Re: [microblaze-uclinux] Re: [PATCH 1/2] microblaze: add stack unwinder

[Michal Simek <monstr@monstr.eu>]

Steven J. Magnani wrote:
> On Fri, 2010-04-16 at 10:32 +0200, Michal Simek wrote:
>> Please apply this patch and do the same testing as I did.
>>
>> diff --git a/arch/microblaze/kernel/reset.c b/arch/microblaze/kernel/reset.c
>> index a1721a3..76f6587 100644
>> --- a/arch/microblaze/kernel/reset.c
>> +++ b/arch/microblaze/kernel/reset.c
>> @@ -112,8 +112,8 @@ void of_platform_reset_gpio_probe(void)
>>   void machine_restart(char *cmd)
>>   {
>>          printk(KERN_NOTICE "Machine restart...\n");
>> +       machine_shutdown();
>>          gpio_system_reset();
>> -       dump_stack();
>>          while (1)
>>                  ;
>>   }
>> @@ -121,6 +121,7 @@ void machine_restart(char *cmd)
>>   void machine_shutdown(void)
>>   {
>>          printk(KERN_NOTICE "Machine shutdown...\n");
>> +       dump_stack();
>>          while (1)
>>                  ;
>>   }
> 
> I get this:
> 
> Call Trace:
> [<20003008>] microblaze_unwind+0x68/0x94
> [<20002c24>] show_stack+0x134/0x174
> [<20002c80>] dump_stack+0x1c/0x3c
> [<20001d84>] machine_shutdown+0x30/0x40
> [<20001dc0>] machine_restart+0x2c/0x48
> [<2002a540>] kernel_restart+0x5c/0x80
> [<2002a6b8>] sys_reboot+0x11c/0x218
> SYSCALL
> [<2d5c0248>] PID 118 [reboot]
> 
> Is your problem on a MMU or noMMU system?
> 
> If the unwinder stops early, it found a return address outside the
> kernel text, or couldn't find the addik that creates a stack frame - but
> there's not enough information here to tell what happened. In your case
> the backtrace goes off the rails before getting to the frame for
> dump_stack(), which is where the stack dump begins. We'd need to see the
> 21 words preceding the dump (show_stack's frame is 13 words, and
> microblaze_unwind's is 8) to know why.
> 
> Can you uncomment the #define DEBUG in unwind.c and try it again?

I finally looked at it and here is what I found.

# ./reboot
Restarting system.
Machine restart...
Machine shutdown...
Stack:
4f3ffdc8: 48004aec 00000008
4f3ffdd0: 00000000 00000001 4f3e0150 00000001 4f3ffdec 48004b14 481dc68c 
48241318
4f3ffdf0: ffffffff 00001099 00003fff 482f49cc 4801f518 481dc6a4 48241318 
ffffffff
4f3ffe10: 00001083 00003fff 482f49cc 48020150 481e3048 00000000 000001a2 
00000000
4f3ffe30: 00000000 00000000 28121969 48006b38 48240dc0 481d549c 481d53a8 
481d549c
4f3ffe50: 00aa4812 481d523c 0000c350 00000035 48029618 4f3ffe70 000001a2 
4f96c04c
4f3ffe70: 481d6390 0000c350 4f3fff58 4f3ffee0 481d639c 481d6370 00000009 
4f3ffee0
4f3ffe90: 00000000 00000000 00000000 4f3ffee0 48029df4 00000001 4f3e0150 
00000001
4f3ffeb0: 00000001 00000001 00000000 00000001 00000001 48029f34 4801b2a8 
4800c5e0
4f3ffed0: 00000020 00000000 0000c350 00000000 00000001 00000000 00000000 
00000035
4f3ffef0: 00ab0b62 00000035 00aa4812 480294e0 482425c0 00000000 00000000 
00000000
4f3fff10: 0000c350 00000001 0000c350 4f3ead40 4f3fff58 00000001 00000000 
00000000
4f3fff30: 00000001 4f3e0150 00000001 48006b38 00000000 4f3eaf68 00000000 
00010000
4f3fff50: 00000000 00000000 00000000 fee1dead 01234567 00000000 00000000 
4f3eaebc
4f3fff70: 00000000 00000000 00000000 fee1dead 28121969 01234567 00000008 
00000000
4f3fff90: 00000000 28121969 00000058 00000000 4f3e0320 4f3e0274 00000000 
00000000
4f3fffb0: 7fffff82 00000000 00000000 00000000 fee1dead 01234567 00000000 
00000000
4f3fffd0: 00000001 4f3e0150 00000001 00000000 00000000 4f96c04c 4f3e0324 
000001a0
4f3ffff0: 00000000 00000000 000001a0 00000000


