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Re: Patch fixed strings in .hex file

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On 17/01/2024 17:39, Stefan Reuther wrote:
> Am 17.01.2024 um 12:54 schrieb pozz:
>> Il 17/01/2024 11:27, David Brown ha scritto:
>>> While it is possible to do all this using patching of odd places in
>>> your file, using specific locations is often a better choice.  Since
>>> you haven't already said "Thanks for the advice - I tried it that way,
>>> it worked, and I'm happy" in response to any post, I would say that
>>> now is the time to take fixed location solutions seriously.
>>
>> There are many suggested solutions and I think all of them can be used
>> with success. Just for sake of curiosity and studying, I'm exploring all
>> of them.
>>
>> Sincerely I don't *like* solutions where you need to choose a fixed
>> location by yourself. Why you should make a job that can be done by the
>> linker?
> 
> It's not you vs. the linker. You co-operate. You need to tell the linker
> about your chip anyway ("code is from 0x1000 to 0xc000, data is from
> 0xc000 to 0xd000"). So you can as well tell it "version stamp is from
> 0xcc00 to 0xd000, data only before 0xcc00".
> 
> If you have your identification information in a fixed place, you can,
> for example, more easily analyze field returns. It's easy for your field
> service has to change something, and it's easy to do software updates
> that preserve the identification information. You don't need to figure
> out which software build is running on the chip and what the address of
> the structure happens to be in that one.
> 
>>> Now your post-build scripts have a simple fixed address to patch the
>>> binaries.
>>
>> How the post-build script should know the exact address of a certain
>> field in the struct?
> 
> By defining the struct in a compatible way. For example....
> 
>> volatile const struct post_build_data {
>>    uint32_t serial_number;
>>    uint64_t mac_address;
> 
> ...this is a bad idea, because in most (but probably not all) chips,
> uint64_t after uint32_t means there's 32 bits of padding, so if you need
> serial-before-mac, you should at least make the padding explicit. There
> also might be endian problems.
> 
> Using only char/uint8_t fields gives you a very high chance of identical
> structure layout everywhere (`uint8_t mac_address[8]`).
> 

You can also keep things safe by making sure that you are aligned by 
"natural" alignment, at least to size 8 bytes (I have never heard of a 
platform that has more than 8 byte alignment for anything).  So two 
uint32_t's followed by an uint64_t is fine.

#pragma GCC diagnostic push
#pragma GCC diagnostic error "-Wpadded"
volatile const struct ...
#pragma GCC diagnostic pop

is a useful check (if you are using gcc or clang).

And a static assert on the size of the struct is another important 
safe-guard.

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Patch fixed strings in .hex file pozz <pozzugno@gmail.com> - 2024-01-16 13:19 +0100
  Re: Patch fixed strings in .hex file David Brown <david.brown@hesbynett.no> - 2024-01-16 13:51 +0100
    Re: Patch fixed strings in .hex file pozz <pozzugno@gmail.com> - 2024-01-16 15:42 +0100
      Re: Patch fixed strings in .hex file David Brown <david.brown@hesbynett.no> - 2024-01-16 16:36 +0100
        Re: Patch fixed strings in .hex file pozz <pozzugno@gmail.com> - 2024-01-16 16:57 +0100
      Re: Patch fixed strings in .hex file dalai lamah <antonio12358@hotmail.com> - 2024-01-16 16:47 +0100
        Re: Patch fixed strings in .hex file David Brown <david.brown@hesbynett.no> - 2024-01-16 18:50 +0100
  Re: Patch fixed strings in .hex file Herbert Kleebauer <klee@unibwm.de> - 2024-01-16 15:07 +0100
    Re: Patch fixed strings in .hex file pozz <pozzugno@gmail.com> - 2024-01-16 15:42 +0100
  Re: Patch fixed strings in .hex file Grant Edwards <invalid@invalid.invalid> - 2024-01-16 15:24 +0000
    Re: Patch fixed strings in .hex file David Brown <david.brown@hesbynett.no> - 2024-01-16 16:38 +0100
      Re: Patch fixed strings in .hex file Grant Edwards <invalid@invalid.invalid> - 2024-01-16 18:32 +0000
    Re: Patch fixed strings in .hex file pozz <pozzugno@gmail.com> - 2024-01-16 17:01 +0100
  Re: Patch fixed strings in .hex file David Brown <david.brown@hesbynett.no> - 2024-01-16 16:39 +0100
    Re: Patch fixed strings in .hex file Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2024-01-17 20:19 +0200
  Re: Patch fixed strings in .hex file Stefan Reuther <stefan.news@arcor.de> - 2024-01-16 17:44 +0100
    Re: Patch fixed strings in .hex file Grant Edwards <invalid@invalid.invalid> - 2024-01-16 18:39 +0000
    Re: Patch fixed strings in .hex file Michael Schwingen <news-1513678000@discworld.dascon.de> - 2024-01-16 19:30 +0000
  Re: Patch fixed strings in .hex file Hans-Bernhard Bröker <HBBroeker@gmail.com> - 2024-01-16 19:35 +0100
    Re: Patch fixed strings in .hex file pozz <pozzugno@gmail.com> - 2024-01-17 08:45 +0100
      Re: Patch fixed strings in .hex file pozz <pozzugno@gmail.com> - 2024-01-17 09:07 +0100
      Re: Patch fixed strings in .hex file David Brown <david.brown@hesbynett.no> - 2024-01-17 11:27 +0100
        Re: Patch fixed strings in .hex file pozz <pozzugno@gmail.com> - 2024-01-17 12:54 +0100
          Re: Patch fixed strings in .hex file David Brown <david.brown@hesbynett.no> - 2024-01-17 13:54 +0100
          Re: Patch fixed strings in .hex file Stefan Reuther <stefan.news@arcor.de> - 2024-01-17 17:39 +0100
            Re: Patch fixed strings in .hex file David Brown <david.brown@hesbynett.no> - 2024-01-17 18:28 +0100
            Re: Patch fixed strings in .hex file Grant Edwards <invalid@invalid.invalid> - 2024-01-17 19:00 +0000
            Re: Patch fixed strings in .hex file pozz <pozzugno@gmail.com> - 2024-01-19 09:10 +0100
      Re: Patch fixed strings in .hex file Hans-Bernhard Bröker <HBBroeker@gmail.com> - 2024-01-18 18:49 +0100
  Re: Patch fixed strings in .hex file pozz <pozzugno@gmail.com> - 2024-01-17 09:57 +0100
  Re: Patch fixed strings in .hex file Don Y <blockedofcourse@foo.invalid> - 2024-01-17 10:03 -0700
  Re: Patch fixed strings in .hex file Paul Rubin <no.email@nospam.invalid> - 2024-01-17 21:42 -0800

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