Date: Thu, 10 Jul 2014 02:55:37 -0700 From: John-Mark Gurney <jmg@funkthat.com> To: Nathan Whitehorn <nwhitehorn@freebsd.org> Cc: Andrew Turner <andrew@freebsd.org>, svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r268310 - head/libexec/rtld-elf/arm Message-ID: <20140710095537.GW45513@funkthat.com> In-Reply-To: <53B9A1CD.2010803@freebsd.org> References: <201407061024.s66AO6R9012248@svn.freebsd.org> <53B9A1CD.2010803@freebsd.org>
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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."
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