[ARM] Fix alignment fault handling for ARMv6 and later CPUs

[linux-2.6-omap-h63xx.git] / arch / arm / mm / alignment.c

diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c
index 133e65d166b315b0e54aba959846a162643bc927..2d5884ce0435fb436a57bee6d314284b9101e87e 100644 (file)
--- 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");