Date: Sun, 6 Jul 2014 10:24:06 +0000 (UTC) From: Andrew Turner <andrew@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r268310 - head/libexec/rtld-elf/arm Message-ID: <201407061024.s66AO6R9012248@svn.freebsd.org>
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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 */
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