Re: [avr-libc-dev] [Patch] Include a device info note section in gcrt1.S

[Senthil Kumar Selvaraj]

Ping!

On Tue, Aug 26, 2014 at 05:20:54PM +0530, Senthil Kumar Selvaraj wrote:
> On Mon, Aug 11, 2014 at 04:26:22PM +0200, Joerg Wunsch wrote:
> > As Senthil Kumar Selvaraj wrote:
> > 
> > > I figured it's easier and less error-prone to embed this information
> > > here and then consume it everywhere else. I have a patch for
> > > binutils, for example, that uses the information in the note section
> > > to print percentage of memory used - like what the WinAVR port of
> > > avr-size does, but without the hardcoding.
> > 
> > I like that idea much more than Eric Weddington's hack.
> > 
> > I think the AVR is ultimately not the only device which might this be
> > a concern of; all flash-based controllers can probably benefit from
> > it.  Thinking a little more about the layout of that device
> > information (so it can e.g. be applied to all flash-based ARM
> > controllers as well) would IMHO much increase the likelihood of this
> > being accepted as a general solution by the binutils folks.  After
> > all, Atmel could go ahead, and apply it to their own ARM devices as
> > a first example. ;-)
> 
> Yes, it makes sense to make it as general as possible.
> > 
> > > +    .section .note.gnu.avr.deviceinfo, "", @note
> > > +#define NOTE_NAME "AVR"
> > > +#ifdef __AVR_DEVICE_NAME__
> > > +    #define DEVICE_NAME STR(__AVR_DEVICE_NAME__)
> > > +#else
> > > +    #define DEVICE_NAME ""
> > > +#endif
> > > +    .long .L__note_name_end - .L__note_name_start
> > > +    .long .L__desc_end - .L__desc_start
> > > +    .long 1 ; Type 1 - this is the only known note type for AVR.
> > > +.L__note_name_start:
> > > +    .asciz NOTE_NAME
> > > +.L__note_name_end:
> > > +.L__desc_start:
> > > +    .long .L__device_name_end - .L__device_name_start
> > > +.L__device_name_start:
> > > +    .asciz DEVICE_NAME
> > > +.L__device_name_end:
> > > +#ifdef PROGMEM_SIZE
> > > +    .long PROGMEM_SIZE
> > > +#elif FLASHEND > 0
> > > +    .long FLASHEND + 1
> > > +#else
> > > +    .long FLASHEND
> > > +#endif
> > > +#ifdef RAMSIZE
> > > +    .long RAMSIZE
> > > +#elif RAMEND > 0
> > > +    .long RAMEND - RAMSTART + 1
> > > +#else
> > > +    .long RAMEND
> > > +#endif
> > > +#ifdef EEPROM_SIZE
> > > +    .long EEPROM_SIZE
> > > +#elif E2END > 0
> > > +    .long E2END + 1
> > > +#else
> > > +    .long E2END
> > > +#endif
> > > +.L__desc_end:
> > > +    .balign 4
> > > +
> > 
> > Few things come to mind:
> > 
> > * Start out with those parts of the information that have a fixed
> >   size, i.e. the sizes of the memory regions, and move the variable
> >   parts behind.  That way, the initial part can be described as a C
> >   structure.
> > 
> > * Wouldn't we also need start addresses?  In particular, if you think
> >   beyond the horizon towards ARMs, their flash usually doesn't start
> >   at 0, but even for the AVR, the RAM starts at a device-dependent
> >   address.  Providing on the the size information without the start is
> >   not very useful.  (OTOH, information that can already be derived
> >   from other sources in the ELF file doesn't need to be duplicated.)
> > 
> > * For the strings, add an offset (or index) table.  That way, in order
> >   to read the second string, you don't have to traverse the first one.
> >   Thus, the actual string array somewhat resembles an ELF string
> >   section.
> > 
> > * Please add a patch that explains the layout in the documentation,
> >   too.
> 
> How does the below patch look? Once you guys find it ok, I'll follow it
> up with a documentation patch. Note that the part above the
> L__desc_start label (and the .balign directive at the end) are there as
> per the ELF spec for a note section.
> 
> diff --git avr-libc/crt1/gcrt1.S avr-libc/crt1/gcrt1.S
> index 2d341a4..721573b 100644
> --- avr-libc/crt1/gcrt1.S
> +++ avr-libc/crt1/gcrt1.S
> @@ -304,3 +304,70 @@ __do_copy_data:
>  #endif /* __AVR_ASM_ONLY__ */
>  ;      .endfunc
>  
> +    .section .note.gnu.avr.deviceinfo, "", @note
> +#define NOTE_NAME "AVR"
> +#ifdef __AVR_DEVICE_NAME__
> +    #define DEVICE_NAME STR(__AVR_DEVICE_NAME__)
> +#else
> +    #define DEVICE_NAME ""
> +#endif
> +
> +    .long .L__note_name_end - .L__note_name_start
> +    .long .L__desc_end - .L__desc_start
> +    .long 1 ; Type 1 - this is the only known note type for AVR.
> +.L__note_name_start:
> +    .asciz NOTE_NAME
> +.L__note_name_end:
> +.L__desc_start:
> +#ifdef FLASHSTART
> +    .long FLASHSTART
> +#else
> +    .long 0
> +#endif
> +#ifdef PROGMEM_SIZE
> +    .long PROGMEM_SIZE
> +#elif FLASHEND > 0
> +    .long FLASHEND + 1
> +#else
> +    .long FLASHEND
> +#endif
> +    .long RAMSTART
> +#ifdef RAMSIZE
> +    .long RAMSIZE
> +#elif RAMEND > 0
> +    .long RAMEND - RAMSTART + 1
> +#else
> +    .long RAMEND
> +#endif
> +#ifdef E2START
> +    .long E2START
> +#else
> +    .long 0
> +#endif
> +#ifdef EEPROM_SIZE
> +    .long EEPROM_SIZE
> +#elif E2END > 0
> +    .long E2END + 1
> +#else
> +    .long E2END
> +#endif
> +    /* String offsets table.
> +    Index 0 - Size of offset table in bytes
> +    Index 1 - Device name byte offset
> +    */
> +.L__stroffsettab_start:
> +.long .L__stroffsettab_end - .L__stroffsettab_start /* Size of index table 
> in bytes */
> +.long .L__device_name_start - .L__strtab_start /* Byte offset of device name 
> */
> +.L__stroffsettab_end:
> +    /* String table for storing arbitrary strings.
> +    Offsets are stored in the string offset table above */
> +.L__strtab_start:
> +    .byte 0
> +.L__device_name_start:
> +    .asciz DEVICE_NAME
> +.L__device_name_end:
> +    .byte 0
> +.L__strtab_end:
> +.L__desc_end:
> +    .balign 4
> +
> 
> > 
> > -- 
> > cheers, Joerg               .-.-.   --... ...--   -.. .  DL8DTL
> > 
> > http://www.sax.de/~joerg/
> > Never trust an operating system you don't have sources for. ;-)
> 
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