On Wed, Jul 20, 2011 at 12:03:45AM +0200, Mark Kettenis wrote: > SSE needs a 16-byte aligned stack. Our kernel on randomizes the stack > to an ALIGNBYTES boundary, which for amd64 means 8-byte aligned. > Therefore we explicitly align the stack in crt0, but "constructors" in > shared libraries get run directly by ld.so, before the crt0 code gets > run. The diff below should fix the issues matthieu is seeing with > pixman. It explicitly aligns the stack in the ld.so startup code as > well. > > ok? > > Index: amd64/ldasm.S > =================================================================== > RCS file: /cvs/src/libexec/ld.so/amd64/ldasm.S,v > retrieving revision 1.7 > diff -u -p -r1.7 ldasm.S > --- amd64/ldasm.S 11 May 2010 16:27:14 -0000 1.7 > +++ amd64/ldasm.S 19 Jul 2011 21:52:38 -0000 > @@ -39,6 +39,11 @@ > .type _dl_start,@function > _dl_start: > movq %rsp, %r12 # save stack pointer for _rtld > + > + subq $8, %rsp # align stack > + andq $~15, %rsp > + addq $8, %rsp > + > pushq %rbx # save ps_strings > subq $DL_DATA_SIZE, %rsp # allocate dl_data >
It seems like fixing up the address in the kernel would be a good idea, However having ld.so validate the alignment is good. ok drahn@ Dale Rahn dr...@dalerahn.com
