svn commit: r268310 - head/libexec/rtld-elf/arm

[John-Mark Gurney]

Nathan Whitehorn wrote this message on Sun, Jul 06, 2014 at 12:21 -0700:
> Thank you! I can now upgrade my AVILA for the first time in 3 years. 
> Most things seem to work fine, despite the long absence.

Per my email to -arm... Let me know if you have any further issues w/
it...

> On 07/06/14 03:24, Andrew Turner wrote:
> >Author: andrew
> >Date: Sun Jul  6 10:24:06 2014
> >New Revision: 268310
> >URL: http://svnweb.freebsd.org/changeset/base/268310
> >
> >Log:
> >   Align the stack in _rtld_bind_start. Normally this is called with the
> >   correct stack alignment, however when we have a leaf function that uses
> >   thread local storage it calls __aeabi_read_tp to get the thread pointer.
> >   Neither GCC or clang see this as a function call so will align the stack
> >   to a 4-byte boundary. This may be a problem as _rtld_bind expects to be
> >   on an 8-byte boundary.
> >   
> >   The solution is to store a copy of the stack pointer and force the
> >   alignment before calling _rtld_bind.
> >   
> >   This fixes a problem with armeb where applications would crash in odd 
> >   ways.
> >   It should also remove the need for a local patch to clang to force the
> >   stack alignment to an 8-byte boundary, even for leaf functions. Further
> >   testing will be needed before reverting this local change to clang as we
> >   may rely on it in other places.
> >   
> >   Reviewed by:	jmg@
> >
> >Modified:
> >   head/libexec/rtld-elf/arm/rtld_start.S
> >
> >Modified: head/libexec/rtld-elf/arm/rtld_start.S
> >==============================================================================
> >--- head/libexec/rtld-elf/arm/rtld_start.S	Sun Jul  6 07:34:18 2014 
> >(r268309)
> >+++ head/libexec/rtld-elf/arm/rtld_start.S	Sun Jul  6 10:24:06 2014 
> >(r268310)
> >@@ -77,7 +77,7 @@ __FBSDID("$FreeBSD$");
> >   *	lr = &GOT[2]
> >   */
> >  _rtld_bind_start:
> >-	stmdb	sp!,{r0-r4,sl,fp}
> >+	stmdb	sp!,{r0-r5,sl,fp}
> >  
> >  	sub	r1, ip, lr		/* r1 = 4 * (n + 1) */
> >  	sub	r1, r1, #4		/* r1 = 4 * n */
> >@@ -86,11 +86,14 @@ _rtld_bind_start:
> >  	ldr	r0, [lr, #-4]		/* get obj ptr from GOT[1] */
> >  	mov	r4, ip			/* save GOT location */
> >  
> >+	mov	r5, sp			/* Save the stack pointer */
> >+	bic	sp, sp, #7		/* Align the stack pointer */
> >  	bl	_rtld_bind		/* Call the binder */
> >+	mov	sp, r5			/* Restore the old stack pointer */
> >  
> >  	str	r0, [r4]		/* save address in GOT */
> >  	mov	ip, r0			/* save new address */
> >  
> >-	ldmia	sp!,{r0-r4,sl,fp,lr}	/* restore the stack */
> >+	ldmia	sp!,{r0-r5,sl,fp,lr}	/* restore the stack */
> >  	mov	pc, ip			/* jump to the new address */
> >  
> >
> 

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."