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