1 files changed, 23 insertions, 3 deletions

diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c
index 133e65d166b3..2d5884ce0435 100644
--- a/arch/arm/mm/alignment.c
+++ b/arch/arm/mm/alignment.c
@@ -70,6 +70,10 @@ static unsigned long ai_dword;
 static unsigned long ai_multi;
 static int ai_usermode;
 
+#define UM_WARN         (1 << 0)
+#define UM_FIXUP        (1 << 1)
+#define UM_SIGNAL       (1 << 2)
+
 #ifdef CONFIG_PROC_FS
 static const char *usermode_action[] = {
         "ignored",
@@ -754,7 +758,7 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
  user:
         ai_user += 1;
 
-        if (ai_usermode & 1)
+        if (ai_usermode & UM_WARN)
                 printk("Alignment trap: %s (%d) PC=0x%08lx Instr=0x%0*lx "
                        "Address=0x%08lx FSR 0x%03x\n", current->comm,
                         task_pid_nr(current), instrptr,
@@ -762,10 +766,10 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
                         thumb_mode(regs) ? tinstr : instr,
                         addr, fsr);
 
-        if (ai_usermode & 2)
+        if (ai_usermode & UM_FIXUP)
                 goto fixup;
 
-        if (ai_usermode & 4)
+        if (ai_usermode & UM_SIGNAL)
                 force_sig(SIGBUS, current);
         else
                 set_cr(cr_no_alignment);
@@ -796,6 +800,22 @@ static int __init alignment_init(void)
         res->write_proc = proc_alignment_write;
 #endif
 
+        /*
+         * ARMv6 and later CPUs can perform unaligned accesses for
+         * most single load and store instructions up to word size.
+         * LDM, STM, LDRD and STRD still need to be handled.
+         *
+         * Ignoring the alignment fault is not an option on these
+         * CPUs since we spin re-faulting the instruction without
+         * making any progress.
+         */
+        if (cpu_architecture() >= CPU_ARCH_ARMv6 && (cr_alignment & CR_U)) {
+                cr_alignment &= ~CR_A;
+                cr_no_alignment &= ~CR_A;
+                set_cr(cr_alignment);
+                ai_usermode = UM_FIXUP;
+        }
+
         hook_fault_code(1, do_alignment, SIGILL, "alignment exception");
         hook_fault_code(3, do_alignment, SIGILL, "alignment exception");