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From d6210c3d053d70175d72ed1d1719497eed76000b Mon Sep 17 00:00:00 2001
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From: Jan Synacek <jsynacek@redhat.com>
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Date: Thu, 17 Oct 2019 09:37:35 +0200
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Subject: [PATCH] udev: introduce CONST key name
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Currently, there is no way to match against system-wide constants, such
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as architecture or virtualization type, without forking helper binaries.
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That potentially results in a huge number of spawned processes which
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output always the same answer.
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This patch introduces a special CONST keyword which takes a hard-coded
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string as its key and returns a value assigned to that key. Currently
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implemented are CONST{arch} and CONST{virt}, which can be used to match
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against the system's architecture and virtualization type.
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(based on commit 4801d8afe2ff1c1c075c9f0bc5631612172e0bb7)
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Resolves: #1762679
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---
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 man/udev.xml              | 26 ++++++++++++++++++++++++++
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 rules/40-redhat.rules     |  6 +++---
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 src/udev/udev-rules.c     | 32 ++++++++++++++++++++++++++++++++
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 test/rule-syntax-check.py |  2 +-
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 4 files changed, 62 insertions(+), 4 deletions(-)
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diff --git a/man/udev.xml b/man/udev.xml
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index bdf901a8f0..8c1eb41787 100644
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--- a/man/udev.xml
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+++ b/man/udev.xml
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@@ -236,6 +236,32 @@
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           </listitem>
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         </varlistentry>
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+        <varlistentry>
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+          <term><varname>CONST{<replaceable>key</replaceable>}</varname></term>
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+          <listitem>
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+            <para>Match against a system-wide constant. Supported keys are:</para>
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+            <variablelist>
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+              <varlistentry>
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+                <term><literal>arch</literal></term>
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+                <listitem>
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+                  <para>System's architecture. See <option>ConditionArchitecture=</option> in
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+                  <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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+                  for possible values.</para>
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+                </listitem>
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+              </varlistentry>
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+              <varlistentry>
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+                <term><literal>virt</literal></term>
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+                <listitem>
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+                  <para>System's virtualization environment. See
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+                  <citerefentry><refentrytitle>systemd-detect-virt</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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+                  for possible values.</para>
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+                </listitem>
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+              </varlistentry>
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+            </variablelist>
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+            <para>Unknown keys will never match.</para>
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+          </listitem>
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+        </varlistentry>
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+
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         <varlistentry>
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           <term><varname>TAG</varname></term>
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           <listitem>
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diff --git a/rules/40-redhat.rules b/rules/40-redhat.rules
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index fadc6e59f1..3c95cd2df0 100644
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--- a/rules/40-redhat.rules
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+++ b/rules/40-redhat.rules
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@@ -6,11 +6,11 @@ SUBSYSTEM=="cpu", ACTION=="add", TEST=="online", ATTR{online}=="0", ATTR{online}
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 # Memory hotadd request
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 SUBSYSTEM!="memory", GOTO="memory_hotplug_end"
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 ACTION!="add", GOTO="memory_hotplug_end"
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-PROGRAM="/bin/uname -p", RESULT=="s390*", GOTO="memory_hotplug_end"
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-PROGRAM="/bin/uname -p", RESULT=="ppc64*", GOTO="memory_hotplug_end"
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+CONST{arch}=="s390*", GOTO="memory_hotplug_end"
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+CONST{arch}=="ppc64*", GOTO="memory_hotplug_end"
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 ENV{.state}="online"
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-PROGRAM="/bin/systemd-detect-virt", RESULT=="none", ENV{.state}="online_movable"
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+CONST{virt}=="none", ENV{.state}="online_movable"
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 ATTR{state}=="offline", ATTR{state}="$env{.state}"
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 LABEL="memory_hotplug_end"
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diff --git a/src/udev/udev-rules.c b/src/udev/udev-rules.c
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index 58af863f3d..a246cbe67e 100644
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--- a/src/udev/udev-rules.c
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+++ b/src/udev/udev-rules.c
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@@ -17,6 +17,7 @@
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 #include <unistd.h>
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 #include "alloc-util.h"
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+#include "architecture.h"
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 #include "conf-files.h"
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 #include "dirent-util.h"
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 #include "escape.h"
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@@ -34,6 +35,7 @@
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 #include "udev.h"
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 #include "user-util.h"
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 #include "util.h"
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+#include "virt.h"
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 #define PREALLOC_TOKEN          2048
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@@ -123,6 +125,7 @@ enum token_type {
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         TK_M_DEVLINK,                   /* val */
