From 35ed81d4f45855b98ea0c517b396662c3ae2a8c5 Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Tue, 23 Oct 2018 17:00:33 -0400 Subject: [PATCH] Avoid GDB SIGTTOU on catch exec + set follow-exec-mode new (PR 23368) Here's a summary of PR 23368: #include int main (void) { char *exec_args[] = { "/bin/ls", NULL }; execve (exec_args[0], exec_args, NULL); } $ gdb -nx t -ex "catch exec" -ex "set follow-exec-mode new" -ex run ... [1] + 13146 suspended (tty output) gdb -q -nx t -ex "catch exec" -ex "set follow-exec-mode new" -ex run $ Here's what happens: when the inferior execs with "follow-exec-mode new", we first "mourn" it before creating the new one. This ends up calling inflow_inferior_exit, which sets the per-inferior terminal state to "is_ours": inf->terminal_state = target_terminal_state::is_ours; At this point, the inferior's terminal_state is is_ours, while the "reality", tracked by gdb_tty_state, is is_inferior (GDB doesn't own the terminal). Later, we continue processing the exec inferior event and decide we want to stop (because of the "catch exec") and call target_terminal::ours to make sure we own the terminal. However, we don't actually go to the target backend to change the settings, because the core thinks that no inferior owns the terminal (inf->terminal_state is target_terminal_state::is_ours, as checked in target_terminal_is_ours_kind, for both inferiors). When something in readline tries to mess with the terminal settings, it generates a SIGTTOU. This patch fixes this by tranferring the state of the terminal from the old inferior to the new inferior. gdb/ChangeLog: PR gdb/23368 * infrun.c (follow_exec): In the follow_exec_mode_new case, transfer terminal state from old new new inferior. * terminal.h (swap_terminal_info): New function. * inflow.c (swap_terminal_info): New function. --- gdb/ChangeLog | 8 ++++++++ gdb/inflow.c | 16 ++++++++++++++++ gdb/infrun.c | 10 ++++++---- gdb/terminal.h | 3 +++ 4 files changed, 33 insertions(+), 4 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 19a87f40fe..5ef217d446 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,11 @@ +2018-10-23 Simon Marchi + + PR gdb/23368 + * infrun.c (follow_exec): In the follow_exec_mode_new case, + transfer terminal state from old new new inferior. + * terminal.h (swap_terminal_info): New function. + * inflow.c (swap_terminal_info): New function. + 2018-10-23 Tom Tromey * record-btrace.c (get_thread_current_frame_id): Rename from diff --git a/gdb/inflow.c b/gdb/inflow.c index caff646207..a0c1c7d884 100644 --- a/gdb/inflow.c +++ b/gdb/inflow.c @@ -702,6 +702,22 @@ copy_terminal_info (struct inferior *to, struct inferior *from) to->terminal_state = from->terminal_state; } +/* See terminal.h. */ + +void +swap_terminal_info (inferior *a, inferior *b) +{ + terminal_info *info_a + = (terminal_info *) inferior_data (a, inflow_inferior_data); + terminal_info *info_b + = (terminal_info *) inferior_data (a, inflow_inferior_data); + + set_inferior_data (a, inflow_inferior_data, info_b); + set_inferior_data (b, inflow_inferior_data, info_a); + + std::swap (a->terminal_state, b->terminal_state); +} + void info_terminal_command (const char *arg, int from_tty) { diff --git a/gdb/infrun.c b/gdb/infrun.c index 72e2496176..9473d1f20f 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -1189,12 +1189,14 @@ follow_exec (ptid_t ptid, char *exec_file_target) /* The user wants to keep the old inferior and program spaces around. Create a new fresh one, and switch to it. */ - /* Do exit processing for the original inferior before adding - the new inferior so we don't have two active inferiors with - the same ptid, which can confuse find_inferior_ptid. */ + /* Do exit processing for the original inferior before setting the new + inferior's pid. Having two inferiors with the same pid would confuse + find_inferior_p(t)id. Transfer the terminal state and info from the + old to the new inferior. */ + inf = add_inferior_with_spaces (); + swap_terminal_info (inf, current_inferior ()); exit_inferior_silent (current_inferior ()); - inf = add_inferior_with_spaces (); inf->pid = pid; target_follow_exec (inf, exec_file_target); diff --git a/gdb/terminal.h b/gdb/terminal.h index 7774eefcd4..da27e46f6e 100644 --- a/gdb/terminal.h +++ b/gdb/terminal.h @@ -29,6 +29,9 @@ extern void new_tty_postfork (void); extern void copy_terminal_info (struct inferior *to, struct inferior *from); +/* Exchange the terminal info and state between inferiors A and B. */ +extern void swap_terminal_info (inferior *a, inferior *b); + extern pid_t create_tty_session (void); /* Set up a serial structure describing standard input. In inflow.c. */