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Align the stack in _rtld_bind_start. Normally this is called with the

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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@
This commit is contained in:
Andrew Turner 2014-07-06 10:24:06 +00:00
parent 99ae56ac82
commit 0685d955d6
1 changed files with 5 additions and 2 deletions
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7
libexec/rtld-elf/arm/rtld_start.S
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@ -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 */