s390/boot: Add prefix filtering to bootdebug messages

Enhance boot debugging by allowing the "bootdebug" kernel parameter to
accept an optional comma-separated list of prefixes. Only debug messages
starting with these prefixes will be printed during boot. For example:

    bootdebug=startup,vmem

Not specifying a filter for the "bootdebug" parameter prints all debug
messages. The `boot_fmt` macro can be defined to set a common prefix:

    #define boot_fmt(fmt) "startup: " fmt

Signed-off-by: Vasily Gorbik <[email protected]>
Acked-by: Heiko Carstens <[email protected]>
Signed-off-by: Alexander Gordeev <[email protected]>

Author: Vasily Gorbik

arch/s390/boot/boot.h

@@ -77,14 +77,18 @@ void print_stacktrace(unsigned long sp);
 void error(char *m);
 int get_random(unsigned long limit, unsigned long *value);
 
-#define boot_emerg(fmt, ...)	boot_printk(KERN_EMERG fmt, ##__VA_ARGS__)
-#define boot_alert(fmt, ...)	boot_printk(KERN_ALERT fmt, ##__VA_ARGS__)
-#define boot_crit(fmt, ...)	boot_printk(KERN_CRIT fmt, ##__VA_ARGS__)
-#define boot_err(fmt, ...)	boot_printk(KERN_ERR fmt, ##__VA_ARGS__)
-#define boot_warn(fmt, ...)	boot_printk(KERN_WARNING fmt, ##__VA_ARGS__)
-#define boot_notice(fmt, ...)	boot_printk(KERN_NOTICE fmt, ##__VA_ARGS__)
-#define boot_info(fmt, ...)	boot_printk(KERN_INFO fmt, ##__VA_ARGS__)
-#define boot_debug(fmt, ...)	boot_printk(KERN_DEBUG fmt, ##__VA_ARGS__)
+#ifndef boot_fmt
+#define boot_fmt(fmt)	fmt
+#endif
+
+#define boot_emerg(fmt, ...)	boot_printk(KERN_EMERG boot_fmt(fmt), ##__VA_ARGS__)
+#define boot_alert(fmt, ...)	boot_printk(KERN_ALERT boot_fmt(fmt), ##__VA_ARGS__)
+#define boot_crit(fmt, ...)	boot_printk(KERN_CRIT boot_fmt(fmt), ##__VA_ARGS__)
+#define boot_err(fmt, ...)	boot_printk(KERN_ERR boot_fmt(fmt), ##__VA_ARGS__)
+#define boot_warn(fmt, ...)	boot_printk(KERN_WARNING boot_fmt(fmt), ##__VA_ARGS__)
+#define boot_notice(fmt, ...)	boot_printk(KERN_NOTICE boot_fmt(fmt), ##__VA_ARGS__)
+#define boot_info(fmt, ...)	boot_printk(KERN_INFO boot_fmt(fmt), ##__VA_ARGS__)
+#define boot_debug(fmt, ...)	boot_printk(KERN_DEBUG boot_fmt(fmt), ##__VA_ARGS__)
 
 extern struct machine_info machine;
 extern int boot_console_loglevel;

arch/s390/boot/ipl_parm.c

@@ -317,8 +317,11 @@ void parse_boot_command_line(void)
 			boot_earlyprintk = true;
 		if (!strcmp(param, "debug"))
 			boot_console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
-		if (!strcmp(param, "bootdebug"))
+		if (!strcmp(param, "bootdebug")) {
 			bootdebug = true;
+			if (val)
+				strncpy(bootdebug_filter, val, sizeof(bootdebug_filter) - 1);
+		}
 		if (!strcmp(param, "quiet"))
 			boot_console_loglevel = CONSOLE_LOGLEVEL_QUIET;
 		if (!strcmp(param, "ignore_loglevel"))

arch/s390/boot/printk.c

@@ -17,6 +17,7 @@ bool boot_ignore_loglevel;
 char __bootdata(boot_rb)[PAGE_SIZE * 2];
 bool __bootdata(boot_earlyprintk);
 size_t __bootdata(boot_rb_off);
+char __bootdata(bootdebug_filter)[128];
 bool __bootdata(bootdebug);
 
 static void boot_rb_add(const char *str, size_t len)
@@ -169,11 +170,12 @@ static void boot_console_earlyprintk(const char *buf)
 	/* always print emergency messages */
 	if (level > LOGLEVEL_EMERG && !boot_earlyprintk)
 		return;
+	buf = printk_skip_level(buf);
 	/* print debug messages only when bootdebug is enabled */
-	if (level == LOGLEVEL_DEBUG && !bootdebug)
+	if (level == LOGLEVEL_DEBUG && (!bootdebug || !bootdebug_filter_match(buf)))
 		return;
 	if (boot_ignore_loglevel || level < boot_console_loglevel)
-		sclp_early_printk(printk_skip_level(buf));
+		sclp_early_printk(buf);
 }
 
 #define va_arg_len_type(args, lenmod, typemod)				\

arch/s390/include/asm/boot_data.h

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _ASM_S390_BOOT_DATA_H
 
+#include <linux/string.h>
 #include <asm/setup.h>
 #include <asm/ipl.h>
 
@@ -18,6 +19,7 @@ extern unsigned long early_ipl_comp_list_size;
 extern char boot_rb[PAGE_SIZE * 2];
 extern bool boot_earlyprintk;
 extern size_t boot_rb_off;
+extern char bootdebug_filter[128];
 extern bool bootdebug;
 
 #define boot_rb_foreach(cb)							\
@@ -30,4 +32,27 @@ extern bool bootdebug;
 			cb(boot_rb + off);					\
 	} while (0)
 
+/*
+ * bootdebug_filter is a comma separated list of strings,
+ * where each string can be a prefix of the message.
+ */
+static inline bool bootdebug_filter_match(const char *buf)
+{
+	char *p = bootdebug_filter, *s;
+	char *end;
+
+	if (!*p)
+		return true;
+
+	end = p + strlen(p);
+	while (p < end) {
+		p = skip_spaces(p);
+		s = memscan(p, ',', end - p);
+		if (!strncmp(p, buf, s - p))
+			return true;
+		p = s + 1;
+	}
+	return false;
+}
+
 #endif /* _ASM_S390_BOOT_DATA_H */

arch/s390/kernel/setup.c

@@ -160,6 +160,7 @@ struct oldmem_data __bootdata_preserved(oldmem_data);
 char __bootdata(boot_rb)[PAGE_SIZE * 2];
 bool __bootdata(boot_earlyprintk);
 size_t __bootdata(boot_rb_off);
+char __bootdata(bootdebug_filter)[128];
 bool __bootdata(bootdebug);
 
 unsigned long __bootdata_preserved(VMALLOC_START);
@@ -886,16 +887,17 @@ static void __init log_component_list(void)
  * Print avoiding interpretation of % in buf and taking bootdebug option
  * into consideration.
  */
-static void __init print_rb_entry(char *buf)
+static void __init print_rb_entry(const char *buf)
 {
 	char fmt[] = KERN_SOH "0boot: %s";
 	int level = printk_get_level(buf);
 
-	if (level == KERN_DEBUG[1] && !bootdebug)
+	buf = printk_skip_level(buf);
+	if (level == KERN_DEBUG[1] && (!bootdebug || !bootdebug_filter_match(buf)))
 		return;
 
 	fmt[1] = level;
-	printk(fmt, printk_skip_level(buf));
+	printk(fmt, buf);
 }
 
 /*