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From: Marco Elver <elver@google.com>
To: elver@google.com
Cc: linux-kernel@vger.kernel.org, vbabka@suse.cz, timur@kernel.org,
	pmladek@suse.com, rostedt@goodmis.org,
	sergey.senozhatsky@gmail.com, andriy.shevchenko@linux.intel.com,
	linux@rasmusvillemoes.dk,
	Geert Uytterhoeven <geert@linux-m68k.org>
Subject: [PATCH 2/2] lib/vsprintf: reduce space taken by no_hash_pointers warning
Date: Fri,  5 Mar 2021 20:42:06 +0100	[thread overview]
Message-ID: <20210305194206.3165917-2-elver@google.com> (raw)
In-Reply-To: <20210305194206.3165917-1-elver@google.com>

Move the no_hash_pointers warning string into __initconst section, so
that it is discarded after init. Remove common start/end characters.
Also remove repeated lines from the array, since the compiler can't
remove duplicate strings for us since the array must appear in
__initconst as defined.

Note, a similar message appears in kernel/trace/trace.c, but compiling
the feature is guarded by CONFIG_TRACING. It is not immediately obvious
if a space-concious kernel would prefer CONFIG_TRACING=n. Therefore, it
makes sense to keep the message for no_hash_pointers as __initconst, and
not move the NOTICE-printing to a common function.

Link: https://lkml.kernel.org/r/CAMuHMdULKZCJevVJcp7TxzLdWLjsQPhE8hqxhnztNi9bjT_cEw@mail.gmail.com
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Marco Elver <elver@google.com>
---
 lib/vsprintf.c | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 4a14889ccb35..1095689c9c97 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2094,26 +2094,30 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
 bool no_hash_pointers __ro_after_init;
 EXPORT_SYMBOL_GPL(no_hash_pointers);
 
+static const char no_hash_pointers_warning[8][55] __initconst = {
+	"******************************************************",
+	"   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   ",
+	" This system shows unhashed kernel memory addresses   ",
+	" via the console, logs, and other interfaces. This    ",
+	" might reduce the security of your system.            ",
+	" If you see this message and you are not debugging    ",
+	" the kernel, report this immediately to your system   ",
+	" administrator!                                       ",
+};
+
 static int __init no_hash_pointers_enable(char *str)
 {
+	/* Indices into no_hash_pointers_warning; -1 is an empty line. */
+	const int lines[] = { 0, 1, -1, 2, 3, 4, -1, 5, 6, 7, -1, 1, 0 };
+	int i;
+
 	if (no_hash_pointers)
 		return 0;
 
 	no_hash_pointers = true;
 
-	pr_warn("**********************************************************\n");
-	pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
-	pr_warn("**                                                      **\n");
-	pr_warn("** This system shows unhashed kernel memory addresses   **\n");
-	pr_warn("** via the console, logs, and other interfaces. This    **\n");
-	pr_warn("** might reduce the security of your system.            **\n");
-	pr_warn("**                                                      **\n");
-	pr_warn("** If you see this message and you are not debugging    **\n");
-	pr_warn("** the kernel, report this immediately to your system   **\n");
-	pr_warn("** administrator!                                       **\n");
-	pr_warn("**                                                      **\n");
-	pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
-	pr_warn("**********************************************************\n");
+	for (i = 0; i < ARRAY_SIZE(lines); i++)
+		pr_warn("**%54s**\n", i == -1 ? "" : no_hash_pointers_warning[lines[i]]);
 
 	return 0;
 }
-- 
2.30.1.766.gb4fecdf3b7-goog


  reply	other threads:[~2021-03-05 19:42 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-05 19:42 [PATCH 1/2] lib/vsprintf: do not show no_hash_pointers message multiple times Marco Elver
2021-03-05 19:42 ` Marco Elver [this message]
2021-03-06 20:27   ` [PATCH 2/2] lib/vsprintf: reduce space taken by no_hash_pointers warning Timur Tabi
2021-03-08 10:16   ` Petr Mladek
2021-03-08 10:51     ` Marco Elver
2021-03-12  3:46       ` Timur Tabi
2021-03-08 12:22     ` Geert Uytterhoeven
2021-03-08 17:23       ` Petr Mladek
2021-03-08 18:23         ` Marco Elver
2021-03-08 18:36           ` Andy Shevchenko
2021-03-09  9:12             ` David Laight
2021-03-08 10:33   ` Andy Shevchenko
2021-03-08 10:01 ` [PATCH 1/2] lib/vsprintf: do not show no_hash_pointers message multiple times Petr Mladek
2021-03-17 19:34   ` Marco Elver
2021-03-19 10:40     ` Petr Mladek

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