2507bc1338
The current debug trap handling code does a number of things that are illegal according to the AVR32 Architecture manual. Most importantly, it may try to schedule from Debug Mode, thus clearing the D bit, which can lead to "undefined behaviour". It seems like this works in most cases, but several people have observed somewhat unstable behaviour when debugging programs, including soft lockups. So there's definitely something which is not right with the existing code. The new code will never schedule from Debug mode, it will always exit Debug mode with a "retd" instruction, and if something not running in Debug mode needs to do something debug-related (like doing a single step), it will enter debug mode through a "breakpoint" instruction. The monitor code will then return directly to user space, bypassing its own saved registers if necessary (since we don't actually care about the trapped context, only the one that came before.) This adds three instructions to the common exception handling code, including one branch. It does not touch super-hot paths like the TLB miss handler. Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
118 lines
3.8 KiB
C
118 lines
3.8 KiB
C
/*
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* Copyright (C) 2004-2006 Atmel Corporation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef __ASM_AVR32_THREAD_INFO_H
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#define __ASM_AVR32_THREAD_INFO_H
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#include <asm/page.h>
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#define THREAD_SIZE_ORDER 1
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#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
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#ifndef __ASSEMBLY__
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#include <asm/types.h>
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struct task_struct;
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struct exec_domain;
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struct thread_info {
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struct task_struct *task; /* main task structure */
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struct exec_domain *exec_domain; /* execution domain */
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unsigned long flags; /* low level flags */
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__u32 cpu;
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__s32 preempt_count; /* 0 => preemptable, <0 => BUG */
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__u32 rar_saved; /* return address... */
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__u32 rsr_saved; /* ...and status register
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saved by debug handler
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when setting up
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trampoline */
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struct restart_block restart_block;
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__u8 supervisor_stack[0];
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};
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#define INIT_THREAD_INFO(tsk) \
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{ \
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.task = &tsk, \
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.exec_domain = &default_exec_domain, \
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.flags = 0, \
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.cpu = 0, \
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.preempt_count = 1, \
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.restart_block = { \
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.fn = do_no_restart_syscall \
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} \
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}
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#define init_thread_info (init_thread_union.thread_info)
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#define init_stack (init_thread_union.stack)
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/*
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* Get the thread information struct from C.
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* We do the usual trick and use the lower end of the stack for this
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*/
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static inline struct thread_info *current_thread_info(void)
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{
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unsigned long addr = ~(THREAD_SIZE - 1);
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asm("and %0, sp" : "=r"(addr) : "0"(addr));
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return (struct thread_info *)addr;
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}
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/* thread information allocation */
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#define alloc_thread_info(ti) \
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((struct thread_info *) __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER))
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#define free_thread_info(ti) free_pages((unsigned long)(ti), 1)
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#define get_thread_info(ti) get_task_struct((ti)->task)
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#define put_thread_info(ti) put_task_struct((ti)->task)
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#endif /* !__ASSEMBLY__ */
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#define PREEMPT_ACTIVE 0x40000000
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/*
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* Thread information flags
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* - these are process state flags that various assembly files may need to access
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* - pending work-to-be-done flags are in LSW
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* - other flags in MSW
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*/
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#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
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#define TIF_SIGPENDING 1 /* signal pending */
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#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
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#define TIF_POLLING_NRFLAG 3 /* true if poll_idle() is polling
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TIF_NEED_RESCHED */
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#define TIF_BREAKPOINT 4 /* enter monitor mode on return */
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#define TIF_SINGLE_STEP 5 /* single step in progress */
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#define TIF_MEMDIE 6
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#define TIF_RESTORE_SIGMASK 7 /* restore signal mask in do_signal */
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#define TIF_CPU_GOING_TO_SLEEP 8 /* CPU is entering sleep 0 mode */
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#define TIF_USERSPACE 31 /* true if FS sets userspace */
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#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
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#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
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#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
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#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
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#define _TIF_SINGLE_STEP (1 << TIF_SINGLE_STEP)
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#define _TIF_MEMDIE (1 << TIF_MEMDIE)
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#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
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#define _TIF_CPU_GOING_TO_SLEEP (1 << TIF_CPU_GOING_TO_SLEEP)
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/* Note: The masks below must never span more than 16 bits! */
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/* work to do on interrupt/exception return */
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#define _TIF_WORK_MASK \
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((1 << TIF_SIGPENDING) \
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| (1 << TIF_NEED_RESCHED) \
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| (1 << TIF_POLLING_NRFLAG) \
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| (1 << TIF_BREAKPOINT) \
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| (1 << TIF_RESTORE_SIGMASK))
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/* work to do on any return to userspace */
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#define _TIF_ALLWORK_MASK (_TIF_WORK_MASK | (1 << TIF_SYSCALL_TRACE))
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/* work to do on return from debug mode */
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#define _TIF_DBGWORK_MASK (_TIF_WORK_MASK & ~(1 << TIF_BREAKPOINT))
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#endif /* __ASM_AVR32_THREAD_INFO_H */
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