/*
   * arch/arm/kernel/unwind.c
   *
   * Copyright (C) 2008 ARM Limited
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
   *
   *
   * Stack unwinding support for ARM
   *
   * An ARM EABI version of gcc is required to generate the unwind
   * tables. For information about the structure of the unwind tables,
   * see "Exception Handling ABI for the ARM Architecture" at:
   *
   * http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html
   */

  #ifndef __CHECKER__

  #if !defined (__ARM_EABI__)
  #warning Your compiler does not have EABI support.
  #warning    ARM unwind is known to compile only with EABI compilers.
  #warning    Change compiler or disable ARM_UNWIND option.
  #elif (__GNUC__ == 4 && __GNUC_MINOR__ <= 2)
  #warning Your compiler is too buggy; it is known to not compile ARM unwind support.
  #warning    Change compiler or disable ARM_UNWIND option.
  #endif

  #endif /* __CHECKER__ */

  #include <linux/kernel.h>
  #include <linux/init.h>

  #include <linux/export.h>

  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/list.h>
  
  #include <asm/stacktrace.h>
  #include <asm/traps.h>
  #include <asm/unwind.h>
  
  /* Dummy functions to avoid linker complaints */
  void __aeabi_unwind_cpp_pr0(void)
  {
  };
  EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
  
  void __aeabi_unwind_cpp_pr1(void)
  {
  };
  EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
  
  void __aeabi_unwind_cpp_pr2(void)
  {
  };
  EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);
  
  struct unwind_ctrl_block {
  	unsigned long vrs[16];		/* virtual register set */

  	const unsigned long *insn;	/* pointer to the current instructions word */

  	int entries;			/* number of entries left to interpret */
  	int byte;			/* current byte number in the instructions word */
  };
  
  enum regs {

  #ifdef CONFIG_THUMB2_KERNEL
  	FP = 7,
  #else

  	FP = 11,

  #endif

  	SP = 13,
  	LR = 14,
  	PC = 15
  };

  extern const struct unwind_idx __start_unwind_idx[];
  static const struct unwind_idx *__origin_unwind_idx;
  extern const struct unwind_idx __stop_unwind_idx[];

  
  static DEFINE_SPINLOCK(unwind_lock);
  static LIST_HEAD(unwind_tables);
  
  /* Convert a prel31 symbol to an absolute address */
  #define prel31_to_addr(ptr)				\
  ({							\
  	/* sign-extend to 32 bits */			\
  	long offset = (((long)*(ptr)) << 1) >> 1;	\
  	(unsigned long)(ptr) + offset;			\
  })
  
  /*

   * Binary search in the unwind index. The entries are

   * guaranteed to be sorted in ascending order by the linker.

   *
   * start = first entry
   * origin = first entry with positive offset (or stop if there is no such entry)
   * stop - 1 = last entry

   */

  static const struct unwind_idx *search_index(unsigned long addr,
  				       const struct unwind_idx *start,
  				       const struct unwind_idx *origin,
  				       const struct unwind_idx *stop)

  {

  	unsigned long addr_prel31;
  
  	pr_debug("%s(%08lx, %p, %p, %p)
  ",
  			__func__, addr, start, origin, stop);
  
  	/*
  	 * only search in the section with the matching sign. This way the
  	 * prel31 numbers can be compared as unsigned longs.
  	 */
  	if (addr < (unsigned long)start)
  		/* negative offsets: [start; origin) */
  		stop = origin;
  	else
  		/* positive offsets: [origin; stop) */
  		start = origin;
  
  	/* prel31 for address relavive to start */
  	addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff;

  	while (start < stop - 1) {
  		const struct unwind_idx *mid = start + ((stop - start) >> 1);
  
  		/*
  		 * As addr_prel31 is relative to start an offset is needed to
  		 * make it relative to mid.
  		 */
  		if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) <
  				mid->addr_offset)
  			stop = mid;
  		else {
  			/* keep addr_prel31 relative to start */
  			addr_prel31 -= ((unsigned long)mid -
  					(unsigned long)start);
  			start = mid;
  		}
  	}
  
  	if (likely(start->addr_offset <= addr_prel31))
  		return start;
  	else {

  		pr_warning("unwind: Unknown symbol address %08lx
  ", addr);
  		return NULL;

  	}
  }

  static const struct unwind_idx *unwind_find_origin(
  		const struct unwind_idx *start, const struct unwind_idx *stop)
  {
  	pr_debug("%s(%p, %p)
  ", __func__, start, stop);

  	while (start < stop) {

  		const struct unwind_idx *mid = start + ((stop - start) >> 1);

  		if (mid->addr_offset >= 0x40000000)
  			/* negative offset */

  			start = mid + 1;

  		else

  			/* positive offset */
  			stop = mid;

  	}

  	pr_debug("%s -> %p
  ", __func__, stop);
  	return stop;

  }

  static const struct unwind_idx *unwind_find_idx(unsigned long addr)

