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Re: [avr-libc-dev] [Patch] Include a device info note section in gcrt1.S
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From: |
Senthil Kumar Selvaraj |
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Subject: |
Re: [avr-libc-dev] [Patch] Include a device info note section in gcrt1.S |
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Date: |
Mon, 10 Nov 2014 10:50:12 +0530 |
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User-agent: |
Mutt/1.5.23 (2014-03-12) |
Ping!
Regards
Senthil
On Mon, Nov 03, 2014 at 04:50:32PM +0530, Senthil Kumar Selvaraj wrote:
> On Tue, Oct 14, 2014 at 04:29:19PM +0530, Senthil Kumar Selvaraj wrote:
> > On Sat, Oct 11, 2014 at 10:35:22AM +0200, Joerg Wunsch wrote:
> > > I finally had a chance to test all this.
> > >
> > > For reference, here's the result for an ATmega1281:
> > >
> > > % avr-objdump -h -j .note.gnu.avr.deviceinfo -s
> > > avr/lib/avr5/atmega1281/crtm1281.o
> > >
> > > avr/lib/avr5/atmega1281/crtm1281.o: file format elf32-avr
> > >
> > > Sections:
> > > Idx Name Size VMA LMA File off Algn
> > > 11 .note.gnu.avr.deviceinfo 00000034 00000000 00000000 0000181c 2**2
> > > CONTENTS, READONLY
> > > Contents of section .note.gnu.avr.deviceinfo:
> > > 0000 04000000 23000000 01000000 41565200 ....#.......AVR.
> > > 0010 00000000 00000200 00020000 00200000 ............. ..
> > > 0020 00000000 00100000 08000000 01000000 ................
> > > 0030 00000000 ....
> > >
> > >
> > > As Senthil Kumar Selvaraj wrote:
> > >
> > > > 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.
> > >
> > > OK, if that's required, we have to stick with that.
> > >
> > > Wouldn't the note name string also possibly need padding
> > > for alignment behind it? (In the case of the "AVR\0",
> > > it only incidentally aligns the following .long values
> > > to a long boundary.)
> >
> > Yes, I figured it's only going to be "AVR\0", so I skipped the align
> > directive. I'll add it.
> > >
> > > For the documentation, please include a C struct definition
> > > as explanation:
> > >
> > > #define __NOTE_NAME_LEN 4
> > > struct __note_gnu_avr_deviceinfo
> > > {
> > > struct
> > > {
> > > uint32_t note_name_len; /* = __NOTE_NAME_LEN */
> > > uint32_t desc_len;
> > > char note_name[__NOTE_NAME_LEN]; /* = "AVR\0" */
> > > }
> > > elfinfo_hdr;
> > > struct
> > > {
> > > uint32_t flash_start;
> > > uint32_t flash_size;
> > > uint32_t sram_start;
> > > uint32_t sram_size;
> > > uint32_t eeprom_start;
> > > uint32_t eeprom_size;
> > > uint32_t offset_table[2]; /* index 0: ... */
> > > // ???
> > > }
> > > avr_desc;
> > > };
> >
> > Ok, will do.
> > >
> > > > +.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:
> > >
> > > I don't quite understand the purpose of the two ".byte 0" definitions.
> >
> > I used the standard ELF string table convention - the first and last
> > bytes are null. From http://man7.org/linux/man-pages/man5/elf.5.html,
> >
> > "String table sections hold null-terminated character sequences,
> > commonly called strings. The object file uses these strings to
> > represent symbol and section names. One references a string as an
> > index into the string table section. The first byte, which is index
> > zero, is defined to hold a null byte ('\0'). Similarly, a string
> > table's last byte is defined to hold a null byte, ensuring null
> > termination for all strings."
> >
> > There's no need to follow that convention though - the descriptor's
> > layout/interpretation can be arbitrary. If you think it is redundant,
> > I'll drop it.
> >
> > I'll send a new patch with all the changes.
> >
>
> Does the below patch look good? I've added documentation about the
> section's layout to doc/api/sections.dox.
>
> Regards
> Senthil
>
> ChangeLog
>
> 2014-11-03 Senthil Kumar Selvaraj <address@hidden>
>
> * crt1/gcrt1.S: Add a note section embedding device info.
> * doc/api/sections.dox: Document it.
>
> diff --git avr-libc/crt1/gcrt1.S avr-libc/crt1/gcrt1.S
> index 2d341a4..777bedb 100644
> --- avr-libc/crt1/gcrt1.S
> +++ avr-libc/crt1/gcrt1.S
> @@ -304,3 +304,71 @@ __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
> + .balign 4
> +.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
> +
> diff --git avr-libc/doc/api/sections.dox avr-libc/doc/api/sections.dox
> index a93dec4..a71f13b 100644
> --- avr-libc/doc/api/sections.dox
> +++ avr-libc/doc/api/sections.dox
> @@ -207,6 +207,51 @@ Unused. User definable.
> Goes into an infinite loop after program termination and completion of any
> _exit() code (execution of code in the .fini9 -> .fini1 sections).
>
> +\section sec_dot_note The .note.gnu.avr.deviceinfo Section
> +
> +This section contains device specific information picked up from the device
> +header file and compiler builtin macros. The layout conforms to the standard
> ELF
> +note section layout
> (http://docs.oracle.com/cd/E23824_01/html/819-0690/chapter6-18048.html).
> +
> +The section contents are laid out as below.
> +
> +\code
> +#define __NOTE_NAME_LEN 4
> +struct __note_gnu_avr_deviceinfo
> +{
> + struct
> + {
> + uint32_t namesz; /* = __NOTE_NAME_LEN */
> + uint32_t descsz; /* = size of avr_desc */
> + uint32_t type; /* = 1 - no other AVR note types exist */
> + char note_name[__NOTE_NAME_LEN]; /* = "AVR\0" */
> + }
> + note_header;
> + struct
> + {
> + uint32_t flash_start;
> + uint32_t flash_size;
> + uint32_t sram_start;
> + uint32_t sram_size;
> + uint32_t eeprom_start;
> + uint32_t eeprom_size;
> + uint32_t offset_table_size;
> + uint32_t offset_table[1]; /* Offset table containing byte offsets
> into
> + string table that immediately follows
> it.
> + index 0: Device name byte offset
> + */
> + char str_table [2 +
> + strlen(__AVR_DEVICE_NAME__)]; /* Standard ELF string table.
> + index 0 : NULL
> + index 1 : Device name
> + index 2 : NULL
> + */
> + }
> + avr_desc;
> +};
> +\endcode
> +
> +
> \section asm_sections Using Sections in Assembler Code
>
> Example:
>
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