Running RTEMS on a LEON2 from ROM

Wed Jul 26 14:17:44 UTC 2017

On 07/26/2017 03:24 PM, Mike Looijmans wrote:
> 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.
>
_Heap_Initialize is called twice, this is normal. However, the SPARC
port has a peculiar way of passing the top of memory, it does that by
writing it to a symbol called rdb_start, which is located at vector
0x7c  in the trap table. In normal cases, rdb_start is at address
400007c0. I guess when the trap table is relocated, the value is lost
somehow and overwritten with a assembly instruction.

Normal leon2 executable:

(gdb) p /x rdb_start
$2 = 0x40fffe80
(gdb)

You binary after boot:

(gdb) p /x rdb_start
$3 = 0x91d020ff
(gdb)

If you recreate the trap table in RAM, make sure that the rdb_start is
properly set to end of RAM.

Jiri.