will be
available in future Intel CPUs.
@@ -403,6 +412,9 @@ show max-value-size

* New remote packets

+QStartupWithShell
+ Indicates whether the inferior must be started with a shell or not.
+
exec stop reason
Indicates that an exec system call was executed.

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 300d78e..01059ca 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -2153,6 +2153,7 @@ This command is available when debugging locally on most targets, excluding
@sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.

@kindex set startup-with-shell
+@anchor{set startup-with-shell}
@item set startup-with-shell
@itemx set startup-with-shell on
@itemx set startup-with-shell off
@@ -20811,6 +20812,10 @@ are:
@tab @code{QDisableRandomization}
@tab @code{set disable-randomization}

+@item @code{startup-with-shell}
+@tab @code{QStartupWithShell}
+@tab @code{set startup-with-shell}
+
@item @code{conditional-breakpoints-packet}
@tab @code{Z0 and Z1}
@tab @code{Support for target-side breakpoint condition evaluation}
@@ -36443,6 +36448,40 @@ by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
This should only be done on targets that actually support disabling
address space randomization.

+@item QStartupWithShell:@var{value}
+@cindex startup with shell, remote request
+@cindex @samp{QStartupWithShell} packet
+On UNIX-like targets, it is possible to start the inferior using a
+shell program. This is the default behavior on both @value{GDBN} and
+@command{gdbserver} (@pxref{set startup-with-shell}). This packet is
+used to inform @command{gdbserver} whether it should start the
+inferior using a shell or not.
+
+If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
+to start the inferior. If @var{value} is @samp{1},
+@command{gdbserver} will use a shell to start the inferior. All other
+values are considered an error.
+
+This packet is only available in extended mode (@pxref{extended
+mode}).
+
+Reply:
+@table @samp
+@item OK
+The request succeeded.
+
+@item E @var{nn}
+An error occurred. The error number @var{nn} is given as hex digits.
+@end table
+
+This packet is not probed by default; the remote stub must request it,
+by supplying an appropriate @samp{qSupported} response
+(@pxref{qSupported}). This should only be done on targets that
+actually support starting the inferior using a shell.
+
+Use of this packet is controlled by the @code{set startup-with-shell}
+command; @pxref{set startup-with-shell}.
+
@item qfThreadInfo
@itemx qsThreadInfo
@cindex list active threads, remote request
diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c
index 31c6a6e..b9ee471 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -876,6 +876,31 @@ handle_general_set (char *own_buf)
return;
}

+ if (startswith (own_buf, "QStartupWithShell:"))
+ {
+ char *value = own_buf + strlen ("QStartupWithShell:");
+
+ if (strcmp (value, "1") == 0)
+ startup_with_shell = true;
+ else if (strcmp (value, "0") == 0)
+ startup_with_shell = false;
+ else
+ {
+ /* Unknown value. */
+ fprintf (stderr, "Unknown value to startup-with-shell: %s\n",
+ own_buf);
+ write_enn (own_buf);
+ return;
+ }
+
+ if (remote_debug)
+ debug_printf (_("[Inferior will %s started with shell]"),
+ startup_with_shell ? "be" : "not be");
+
+ write_ok (own_buf);
+ return;
+ }
+
/* Otherwise we didn't know what packet it was. Say we didn't
understand it. */
own_buf[0] = 0;
@@ -2312,7 +2337,7 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
}

sprintf (own_buf,
- "PacketSize=%x;QPassSignals+;QProgramSignals+",
+ "PacketSize=%x;QPassSignals+;QProgramSignals+;QStartupWithShell+",
PBUFSIZ - 1);

if (target_supports_catch_syscall ())
@@ -3419,6 +3444,13 @@ gdbserver_usage (FILE *stream)
" --no-disable-randomization\n"
" Don't disable address space randomization when\n"
" starting PROG.\n"
+ " --startup-with-shell\n"
+ " Start PROG using a shell. I.e., execs a shell that\n"
+ " then execs PROG. (default)\n"
+ " --no-startup-with-shell\n"
+ " Exec PROG directly instead of using a shell.\n"
+ " Disables argument globbing and variable substitution\n"
+ " on UNIX-like systems.\n"
"\n"
"Debug options:\n"
"\n"
@@ -3702,6 +3734,10 @@ captured_main (int argc, char *argv[])
disable_randomization = 1;
else if (strcmp (*next_arg, "--no-disable-randomization") == 0)
disable_randomization = 0;
+ else if (strcmp (*next_arg, "--startup-with-shell") == 0)
+ startup_with_shell = true;
+ else if (strcmp (*next_arg, "--no-startup-with-shell") == 0)
+ startup_with_shell = false;
else if (strcmp (*next_arg, "--once") == 0)
run_once = 1;
else
diff --git a/gdb/remote.c b/gdb/remote.c
index 92e3e6e..05fc4ee 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1428,6 +1428,7 @@ enum {
PACKET_QPassSignals,
PACKET_QCatchSyscalls,
PACKET_QProgramSignals,
+ PACKET_QStartupWithShell,
PACKET_qCRC,
PACKET_qSearch_memory,
PACKET_vAttach,
@@ -4633,6 +4634,8 @@ static const struct protocol_feature remote_protocol_features[] = {
PACKET_QCatchSyscalls },
{ "QProgramSignals", PACKET_DISABLE, remote_supported_packet,
PACKET_QProgramSignals },
+ { "QStartupWithShell", PACKET_DISABLE, remote_supported_packet,
+ PACKET_QStartupWithShell },
{ "QStartNoAckMode", PACKET_DISABLE, remote_supported_packet,
PACKET_QStartNoAckMode },
{ "multiprocess", PACKET_DISABLE, remote_supported_packet,
@@ -9614,6 +9617,20 @@ extended_remote_create_inferior (struct target_ops *ops,
if (extended_remote_supports_disable_randomization (ops))
extended_remote_disable_randomization (disable_randomization);

