Subject: Re: the printk problem

From: Ingo Molnar <[email-masked]>
Date: Sun, 6 Jul 2008 07:27:41 +0200

* Linus Torvalds <[email-masked]> wrote:

> > Still all happily untested, of course. And still with no actual 
> > users converted.
> 
> Ok, it's tested, and here's an example usage conversion.
> 
> The diffstat pretty much says it all. It _does_ change the format of 
> the stack trace entry a bit, but I don't think it's for the worse 
> (unless it breaks things like the oops tracker - Arjan?)
> 
> It changes the symbol-in-module format from
> 
> 	:ext3:add_dirent_to_buf+0x6c/0x26c
> 
> to
> 
> 	add_dirent_to_buf+0x6c/0x26c [ext3]
> 
> but quite frankly, the latter was the standard format anyway (it's 
> what "sprint_symbol()" gives you), and traps_64.c was the odd man out.
> 
> In fact, traps_32.c already uses the standard print_symbol() format, 
> so it really was an issue of the 64-bit code being odd (and I assume 
> that this also means that it cannot break the oops tracker, since it 
> already had to be able to handle both formats).
> 
> I also removed the KALLSYMS dependency, so if KALLSYMS isn't enabled 
> it will now give the same hex format twice, but I doubt we really care 
> (such stack traces are unreadable whether it shows up once or twice, 
> and the simplicity is worth it).
> 
> If people do just a few more conversions like this, then the 52 added 
> lines in lib/vsnprintf.c are more than made up for by removed lines 
> elsewhere (and more readable source code).

applied (with the commit message below) to tip/x86/debug for v2.6.27 
merging, thanks Linus. Can i add your SOB too?

	Ingo

-------------------->
commit 4afd2534d6d4a77f4b7497c92f1ff7528d8f4eaa
Author: Linus Torvalds <[email-masked]>
Date:   Sat Jul 5 15:32:41 2008 -0700

    x86, 64-bit: standardize printk_address()
    
    Changes the symbol-in-module format from
    
    	:ext3:add_dirent_to_buf+0x6c/0x26c
    
    to
    
    	add_dirent_to_buf+0x6c/0x26c [ext3]
    
    the latter was the standard format anyway (it's what "sprint_symbol()"
    gives you), and traps_64.c was the odd man out.
    
    In fact, traps_32.c already uses the standard print_symbol() format, so
    it really was an issue of the 64-bit code being odd (and I assume that
    this also means that it cannot break the oops tracker, since it already
    had to be able to handle both formats).
    
    I also removed the KALLSYMS dependency, so if KALLSYMS isn't enabled it
    will now give the same hex format twice, but I doubt we really care
    (such stack traces are unreadable whether it shows up once or twice, and
    the simplicity is worth it).
    
    If people do just a few more conversions like this, then the 52 added
    lines in lib/vsnprintf.c are more than made up for by removed lines
    elsewhere (and more readable source code).
    
    Signed-off-by: Ingo Molnar <[email-masked]>

diff --git a/arch/x86/kernel/traps_64.c b/arch/x86/kernel/traps_64.c
index adff76e..f1a95d1 100644
--- a/arch/x86/kernel/traps_64.c
+++ b/arch/x86/kernel/traps_64.c
@@ -104,30 +104,7 @@ int kstack_depth_to_print = 12;
 
 void printk_address(unsigned long address, int reliable)
 {
-#ifdef CONFIG_KALLSYMS
-	unsigned long offset = 0, symsize;
-	const char *symname;
-	char *modname;
-	char *delim = ":";
-	char namebuf[KSYM_NAME_LEN];
-	char reliab[4] = "";
-
-	symname = kallsyms_lookup(address, &symsize, &offset,
-					&modname, namebuf);
-	if (!symname) {
-		printk(" [<%016lx>]\n", address);
-		return;
-	}
-	if (!reliable)
-		strcpy(reliab, "? ");
-
-	if (!modname)
-		modname = delim = "";
-	printk(" [<%016lx>] %s%s%s%s%s+0x%lx/0x%lx\n",
-		address, reliab, delim, modname, delim, symname, offset, symsize);
-#else
-	printk(" [<%016lx>]\n", address);
-#endif
+	printk(" [<%016lx>] %s%pS\n", address, reliable ? "": "? ", (void *) address);
 }
 
 static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,