Risc-v memory issue

Wed Jun 14 04:58:03 UTC 2017

2017-06-14 2:18 GMT+03:00 Hesham Almatary <heshamelmatary at gmail.com>:

>
>
> On Tue, Jun 13, 2017 at 10:20 PM, Joel Sherrill <joel at rtems.org> wrote:
>
>>
>>
>> On Jun 12, 2017 3:10 PM, "Hesham Almatary" <heshamelmatary at gmail.com>
>> wrote:
>>
>>
>>
>> On Tue, Jun 13, 2017 at 2:09 AM, Denis Obrezkov <denisobrezkov at gmail.com>
>> wrote:
>> > Hello all,
>> >
>> > I was able to debug my program on top of HiFive1 board.
>> > I found out that I can't use next and until commands from gdb,
>> > they just hang gdb.
>> > And now I have a problem, this is my backtrace:
>> >
>> > #0  0x2041d728 in _User_extensions_Iterate (arg=0x80002eb8,
>> > visitor=0x2041d64e <_User_extensions_Fatal_visitor>,
>> > direction=CHAIN_ITERATOR_FORWARD)
>> >     at
>> > /home/reprofy/Projects/riscv/rtems/development/rtems/kernel/
>> rtems-riscv/c/src/../../cpukit/score/src/userextiterate.c:155
>> > #1  0x20410ed4 in _User_extensions_Fatal (source=INTERNAL_ERROR_CORE,
>> > error=2) at
>> > ../../cpukit/../../../hifive1/lib/include/rtems/score/userextimpl.h:307
>> > #2  0x20410ef8 in _Terminate (the_source=INTERNAL_ERROR_CORE,
>> the_error=2)
>> > at
>> > /home/reprofy/Projects/riscv/rtems/development/rtems/kernel/
>> rtems-riscv/c/src/../../cpukit/score/src/interr.c:35
>> > #3  0x20410f40 in _Internal_error
>> > (core_error=INTERNAL_ERROR_TOO_LITTLE_WORKSPACE) at
>> > /home/reprofy/Projects/riscv/rtems/development/rtems/kernel/
>> rtems-riscv/c/src/../../cpukit/score/src/interr.c:44
>> > #4  0x2041e484 in _Workspace_Handler_initialization (areas=0x80002f78,
>> > area_count=1, extend=0x0) at
>> > /home/reprofy/Projects/riscv/rtems/development/rtems/kernel/
>> rtems-riscv/c/src/../../cpukit/score/src/wkspace.c:123
>> > #5  0x2040031c in bsp_work_area_initialize_default
>> (area_begin=0x80001d58,
>> > area_size=8872) at
>> > ../../../../../.././hifive1/lib/include/bsp/bootcard.h:147
>> > #6  0x20400372 in bsp_work_area_initialize () at
>> > /home/reprofy/Projects/riscv/rtems/development/rtems/kernel/
>> rtems-riscv/c/src/lib/libbsp/riscv32/hifive1/../../shared/bs
>> pgetworkarea.c:61
>> > #7  0x2040f3ce in rtems_initialize_executive () at
>> > /home/reprofy/Projects/riscv/rtems/development/rtems/kernel/
>> rtems-riscv/c/src/../../cpukit/sapi/src/exinit.c:95
>> > #8  0x204002cc in boot_card (cmdline=0x0) at
>> > /home/reprofy/Projects/riscv/rtems/development/rtems/kernel/
>> rtems-riscv/c/src/lib/libbsp/riscv32/hifive1/../../shared/bootcard.c:76
>> > #9  0x20400064 in _end_clear_bss () at
>> > /home/reprofy/Projects/riscv/rtems/development/rtems/kernel/
>> rtems-riscv/c/src/lib/libbsp/riscv32/hifive1/start/start.S:116
>> >
>> > So, I think I should increase a workspace.
>> > Now, I have some questions:
>> > I took Hesham's linker file for riscv-generic, and there were no stack
>> > space,
>> > I allocated 0x1000 for stack. Should I make it zero again, or should I
>> > decrease its size?
>> > what size for stack should be enough?
>>
>>>                 /*
>>>                  * The stack section will occupy the remaining
>>> REGION_STACK region and may
>>>                  * contain the task stacks.  Depending on the region
>>> distribution this
>>>                  * section may be of zero size.
>>>                  */
>>>
>> This means that the stack_end address is starting at your very top
>> address space (i.e. 16KiB if you set your linker size to 16KiB). The stack
>> grows dynamically downwards, so it might overflow other sections (e.g.
>> work, heap, data, etc) if you don't have enough memory size to fit. You can
>> try to see how much size each section occupies (riscv32-rtems4.12-objdump
>> -h hello.exe), especially work space.
>>
>>
>> This is how the SPARC start up stack is done. If you aren't careful, this
>> may not match the assumption in the default method that carves up the
>> workspace.
>>
>> You need to be careful that the memory regions don't overlap.
>>
>>
>>
>>
>> > And why there were no space for stack? is it possible to work without
>> stack
>> > allocated in
>> > linkcmd file?
>> > Can RTEMS work with a smaller workspace?
>> >
>> As far as I remember, 4KiB was the smallest I could allocate for
>> workspace to work (with Epiphany). As I suggested before, you might want to
>> start saving up memory by using the local instruction memory (on HiFive)
>> and compressed version of RISC-V ISA.
>>
>>
>> Is this a characteristic of this board or the architecture in general? I
>> had the impression that the RISC-V was quite general purpose and could
>> handle plenty of RAM even if some boards don't have much.
>>
>>
>> RISC-V itself doesn't put such restrictions on the size of memory (e.g.
> Linux, seL4, RTEMS can run on FPGA and/or simulators). There's a compressed
> extension for RISC-V (like thumb) for platforms that have small memories
> same as HiFive. Having such small memory is only HiFive related, not RISC-V.
>
>>
>> > --
>> > Regards, Denis Obrezkov
>>
>>
>>
>> --
>> Hesha
>>
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>> http://lists.rtems.org/mailman/listinfo/devel
>>
>>
>>
>
>
> --
> Hesham
>
I think that RISC-V Compressed ISA can't reduce .bss and .data sections, am
I right?
So, it seems that space allocated by rtems for its workspace should be
reduced.


-- 
Regards, Denis Obrezkov
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