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 <senthil_kumar.selva...@atmel.com>
* 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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