Re: spinlocks() are severely broken in 2.2.X and 2.4.X for modules

[Andi Kleen]

On Sat, Jul 01, 2000 at 11:59:11AM +0200, Manfred Spraul wrote:
> Andi Kleen wrote:
> > 
> > I had it happen to me in the past too for my sysctl rewrite. In this
> > case it happened in the main kernel for a .sysctl -> .data relocation.
> > It happened in the main vmlinux. It seems to require some complex
> > input to trigger (it is not as simple as intersegment relocation does not
> > work). In my case I had a few hundred relocations and one was wrong
> > and caused crashes.
> > 
> 
> Is it possible to detect the problem automatically until binutils is
> fixed? (objdump + script)

Here is a quick hack. The results are slightly off because of section
padding though. It only works on object files or modules (vmlinux doesn't
have any reloc records) 

NAME                        SSIZE        NUMSPIN    NUMREF   NUMREL
kernel/acct.o               0            0          0        0
kernel/capability.o         112          8          8        16
kernel/dma.o                0            0          0        0
kernel/exec_domain.o        14           1          1        2
kernel/exit.o               334          23.85714   22       44
kernel/fork.o               192          13.71428   15       30
kernel/info.o               0            0          0        0
kernel/itimer.o             0            0          0        0
kernel/kernel.o             2356         168.2857   162.5    325
                                         ^^^^^^^^^^^^^^^^^
					this looks bogus
kernel/ksyms.o              0            0          0        0
kernel/module.o             70           5          5        10
kernel/panic.o              0            0          0        0
kernel/printk.o             228          16.28571   16       32
kernel/resource.o           0            0          0        0
kernel/sched.o              768          54.85714   53       106
kernel/signal.o             315          22.5       17       34
kernel/softirq.o            0            0          0        0
kernel/sysctl.o             34           2.428571   3        6
kernel/sys.o                220          15.71428   18       36
kernel/time.o               69           4.928571   4.5      9

-Andi

#!/usr/bin/perl 

$SPINSIZE = 14;

while ($fn = $ARGV[0]) { 
    open(P,"objdump --section-headers $fn |") || die("no $fn: $!\n");
    
    $size = 0; 
    while (<P>) { 
	if (/\d\s+.text\.lock\s+([a-f0-9]+)/) { 
	    $size = hex($1);
	    last; 
	} 
    } 
    close P; 

    $numrel = 0; 
    open(P,"objdump --reloc --section=.text.lock $fn |") || die "no $fn: $!\n"; 
    while (<P>) { 
	$numrel++ if (/^0/); 	
    } 
 
    $numref = $numrel / 2; 
    $numspin = $size / $SPINSIZE; 
  
    write;

    shift(@ARGV); 
}

format STDOUT_TOP = 
NAME                        SSIZE        NUMSPIN    NUMREF   NUMREL
.

format STDOUT = 
@<<<<<<<<<<<<<<<<<<<<<<<<<< @<<<<<<<<<<< @<<<<<<<   @<<<<<<< @<<<<<<<
$fn			    $size        $numspin   $numref  $numrel
.