Some old GNU assemblers, such as v2.14 (ELDK 3.1.1), v2.16 (ELDK 4.1.0),
warns illegal global symbol references by bal (and jal also) instruction.
This does not happen with the latest binutils v2.18.
Here's an example on gth2_config:
mips_4KC-gcc -D__ASSEMBLY__ -g -Os -D__KERNEL__ -DTEXT_BASE=0x90000000 -I/home/skuribay/devel/u-boot.git/include -fno-builtin -ffreestanding -nostdinc -isy
stem /opt/eldk311/usr/bin/../lib/gcc-lib/mips-linux/3.3.3/include -pipe -DCONFIG_MIPS -D__MIPS__ -G 0 -mabicalls -fpic -pipe -msoft-float -march=4kc -mtune=4k
c -EB -c -o cache.o cache.S
cache.S: Assembler messages:
cache.S:243: Warning: Pretending global symbol used as branch target is local.
cache.S:250: Warning: Pretending global symbol used as branch target is local.
In principle, gas might be sensitive to global symbol references in PIC
code because they should be processed through GOT (global offset table).
But if `bal' instruction is used, it results in PC-based offset jump.
This is the cause of this warning.
In practice, we know it doesn't matter whether PC-based reference or GOT-
based. As for this case, both will work before/after relocation. But let's
fix the code.
This patch explicitly sets up a target address, then jump there.
Here's an example of disassembled code with/without this patch.
90000668: 1485ffef bne a0,a1,90000628 <mips_cache_reset+0x20>
9000066c: ac80fffc sw zero,-4(a0)
90000670: 01402821 move a1,t2
-90000674: 0411ffba bal 90000560 <mips_init_icache>
-90000678: 01803021 move a2,t4
-9000067c: 01602821 move a1,t3
-90000680: 0411ffcc bal 900005b4 <mips_init_dcache>
-90000684: 01a03021 move a2,t5
-90000688: 03000008 jr t8
-9000068c: 00000000 nop
+90000674: 01803021 move a2,t4
+90000678: 8f8f83ec lw t7,-31764(gp)
+9000067c: 01e0f809 jalr t7
+90000680: 00000000 nop
+90000684: 01602821 move a1,t3
+90000688: 01a03021 move a2,t5
+9000068c: 8f8f81e0 lw t7,-32288(gp)
+90000690: 01e0f809 jalr t7
+90000694: 00000000 nop
+90000698: 03000008 jr t8
+9000069c: 00000000 nop
Signed-off-by: Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>
Shinya Kuribayashi
49387dba91