Merge tag 'printk-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - New "no_hash_pointers" kernel parameter causes that %p shows raw
   pointer values instead of hashed ones. It is intended only for
   debugging purposes. Misuse is prevented by a fat warning message that
   is inspired by trace_printk().

 - Prevent a possible deadlock when flushing printk_safe buffers during
   panic().

 - Fix performance regression caused by the lockless printk ringbuffer.
   It was visible with huge log buffer and long messages.

 - Documentation fix-up.

* tag 'printk-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  lib/vsprintf: no_hash_pointers prints all addresses as unhashed
  kselftest: add support for skipped tests
  lib: use KSTM_MODULE_GLOBALS macro in kselftest drivers
  printk: avoid prb_first_valid_seq() where possible
  printk: fix deadlock when kernel panic
  printk: rectify kernel-doc for prb_rec_init_wr()

3 files changed, 45 insertions, 6 deletions

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 4425a1dd4ef1..0ea0e8258f14 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -16,8 +16,7 @@
 
 #include "../tools/testing/selftests/kselftest_module.h"
 
-static unsigned total_tests __initdata;
-static unsigned failed_tests __initdata;
+KSTM_MODULE_GLOBALS();
 
 static char pbl_buffer[PAGE_SIZE] __initdata;
 
diff --git a/lib/test_printf.c b/lib/test_printf.c
index 7d60f24240a4..95a2f82427c7 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -30,11 +30,13 @@
 #define PAD_SIZE 16
 #define FILL_CHAR '$'
 
-static unsigned total_tests __initdata;
-static unsigned failed_tests __initdata;
+KSTM_MODULE_GLOBALS();
+
 static char *test_buffer __initdata;
 static char *alloced_buffer __initdata;
 
+extern bool no_hash_pointers;
+
 static int __printf(4, 0) __init
 do_test(int bufsize, const char *expect, int elen,
 	const char *fmt, va_list ap)
@@ -301,6 +303,12 @@ plain(void)
 {
 	int err;
 
+	if (no_hash_pointers) {
+		pr_warn("skipping plain 'p' tests");
+		skipped_tests += 2;
+		return;
+	}
+
 	err = plain_hash();
 	if (err) {
 		pr_warn("plain 'p' does not appear to be hashed\n");
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 3b53c73580c5..41ddc353ebb8 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2090,6 +2090,32 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
 	return widen_string(buf, buf - buf_start, end, spec);
 }
 
+/* Disable pointer hashing if requested */
+bool no_hash_pointers __ro_after_init;
+EXPORT_SYMBOL_GPL(no_hash_pointers);
+
+static int __init no_hash_pointers_enable(char *str)
+{
+	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");
+
+	return 0;
+}
+early_param("no_hash_pointers", no_hash_pointers_enable);
+
 /*
  * Show a '%p' thing.  A kernel extension is that the '%p' is followed
  * by an extra set of alphanumeric characters that are extended format
@@ -2297,8 +2323,14 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 		}
 	}
 
-	/* default is to _not_ leak addresses, hash before printing */
-	return ptr_to_id(buf, end, ptr, spec);
+	/*
+	 * default is to _not_ leak addresses, so hash before printing,
+	 * unless no_hash_pointers is specified on the command line.
+	 */
+	if (unlikely(no_hash_pointers))
+		return pointer_string(buf, end, ptr, spec);
+	else
+		return ptr_to_id(buf, end, ptr, spec);
 }
 
 /*