145 lines
3.6 KiB
C
145 lines
3.6 KiB
C
/*
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* Arm specific backtracing code for oprofile
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*
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* Copyright 2005 Openedhand Ltd.
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*
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* Author: Richard Purdie <rpurdie@openedhand.com>
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*
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* Based on i386 oprofile backtrace code by John Levon, David Smith
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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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*/
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#include <linux/oprofile.h>
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <asm/ptrace.h>
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#include <asm/uaccess.h>
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/*
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* The registers we're interested in are at the end of the variable
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* length saved register structure. The fp points at the end of this
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* structure so the address of this struct is:
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* (struct frame_tail *)(xxx->fp)-1
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*/
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struct frame_tail {
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struct frame_tail *fp;
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unsigned long sp;
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unsigned long lr;
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} __attribute__((packed));
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#ifdef CONFIG_FRAME_POINTER
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static struct frame_tail* kernel_backtrace(struct frame_tail *tail)
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{
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oprofile_add_trace(tail->lr);
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/* frame pointers should strictly progress back up the stack
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* (towards higher addresses) */
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if (tail >= tail->fp)
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return NULL;
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return tail->fp-1;
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}
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#endif
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static struct frame_tail* user_backtrace(struct frame_tail *tail)
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{
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struct frame_tail buftail;
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/* hardware pte might not be valid due to dirty/accessed bit emulation
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* so we use copy_from_user and benefit from exception fixups */
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if (copy_from_user(&buftail, tail, sizeof(struct frame_tail)))
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return NULL;
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oprofile_add_trace(buftail.lr);
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/* frame pointers should strictly progress back up the stack
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* (towards higher addresses) */
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if (tail >= buftail.fp)
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return NULL;
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return buftail.fp-1;
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}
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/* Compare two addresses and see if they're on the same page */
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#define CMP_ADDR_EQUAL(x,y,offset) ((((unsigned long) x) >> PAGE_SHIFT) \
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== ((((unsigned long) y) + offset) >> PAGE_SHIFT))
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/* check that the page(s) containing the frame tail are present */
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static int pages_present(struct frame_tail *tail)
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{
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struct mm_struct * mm = current->mm;
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if (!check_user_page_readable(mm, (unsigned long)tail))
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return 0;
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if (CMP_ADDR_EQUAL(tail, tail, 8))
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return 1;
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if (!check_user_page_readable(mm, ((unsigned long)tail) + 8))
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return 0;
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return 1;
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}
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/*
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* | | /\ Higher addresses
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* | |
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* --------------- stack base (address of current_thread_info)
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* | thread info |
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* . .
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* | stack |
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* --------------- saved regs->ARM_fp value if valid (frame_tail address)
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* . .
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* --------------- struct pt_regs stored on stack (struct pt_regs *)
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* | |
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* . .
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* | |
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* --------------- %esp
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* | |
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* | | \/ Lower addresses
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*
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* Thus, &pt_regs <-> stack base restricts the valid(ish) fp values
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*/
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static int valid_kernel_stack(struct frame_tail *tail, struct pt_regs *regs)
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{
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unsigned long tailaddr = (unsigned long)tail;
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unsigned long stack = (unsigned long)regs;
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unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
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return (tailaddr > stack) && (tailaddr < stack_base);
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}
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void arm_backtrace(struct pt_regs const *regs, unsigned int depth)
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{
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struct frame_tail *tail;
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unsigned long last_address = 0;
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tail = ((struct frame_tail *) regs->ARM_fp) - 1;
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if (!user_mode(regs)) {
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#ifdef CONFIG_FRAME_POINTER
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while (depth-- && tail && valid_kernel_stack(tail, regs)) {
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tail = kernel_backtrace(tail);
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}
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#endif
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return;
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}
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while (depth-- && tail && !((unsigned long) tail & 3)) {
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if ((!CMP_ADDR_EQUAL(last_address, tail, 0)
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|| !CMP_ADDR_EQUAL(last_address, tail, 8))
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&& !pages_present(tail))
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return;
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last_address = (unsigned long) tail;
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tail = user_backtrace(tail);
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}
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}
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