[PATCH] x86_64 stack trace cleanup

[Andres Salomon <dilinger@debian.org>]

Hi,

This patch cleans up the clutter of x86_64 stack traces, making the
output closer to what i386 and sparc64 stack traces look like.  It uses
print_symbol instead of resolving the symbols manually, and prints one
frame per line instead of displaying multiple frames per line.  I left
the other stuff in the stack dump alone; this affects only the frame
list.

I know this has been brought up before
(http://www.uwsg.iu.edu/hypermail/linux/kernel/0602.0/2238.html,
although I noticed a slight problem w/ that patch, as __print_symbol
returns void); however, for people that don't spend all their time
looking at x86_64 backtraces, I think this consistency shouldn't be
scoffed at.  When you switch back and forth between different archs,
x86_64's backtrace is cluttered and confusing in comparison.

With this patch, traces end up looking as follows:

 getty         S ffff81001e7d1db8     0  3812      1          3814  3811
(NOTLB)
 ffff81001e7d1db8 0000000000000008 ffffffff80240323 0000000000001d93
        ffff81001f82a2d8 ffff81001f82a0c0 ffff81001f68b0c0
0000000000000000
        ffff81001fa841fc ffff81001e7d0000
 Call Trace:
  [<ffffffff80240323>] do_con_write+0x1853/0x1890
  [<ffffffff80164daa>] __pagevec_free+0x2a/0x40
  [<ffffffff802e0e55>] schedule_timeout+0x25/0xd0
  [<ffffffff80134868>] release_console_sem+0x1a8/0x220
  [<ffffffff8014b93c>] add_wait_queue+0x1c/0x60
  [<ffffffff8023441f>] read_chan+0x48f/0x6e2
  [<ffffffff8012e7e0>] default_wake_function+0x0/0x10
  [<ffffffff8022f292>] tty_read+0xa2/0x110
  [<ffffffff80185eff>] vfs_read+0xdf/0x1a0
  [<ffffffff80186b63>] sys_read+0x53/0x90
  [<ffffffff8010afee>] system_call+0x7e/0x83


The old-style trace:

 pdflush       D ffff810037a417a0 0  4293     11          4294  4292
(L-TLB)
 ffff810031fb3d68 0000000000000046 ffff8100107b1d78 0000000000000f60
        0000000000000160 ffff810037a419b8 ffff810037a417a0 f
fff810037a40300
        ffff810001707d80 ffffffff80146b79
 Call Trace:<ffffffff80146b79>{lock_timer_base+41}
<ffffffff8014785d>{__mod_timer+189}
        <ffffffff80154690>{keventd_create_kthread+0}
<ffffffff8030f96a>{schedule_timeout+154}
        <ffffffff80147110>{process_timeout+0}
<ffffffff8030e621>{__sched_text_start+49}
        <ffffffff801fd279>{blk_congestion_wait+153}
<ffffffff80154bc0>{autoremove_wake_function+0}
        <ffffffff801b4051>{writeback_inodes+177}
<ffffffff8016d2d5>{background_writeout+165}
        <ffffffff8016df40>{pdflush+0} <ffffffff8016e095>{pdflush+341}




Signed-off-by: Andres Salomon <dilinger@debian.org>

diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 28d50dc..7598107 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -17,6 +17,7 @@
 #include <linux/config.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
+#include <linux/kallsyms.h> 
 #include <linux/string.h>
 #include <linux/errno.h>
 #include <linux/ptrace.h>
@@ -106,30 +107,11 @@ static inline void preempt_conditional_c
 
 static int kstack_depth_to_print = 10;
 
-#ifdef CONFIG_KALLSYMS
-#include <linux/kallsyms.h> 
-int printk_address(unsigned long address)
+void printk_address(unsigned long address)
 { 
-	unsigned long offset = 0, symsize;
-	const char *symname;
-	char *modname;
-	char *delim = ":"; 
-	char namebuf[128];
-
-	symname = kallsyms_lookup(address, &symsize, &offset, &modname, namebuf); 
-	if (!symname) 
-		return printk("[<%016lx>]", address);
-	if (!modname) 
-		modname = delim = ""; 		
-        return printk("<%016lx>{%s%s%s%s%+ld}",
-		      address,delim,modname,delim,symname,offset); 
+	printk(" [<%016lx>] ", address);
+	print_symbol("%s\n", address);
 } 
-#else
-int printk_address(unsigned long address)
-{ 
-	return printk("[<%016lx>]", address);
-} 
-#endif
 
 static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
 					unsigned *usedp, const char **idp)
@@ -205,24 +187,23 @@ void show_trace(unsigned long *stack)
 	printk("\nCall Trace:");
 
 #define HANDLE_STACK(cond) \
-	do while (cond) { \
-		unsigned long addr = *stack++; \
-		if (kernel_text_address(addr)) { \
-			if (i > 50) { \
-				printk("\n       "); \
-				i = 0; \
+	do { \
+		i = 0; \
+		printk("\n"); \
+		while (cond) { \
+			unsigned long addr = *stack++; \
+			if (kernel_text_address(addr)) { \
+				/* \
+				 * If the address is either in the text segment \
+				 * of the kernel, or in the region which \
+				 * contains vmalloc'ed memory, it *may* be the \
+				 * address of a calling routine; if so, print it \
+				 * so that someone tracing down the cause of the \
+				 * crash will be able to figure out the call \
+				 * path that was taken. \
+				 */ \
+				printk_address(addr); \
 			} \
-			else \
-				i += printk(" "); \
-			/* \
-			 * If the address is either in the text segment of the \
-			 * kernel, or in the region which contains vmalloc'ed \
-			 * memory, it *may* be the address of a calling \
-			 * routine; if so, print it so that someone tracing \
-			 * down the cause of the crash will be able to figure \
-			 * out the call path that was taken. \
-			 */ \
-			i += printk_address(addr); \
 		} \
 	} while (0)
 
diff --git a/include/asm-x86_64/kdebug.h b/include/asm-x86_64/kdebug.h
index b9ed4c0..72f5261 100644
--- a/include/asm-x86_64/kdebug.h
+++ b/include/asm-x86_64/kdebug.h
@@ -48,7 +48,7 @@ static inline int notify_die(enum die_va
 	return notifier_call_chain(&die_chain, val, &args); 
 } 
 
-extern int printk_address(unsigned long address);
+extern void printk_address(unsigned long address);
 extern void die(const char *,struct pt_regs *,long);
 extern void __die(const char *,struct pt_regs *,long);
 extern void show_registers(struct pt_regs *regs);

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