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Re: arm-gcc: avoid calling other system functions

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On 2018-05-17, pozz <pozzugno@gmail.com> wrote:
> Il 17/05/2018 15:27, Grant Edwards ha scritto:
>> On 2018-05-17, pozz <pozzugno@gmail.com> wrote:
>> 
>>> I'm trying to put all ISRs in RAM[*]. Unfortunately, depending on
>>> the code, arm-gcc could call some system functions that are located
>>> in Flash.
>> 
>> By "system functions" do you mean gcc built-in functions from libgcc?
>
> Yes, now I know those functions come from libgcc.
>
>> Or functions from /usr/lib/*whatever*?
>> 
>>> For example, if I use a switch statement, the compiler calls a piece of
>>> code of system libraries (that are in Flash) that use a table lookup to
>>> manage the switch.
>> 
>> If you're talking about libgcc, that's not what most people mean when
>> they refer to "system libraries".
>
> Built-in functions is a better name?

Calling them "libgcc functions" is probably the best choice.  Anybody
familiar with gcc will know what you mean.

>> No, I don't think there's any way to prevent gcc from emitting calls
>> to functions provided by libgcc.  However, you should be able to put
>> the ISR code in a separate file and link it statically with libgcc,
>> and then locate the resulting object file's code in RAM.
>
> It seems complex.

Embedded systems development usually is. :)

>> Alternatively, you could just manually tweak your linker script to
>> place the specific libgcc functions used by your ISR functions in RAM.
>
> Any help?

https://sourceware.org/binutils/docs-2.30/ld/Scripts.html#Scripts
https://wiki.osdev.org/Linker_Scripts
http://www.bravegnu.org/gnu-eprog/
https://www.embedded.com/design/mcus-processors-and-socs/4026080/Building-Bare-Metal-ARM-Systems-with-GNU-Part-3

>> Using ISRs to program flash seems pretty strange...
>
> No, I need to serve interrupts *during* Flash erasing/writing. So the 
> ISR code must be placed in RAM.

OK, that makes more sense.

-- 
Grant Edwards               grant.b.edwards        Yow! I feel like I am
                                  at               sharing a ``CORN-DOG''
                              gmail.com            with NIKITA KHRUSCHEV ...

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arm-gcc: avoid calling other system functions pozz <pozzugno@gmail.com> - 2018-05-17 14:37 +0200
  Re: arm-gcc: avoid calling other system functions Grant Edwards <invalid@invalid.invalid> - 2018-05-17 13:27 +0000
    Re: arm-gcc: avoid calling other system functions pozz <pozzugno@gmail.com> - 2018-05-17 15:35 +0200
      Re: arm-gcc: avoid calling other system functions Grant Edwards <invalid@invalid.invalid> - 2018-05-17 14:18 +0000
        Re: arm-gcc: avoid calling other system functions David Brown <david.brown@hesbynett.no> - 2018-05-17 17:08 +0200
        Re: arm-gcc: avoid calling other system functions pozz <pozzugno@gmail.com> - 2018-05-18 08:47 +0200
  Re: arm-gcc: avoid calling other system functions pozz <pozzugno@gmail.com> - 2018-05-17 15:30 +0200
  Re: arm-gcc: avoid calling other system functions David Brown <david.brown@hesbynett.no> - 2018-05-17 17:06 +0200
    Re: arm-gcc: avoid calling other system functions pozz <pozzugno@gmail.com> - 2018-05-18 09:07 +0200
      Re: arm-gcc: avoid calling other system functions David Brown <david.brown@hesbynett.no> - 2018-05-18 09:51 +0200
        Re: arm-gcc: avoid calling other system functions pozz <pozzugno@gmail.com> - 2018-05-21 09:14 +0200
          Re: arm-gcc: avoid calling other system functions David Brown <david.brown@hesbynett.no> - 2018-05-21 12:50 +0200
        Re: arm-gcc: avoid calling other system functions Joe Chisolm <jchisolm6@earthlink.net> - 2018-05-21 10:15 -0500
          Re: arm-gcc: avoid calling other system functions David Brown <david.brown@hesbynett.no> - 2018-05-21 19:31 +0200
            Re: arm-gcc: avoid calling other system functions pozz <pozzugno@gmail.com> - 2018-05-22 09:05 +0200
              Re: arm-gcc: avoid calling other system functions David Brown <david.brown@hesbynett.no> - 2018-05-22 10:59 +0200
              Re: arm-gcc: avoid calling other system functions Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-05-22 15:24 +0300
                Re: arm-gcc: avoid calling other system functions pozz <pozzugno@gmail.com> - 2018-05-22 14:55 +0200
  Re: arm-gcc: avoid calling other system functions Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-05-18 12:41 +0300

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