  {

  	const struct unwind_idx *idx = NULL;

  	unsigned long flags;
  
  	pr_debug("%s(%08lx)
  ", __func__, addr);

  	if (core_kernel_text(addr)) {
  		if (unlikely(!__origin_unwind_idx))
  			__origin_unwind_idx =
  				unwind_find_origin(__start_unwind_idx,
  						__stop_unwind_idx);

  		/* main unwind table */
  		idx = search_index(addr, __start_unwind_idx,

  				   __origin_unwind_idx,
  				   __stop_unwind_idx);
  	} else {

  		/* module unwind tables */
  		struct unwind_table *table;
  
  		spin_lock_irqsave(&unwind_lock, flags);
  		list_for_each_entry(table, &unwind_tables, list) {
  			if (addr >= table->begin_addr &&
  			    addr < table->end_addr) {
  				idx = search_index(addr, table->start,

  						   table->origin,
  						   table->stop);

  				/* Move-to-front to exploit common traces */
  				list_move(&table->list, &unwind_tables);

  				break;
  			}
  		}
  		spin_unlock_irqrestore(&unwind_lock, flags);
  	}
  
  	pr_debug("%s: idx = %p
  ", __func__, idx);
  	return idx;
  }
  
  static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
  {
  	unsigned long ret;
  
  	if (ctrl->entries <= 0) {
  		pr_warning("unwind: Corrupt unwind table
  ");
  		return 0;
  	}
  
  	ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
  
  	if (ctrl->byte == 0) {
  		ctrl->insn++;
  		ctrl->entries--;
  		ctrl->byte = 3;
  	} else
  		ctrl->byte--;
  
  	return ret;
  }
  
  /*
   * Execute the current unwind instruction.
   */
  static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
  {
  	unsigned long insn = unwind_get_byte(ctrl);
  
  	pr_debug("%s: insn = %08lx
  ", __func__, insn);
  
  	if ((insn & 0xc0) == 0x00)
  		ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
  	else if ((insn & 0xc0) == 0x40)
  		ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
  	else if ((insn & 0xf0) == 0x80) {
  		unsigned long mask;
  		unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
  		int load_sp, reg = 4;
  
  		insn = (insn << 8) | unwind_get_byte(ctrl);
  		mask = insn & 0x0fff;
  		if (mask == 0) {
  			pr_warning("unwind: 'Refuse to unwind' instruction %04lx
  ",
  				   insn);
  			return -URC_FAILURE;
  		}
  
  		/* pop R4-R15 according to mask */
  		load_sp = mask & (1 << (13 - 4));
  		while (mask) {
  			if (mask & 1)
  				ctrl->vrs[reg] = *vsp++;
  			mask >>= 1;
  			reg++;
  		}
  		if (!load_sp)
  			ctrl->vrs[SP] = (unsigned long)vsp;
  	} else if ((insn & 0xf0) == 0x90 &&
  		   (insn & 0x0d) != 0x0d)
  		ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
  	else if ((insn & 0xf0) == 0xa0) {
  		unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
  		int reg;
  
  		/* pop R4-R[4+bbb] */
  		for (reg = 4; reg <= 4 + (insn & 7); reg++)
  			ctrl->vrs[reg] = *vsp++;
  		if (insn & 0x80)
  			ctrl->vrs[14] = *vsp++;
  		ctrl->vrs[SP] = (unsigned long)vsp;
  	} else if (insn == 0xb0) {

  		if (ctrl->vrs[PC] == 0)
  			ctrl->vrs[PC] = ctrl->vrs[LR];

  		/* no further processing */
  		ctrl->entries = 0;
  	} else if (insn == 0xb1) {
  		unsigned long mask = unwind_get_byte(ctrl);
  		unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
  		int reg = 0;
  
  		if (mask == 0 || mask & 0xf0) {
  			pr_warning("unwind: Spare encoding %04lx
  ",
  			       (insn << 8) | mask);
  			return -URC_FAILURE;
  		}
  
  		/* pop R0-R3 according to mask */
  		while (mask) {
  			if (mask & 1)
  				ctrl->vrs[reg] = *vsp++;
  			mask >>= 1;
  			reg++;
  		}
  		ctrl->vrs[SP] = (unsigned long)vsp;
  	} else if (insn == 0xb2) {
  		unsigned long uleb128 = unwind_get_byte(ctrl);
  
  		ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
  	} else {
  		pr_warning("unwind: Unhandled instruction %02lx
  ", insn);
  		return -URC_FAILURE;
  	}
  
  	pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx
  ", __func__,
  		 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
  
  	return URC_OK;
  }
  
  /*
   * Unwind a single frame starting with *sp for the symbol at *pc. It
   * updates the *pc and *sp with the new values.
   */
  int unwind_frame(struct stackframe *frame)
  {
  	unsigned long high, low;

  	const struct unwind_idx *idx;

  	struct unwind_ctrl_block ctrl;
  