+ /* If startup-with-shell is on, we inform gdbserver to start the
+ remote inferior using a shell. */
+ if (packet_support (PACKET_QStartupWithShell) != PACKET_DISABLE)
+ {
+ xsnprintf (rs->buf, get_remote_packet_size (),
+ "QStartupWithShell:%d", startup_with_shell ? 1 : 0);
+ putpkt (rs->buf);
+ getpkt (&rs->buf, &rs->buf_size, 0);
+ if (strcmp (rs->buf, "OK") != 0)
+ error (_("\
+Remote replied unexpectedly while setting startup-with-shell: %s"),
+ rs->buf);
+ }
+
/* Now restart the remote server. */
run_worked = extended_remote_run (args) != -1;
if (!run_worked)
@@ -14112,6 +14129,9 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
add_packet_config_cmd (&remote_protocol_packets[PACKET_QProgramSignals],
"QProgramSignals", "program-signals", 0);

+ add_packet_config_cmd (&remote_protocol_packets[PACKET_QStartupWithShell],
+ "QStartupWithShell", "startup-with-shell", 0);
+
add_packet_config_cmd (&remote_protocol_packets[PACKET_qSymbol],
"qSymbol", "symbol-lookup", 0);

diff --git a/gdb/testsuite/gdb.base/startup-with-shell.c b/gdb/testsuite/gdb.base/startup-with-shell.c
new file mode 100644
index 0000000..6278447
--- /dev/null
+++ b/gdb/testsuite/gdb.base/startup-with-shell.c
@@ -0,0 +1,29 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2017 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/>. */
+
+#include <stdio.h>
+
+int
+main (int argc, char *argv[])
+{
+ int i;
+
+ for (i = 0; argv[i] != NULL; ++i)
+ printf ("ARG %d = %s\n", i, argv[i]);
+
+ return 0;
+}
diff --git a/gdb/testsuite/gdb.base/startup-with-shell.exp b/gdb/testsuite/gdb.base/startup-with-shell.exp
new file mode 100644
index 0000000..1284829
--- /dev/null
+++ b/gdb/testsuite/gdb.base/startup-with-shell.exp
@@ -0,0 +1,79 @@
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2017 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 test doesn't make sense on native-gdbserver.
+if { [use_gdb_stub] } {
+ untested "not supported"
+ return
+}
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile debug] } {
+ return -1
+}
+
+set unique_file [standard_output_file "unique-file.unique-extension"]
+
+# Initial setup for simple test (wildcard expansion, variable substitution).
+
+proc initial_setup_simple { startup_with_shell run_args } {
+ global hex decimal binfile unique_file
+
+ clean_restart $binfile
+
+ gdb_test_no_output "set startup-with-shell $startup_with_shell"
+
+ gdb_test_no_output "set args $run_args"
+
+ set test "inferior started"
+ if { [runto_main] } {
+ pass $test
+ } else {
+ fail $test
+ }
+}
+
+## Run the actual tests
+
+with_test_prefix "startup_with_shell = on; run_args = *.unique-extension" {
+ initial_setup_simple "on" "*.unique-extension"
+ gdb_test "print argv\[1\]" "\\\$$decimal = $hex \"unique-file\.unique-extension\"" \
+ "first argument expanded"
+}
+
+with_test_prefix "startup_with_shell = off; run_args = *.unique-extension" {
+ initial_setup_simple "off" "*.unique-extension"
+ gdb_test "print argv\[1\]" "\\\$$decimal = $hex \"\\\*\.unique-extension\"" \
+ "first argument not expanded"
+}
+
+with_test_prefix "startup_with_shell = on; run_args = \$TEST" {
+ set env(TEST) "1234"
+ initial_setup_simple "on" "\$TEST"
+ gdb_test "print argv\[1\]" "\\\$$decimal = $hex \"1234\"" \
+ "testing first argument"
+ unset env(TEST)
+}
+
+with_test_prefix "startup_with_shell = off; run_args = \$TEST" {
+ set env(TEST) "1234"
+ initial_setup_simple "off" "\$TEST"
+ gdb_test "print argv\[1\]" "\\\$$decimal = $hex \"\\\$TEST\"" \
+ "testing first argument"
+ unset env(TEST)
+}
--
2.9.3