/*
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* OpenRISC unwinder.c
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*
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* Reusable arch specific api for unwinding stacks.
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*
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* Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
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*
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* This file is licensed under the terms of the GNU General Public License
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* version 2. This program is licensed "as is" without any warranty of any
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* kind, whether express or implied.
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*/
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#include <linux/sched/task_stack.h>
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#include <linux/kernel.h>
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#include <asm/unwinder.h>
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#ifdef CONFIG_FRAME_POINTER
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struct or1k_frameinfo {
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unsigned long *fp;
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unsigned long ra;
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unsigned long top;
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};
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/*
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* Verify a frameinfo structure. The return address should be a valid text
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* address. The frame pointer may be null if its the last frame, otherwise
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* the frame pointer should point to a location in the stack after the the
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* top of the next frame up.
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*/
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static inline int or1k_frameinfo_valid(struct or1k_frameinfo *frameinfo)
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{
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return (frameinfo->fp == NULL ||
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(!kstack_end(frameinfo->fp) &&
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frameinfo->fp > &frameinfo->top)) &&
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__kernel_text_address(frameinfo->ra);
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}
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/*
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* Create a stack trace doing scanning which is frame pointer aware. We can
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* get reliable stack traces by matching the previously found frame
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* pointer with the top of the stack address every time we find a valid
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* or1k_frameinfo.
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*
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* Ideally the stack parameter will be passed as FP, but it can not be
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* guaranteed. Therefore we scan each address looking for the first sign
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* of a return address.
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*
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* The OpenRISC stack frame looks something like the following. The
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* location SP is held in r1 and location FP is held in r2 when frame pointers
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* enabled.
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*
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* SP -> (top of stack)
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* - (callee saved registers)
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* - (local variables)
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* FP-8 -> previous FP \
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* FP-4 -> return address |- or1k_frameinfo
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* FP -> (previous top of stack) /
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*/
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void unwind_stack(void *data, unsigned long *stack,
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void (*trace)(void *data, unsigned long addr, int reliable))
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{
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unsigned long *next_fp = NULL;
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struct or1k_frameinfo *frameinfo = NULL;
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int reliable = 0;
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while (!kstack_end(stack)) {
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frameinfo = container_of(stack,
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struct or1k_frameinfo,
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top);
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if (__kernel_text_address(frameinfo->ra)) {
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if (or1k_frameinfo_valid(frameinfo) &&
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(next_fp == NULL ||
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next_fp == &frameinfo->top)) {
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reliable = 1;
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next_fp = frameinfo->fp;
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} else
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reliable = 0;
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trace(data, frameinfo->ra, reliable);
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}
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stack++;
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}
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}
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#else /* CONFIG_FRAME_POINTER */
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/*
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* Create a stack trace by doing a simple scan treating all text addresses
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* as return addresses.
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*/
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void unwind_stack(void *data, unsigned long *stack,
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void (*trace)(void *data, unsigned long addr, int reliable))
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{
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unsigned long addr;
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while (!kstack_end(stack)) {
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addr = *stack++;
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if (__kernel_text_address(addr))
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trace(data, addr, 0);
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}
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}
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#endif /* CONFIG_FRAME_POINTER */
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