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         TK_M_NAME,                      /* val */
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         TK_M_ENV,                       /* val, attr */
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+        TK_M_CONST,                     /* val, attr */
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         TK_M_TAG,                       /* val */
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         TK_M_SUBSYSTEM,                 /* val */
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         TK_M_DRIVER,                    /* val */
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@@ -259,6 +262,7 @@ static const char *token_str(enum token_type type) {
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                 [TK_M_DEVLINK] =                "M DEVLINK",
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                 [TK_M_NAME] =                   "M NAME",
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                 [TK_M_ENV] =                    "M ENV",
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+                [TK_M_CONST] =                  "M CONST",
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                 [TK_M_TAG] =                    "M TAG",
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                 [TK_M_SUBSYSTEM] =              "M SUBSYSTEM",
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                 [TK_M_DRIVER] =                 "M DRIVER",
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@@ -370,6 +374,7 @@ static void dump_token(struct udev_rules *rules, struct token *token) {
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         case TK_M_SYSCTL:
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         case TK_M_ATTRS:
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         case TK_M_ENV:
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+        case TK_M_CONST:
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         case TK_A_ATTR:
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         case TK_A_SYSCTL:
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         case TK_A_ENV:
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@@ -903,6 +908,7 @@ static void rule_add_key(struct rule_tmp *rule_tmp, enum token_type type,
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                 token->key.builtin_cmd = *(enum udev_builtin_cmd *)data;
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                 break;
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         case TK_M_ENV:
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+        case TK_M_CONST:
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         case TK_M_ATTR:
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         case TK_M_SYSCTL:
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         case TK_M_ATTRS:
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@@ -1226,6 +1232,17 @@ static void add_rule(struct udev_rules *rules, char *line,
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                                 rule_add_key(&rule_tmp, TK_A_ENV, op, value, attr);
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                         }
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+                } else if (startswith(key, "CONST{")) {
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+                        attr = get_key_attribute(rules->udev, key + STRLEN("CONST"));
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+                        if (attr == NULL || !STR_IN_SET(attr, "arch", "virt"))
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+                                LOG_AND_RETURN("error parsing %s attribute", "CONST");
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+
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+                        if (op == OP_REMOVE)
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+                                LOG_AND_RETURN("invalid %s operation", "CONST");
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+
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+                        if (op < OP_MATCH_MAX)
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+                                rule_add_key(&rule_tmp, TK_M_CONST, op, value, attr);
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+
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                 } else if (streq(key, "TAG")) {
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                         if (op < OP_MATCH_MAX)
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                                 rule_add_key(&rule_tmp, TK_M_TAG, op, value, NULL);
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@@ -1855,6 +1872,21 @@ void udev_rules_apply_to_event(struct udev_rules *rules,
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                                 goto nomatch;
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                         break;
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                 }
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+                case TK_M_CONST: {
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+                        const char *key_name = rules_str(rules, cur->key.attr_off);
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+                        const char *value = NULL;
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+
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+                        if (streq(key_name, "arch")) {
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+                                value = architecture_to_string(uname_architecture());
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+                        } else if (streq(key_name, "virt")) {
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+                                value = virtualization_to_string(detect_virtualization());
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+                        } else
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+                                assert_not_reached("Invalid CONST key");
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+
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+                        if (match_key(rules, cur, value))
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+                                goto nomatch;
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+                        break;
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+                }
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                 case TK_M_TAG: {
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                         struct udev_list_entry *list_entry;
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                         bool match = false;
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diff --git a/test/rule-syntax-check.py b/test/rule-syntax-check.py
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index c7c0a1a656..6e59f421f5 100755
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--- a/test/rule-syntax-check.py
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+++ b/test/rule-syntax-check.py
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@@ -19,7 +19,7 @@ quoted_string_re = r'"(?:[^\\"]|\\.)*"'
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 no_args_tests = re.compile(r'(ACTION|DEVPATH|KERNELS?|NAME|SYMLINK|SUBSYSTEMS?|DRIVERS?|TAG|PROGRAM|RESULT|TEST)\s*(?:=|!)=\s*' + quoted_string_re + '$')
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 # PROGRAM can also be specified as an assignment.
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 program_assign = re.compile(r'PROGRAM\s*=\s*' + quoted_string_re + '$')
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-args_tests = re.compile(r'(ATTRS?|ENV|TEST){([a-zA-Z0-9/_.*%-]+)}\s*(?:=|!)=\s*' + quoted_string_re + '$')
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+args_tests = re.compile(r'(ATTRS?|ENV|CONST|TEST){([a-zA-Z0-9/_.*%-]+)}\s*(?:=|!)=\s*' + quoted_string_re + '$')
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 no_args_assign = re.compile(r'(NAME|SYMLINK|OWNER|GROUP|MODE|TAG|RUN|LABEL|GOTO|WAIT_FOR|OPTIONS|IMPORT)\s*(?:\+=|:=|=)\s*' + quoted_string_re + '$')
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 args_assign = re.compile(r'(ATTR|ENV|IMPORT|RUN){([a-zA-Z0-9/_.*%-]+)}\s*(=|\+=)\s*' + quoted_string_re + '$')
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 # Find comma-separated groups, but allow commas that are inside quoted strings.