Running RTEMS on a LEON2 from ROM

[Mike Looijmans]

On 26-07-17 17:41, Jiri Gaisler wrote:
> 
> 
> On 07/26/2017 04:17 PM, Jiri Gaisler wrote:
>>
>> 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.
> Let me clarify this. The rdb_start is set by either the prom loader,
> grmon or simulator to the top of available RAM (64-byte aligned), RTEMS
> then use the value to allocate the stack and heap. So your boot code
> must write this value before the system starts initializing. If you have
> 1 Mbyte of RAM, then set 0x400007c0 = 0x400fffe0 and it should work. The
> reason for this is historical, but it allows the same executable to run
> on different boards with varying amount of memory.

Ok, adding ".word RAM_END-16" at that location fixes the crash in the heap init.
Also printk seems to work now.


sis> go
resuming at 0x00000000
work_area_start = 0x40003540
work_area_size = 1018496 0x000F8A80
end = 0x400FBFC0
current stack pointer = 0x400FFF40
rdb_start = 0x400FFFC0
work_area_start = 0x40003540
work_area_size = 1018496 0x000F8A80
end = 0x400FBFC0
current stack pointer = 0x400FFF40
heap_start = 0x4000737E
heap_size = 1002562
Memory exception at 1000014 (illegal address)
IU in error mode (255)
     78366  40000090  91d020ff  ta  0xff

The cause is at 0x8f84, disassembling that points to the 
"_Scheduler_Update_heir" routine, which was called from 
_Scheduler_default_Start_idle

Some thread object here points at 0x10000000 which is an invalid memory location.


Kind regards,

Mike Looijmans
System Expert

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