Re: [suse-amd64] Creating PIC code from .asm under x86_64

Andi Kleen writes:

On Sat, 15 Nov 2003 06:09:32 -0500 Mike Phillips wrote:

...

...

cpuid.o: relocation R_X86_64_32 can not be used when making a shared object; recompile with -fPIC

Of course recompiling with -fPIC isn't an option as cpuid.o is built from cpuid.asm.

When it is a code like

movl bla,%edi

replace it with

movl bla(%rip),%edi

That's the right way. In glibc I did e.g.: /* * Written by J.T. Conklin . * Adapted for use as log2 by Ulrich Drepper . * Public domain. * * Changed to use fyl2xp1 for values near 1, . * Adapted for x86-64 by Andreas Jaeger . */ #include #ifdef __ELF__ .section .rodata #else .text #endif .align ALIGNARG(4) ASM_TYPE_DIRECTIVE(one,@object) one: .double 1.0 ASM_SIZE_DIRECTIVE(one) /* It is not important that this constant is precise. It is only a value which is known to be on the safe side for using the fyl2xp1 instruction. */ ASM_TYPE_DIRECTIVE(limit,@object) limit: .double 0.29 ASM_SIZE_DIRECTIVE(limit) #ifdef PIC #define MO(op) op##(%rip) #else #define MO(op) op #endif .text ENTRY(__ieee754_log2l) fldl MO(one) fldt 8(%rsp) // x : 1 fxam fnstsw fld %st // x : x : 1 andb $1,%ah jnz 3f // in case x is NaN or ±Inf 4: fsub %st(2), %st // x-1 : x : 1 fld %st // x-1 : x-1 : x : 1 fabs // |x-1| : x-1 : x : 1 fcompl MO(limit) // x-1 : x : 1 fnstsw // x-1 : x : 1 andb $0x45, %ah jz 2f fstp %st(1) // x-1 : 1 fyl2xp1 // log(x) ret 2: fstp %st(0) // x : 1 fyl2x // log(x) ret 3: jp 4b // in case x is ±Inf fstp %st(1) fstp %st(1) ret END (__ieee754_log2l)

Otherwise I would write a small C test program for the construct you want and look what gcc generates for it with gcc -S.

You also might want to add the frame unwind information (check how glibc defines ENTRY and END)... Andreas -- Andreas Jaeger, aj@suse.de, http://www.suse.de/~aj SuSE Linux AG, Deutschherrnstr. 15-19, 90429 Nürnberg, Germany GPG fingerprint = 93A3 365E CE47 B889 DF7F FED1 389A 563C C272 A126