[U-Boot-Users] [PATCH] Fixed the _gp/_G_O_T_ confusion for good

[U-Boot-Users] [PATCH] Fixed the _gp/_G_O_T_ confusion for good

[Vlad Lungu]

$gp is loaded with _gp
the GOT is updated starting from _G_O_T_+8 up to (but not including) __got_end
__got_start is unused 
num_got_entries is unused and could be removed from ld scripts

To test:
        _gp =ALIGN(16)+4;

        __got_start = .;
        . += 4;
        .got  : { *(.got) }
        __got_end = .;

produces

                0x00000000bfc1f564                _gp = (ALIGN (0x10) + 0x4)
                0x00000000bfc1f560                __got_start = .
                0x00000000bfc1f564                . = (. + 0x4)

.got            0x00000000bfc1f570      0x500
 *(.got)
 .got           0x00000000bfc1f570      0x500 cpu/mips/start.o
                0x00000000bfc1f570                _GLOBAL_OFFSET_TABLE_
                0x00000000bfc1fa70                __got_end = .
                0x00000000bfc1fa70                . = .

The boards boots and the command line is working

Signed-off-by: Vlad Lungu <vlad@comsys.ro>
---
 cpu/mips/start.S |   23 +++++++++++++----------
 1 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/cpu/mips/start.S b/cpu/mips/start.S
index e91e213..816c23a 100644
--- a/cpu/mips/start.S
+++ b/cpu/mips/start.S
@@ -234,11 +234,11 @@ reset:
 	li	t0, CONF_CM_UNCACHED
 	mtc0	t0, CP0_CONFIG
 
-	/* Initialize GOT pointer.
+	/* Initialize $gp.
 	*/
 	bal     1f
 	nop
-	.word   _GLOBAL_OFFSET_TABLE_
+	.word   _gp
 	1:
 	move    gp, ra
 	lw      t1, 0(ra)
@@ -306,9 +306,9 @@ relocate_code:
 	move	t1, a2
 
 	/*
-	 * Fix GOT pointer:
+	 * Fix _gp:
 	 *
-	 * New GOT-PTR = (old GOT-PTR - CFG_MONITOR_BASE) + Destination Address
+	 * New _gp = (old _gp - CFG_MONITOR_BASE) + Destination Address
 	 */
 	move	t6, gp
 	sub	gp, CFG_MONITOR_BASE
@@ -341,25 +341,28 @@ relocate_code:
 	j	t0
 	nop
 
+	.gpword _GLOBAL_OFFSET_TABLE_
 	.word	uboot_end_data
 	.word	uboot_end
-	.word	num_got_entries
+	.gpword	__got_end
 
 in_ram:
 	/* Now we want to update GOT.
 	 */
-	lw	t3, -4(t0)	/* t3 <-- num_got_entries	*/
+	lw	t3, -16(t0)	/* t3 <-- _G_O_T_-_gp	*/
 	addi	t4, gp, 8	/* Skipping first two entries.	*/
-	li	t2, 2
+	add	t4, t4, t3	/* Actual &(_G_O_T_[2]) */
+	lw	t3, -4(t0)	/* t3 <-- __got_end-_gp	*/
+	add    t3,gp
 1:
 	lw	t1, 0(t4)
 	beqz	t1, 2f
 	add	t1, t6
 	sw	t1, 0(t4)
 2:
-	addi	t2, 1
-	blt	t2, t3, 1b
-	addi	t4, 4		/* delay slot			*/
+	addi	t4, 4	
+	blt	t4, t3, 1b
+	nop
 
 	/* Clear BSS.
 	 */
-- 
1.5.2.2

[U-Boot-Users] [PATCH] Fixed the _gp/_G_O_T_ confusion for good

[Shinya Kuribayashi]

Sorry for late.

Vlad Lungu wrote:
> $gp is loaded with _gp
> the GOT is updated starting from _G_O_T_+8 up to (but not including) 
> __got_end
> __got_start is unused num_got_entries is unused and could be removed 
> from ld scripts

I'll take this fix except for removing __got_start and num_got_entries.
I know you want to make it work whether __got_start is out of alignment
or not, but that is a little mess. We should fix num_got_entries part
instead, and update GOT entries using _GLOBAL_OFFSET_TABLE_ and
num_got_entries. This is easily understandable and straight forward :-)

I've submitted patches. Plase review.

thanks,

  Shinya