Re: Patch fixed strings in .hex file

From	Tauno Voipio <tauno.voipio@notused.fi.invalid>
Newsgroups	comp.arch.embedded
Subject	Re: Patch fixed strings in .hex file
Date	2024-01-17 20:19 +0200
Organization	A noiseless patient Spider
Message-ID	<uo95o3$2542a$1@dont-email.me> (permalink)
References	<uo5s8d$1cjl8$1@dont-email.me> <uo67vv$1ggju$2@dont-email.me>

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On 16.1.2024 17.39, David Brown wrote:
> On 16/01/2024 13:19, pozz wrote:
>> In one project I have many quasi-fixed strings that I'd like to keep 
>> in non volatile memory (Flash) to avoid losing precious RAM space.
>>
>> static const char s1[] = "/my/very/long/string/of/01020304";
>> static const char s2[] = "/another/string/01020304";
>> ...
>>
>> Substring "01020304" is a serial number that changes during production 
>> with specific device. It has the same length in bytes (it's a simple 
>> hex representation of a 32-bits integer).
>>
>> Of course it's too difficult and slow to rebuild the firmware during 
>> production passing to the compiler the real serial number. I think a 
>> better solution is to patch the .hex file generated by the compiler.
>>
>> I'm wondering how to detect the exact positions (addresses) of serial 
>> numbers to fix.
>>
>> The build system is gcc, so I could search for s1 in the elf file. Do 
>> you know of a tool that returns the address of a symbol in the elf or 
>> map file?
>>
>> Could you suggest a better approach?
>>
> 
> Another - perhaps more reliable - method would be to put the string in 
> its own section with __attribute__((section('serial_number'))), and then 
> have a linker file entry to fix it at a specific known address.
> 

My vote for this.

If there are many strings, they could be set into
a const volatile struct which then is located into
a known place.

-- 

-TV

Thread

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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