Re: in-kernel linking issues

[Richard Henderson]

On Fri, Nov 15, 2002 at 01:16:45PM +0000, Russell King wrote:
> I'm slightly worried about this.  For things like shared libraries to be
> relocatable on ARM on current toolchains, you need to build with -fPIC.

Err, no you don't.  You only need that if you want to share pages,
which is clearly not an issue with kernel modules.  There are no
restrictions of which I am aware that require ARM to build with -fpic.

My test case,

	int i;
	int foo() { return bar() + i; }
	int j __attribute__((section(".init.data")));
	int __attribute__((section(".init.text")))
	baz() { return i + j; }

works exactly as desired on ARM:

Disassembly of section .text:

00000000 <foo>:
   0:   e52de004        str     lr, [sp, -#4]!
   4:   ebfffffe        bl      4 <foo+0x4>
   8:   e59f3008        ldr     r3, [pc, #8]    ; 18 <foo+0x18>
   c:   e5933000        ldr     r3, [r3]
  10:   e0800003        add     r0, r0, r3
  14:   e49df004        ldr     pc, [sp], #4

Disassembly of section .init.text:

00001000 <baz>:
    1000:       e59f3010        ldr     r3, [pc, #16]   ; 1018 <baz+0x18>
    1004:       e5930000        ldr     r0, [r3]
    1008:       e59f300c        ldr     r3, [pc, #12]   ; 101c <baz+0x1c>
    100c:       e5933000        ldr     r3, [r3]
    1010:       e0800003        add     r0, r0, r3
    1014:       e1a0f00e        mov     pc, lr

Relocation section '.rel.dyn' at offset 0x11258 contains 4 entries:
 Offset     Info    Type            Sym.Value  Sym. Name
00000004  00001501 R_ARM_PC24        00000000   bar
00000018  00001202 R_ARM_ABS32       00000040   i
00001018  00001202 R_ARM_ABS32       00000040   i
0000101c  00000f02 R_ARM_ABS32       00001020   j

r~