  	/* only go to a higher address on the stack */
  	low = frame->sp;

  	high = ALIGN(low, THREAD_SIZE);

  
  	pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)
  ", __func__,
  		 frame->pc, frame->lr, frame->sp);
  
  	if (!kernel_text_address(frame->pc))
  		return -URC_FAILURE;
  
  	idx = unwind_find_idx(frame->pc);
  	if (!idx) {
  		pr_warning("unwind: Index not found %08lx
  ", frame->pc);
  		return -URC_FAILURE;
  	}
  
  	ctrl.vrs[FP] = frame->fp;
  	ctrl.vrs[SP] = frame->sp;
  	ctrl.vrs[LR] = frame->lr;
  	ctrl.vrs[PC] = 0;
  
  	if (idx->insn == 1)
  		/* can't unwind */
  		return -URC_FAILURE;
  	else if ((idx->insn & 0x80000000) == 0)
  		/* prel31 to the unwind table */
  		ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
  	else if ((idx->insn & 0xff000000) == 0x80000000)
  		/* only personality routine 0 supported in the index */
  		ctrl.insn = &idx->insn;
  	else {
  		pr_warning("unwind: Unsupported personality routine %08lx in the index at %p
  ",
  			   idx->insn, idx);
  		return -URC_FAILURE;
  	}
  
  	/* check the personality routine */
  	if ((*ctrl.insn & 0xff000000) == 0x80000000) {
  		ctrl.byte = 2;
  		ctrl.entries = 1;
  	} else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
  		ctrl.byte = 1;
  		ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
  	} else {
  		pr_warning("unwind: Unsupported personality routine %08lx at %p
  ",
  			   *ctrl.insn, ctrl.insn);
  		return -URC_FAILURE;
  	}
  
  	while (ctrl.entries > 0) {

  		int urc = unwind_exec_insn(&ctrl);

  		if (urc < 0)
  			return urc;

  		if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
  			return -URC_FAILURE;

  	}
  
  	if (ctrl.vrs[PC] == 0)
  		ctrl.vrs[PC] = ctrl.vrs[LR];

  	/* check for infinite loop */
  	if (frame->pc == ctrl.vrs[PC])
  		return -URC_FAILURE;

  	frame->fp = ctrl.vrs[FP];
  	frame->sp = ctrl.vrs[SP];
  	frame->lr = ctrl.vrs[LR];
  	frame->pc = ctrl.vrs[PC];
  
  	return URC_OK;
  }
  
  void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
  {
  	struct stackframe frame;

  	register unsigned long current_sp asm ("sp");
  
  	pr_debug("%s(regs = %p tsk = %p)
  ", __func__, regs, tsk);
  
  	if (!tsk)
  		tsk = current;
  
  	if (regs) {
  		frame.fp = regs->ARM_fp;
  		frame.sp = regs->ARM_sp;
  		frame.lr = regs->ARM_lr;

  		/* PC might be corrupted, use LR in that case. */
  		frame.pc = kernel_text_address(regs->ARM_pc)
  			 ? regs->ARM_pc : regs->ARM_lr;

  	} else if (tsk == current) {
  		frame.fp = (unsigned long)__builtin_frame_address(0);
  		frame.sp = current_sp;
  		frame.lr = (unsigned long)__builtin_return_address(0);
  		frame.pc = (unsigned long)unwind_backtrace;
  	} else {
  		/* task blocked in __switch_to */
  		frame.fp = thread_saved_fp(tsk);
  		frame.sp = thread_saved_sp(tsk);
  		/*
  		 * The function calling __switch_to cannot be a leaf function
  		 * so LR is recovered from the stack.
  		 */
  		frame.lr = 0;
  		frame.pc = thread_saved_pc(tsk);
  	}

  	while (1) {
  		int urc;
  		unsigned long where = frame.pc;
  
  		urc = unwind_frame(&frame);
  		if (urc < 0)
  			break;
  		dump_backtrace_entry(where, frame.pc, frame.sp - 4);
  	}
  }
  
  struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
  				      unsigned long text_addr,
  				      unsigned long text_size)
  {
  	unsigned long flags;

  	struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
  
  	pr_debug("%s(%08lx, %08lx, %08lx, %08lx)
  ", __func__, start, size,
  		 text_addr, text_size);
  
  	if (!tab)
  		return tab;

  	tab->start = (const struct unwind_idx *)start;
  	tab->stop = (const struct unwind_idx *)(start + size);
  	tab->origin = unwind_find_origin(tab->start, tab->stop);

  	tab->begin_addr = text_addr;
  	tab->end_addr = text_addr + text_size;

  	spin_lock_irqsave(&unwind_lock, flags);
  	list_add_tail(&tab->list, &unwind_tables);
  	spin_unlock_irqrestore(&unwind_lock, flags);
  
  	return tab;
  }
  
  void unwind_table_del(struct unwind_table *tab)
  {
  	unsigned long flags;
  
  	if (!tab)
  		return;
  
  	spin_lock_irqsave(&unwind_lock, flags);
  	list_del(&tab->list);
  	spin_unlock_irqrestore(&unwind_lock, flags);
  
  	kfree(tab);
  }