116 lines
4.1 KiB
Diff
116 lines
4.1 KiB
Diff
From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
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From: Simon Marchi <simon.marchi@polymtl.ca>
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Date: Tue, 23 Oct 2018 17:00:33 -0400
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Subject: gdb-rhbz2015131-avoid-sigttou-forks-2of2.patch
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;; Avoid GDB SIGTTOU on catch exec + set follow-exec-mode new (PR 23368)
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;; (Simon Marchi, related to RHBZ 2015131)
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Here's a summary of PR 23368:
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#include <unistd.h>
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int main (void)
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{
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char *exec_args[] = { "/bin/ls", NULL };
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execve (exec_args[0], exec_args, NULL);
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}
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$ gdb -nx t -ex "catch exec" -ex "set follow-exec-mode new" -ex run
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...
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[1] + 13146 suspended (tty output) gdb -q -nx t -ex "catch exec" -ex "set follow-exec-mode new" -ex run
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$
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Here's what happens: when the inferior execs with "follow-exec-mode
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new", we first "mourn" it before creating the new one. This ends up
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calling inflow_inferior_exit, which sets the per-inferior terminal state
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to "is_ours":
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inf->terminal_state = target_terminal_state::is_ours;
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At this point, the inferior's terminal_state is is_ours, while the
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"reality", tracked by gdb_tty_state, is is_inferior (GDB doesn't own the
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terminal).
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Later, we continue processing the exec inferior event and decide we want
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to stop (because of the "catch exec") and call target_terminal::ours to
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make sure we own the terminal. However, we don't actually go to the
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target backend to change the settings, because the core thinks that no
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inferior owns the terminal (inf->terminal_state is
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target_terminal_state::is_ours, as checked in
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target_terminal_is_ours_kind, for both inferiors). When something in
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readline tries to mess with the terminal settings, it generates a
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SIGTTOU.
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This patch fixes this by tranferring the state of the terminal from the
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old inferior to the new inferior.
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gdb/ChangeLog:
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PR gdb/23368
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* infrun.c (follow_exec): In the follow_exec_mode_new case,
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transfer terminal state from old new new inferior.
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* terminal.h (swap_terminal_info): New function.
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* inflow.c (swap_terminal_info): New function.
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diff --git a/gdb/inflow.c b/gdb/inflow.c
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--- a/gdb/inflow.c
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+++ b/gdb/inflow.c
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@@ -671,6 +671,22 @@ copy_terminal_info (struct inferior *to, struct inferior *from)
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to->terminal_state = from->terminal_state;
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}
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+/* See terminal.h. */
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+
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+void
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+swap_terminal_info (inferior *a, inferior *b)
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+{
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+ terminal_info *info_a
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+ = (terminal_info *) inferior_data (a, inflow_inferior_data);
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+ terminal_info *info_b
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+ = (terminal_info *) inferior_data (a, inflow_inferior_data);
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+
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+ set_inferior_data (a, inflow_inferior_data, info_b);
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+ set_inferior_data (b, inflow_inferior_data, info_a);
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+
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+ std::swap (a->terminal_state, b->terminal_state);
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+}
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+
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void
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info_terminal_command (const char *arg, int from_tty)
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{
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diff --git a/gdb/infrun.c b/gdb/infrun.c
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--- a/gdb/infrun.c
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+++ b/gdb/infrun.c
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@@ -1197,12 +1197,14 @@ follow_exec (ptid_t ptid, char *exec_file_target)
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/* The user wants to keep the old inferior and program spaces
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around. Create a new fresh one, and switch to it. */
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- /* Do exit processing for the original inferior before adding
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- the new inferior so we don't have two active inferiors with
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- the same ptid, which can confuse find_inferior_ptid. */
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+ /* Do exit processing for the original inferior before setting the new
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+ inferior's pid. Having two inferiors with the same pid would confuse
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+ find_inferior_p(t)id. Transfer the terminal state and info from the
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+ old to the new inferior. */
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+ inf = add_inferior_with_spaces ();
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+ swap_terminal_info (inf, current_inferior ());
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exit_inferior_silent (current_inferior ());
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- inf = add_inferior_with_spaces ();
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inf->pid = pid;
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target_follow_exec (inf, exec_file_target);
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diff --git a/gdb/terminal.h b/gdb/terminal.h
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--- a/gdb/terminal.h
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+++ b/gdb/terminal.h
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@@ -29,6 +29,9 @@ extern void new_tty_postfork (void);
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extern void copy_terminal_info (struct inferior *to, struct inferior *from);
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+/* Exchange the terminal info and state between inferiors A and B. */
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+extern void swap_terminal_info (inferior *a, inferior *b);
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+
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extern pid_t create_tty_session (void);
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/* Set up a serial structure describing standard input. In inflow.c. */
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