Running RTEMS on a LEON2 from ROM
Mike Looijmans
mike.looijmans at topic.nl
Thu Jul 27 05:49:29 UTC 2017
On 27-07-17 07:46, Mike Looijmans wrote:
> 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.
This smells like another "special" trap table entry - 0x1000000000 is the
"nop" instruction, which fills about three quarters of the trap table.
Kind regards,
Mike Looijmans
System Expert
TOPIC Products
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