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From 613a02b7d67864af1860e9137e2ee101d603463e Mon Sep 17 00:00:00 2001
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From: Jan Synacek <jsynacek@redhat.com>
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Date: Thu, 25 Apr 2019 12:19:16 +0200
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Subject: [PATCH] debug-generator: enable custom systemd.debug_shell tty
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(cherry picked from commit 93912e872fb14e9c372e090409e429084a6450f5)
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Resolves: #1723722
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---
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 man/custom-entities.ent.in            |  1 +
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 man/systemd-debug-generator.xml       | 13 ++++++---
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 meson.build                           |  1 +
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 src/debug-generator/debug-generator.c | 41 +++++++++++++++++++++------
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 4 files changed, 43 insertions(+), 13 deletions(-)
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diff --git a/man/custom-entities.ent.in b/man/custom-entities.ent.in
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index e2bd44e5e7..85805777a0 100644
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--- a/man/custom-entities.ent.in
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+++ b/man/custom-entities.ent.in
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@@ -8,3 +8,4 @@
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+
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diff --git a/man/systemd-debug-generator.xml b/man/systemd-debug-generator.xml
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index fa88e8ac01..25d8b1a873 100644
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--- a/man/systemd-debug-generator.xml
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+++ b/man/systemd-debug-generator.xml
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@@ -1,6 +1,10 @@
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-
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+
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+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
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+
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+%entities;
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+]>
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   SPDX-License-Identifier: LGPL-2.1+
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 -->
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@@ -57,9 +61,10 @@
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     <option>rd.systemd.debug_shell</option> option is
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     specified, the debug shell service
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     <literal>debug-shell.service</literal> is pulled into the boot
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-    transaction. It will spawn a debug shell on tty9 during early
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-    system startup. Note that the shell may also be turned on
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-    persistently by enabling it with
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+    transaction and a debug shell will be spawned during early boot.
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+    By default, <filename>&DEBUGTTY;</filename> is used, but a specific tty can also be set,
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+    either with or without the <filename>/dev/</filename> prefix.
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+    Note that the shell may also be turned on persistently by enabling it with
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     <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
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     <command>enable</command> command.
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     <option>rd.systemd.debug_shell=</option> is honored only by initial
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diff --git a/meson.build b/meson.build
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index fe82ca4ac2..70811c29cf 100644
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--- a/meson.build
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+++ b/meson.build
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@@ -768,6 +768,7 @@ conf.set_quoted('GETTEXT_PACKAGE', meson.project_name())
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 substs.set('SUSHELL', get_option('debug-shell'))
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 substs.set('DEBUGTTY', get_option('debug-tty'))
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+conf.set_quoted('DEBUGTTY', get_option('debug-tty'))
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 enable_debug_hashmap = false
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 enable_debug_mmap_cache = false
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diff --git a/src/debug-generator/debug-generator.c b/src/debug-generator/debug-generator.c
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index 800d31cebe..ddef385833 100644
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--- a/src/debug-generator/debug-generator.c
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+++ b/src/debug-generator/debug-generator.c
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@@ -1,8 +1,11 @@
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 /* SPDX-License-Identifier: LGPL-2.1+ */
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 #include "alloc-util.h"
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+#include "dropin.h"
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+#include "generator.h"
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 #include "mkdir.h"
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 #include "parse-util.h"
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+#include "path-util.h"
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 #include "proc-cmdline.h"
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 #include "special.h"
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 #include "string-util.h"
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@@ -14,7 +17,7 @@ static char *arg_default_unit = NULL;
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 static const char *arg_dest = "/tmp";
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 static char **arg_mask = NULL;
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 static char **arg_wants = NULL;
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-static bool arg_debug_shell = false;
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+static char *arg_debug_shell = NULL;
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 static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
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         int r;
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@@ -50,15 +53,16 @@ static int parse_proc_cmdline_item(const char *key, const char *value, void *dat
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                         return log_oom();
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         } else if (proc_cmdline_key_streq(key, "systemd.debug_shell")) {
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+                const char *t = NULL;
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-                if (value) {
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-                        r = parse_boolean(value);
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-                        if (r < 0)
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-                                log_error("Failed to parse systemd.debug_shell= argument '%s', ignoring.", value);
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-                        else
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-                                arg_debug_shell = r;
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-                } else
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-                        arg_debug_shell = true;
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+                r = value ? parse_boolean(value) : 1;
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+                if (r < 0)
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+                        t = skip_dev_prefix(value);
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+                else if (r > 0)
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+                        t = skip_dev_prefix(DEBUGTTY);
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+
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+                if (free_and_strdup(&arg_debug_shell, t) < 0)
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+                        return log_oom();
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         } else if (streq(key, "systemd.unit")) {
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@@ -136,6 +140,23 @@ static int generate_wants_symlinks(void) {
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         return r;
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 }
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+static void install_debug_shell_dropin(const char *dir) {
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+        int r;
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+
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+        if (streq(arg_debug_shell, skip_dev_prefix(DEBUGTTY)))
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+                return;
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+
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+        r = write_drop_in_format(dir, "debug-shell.service", 50, "tty",
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+                        "[Unit]\n"
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+                        "Description=Early root shell on /dev/%s FOR DEBUGGING ONLY\n"
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+                        "ConditionPathExists=\n"
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+                        "[Service]\n"
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+                        "TTYPath=/dev/%s",
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+                        arg_debug_shell, arg_debug_shell);
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+        if (r < 0)
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+                log_warning_errno(r, "Failed to write drop-in for debug-shell.service, ignoring: %m");
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+}
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+
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 int main(int argc, char *argv[]) {
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         int r, q;
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@@ -164,6 +185,8 @@ int main(int argc, char *argv[]) {
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                         r = log_oom();
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                         goto finish;
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                 }
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+
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+                install_debug_shell_dropin(arg_dest);
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         }
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         r = generate_mask_symlinks();