diff options
Diffstat (limited to 'arch/avr32/kernel/entry-avr32b.S')
| -rw-r--r-- | arch/avr32/kernel/entry-avr32b.S | 59 |
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 |
