linux-kernel - [PATCHv2 25/50] parisc: Add show_stack

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Date:   Mon, 16 Mar 2020 14:38:51 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        Dmitry Safonov <dima@...sta.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>, Jiri Slaby <jslaby@...e.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Helge Deller <deller@....de>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        linux-parisc@...r.kernel.org
Subject: [PATCHv2 25/50] parisc: Add show_stack_loglvl()

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Introduce show_stack_loglvl(), that eventually will substitute
show_stack().

Cc: Helge Deller <deller@....de>
Cc: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
Cc: linux-parisc@...r.kernel.org
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
 arch/parisc/kernel/traps.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index 82fc01189488..c2411de3730f 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -49,7 +49,7 @@
 #include "../math-emu/math-emu.h"	/* for handle_fpe() */
 
 static void parisc_show_stack(struct task_struct *task,
-	struct pt_regs *regs);
+	struct pt_regs *regs, const char *loglvl);
 
 static int printbinary(char *buf, unsigned long x, int nbits)
 {
@@ -155,7 +155,7 @@ void show_regs(struct pt_regs *regs)
 		printk("%s IAOQ[1]: %pS\n", level, (void *) regs->iaoq[1]);
 		printk("%s RP(r2): %pS\n", level, (void *) regs->gr[2]);
 
-		parisc_show_stack(current, regs);
+		parisc_show_stack(current, regs, KERN_DEFAULT);
 	}
 }
 
@@ -170,37 +170,43 @@ static DEFINE_RATELIMIT_STATE(_hppa_rs,
 }
 
 
-static void do_show_stack(struct unwind_frame_info *info)
+static void do_show_stack(struct unwind_frame_info *info, const char *loglvl)
 {
 	int i = 1;
 
-	printk(KERN_CRIT "Backtrace:\n");
+	printk("%sBacktrace:\n", loglvl);
 	while (i <= MAX_UNWIND_ENTRIES) {
 		if (unwind_once(info) < 0 || info->ip == 0)
 			break;
 
 		if (__kernel_text_address(info->ip)) {
-			printk(KERN_CRIT " [<" RFMT ">] %pS\n",
-				info->ip, (void *) info->ip);
+			printk("%s [<" RFMT ">] %pS\n",
+				loglvl, info->ip, (void *) info->ip);
 			i++;
 		}
 	}
-	printk(KERN_CRIT "\n");
+	printk("%s\n", loglvl);
 }
 
 static void parisc_show_stack(struct task_struct *task,
-	struct pt_regs *regs)
+	struct pt_regs *regs, const char *loglvl)
 {
 	struct unwind_frame_info info;
 
 	unwind_frame_init_task(&info, task, regs);
 
-	do_show_stack(&info);
+	do_show_stack(&info, loglvl);
+}
+
+void show_stack_loglvl(struct task_struct *t, unsigned long *sp,
+		       const char *loglvl)
+{
+	parisc_show_stack(t, NULL, loglvl);
 }
 
 void show_stack(struct task_struct *t, unsigned long *sp)
 {
-	parisc_show_stack(t, NULL);
+	show_stack_loglvl(t, sp, KERN_CRIT)
 }
 
 int is_valid_bugaddr(unsigned long iaoq)
@@ -446,7 +452,7 @@ void parisc_terminate(char *msg, struct pt_regs *regs, int code, unsigned long o
 		/* show_stack(NULL, (unsigned long *)regs->gr[30]); */
 		struct unwind_frame_info info;
 		unwind_frame_init(&info, current, regs);
-		do_show_stack(&info);
+		do_show_stack(&info, KERN_CRIT);
 	}
 
 	printk("\n");
-- 
2.25.1