Call Trace:
     Unwinding with PC=480050d4, FP=4f3ffd74
[<480050d4>] microblaze_unwind+0xa8/0xc4
pc 0x480050ac instr 0x30210024
     Invalid frame size -36 at 0x480050ac
     Failed to find previous stack frame

Below is the dump - then you can see that 36 is correct.
That could be due to different toolchain behavior.

Thanks,
Michal


4800502c <microblaze_unwind>:
4800502c:       b000482f        imm     18479
48005030:       e86043a8        lwi     r3, r0, 17320   // 482f43a8 <mbc>
48005034:       3021ffdc        addik   r1, r1, -36
48005038:       fa61001c        swi     r19, r1, 28
4800503c:       fac10020        swi     r22, r1, 32
48005040:       f9e10000        swi     r15, r1, 0
48005044:       e8830020        lwi     r4, r3, 32
48005048:       12650000        addk    r19, r5, r0
4800504c:       99fc2000        brald   r15, r4
48005050:       12c60000        addk    r22, r6, r0
48005054:       b000482f        imm     18479
48005058:       e86043a8        lwi     r3, r0, 17320   // 482f43a8 <mbc>
4800505c:       e8830008        lwi     r4, r3, 8
48005060:       99fc2000        brald   r15, r4
48005064:       80000000        or      r0, r0, r0
48005068:       be130068        beqid   r19, 104                // 480050d0
4800506c:       10b30000        addk    r5, r19, r0
48005070:       b0004800        imm     18432
48005074:       30c069e0        addik   r6, r0, 27104   // 480069e0 
<_switch_to>
48005078:       165f9800        rsubk   r18, r31, r19
4800507c:       be120034        beqid   r18, 52         // 480050b0
48005080:       11360000        addk    r9, r22, r0
48005084:       e8730004        lwi     r3, r19, 4
48005088:       10b30000        addk    r5, r19, r0
4800508c:       e903004c        lwi     r8, r3, 76
48005090:       e8e3003c        lwi     r7, r3, 60
48005094:       b9f4fc7c        brlid   r15, -900       // 48004d10 
<microblaze_unwind_inner>
48005098:       11360000        addk    r9, r22, r0
4800509c:       e9e10000        lwi     r15, r1, 0
480050a0:       ea61001c        lwi     r19, r1, 28
480050a4:       eac10020        lwi     r22, r1, 32
480050a8:       b60f0008        rtsd    r15, 8
480050ac:       30210024        addik   r1, r1, 36
480050b0:       e8730004        lwi     r3, r19, 4
480050b4:       30631f68        addik   r3, r3, 8040
480050b8:       e903003c        lwi     r8, r3, 60
480050bc:       e8c30080        lwi     r6, r3, 128
480050c0:       e8e30004        lwi     r7, r3, 4
480050c4:       b9f4fc4c        brlid   r15, -948       // 48004d10 
<microblaze_unwind_inner>
480050c8:       80000000        or      r0, r0, r0
480050cc:       b800ffd0        bri     -48             // 4800509c
480050d0:       80e10000        or      r7, r1, r0
480050d4:       b8d40008        brlid   r6, 8
480050d8:       80000000        or      r0, r0, r0
480050dc:       11130000        addk    r8, r19, r0
480050e0:       11360000        addk    r9, r22, r0
480050e4:       b9f4fc2c        brlid   r15, -980       // 48004d10 
<microblaze_unwind_inner>
480050e8:       10bf0000        addk    r5, r31, r0
480050ec:       b800ffb0        bri     -80             // 4800509c






> 
> Thanks,
> ------------------------------------------------------------------------
>  Steven J. Magnani               "I claim this network for MARS!
>  www.digidescorp.com              Earthling, return my space modulator!"
> 
>  #include <standard.disclaimer>
> 
> 
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-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian