path: root/arch/sh/kernel/dwarf.c

/*
 * Copyright (C) 2009 Matt Fleming <matt@console-pimps.org>
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * This is an implementation of a DWARF unwinder. Its main purpose is
 * for generating stacktrace information. Based on the DWARF 3
 * specification from http://www.dwarfstd.org.
 *
 * TODO:
 *	- DWARF64 doesn't work.
 *	- Registers with DWARF_VAL_OFFSET rules aren't handled properly.
 */

/* #define DEBUG */
#include <linux/kernel.h>
#include <linux/io.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/mm.h>
#include <linux/elf.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <asm/dwarf.h>
#include <asm/unwinder.h>
#include <asm/sections.h>
#include <asm/unaligned.h>
#include <asm/stacktrace.h>

/* Reserve enough memory for two stack frames */
#define DWARF_FRAME_MIN_REQ	2
/* ... with 4 registers per frame. */
#define DWARF_REG_MIN_REQ	(DWARF_FRAME_MIN_REQ * 4)

static struct kmem_cache *dwarf_frame_cachep;
static mempool_t *dwarf_frame_pool;

static struct kmem_cache *dwarf_reg_cachep;
static mempool_t *dwarf_reg_pool;

static struct rb_root cie_root;
static DEFINE_SPINLOCK(dwarf_cie_lock);

static struct rb_root fde_root;
static DEFINE_SPINLOCK(dwarf_fde_lock);

static struct dwarf_cie *cached_cie;

static unsigned int dwarf_unwinder_ready;

/**
 *	dwarf_frame_alloc_reg - allocate memory for a DWARF register
 *	@frame: the DWARF frame whose list of registers we insert on
 *	@reg_num: the register number
 *
 *	Allocate space for, and initialise, a dwarf reg from
 *	dwarf_reg_pool and insert it onto the (unsorted) linked-list of
 *	dwarf registers for @frame.
 *
 *	Return the initialised DWARF reg.
 */
static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
					       unsigned int reg_num)
{
	struct dwarf_reg *reg;

	reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC);
	if (!reg) {
		printk(KERN_WARNING "Unable to allocate a DWARF register\n");
		/*
		 * Let's just bomb hard here, we have no way to
		 * gracefully recover.
		 */
		UNWINDER_BUG();
	}

	reg->number = reg_num;
	reg->addr = 0;
	reg->flags = 0;

	list_add(&reg->link, &frame->reg_list);

	return reg;
}

static void dwarf_frame_free_regs(struct dwarf_frame *frame)
{
	struct dwarf_reg *reg, *n;

	list_for_each_entry_safe(reg, n, &frame->reg_list, link) {
		list_del(&reg->link);
		mempool_free(reg, dwarf_reg_pool);
	}
}

/**
 *	dwarf_frame_reg - return a DWARF register
 *	@frame: the DWARF frame to search in for @reg_num
 *	@reg_num: the register number to search for
 *
 *	Lookup and return the dwarf reg @reg_num for this frame. Return
 *	NULL if @reg_num is an register invalid number.
 */
static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame,
					 unsigned int reg_num)
{
	struct dwarf_reg *reg;

	list_for_each_entry(reg, &frame->reg_list, link) {
		if (reg->number == reg_num)
			return reg;
	}

	return NULL;
}

/**
 *	dwarf_read_addr - read dwarf data
 *	@src: source address of data
 *	@dst: destination address to store the data to
 *
 *	Read 'n' bytes from @src, where 'n' is the size of an address on
 *	the native machine. We return the number of bytes read, which
 *	should always be 'n'. We also have to be careful when reading
 *	from @src and writing to @dst, because they can be arbitrarily
 *	aligned. Return 'n' - the number of bytes read.
 */
static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
{
	u32 val = get_unaligned(src);
	put_unaligned(val, dst);
	return sizeof(unsigned long *);
}

/**