4 files changed, 32 insertions, 9 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index db524e75c4a2..290a4b57617f 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1229,7 +1229,7 @@ config SMP
 config SMP_ON_UP
         bool "Allow booting SMP kernel on uniprocessor systems (EXPERIMENTAL)"
         depends on EXPERIMENTAL
-        depends on SMP && !XIP && !THUMB2_KERNEL
+        depends on SMP && !XIP
         default y
         help
           SMP kernels contain instructions which fail on non-SMP processors.
diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 749bb6622404..72d3389e9c12 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -157,16 +157,24 @@
 #ifdef CONFIG_SMP
 #define ALT_SMP(instr...)                                       \
 9998:   instr
+/*
+ * Note: if you get assembler errors from ALT_UP() when building with
+ * CONFIG_THUMB2_KERNEL, you almost certainly need to use
+ * ALT_SMP( W(instr) ... )
+ */
 #define ALT_UP(instr...)                                        \
         .pushsection ".alt.smp.init", "a"                       ;\
         .long   9998b                                           ;\
-        instr                                                   ;\
+9997:   instr                                                   ;\
+        .if . - 9997b != 4                                      ;\
+                .error "ALT_UP() content must assemble to exactly 4 bytes";\
+        .endif                                                  ;\
         .popsection
 #define ALT_UP_B(label)                                 \
         .equ    up_b_offset, label - 9998b                      ;\
         .pushsection ".alt.smp.init", "a"                       ;\
         .long   9998b                                           ;\
-        b       . + up_b_offset                                 ;\
+        W(b)    . + up_b_offset                                 ;\
         .popsection
 #else
 #define ALT_SMP(instr...)
@@ -177,16 +185,24 @@
 /*
  * SMP data memory barrier
  */
-        .macro  smp_dmb
+        .macro  smp_dmb mode
 #ifdef CONFIG_SMP
 #if __LINUX_ARM_ARCH__ >= 7
+        .ifeqs "\mode","arm"
         ALT_SMP(dmb)
+        .else
+        ALT_SMP(W(dmb))
+        .endif
 #elif __LINUX_ARM_ARCH__ == 6
         ALT_SMP(mcr     p15, 0, r0, c7, c10, 5) @ dmb
 #else
 #error Incompatible SMP platform
 #endif
+        .ifeqs "\mode","arm"
         ALT_UP(nop)
+        .else
+        ALT_UP(W(nop))
+        .endif
 #endif
         .endm
 
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 955cf5f539ed..7f22a11a5105 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -842,7 +842,7 @@ __kuser_helper_start:
  */
 
 __kuser_memory_barrier:                         @ 0xffff0fa0
-        smp_dmb
+        smp_dmb arm
         usr_ret lr
 
         .align  5
@@ -959,7 +959,7 @@ kuser_cmpxchg_fixup:
 
 #else
 
-        smp_dmb
+        smp_dmb arm
 1:      ldrex   r3, [r2]
         subs    r3, r3, r0
         strexeq r3, r1, [r2]
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index fd94e4e82fc9..359e54e83bd5 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -412,10 +412,17 @@ __fixup_smp_on_up:
         add     r4, r4, r3
         add     r5, r5, r3
 2:      cmp     r4, r5
+        movhs   pc, lr
         ldmia   r4!, {r0, r6}
-        strlo   r6, [r0, r3]
-        blo     2b
-        mov     pc, lr
+ ARM(   str     r6, [r0, r3]    )
+ THUMB( add     r0, r0, r3      )
+#ifdef __ARMEB__
+ THUMB( mov     r6, r6, ror #16 )       @ Convert word order for big-endian.
+#endif
+ THUMB( strh    r6, [r0], #2    )       @ For Thumb-2, store as two halfwords
+ THUMB( mov     r6, r6, lsr #16 )       @ to be robust against misaligned r3.
+ THUMB( strh    r6, [r0]        )
+        b       2b
 ENDPROC(__fixup_smp)
 
 1:      .word   .