[U-Boot-Users] What's going on here: global offset table

[U-Boot-Users] What's going on here: global offset table

[ming lei]

I am a newbie to u-boot. I found some macros in file
u-boot-1.1.3\include\ppc_asm.tmpl

#define START_GOT			\
	.section	".got2","aw";	\
.LCTOC1 = .+32768

#define END_GOT				\
	.text

#define GET_GOT				\
	bl	1f		;	\
	.text	2		;	\
0:	.long	.LCTOC1-1f	;	\
	.text			;	\
1:	mflr	r14		;	\
	lwz	r0,0b-1b(r14)	;	\
	add	r14,r0,r14	;

#define GOT_ENTRY(NAME)		.L_ ## NAME = . - .LCTOC1 ; .long NAME

#define GOT(NAME)		.L_ ## NAME (r14)

in file u-boot-1.1.3\cpu\mpc8260\start.S, I found some statements as follows
START_GOT
	GOT_ENTRY(_GOT2_TABLE_)
	GOT_ENTRY(_FIXUP_TABLE_)

	GOT_ENTRY(_start)
	GOT_ENTRY(_start_of_vectors)
	GOT_ENTRY(_end_of_vectors)
	GOT_ENTRY(transfer_to_handler)

	GOT_ENTRY(__init_end)
	GOT_ENTRY(_end)
	GOT_ENTRY(__bss_start)
#if defined(CONFIG_HYMOD)
	GOT_ENTRY(environment)
#endif
	END_GOT

I thougt that these statement will be something as follows after
preprocessed by gasp
.section	".got2","aw";	
.LCTOC1 = .+32768

.L___GOT2_TABLE _= . - .LCTOC1;
.long _GOT2_TABLE_
................
...............

My questions are:
(1)   what is the meaning of the "LCT0C1"?  is ".LCTOC1" a symbol or a
directive ?      if ".LCTOC1" is a symbol ,why I can not see it using 
nm or objdump?

(2) what is the meaning of the ".L__GOT2_TABLE_". what is the relation
between ".L__GOT2_TABLE_"  and "_GOT2_TABLE_" defined in u-boot.lds?

THANKS!

[U-Boot-Users] What's going on here: global offset table

[Wolfgang Denk]

In message <bdc2f4990511010133m311cfefv@mail.gmail.com> you wrote:
>
> (1)   what is the meaning of the "LCT0C1"?  is ".LCTOC1" a symbol or a
> directive ?      if ".LCTOC1" is a symbol ,why I can not see it using 
> nm or objdump?

It's a local symbol. [This answers both questions.]

> (2) what is the meaning of the ".L__GOT2_TABLE_". what is the relation
> between ".L__GOT2_TABLE_"  and "_GOT2_TABLE_" defined in u-boot.lds?

I recommend to read the C  source  (instead  of  generated  assembler
code), which has some comments.

Also reading  some  background  information  about  the  GOT  may  be
helpful.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Those who hate and fight must stop themselves -- otherwise it is  not
stopped.
	-- Spock, "Day of the Dove", stardate unknown