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List:       busybox
Subject:    [PATCH] [2/2] modinfo: Add -k option to use a different kernel version
From:       Jeff Pohlmeyer <yetanothergeek () gmail ! com>
Date:       2024-02-07 13:57:16
Message-ID: CAEuRe+0AeNGAVjGgmLwhcSeQFHbg=wsxy9wtAbQwfVT+ZPCRzw () mail ! gmail ! com
[Download RAW message or body]

(These two patches are somewhat related but do not depend on each other and
can be applied separately.)

Support -k to use another kernel version (30 bytes)

Normally modinfo will use version information from the currently running
kernel (similar to `uname -r`). This patch adds a compile-time configuration
option to enable the -k switch, which allows specifying a different kernel
version. This can be useful with the -F {depends,softdep} options to determine
module dependencies when building a new initramfs aftera kernel upgrade.


function                                             old     new   delta
modinfo_main                                         380     430     +50
.rodata                                           103911  103913      +2
packed_usage                                       34776   34754     -22
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 52/-22)             Total: 30 bytes
   text       data        bss        dec        hex    filename
1180482       7435       4984    1192901     1233c5    busybox_old
1180512       7435       4984    1192931     1233e3    busybox_unstripped

["modinfo-add-set-version-option.patch" (text/x-patch)]

From 1754febf622c743855913e56b823296dd29335b0 Mon Sep 17 00:00:00 2001
From: Jeff Pohlmeyer <yetanothergeek@gmail.com>
Date: Fri, 2 Feb 2024 05:48:29 -0600
Subject: [PATCH] modinfo: Add -k option to use a different kernel version

---
 modutils/modinfo.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/modutils/modinfo.c b/modutils/modinfo.c
index 0a86c3296..d4370aeb0 100644
--- a/modutils/modinfo.c
+++ b/modutils/modinfo.c
@@ -10,6 +10,17 @@
 //config:	default y
 //config:	help
 //config:	Show information about a Linux Kernel module
+//config:config FEATURE_MODINFO_SET_VER
+//config:	bool "Support -k to use another kernel version (30 bytes)"
+//config:	default n
+//config:	depends on MODINFO
+//config:	help
+//config:	Normally modinfo will use version information from the currently
+//config:	running kernel (a la `uname -r`). Say 'y' here to enable the -k
+//config:	option, which will allow specifying a different kernel version.
+//config:	This can be useful when used with the -F depends and -F softdep
+//config:	options  to determine module dependencies when building a new
+//config:	initramfs after a kernel upgrade.
 
 //applet:IF_MODINFO(APPLET_NOEXEC(modinfo, modinfo, BB_DIR_SBIN, BB_SUID_DROP, modinfo))
 
@@ -43,6 +54,7 @@ enum {
 	 * fields not selectable with "shortcut" options
 	 */
 	OPT_n = (1 << 2),
+	OPT_k = (1 << 7) * ENABLE_FEATURE_MODINFO_SET_VER,
 	OPT_TAGS = ((1 << ARRAY_SIZE(shortcuts)) - 1) << 2,
 };
 
@@ -132,13 +144,20 @@ static void modinfo(const char *path, const char *version,
 ////usage:     "\n	-n		Shortcut for '-F filename'"
 //usage:     "\n	-F keyword	Keyword to look for"
 //usage:     "\n	-0		NUL terminated output"
+//usage:	IF_FEATURE_MODINFO_SET_VER(
+//usage:     "\n	-k VERSION	Use kernel VERSION"
+//usage:	)
 //usage:#define modinfo_example_usage
 //usage:       "$ modinfo -F vermagic loop\n"
 
+#define MODINFO_OPTS "^" "0F:nadlp" IF_FEATURE_MODINFO_SET_VER("k:") \
+"\0" "-1" /*minimum one arg*/
+
 int modinfo_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int modinfo_main(int argc UNUSED_PARAM, char **argv)
 {
 	const char *field;
+	IF_FEATURE_MODINFO_SET_VER(const char *version = NULL;)
 	char name[MODULE_NAME_LEN];
 	struct utsname uts;
 	parser_t *parser;
@@ -147,13 +166,20 @@ int modinfo_main(int argc UNUSED_PARAM, char **argv)
 	unsigned i;
 
 	field = NULL;
-	opts = getopt32(argv, "^" "0F:nadlp" "\0" "-1"/*minimum one arg*/, &field);
+	opts = getopt32(argv, MODINFO_OPTS, &field IF_FEATURE_MODINFO_SET_VER(, &version));
+
+	uname(&uts);
+	IF_FEATURE_MODINFO_SET_VER(
+		if (opts & OPT_k) {
+			safe_strncpy(uts.release, version, sizeof(uts.release));
+			opts = (option_mask32 &= ~OPT_k);
+		}
+	)
 	/* If no field selected, show all */
 	if (!(opts & (OPT_TAGS|OPT_F)))
 		option_mask32 |= OPT_TAGS;
 	argv += optind;
 
-	uname(&uts);
 	parser = config_open2(
 		xasprintf("%s/%s/%s", CONFIG_DEFAULT_MODULES_DIR, uts.release, CONFIG_DEFAULT_DEPMOD_FILE),
 		xfopen_for_read
-- 
2.43.0



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