From e671cd59d74cec9f53e110ce887128d1eeadb7f2 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Tue, 30 Jan 2018 14:23:51 +0000 Subject: Per-inferior target_terminal state, fix PR gdb/13211, more In my multi-target branch I ran into problems with GDB's terminal handling that exist in master as well, with multi-inferior debugging. This patch adds a testcase for said problems (gdb.multi/multi-term-settings.exp), fixes the problems, fixes PR gdb/13211 as well (and adds a testcase for that too, gdb.base/interrupt-daemon.exp). The basis of the problem I ran into is the following. Consider a scenario where you have: - inferior 1 - started with "attach", process is running on some other terminal. - inferior 2 - started with "run", process is sharing gdb's terminal. In this scenario, when you stop/resume both inferiors, you want GDB to save/restore the terminal settings of inferior 2, the one that is sharing GDB's terminal. I.e., you want inferior 2 to "own" the terminal (in target_terminal::is_ours/target_terminal::is_inferior sense). Unfortunately, that's not what you get currently. Because GDB doesn't know whether an attached inferior is actually sharing GDB's terminal, it tries to save/restore its settings anyway, ignoring errors. In this case, this is pointless, because inferior 1 is running on a different terminal, but GDB doesn't know better. And then, because it is only possible to have the terminal settings of a single inferior be in effect at a time, or make one inferior/pgrp be the terminal's foreground pgrp (aka, only one inferior can "own" the terminal, ignoring fork children here), if GDB happens to try to restore the terminal settings of inferior 1 first, then GDB never restores the terminal settings of inferior 2. This patch fixes that and a few things more along the way: - Moves enum target_terminal::terminal_state out of the target_terminal class (it's currently private) and makes it a scoped enum so that it can be easily used elsewhere. - Replaces the inflow.c:terminal_is_ours boolean with a target_terminal_state variable. This allows distinguishing is_ours and is_ours_for_output states. This allows finally making child_terminal_ours_1 do something with its "output_only" parameter. - Makes each inferior have its own copy of the is_ours/is_ours_for_output/is_inferior state. - Adds a way for GDB to tell whether the inferior is sharing GDB's terminal. Works best on Linux and Solaris; the fallback works just as well as currently. - With that, we can remove the inf->attach_flag tests from child_terminal_inferior/child_terminal_ours. - Currently target_ops.to_ours is responsible for both saving the current inferior's terminal state, and restoring gdb's state. Because each inferior has its own terminal state (possibly handled by different targets in a multi-target world, even), we need to split the inferior-saving part from the gdb-restoring part. The patch adds a new target_ops.to_save_inferior target method for that. - Adds a new target_terminal::save_inferior() function, so that sequences like: scoped_restore_terminal_state save_state; target_terminal::ours_for_output (); ... restore back inferiors that were target_terminal_state::is_inferior before back to is_inferior, and leaves inferiors that were is_ours alone. - Along the way, this adds a default implementation of target_pass_ctrlc to inflow.c (for inf-child.c), that handles passing the Ctrl-C to a process running on GDB's terminal or to some other process otherwise. - Similarly, adds a new target default implementation of target_interrupt, for the "interrupt" command. The current implementation of this hook in inf-ptrace.c kills the whole process group, but that's incorrect/undesirable because we may not be attached to all processes in the process group. And also, it's incorrect because inferior_process_group() doesn't really return the inferior's real process group id if the inferior is not a process group leader... This is the cause of PR gdb/13211 [1], which this patch fixes. While at it, that target method's "ptid" parameter is eliminated, because it's not really used. - A new test is included that exercises and fixes PR gdb/13211, and also fixes a GDB issue reported on stackoverflow that I ran into while working on this [2]. The problem is similar to PR gdb/13211, except that it also triggers with Ctrl-C. When debugging