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-rw-r--r--arch/avr32/kernel/entry-avr32b.S59
1 files changed, 57 insertions, 2 deletions
diff --git a/arch/avr32/kernel/entry-avr32b.S b/arch/avr32/kernel/entry-avr32b.S
index 2b398cae110c..33d49377b8be 100644
--- 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
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