linux-kernel - [PATCH v2] stacktrace: fix address, newline ugliness

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Date:   Tue,  7 Feb 2017 15:33:20 -0800
From:   Omar Sandoval <osandov@...ndov.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Cc:     kernel-team@...com, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v2] stacktrace: fix address, newline ugliness

From: Omar Sandoval <osandov@...com>

Since KERN_CONT became meaningful again, lockdep stack traces have had
annoying extra newlines, like this:

[    5.561122] -> #1 (B){+.+...}:
[    5.561528]
[    5.561532] [<ffffffff810d8873>] lock_acquire+0xc3/0x210
[    5.562178]
[    5.562181] [<ffffffff816f6414>] mutex_lock_nested+0x74/0x6d0
[    5.562861]
[    5.562880] [<ffffffffa01aa3c3>] init_btrfs_fs+0x21/0x196 [btrfs]
[    5.563717]
[    5.563721] [<ffffffff81000472>] do_one_initcall+0x52/0x1b0
[    5.564554]
[    5.564559] [<ffffffff811a3af6>] do_init_module+0x5f/0x209
[    5.565357]
[    5.565361] [<ffffffff81122f4d>] load_module+0x218d/0x2b80
[    5.566020]
[    5.566021] [<ffffffff81123beb>] SyS_finit_module+0xeb/0x120
[    5.566694]
[    5.566696] [<ffffffff816fd241>] entry_SYSCALL_64_fastpath+0x1f/0xc2

That's happening because each printk() call now gets printed on its own
line, and we do a separate call to print the spaces before the symbol.
Fix it by doing the printk() directly instead of using the
print_ip_sym() helper.

Additionally, the symbol address isn't very helpful, so let's get rid of
that, too. The final result looks like this:

[    5.194518] -> #1 (B){+.+...}:
[    5.195002]        lock_acquire+0xc3/0x210
[    5.195439]        mutex_lock_nested+0x74/0x6d0
[    5.195976]        init_btrfs_fs+0x21/0x196 [btrfs]
[    5.196491]        do_one_initcall+0x52/0x1b0
[    5.196939]        do_init_module+0x5f/0x209
[    5.197355]        load_module+0x218d/0x2b80
[    5.197792]        SyS_finit_module+0xeb/0x120
[    5.198251]        entry_SYSCALL_64_fastpath+0x1f/0xc2

Fixes: 4bcc595ccd80 ("printk: reinstate KERN_CONT for printing continuation lines")
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Omar Sandoval <osandov@...com>
---
 kernel/stacktrace.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index b6e4c16377c7..9c15a9124e83 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -18,10 +18,8 @@ void print_stack_trace(struct stack_trace *trace, int spaces)
 	if (WARN_ON(!trace->entries))
 		return;
 
-	for (i = 0; i < trace->nr_entries; i++) {
-		printk("%*c", 1 + spaces, ' ');
-		print_ip_sym(trace->entries[i]);
-	}
+	for (i = 0; i < trace->nr_entries; i++)
+		printk("%*c%pS\n", 1 + spaces, ' ', (void *)trace->entries[i]);
 }
 EXPORT_SYMBOL_GPL(print_stack_trace);
 
@@ -29,7 +27,6 @@ int snprint_stack_trace(char *buf, size_t size,
 			struct stack_trace *trace, int spaces)
 {
 	int i;
-	unsigned long ip;
 	int generated;
 	int total = 0;
 
@@ -37,9 +34,8 @@ int snprint_stack_trace(char *buf, size_t size,
 		return 0;
 
 	for (i = 0; i < trace->nr_entries; i++) {
-		ip = trace->entries[i];
-		generated = snprintf(buf, size, "%*c[<%p>] %pS\n",
-				1 + spaces, ' ', (void *) ip, (void *) ip);
+		generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
+				     (void *)trace->entries[i]);
 
 		total += generated;
 
-- 
2.11.1