[PATCH] grub-core/kern/arm/misc.S: fix unaligned grub_uint64_t local variable

[David Kozub]

The unaligned local in __aeabi_uidivmod leads to a store to a 64bit
value at an address that is not divisible by 8 (in grub_divmod64).
The compiler most likely generates a STRD instruction to store it and
this causes an exception.

Fixes Savannah bug #43632.

This includes improvements done by Leif Lindholm.
---
 ChangeLog                 |  6 ++++++
 grub-core/kern/arm/misc.S | 14 +++++++-------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 6fbec06..8728c04 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2014-11-21  David Kozub  <address@hidden>
+
+       * grub-core/kern/arm/misc.S: fix unaligned 64bit local variable
+       in __aeabi_uidivmod
+       Fixes Savannah bug #43632.
+
 2014-11-20  Andrei Borzenkov  <address@hidden>
 
        * tests/util/grub-fs-tester.in: Consistently print output
diff --git a/grub-core/kern/arm/misc.S b/grub-core/kern/arm/misc.S
index 8943cc3..16b6f8e 100644
--- a/grub-core/kern/arm/misc.S
+++ b/grub-core/kern/arm/misc.S
@@ -60,17 +60,17 @@ FUNCTION(__aeabi_lmul)
 
        .macro division parent
 
-        stmfd   sp!, {lr}
-        sub     sp, sp, #12
+        sub     sp, sp, #8      @ Allocate naturally aligned 64-bit space
+        stmfd   sp!, {r3,lr}    @ Dummy r3 to maintain stack alignment
+        add     r3, sp, #8      @ Set r3 to address of 64-bit space
+        str     r3, [sp]        @ Stack parameter, pointer to 64-bit space
         mov     r2, r1
-        add     r1, sp, #4
-        str     r1, [sp, #0]
         mov     r1, #0
         mov     r3, #0
         bl      \parent
-       ldr     r1, [sp, #4]
-        add     sp, sp, #12
-        ldmfd   sp!, {lr}
+        ldr     r1, [sp, #8]    @ Extract remainder
+        ldmfd   sp!, {r3,lr}    @ Pop into an unused arg/scratch register
+        add     sp, sp, #8
         bx      lr
        .endm
 
-- 
2.1.1