Merge branches 'sched/devel', 'sched/cpu-hotplug', 'sched/cpusets' and 'sched/urgent...

[linux-2.6-omap-h63xx.git] / arch / avr32 / kernel / entry-avr32b.S

diff --git a/arch/avr32/kernel/entry-avr32b.S b/arch/avr32/kernel/entry-avr32b.S
index 2b398cae110c839fc5b3c3be3d9d7a48fcf3a2ec..33d49377b8beda6ae217cf40928d304d5eabfa6d 100644 (file)
--- a/arch/avr32/kernel/entry-avr32b.S
+++ b/arch/avr32/kernel/entry-avr32b.S
@@ -334,9 +334,64 @@ save_full_context_ex:
 
        /* Low-level exception handlers */
 handle_critical:
+       /*
+        * AT32AP700x errata:
+        *
+        * After a Java stack overflow or underflow trap, any CPU
+        * memory access may cause erratic behavior. This will happen
+        * when the four least significant bits of the JOSP system
+        * register contains any value between 9 and 15 (inclusive).
+        *
+        * Possible workarounds:
+        *   - Don't use the Java Extension Module
+        *   - Ensure that the stack overflow and underflow trap
+        *     handlers do not do any memory access or trigger any
+        *     exceptions before the overflow/underflow condition is
+        *     cleared (by incrementing or decrementing the JOSP)
+        *   - Make sure that JOSP does not contain any problematic
+        *     value before doing any exception or interrupt
+        *     processing.
+        *   - Set up a critical exception handler which writes a
+        *     known-to-be-safe value, e.g. 4, to JOSP before doing
+        *     any further processing.
+        *
+        * We'll use the last workaround for now since we cannot
+        * guarantee that user space processes don't use Java mode.
+        * Non-well-behaving userland will be terminated with extreme
+        * prejudice.
+        */
+#ifdef CONFIG_CPU_AT32AP700X
+       /*
+        * There's a chance we can't touch memory, so temporarily
+        * borrow PTBR to save the stack pointer while we fix things
+        * up...
+        */
+       mtsr    SYSREG_PTBR, sp
+       mov     sp, 4
+       mtsr    SYSREG_JOSP, sp
+       mfsr    sp, SYSREG_PTBR
+       sub     pc, -2
+
+       /* Push most of pt_regs on stack. We'll do the rest later */
        sub     sp, 4
-       stmts   --sp, r0-lr
-       rcall   save_full_context_ex
+       pushm   r0-r12
+
+       /* PTBR mirrors current_thread_info()->task->active_mm->pgd */
+       get_thread_info r0
+       ld.w    r1, r0[TI_task]
+       ld.w    r2, r1[TSK_active_mm]
+       ld.w    r3, r2[MM_pgd]
+       mtsr    SYSREG_PTBR, r3
+#else
+       sub     sp, 4
+       pushm   r0-r12
+#endif
+       sub     r0, sp, -(14 * 4)
+       mov     r1, lr
+       mfsr    r2, SYSREG_RAR_EX
+       mfsr    r3, SYSREG_RSR_EX
+       pushm   r0-r3
+
        mfsr    r12, SYSREG_ECR
        mov     r11, sp
        rcall   do_critical_exception