Building on android - compiled program segfaults

[Nathan Hüsken]

The disassembly at the moment of segfault looks like this:

Dump of assembler code for function stg_returnToStackTop:
   0x003f059c <+0>:	push	{r4, lr}
   0x003f05a0 <+4>:	sub	sp, sp, #16
   0x003f05a4 <+8>:	ldr	r1, [r0, #140]	; 0x8c
=> 0x003f05a8 <+12>:	ldr	r12, [r1, #12]
   0x003f05ac <+16>:	ldr	r1, [r12, #12]
   0x003f05b0 <+20>:	mov	r2, #0
   0x003f05b4 <+24>:	str	r2, [r0, #156]	; 0x9c
   0x003f05b8 <+28>:	ldr	r4, [r0, #148]	; 0x94
   0x003f05bc <+32>:	ldm	r4, {r2, lr}
   0x003f05c0 <+36>:	ldr	r4, [r4, #28]
   0x003f05c4 <+40>:	add	r2, r2, r4, lsl #12
   0x003f05c8 <+44>:	sub	r2, r2, #1
   0x003f05cc <+48>:	str	r2, [r0, #132]	; 0x84
   0x003f05d0 <+52>:	subs	r2, lr, #4

If I see this correctly, r12 is loaded with the value at ($r1+12)
The value of $r1 is:

r1             0xe24dd010	-498216944

which seems way out of bounds (if I look at the values of the other
registers).
The value of r1 comes from ($r0+140) in the instruction above.
But where is this value written?

I am sorry that I am so helpless. Some Idea where I could go from here?

On 01/11/2013 03:36 PM, Simon Marlow wrote:
> On 11/01/13 13:47, Nathan Hüsken wrote:
>> I just find out how to get in usefull backtrace with android ndk
>> (unfortantly I am also new to the ndk).
>>
>> Now I get:
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x003f05a8 in stg_returnToStackTop ()
>> (gdb) bt
>> #0  0x003f05a8 in stg_returnToStackTop ()
>> #1  0x003c2e74 in schedule (initialCapability=0x3f059c, task=0x530350)
>>      at rts/Schedule.c:463
>> #2  0x003c2e74 in schedule (initialCapability=0x530340, task=0x400a42f0)
>>      at rts/Schedule.c:463
>> #3  0x003c4c50 in scheduleWaitThread (tso=0x401033c0, ret=0x0,
>> pcap=0xbe89ab6c)
>>      at rts/Schedule.c:2345
>> #4  0x00408544 in rts_evalLazyIO (cap=0xbe89ab6c, p=0x50a020, ret=0x0)
>>      at rts/RtsAPI.c:499
>> #5  0x003c08c8 in real_main () at rts/RtsMain.c:68
>> #6  0x003c0a54 in hs_main (argc=1, argv=0xbe89abf4,
>> main_closure=0x50a020,
>>      rts_config=...) at rts/RtsMain.c:123
>> #7  0x0000a23c in main ()
>>
>> stg_returnToStackTop is defined in rts/StgStartup.cmm (a c-- file).
>>
>> I would guess that
>>
>> jump %ENTRY_CODE(Sp(0)) [];
>>
>> could be the problem. Since p8 $r13 gives me
>>
>> 0xbef00a74:    0x0
>> (...)
>>
>> Sp(0) would be 0x0, correct?
> 
> It's dying pretty quickly after entering Haskell: stg_returnToStackTop
> is the first bit of code to execute on the Haskell side.  You should be
> able to disassemble that function and see whether it makes sense, and/or
> step through it to see where things go wrong.  It does look like $r13 is
> not pointing to stack data for some reason.
> 
> Cheers,
>     Simon
> 
> 
>> On 01/11/2013 02:16 PM, Simon Marlow wrote:
>>> On 11/01/13 11:36, Nathan Hüsken wrote:
>>>> Hi,
>>>>
>>>> I was succesfull in building ghc (pulled from git) to compile for
>>>> arm-linux-androideabi!
>>>>
>>>> Now using "inplace/bin/ghc-stage1 -dcore-lint -debug" I compiler this
>>>> Main.hs:
>>>>
>>>> main = putStrLn "Hello, World"
>>>>
>>>> I get an executable, which I can run on my android device. Unfortantly
>>>> it segfaults.
>>>>
>>>> Running it with ./Main +RTS -DS gives:
>>>>
>>>> cap 0: initialised
>>>>
>>>> Now I am trying to debug this in gdb. When I try to display the stack
>>>> (which should be in r13 on arm of I understand correctly, I get);
>>>
>>> First establish whether the crash is in C or Haskell: what does 'bt'
>>> tell you in gdb?
>>>
>>> Cheers,
>>>      Simon
>>>
>>>
>>>> (gdb) p8 $r13
>>>> 0xbef00a74:    0x0
>>>> 0xbef00a70:    0x0
>>>> 0xbef00a6c:    0x3c2e74
>>>> 0xbef00a68:    0x530350
>>>> 0xbef00a64:    0x0
>>>> 0xbef00a60:    0x0
>>>> 0xbef00a5c:    0x0
>>>> 0xbef00a58:    0x0
>>>>
>>>> And now I am clueless. So I tried the good old printf debugging in the
>>>> rts. Using this, I see that it gets before the call to
>>>> scheduleWaitThread in the function rts_evalLazyIO (in RtsAPI.c).
>>>>
>>>> But when I put a printf in the beginning of scheduleWaitThread (in
>>>> Schedule.c) it is not shown.
>>>>
>>>> What else can I do to find out more?
>>>> Thanks!
>>>> Nathan
>>>>
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>>>> ghc-devs at haskell.org
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>>>>
>>>
>>
>