a daemon (i.e., a process that disconnects from the controlling terminal and is not a process group leader, then Ctrl-C doesn't work, you just can't interrupt the inferior at all, resulting in a hung debug session. The problem is that since the inferior is no longer associated with gdb's session / controlling terminal, then trying to put the inferior in the foreground fails. And so Ctrl-C never reaches the inferior directly. pass_signal is only used when the inferior is attached, but that is not the case here. This is fixed by the new child_pass_ctrlc. Without the fix, the new interrupt-daemon.exp testcase fails with timeout waiting for a SIGINT that never arrives. [1] PR gdb/13211 - Async / Process group and interrupt not working https://sourceware.org/bugzilla/show_bug.cgi?id=13211 [2] GDB not reacting Ctrl-C when after fork() and setsid() https://stackoverflow.com/questions/46101292/gdb-not-reacting-ctrl-c-when-after-fork-and-setsid Note this patch does _not_ fix: - PR gdb/14559 - The 'interrupt' command does not work if sigwait is in use https://sourceware.org/bugzilla/show_bug.cgi?id=14559 - PR gdb/9425 - When using "sigwait" GDB doesn't trap SIGINT. Ctrl+C terminates program when should break gdb. https://sourceware.org/bugzilla/show_bug.cgi?id=9425 The only way to fix that that I know of (without changing the kernel) is to make GDB put inferiors in a separate session (create a pseudo-tty master/slave pair, make the inferior run with the slave as its terminal, and have gdb pump output/input on the master end). gdb/ChangeLog: 2018-01-30 Pedro Alves PR gdb/13211 * config.in, configure: Regenerate. * configure.ac: Check for getpgid. * go32-nat.c (go32_pass_ctrlc): New. (go32_target): Install it. * inf-child.c (inf_child_target): Install child_terminal_save_inferior, child_pass_ctrlc and child_interrupt. * inf-ptrace.c (inf_ptrace_interrupt): Delete. (inf_ptrace_target): No longer install it. * infcmd.c (interrupt_target_1): Adjust. * inferior.h (child_terminal_save_inferior, child_pass_ctrlc) (child_interrupt): Declare. (inferior::terminal_state): New. * inflow.c (struct terminal_info): Update comments. (inferior_process_group): Delete. (terminal_is_ours): Delete. (gdb_tty_state): New. (child_terminal_init): Adjust. (is_gdb_terminal, sharing_input_terminal_1) (sharing_input_terminal): New functions. (child_terminal_inferior): Adjust. Use sharing_input_terminal. Set the process's actual process group in the foreground if possible. Handle is_ours_for_output/is_ours distinction. Don't mark terminal as the inferior's if not sharing GDB's terminal. Don't check attach_flag. (child_terminal_ours_for_output, child_terminal_ours): Adjust to pass down a target_terminal_state. (child_terminal_save_inferior): New, factored out from ... (child_terminal_ours_1): ... this. Handle target_terminal_state::is_ours_for_output. (child_interrupt, child_pass_ctrlc): New. (inflow_inferior_exit): Clear the inferior's terminal_state. (copy_terminal_info): Copy the inferior's terminal state. (_initialize_inflow): Remove reference to terminal_is_ours. * inflow.h (inferior_process_group): Delete. * nto-procfs.c (nto_handle_sigint, procfs_interrupt): Adjust. * procfs.c (procfs_target): Don't install procfs_interrupt. (procfs_interrupt): Delete. * remote.c (remote_serial_quit_handler): Adjust. (remote_interrupt): Remove ptid parameter. Adjust. * target-delegates.c: Regenerate. * target.c: Include "terminal.h". (target_terminal::terminal_state): Rename to ... (target_terminal::m_terminal_state): ... this. (target_terminal::init): Adjust. (target_terminal::inferior): Adjust to per-inferior terminal_state. (target_terminal::restore_inferior, target_terminal_is_ours_kind): New. (target_terminal::ours, target_terminal::ours_for_output): Use target_terminal_is_ours_kind. (target_interrupt): Remove ptid parameter. Adjust. (default_target_pass_ctrlc): Adjust. * target.h (target_ops::to_terminal_save_inferior): New field. (target_ops::to_interrupt): Remove ptid_t parameter. (target_interrupt): Remove ptid_t parameter. Update comment. (target_pass_ctrlc): Update comment. * target/target.h (target_terminal_state): New scoped enum, factored out of ... (target_terminal::terminal_state): ... here. (target_terminal::inferior): Update comments. (target_terminal::restore_inferior): New. (target_terminal::is_inferior, target_terminal::is_ours) (target_terminal::is_ours_for_output): Adjust. (target_terminal::scoped_restore_terminal_state): Adjust to rename, and call restore_inferior() instead of inferior(). (target_terminal::scoped_restore_terminal_state::m_state): Change type. (target_terminal::terminal_state): Rename to ... (target_terminal::m_terminal_state): ... this and change type. gdb/gdbserver/ChangeLog: 2018-01-30 Pedro Alves PR gdb/13211 * target.c (target_terminal::terminal_state): Rename to ... (target_terminal::m_terminal_state): ... this. gdb/testsuite/ChangeLog: 2018-01-30 Pedro Alves PR gdb/13211 * gdb.base/interrupt-daemon.c: New. * gdb.base/interrupt-daemon.exp: New. * gdb.multi/multi-term-settings.c: New. * gdb.multi/multi-term-settings.exp: New. --- gdb/target/target.h | 67 ++++++++++++++++++++++++++++++----------------------- 1 file changed, 38 insertions(+), 29 deletions(-) (limited to 'gdb/target') diff --git a/gdb/target/target.h b/gdb/target/target.h index 5571e16..879e730 100644 --- a/gdb/target/target.h +++ b/gdb/target/target.h @@ -95,6 +95,21 @@ extern void target_mourn_inferior (ptid_t ptid); extern int target_supports_multi_process (void); +/* Possible terminal states. */ + +enum class target_terminal_state + { + /* The inferior's terminal settings are in effect. */ + is_inferior = 0, + + /* Some of our terminal settings are in effect, enough to get + proper output. */ + is_ours_for_output = 1, + + /* Our terminal settings are in effect, for output and input. */ + is_ours = 2 + }; + /* Represents the state of the target terminal. */ class target_terminal { @@ -108,9 +123,9 @@ public: before we actually run the inferior. */ static void init (); - /* Put the inferior's terminal settings into effect. This is - preparation for starting or resuming the inferior. This is a no-op - unless called with the main UI as current UI. */ + /* Put the current inferior's terminal settings into effect. This + is preparation for starting or resuming the inferior. This is a + no-op unless called with the main UI as current UI. */ static void inferior (); /* Put our terminal settings into effect. First record the inferior's @@ -125,40 +140,34 @@ public: UI as current UI. */ static void ours_for_output (); + /* Restore terminal settings of inferiors that are in + is_ours_for_output state back to "inferior". Used when we need + to temporarily switch to is_ours_for_output state. */ + static void restore_inferior (); + /* Returns true if the terminal settings of the inferior are in effect. */ static bool is_inferior () { - return terminal_state == terminal_is_inferior; + return m_terminal_state == target_terminal_state::is_inferior; } /* Returns true if our terminal settings are in effect. */ static bool is_ours () { - return terminal_state == terminal_is_ours; + return m_terminal_state == target_terminal_state::is_ours; + } + + /* Returns true if our terminal settings are in effect. */ + static bool is_ours_for_output () + { + return m_terminal_state == target_terminal_state::is_ours_for_output; } /* Print useful information about our terminal status, if such a thing exists. */ static void info (const char *arg, int from_tty); -private: - - /* Possible terminal states. */ - - enum terminal_state - { - /* The inferior's terminal settings are in effect. */ - terminal_is_inferior = 0, - - /* Some of our terminal settings are in effect, enough to get - proper output. */ - terminal_is_ours_for_output = 1, - - /* Our terminal settings are in effect, for output and input. */ - terminal_is_ours = 2 - }; - public: /* A class that restores the state of the terminal to the current @@ -168,7 +177,7 @@ public: public: scoped_restore_terminal_state () - : m_state (terminal_state) + : m_state (m_terminal_state) { } @@ -176,14 +185,14 @@ public: { switch (m_state) { - case terminal_is_ours: + case target_terminal_state::is_ours: ours (); break; - case terminal_is_ours_for_output: + case target_terminal_state::is_ours_for_output: ours_for_output (); break; - case terminal_is_inferior: - inferior (); + case target_terminal_state::is_inferior: + restore_inferior (); break; } } @@ -192,12 +201,12 @@ public: private: - target_terminal::terminal_state m_state; + target_terminal_state m_state; }; private: - static terminal_state terminal_state; + static target_terminal_state m_terminal_state; }; #endif /* TARGET_COMMON_H */ -- cgit v1.1