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

ming lei leiming2005 at gmail.com
Tue Nov 1 10:33:11 CET 2005


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!




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