Patch "um: add show_stack_loglvl()" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    um: add show_stack_loglvl()

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     um-add-show_stack_loglvl.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit f30e6738781824d4c22de56dbad45818e5b0caf0
Author: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
Date:   Mon Jun 8 21:31:45 2020 -0700

    um: add show_stack_loglvl()
    
    [ Upstream commit 1ad87824f4cf16a7f381e1f94943a96bb7a99062 ]
    
    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().
    
    [1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@xxxxxxxxxx/T/#u
    
    Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
    Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Cc: Anton Ivanov <anton.ivanov@xxxxxxxxxxxxxxxxxx>
    Cc: Jeff Dike <jdike@xxxxxxxxxxx>
    Cc: Richard Weinberger <richard@xxxxxx>
    Link: http://lkml.kernel.org/r/20200418201944.482088-37-dima@xxxxxxxxxx
    Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
    Stable-dep-of: 0f659ff362ea ("um: Always dump trace for specified task in show_stack")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/um/kernel/sysrq.c b/arch/um/kernel/sysrq.c
index c831a1c2eb94a..1b54b6431499b 100644
--- a/arch/um/kernel/sysrq.c
+++ b/arch/um/kernel/sysrq.c
@@ -17,7 +17,9 @@
 
 static void _print_addr(void *data, unsigned long address, int reliable)
 {
-	pr_info(" [<%08lx>] %s%pS\n", address, reliable ? "" : "? ",
+	const char *loglvl = data;
+
+	printk("%s [<%08lx>] %s%pS\n", loglvl, address, reliable ? "" : "? ",
 		(void *)address);
 }
 
@@ -25,7 +27,8 @@ static const struct stacktrace_ops stackops = {
 	.address = _print_addr
 };
 
-void show_stack(struct task_struct *task, unsigned long *stack)
+void show_stack_loglvl(struct task_struct *task, unsigned long *stack,
+		       const char *loglvl)
 {
 	struct pt_regs *segv_regs = current->thread.segv_regs;
 	int i;
@@ -39,17 +42,22 @@ void show_stack(struct task_struct *task, unsigned long *stack)
 	if (!stack)
 		stack = get_stack_pointer(task, segv_regs);
 
-	pr_info("Stack:\n");
+	printk("%sStack:\n", loglvl);
 	for (i = 0; i < 3 * STACKSLOTS_PER_LINE; i++) {
 		if (kstack_end(stack))
 			break;
 		if (i && ((i % STACKSLOTS_PER_LINE) == 0))
-			pr_cont("\n");
+			printk("%s\n", loglvl);
 		pr_cont(" %08lx", *stack++);
 	}
-	pr_cont("\n");
+	printk("%s\n", loglvl);
+
+	printk("%sCall Trace:\n", loglvl);
+	dump_trace(current, &stackops, (void *)loglvl);
+	printk("%s\n", loglvl);
+}
 
-	pr_info("Call Trace:\n");
-	dump_trace(current, &stackops, NULL);
-	pr_info("\n");
+void show_stack(struct task_struct *task, unsigned long *stack)
+{
+	show_stack_loglvl(task, stack, KERN_INFO);
 }