Running RTEMS on a LEON2 from ROM

[Mike Looijmans]

On 26-07-17 13:36, Mike Looijmans wrote:
> On 26-07-17 13:10, Mike Looijmans wrote:
>> On 26-07-17 10:21, Jiri Gaisler wrote:
>>>
>>>
>>> On 07/26/2017 07:25 AM, Mike Looijmans wrote:
>>>>
>>>>> how you do it with standalone sis:
>>>>>
>>>>> $ sparc-rtems4.12-sis -leon2 application.exe
>>>>>
>>>>>> hi 100
>>>>>> go
>>>>>> hi
>>>>>> reg
>>>>
>>>> Doesn't get very far, there's apparently no (working) memory at
>>>> 0x40000000 in the simulator, it always reads back as "0", so any
>>>> access to RAM results in a crash in the simulator.
>>>>
>>>>
>>>>
>>>
>>> Are  you sure you are building sis and gdb from RSB head? sis in the
>>> regular gdb does not support leon2 yet.
>>> To advance things, you can send me your application binary and I can run
>>> it in the simulator and send you the traces. If you are on 64-bit ubuntu
>>> 16.04, I can also provide you with binaries for sis/gdb, or the whole RSB.
>>
>> I built the current HEAD of the RSB, and ran using the simulator from that. 
>> The result is the same.
>>
>> Did some more digging. The problem appears to be that the simulator 
>> populates the memory segments using the VMA values instead of the LMA 
>> values. So it writes the data segment to RAM at 0x40000000, instead of in 
>> ROM, directly following the text segment, as the boot code expects. I can 
>> see the data segment contents there just after loading the elf.
>>
>> When the code starts, it copies the data segment from ROM into RAM and that 
>> will copy the empty ROM part onto the RAM, resulting in the all-zero data in 
>> RAM that I see.
>>
>> Can I load a binary image into sis? (so not an elf but a raw ROM image)
>>
>> I'll try using objdump to concat the text and data into a single segment elf 
>> for the simulator. Or maybe patch the VMA address to match the LMA.
> 
> That worked. According to SIS, the crash happens here:
> 
> https://git.rtems.org/rtems/tree/cpukit/score/src/heap.c?h=4.11#n274
> 
>  From sis, i can see:
> 
>      18156  0000da3c  81c3e008  retl
>      18158  0000da40  01000000  nop
>      18159  00006eec  c41fbff8  ldd  [ %fp + -8 ], %g2
>      18162  00006ef0  b406401a  add  %i1, %i2, %i2
>      18163  00006ef4  f020a008  st  %i0, [ %g2 + 8 ]
>      18166  00006ef8  f020a00c  st  %i0, [ %g2 + 0xc ]
>      18169  00006efc  f4208000  st  %i2, [ %g2 ]
>      18172  00006f00  8220c002  sub  %g3, %g2, %g1
>      18173  00006f04  88106001  or  %g1, 1, %g4
>      18174  00006f08  c820a004  st  %g4, [ %g2 + 4 ]
>      18177  00006f0c  c43e2020  std  %g2, [ %i0 + 0x20 ]
>      18181  00006f10  c4262008  st  %g2, [ %i0 + 8 ]
>      18184  00006f14  c426200c  st  %g2, [ %i0 + 0xc ]
>      18187  00006f18  f6262010  st  %i3, [ %i0 + 0x10 ]
>      18190  00006f1c  fa262014  st  %i5, [ %i0 + 0x14 ]
>      18193  00006f20  f2262018  st  %i1, [ %i0 + 0x18 ]
>      18196  00006f24  f426201c  st  %i2, [ %i0 + 0x1c ]
>      18199  00006f28  c220c000  st  %g1, [ %g3 ]
>      18203  40000090  91d020ff  ta  0xff
> sis> reg
> 
>        INS       LOCALS      OUTS     GLOBALS
>     0:  40002500   91CFE0F0   51CF6D70   00000000
>     1:  00000000   00006F28   00000008   51CF6D70
>     2:  00000068   00006F2C   0A39EDAF   40007380
>     3:  00000010   00000000   00000007   91CFE0F0
>     4:  400FFE70   00000000   FFFFFFFF   51CF6D71
>     5:  40002568   00000000   00000008   00000000
>     6:  400FFE10   00000000   400FFDB0   00000000
>     7:  00006EE4   00000000   00006DD0   00000000
> 
>   psr: 00400FC3   wim: 00000002   tbr: 40000090   y: 00000000
> 
> 
> Looked this address up in the "objdump -S" output, and that shows the 
> following source code and assembly there:
> 
>    /* Heap control */
>    heap->page_size = page_size;
>      6f18:    f6 26 20 10     st  %i3, [ %i0 + 0x10 ]
>    heap->min_block_size = min_block_size;
>      6f1c:    fa 26 20 14     st  %i5, [ %i0 + 0x14 ]
>    heap->area_begin = heap_area_begin;
>      6f20:    f2 26 20 18     st  %i1, [ %i0 + 0x18 ]
>    heap->area_end = heap_area_end;
>      6f24:    f4 26 20 1c     st  %i2, [ %i0 + 0x1c ]
>    heap->last_block = last_block;
>    _Heap_Free_list_head( heap )->next = first_block;
>    _Heap_Free_list_tail( heap )->prev = first_block;
> 
>    /* Last block */
>    last_block->prev_size = first_block_size;
>      6f28:    c2 20 c0 00     st  %g1, [ %g3 ]
> 
> 
> Something's up with the heap initialization. Haven't found out what exactly 
> though. %g3=91CFE0F0 but should be in the RAM range (400XXXXX) for that "st" 
> to make sense.
> 
"_Heap_Initialize" is called twice. Once from 
_Workspace_Handler_initialization with sensible values, and the second time 
it's called from RTEMS_Malloc_Initialize, with the heap_end set to 0x91CFE0FF 
which isn't valid and causes the crash.



Kind regards,

Mike Looijmans
System Expert

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