From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v2] bootconfig: do not put quotes on cmdline items unless necessary
Date: Fri,  8 Mar 2024 13:44:01 +0100	[thread overview]
Message-ID: <20240308124401.1702046-1-linux@rasmusvillemoes.dk> (raw)

When trying to migrate to using bootconfig to embed the kernel's and
PID1's command line with the kernel image itself, and so allowing
changing that without modifying the bootloader, I noticed that
/proc/cmdline changed from e.g.

  console=ttymxc0,115200n8 cma=128M quiet -- --log-level=notice

to

  console="ttymxc0,115200n8" cma="128M" quiet -- --log-level="notice"

The kernel parameters are parsed just fine, and the quotes are indeed
stripped from the actual argv[] given to PID1. However, the quoting
doesn't really serve any purpose and looks excessive, and might
confuse some (naive) userspace tool trying to parse /proc/cmdline. So
do not quote the value unless it contains whitespace.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---

v2: use strpbrk(, " \t\r\n") instead of a loop doing isspace().
Technically not quite equivalent, but much more readable, and it's
quite unlikely anybody has \f or \v or 0xa0 bytes in kernel command
line arguments. Perhaps \r and \n, and maybe even \t, could also be
dropped from that list, but those at least have some chance of
appearing in the wild.

 init/main.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/init/main.c b/init/main.c
index e24b0780fdff..3dd630132209 100644
--- a/init/main.c
+++ b/init/main.c
@@ -324,7 +324,7 @@ static int __init xbc_snprint_cmdline(char *buf, size_t size,
 {
 	struct xbc_node *knode, *vnode;
 	char *end = buf + size;
-	const char *val;
+	const char *val, *q;
 	int ret;
 
 	xbc_node_for_each_key_value(root, knode, val) {
@@ -342,8 +342,9 @@ static int __init xbc_snprint_cmdline(char *buf, size_t size,
 			continue;
 		}
 		xbc_array_for_each_value(vnode, val) {
-			ret = snprintf(buf, rest(buf, end), "%s=\"%s\" ",
-				       xbc_namebuf, val);
+			q = strpbrk(val, " \t\r\n") ? "\"" : "";
+			ret = snprintf(buf, rest(buf, end), "%s=%s%s%s ",
+				       xbc_namebuf, q, val, q);
 			if (ret < 0)
 				return ret;
 			buf += ret;
-- 
2.40.1.1.g1c60b9335d

next             reply	other threads:[~2024-03-08 12:44 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-08 12:44 Rasmus Villemoes [this message]
2024-03-10  1:25 ` [PATCH v2] bootconfig: do not put quotes on cmdline items unless necessary Masami Hiramatsu

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