unwind.c

xen虚拟机源代码安装包

	if (r->where == UNW_WHERE_NONE || r->when >= sr->when_target)
		return;

	opc = UNW_INSN_MOVE;
	val = rval = r->val;
	need_nat_info = (i >= UNW_REG_R4 && i <= UNW_REG_R7);

	switch (r->where) {
	      case UNW_WHERE_GR:
		if (rval >= 32) {
			opc = UNW_INSN_MOVE_STACKED;
			val = rval - 32;
		} else if (rval >= 4 && rval <= 7) {
			if (need_nat_info) {
				opc = UNW_INSN_MOVE2;
				need_nat_info = 0;
			}
			val = unw.preg_index[UNW_REG_R4 + (rval - 4)];
		} else if (rval == 0) {
			opc = UNW_INSN_MOVE_CONST;
			val = 0;
		} else {
			/* register got spilled to a scratch register */
			opc = UNW_INSN_MOVE_SCRATCH;
			val = pt_regs_off(rval);
		}
		break;

	      case UNW_WHERE_FR:
		if (rval <= 5)
			val = unw.preg_index[UNW_REG_F2  + (rval -  2)];
		else if (rval >= 16 && rval <= 31)
			val = unw.preg_index[UNW_REG_F16 + (rval - 16)];
		else {
			opc = UNW_INSN_MOVE_SCRATCH;
			if (rval <= 11)
				val = offsetof(struct pt_regs, f6) + 16*(rval - 6);
			else
				UNW_DPRINT(0, "unwind.%s: kernel may not touch f%lu\n",
					   __FUNCTION__, rval);
		}
		break;

	      case UNW_WHERE_BR:
		if (rval >= 1 && rval <= 5)
			val = unw.preg_index[UNW_REG_B1 + (rval - 1)];
		else {
			opc = UNW_INSN_MOVE_SCRATCH;
			if (rval == 0)
				val = offsetof(struct pt_regs, b0);
			else if (rval == 6)
				val = offsetof(struct pt_regs, b6);
			else
				val = offsetof(struct pt_regs, b7);
		}
		break;

	      case UNW_WHERE_SPREL:
		opc = UNW_INSN_ADD_SP;
		break;

	      case UNW_WHERE_PSPREL:
		opc = UNW_INSN_ADD_PSP;
		break;

	      default:
		UNW_DPRINT(0, "unwind%s: register %u has unexpected `where' value of %u\n",
			   __FUNCTION__, i, r->where);
		break;
	}
	insn.opc = opc;
	insn.dst = unw.preg_index[i];
	insn.val = val;
	script_emit(script, insn);
	if (need_nat_info)
		emit_nat_info(sr, i, script);

	if (i == UNW_REG_PSP) {
		/*
		 * info->psp must contain the _value_ of the previous
		 * sp, not it's save location.  We get this by
		 * dereferencing the value we just stored in
		 * info->psp:
		 */
		insn.opc = UNW_INSN_LOAD;
		insn.dst = insn.val = unw.preg_index[UNW_REG_PSP];
		script_emit(script, insn);
	}
}

static inline const struct unw_table_entry *
lookup (struct unw_table *table, unsigned long rel_ip)
{
	const struct unw_table_entry *e = NULL;
	unsigned long lo, hi, mid;

	/* do a binary search for right entry: */
	for (lo = 0, hi = table->length; lo < hi; ) {
		mid = (lo + hi) / 2;
		e = &table->array[mid];
		if (rel_ip < e->start_offset)
			hi = mid;
		else if (rel_ip >= e->end_offset)
			lo = mid + 1;
		else
			break;
	}
	if (rel_ip < e->start_offset || rel_ip >= e->end_offset)
		return NULL;
	return e;
}

/*
 * Build an unwind script that unwinds from state OLD_STATE to the
 * entrypoint of the function that called OLD_STATE.
 */
static inline struct unw_script *
build_script (struct unw_frame_info *info)
{
	const struct unw_table_entry *e = NULL;
	struct unw_script *script = NULL;
	struct unw_labeled_state *ls, *next;
	unsigned long ip = info->ip;
	struct unw_state_record sr;
	struct unw_table *table;
	struct unw_reg_info *r;
	struct unw_insn insn;
	u8 *dp, *desc_end;
	u64 hdr;
	int i;
	STAT(unsigned long start, parse_start;)

	STAT(++unw.stat.script.builds; start = ia64_get_itc());

	/* build state record */
	memset(&sr, 0, sizeof(sr));
	for (r = sr.curr.reg; r < sr.curr.reg + UNW_NUM_REGS; ++r)
		r->when = UNW_WHEN_NEVER;
	sr.pr_val = info->pr;

	UNW_DPRINT(3, "unwind.%s: ip 0x%lx\n", __FUNCTION__, ip);
	script = script_new(ip);
	if (!script) {
		UNW_DPRINT(0, "unwind.%s: failed to create unwind script\n",  __FUNCTION__);
		STAT(unw.stat.script.build_time += ia64_get_itc() - start);
		return NULL;
	}
	unw.cache[info->prev_script].hint = script - unw.cache;

	/* search the kernels and the modules' unwind tables for IP: */

	STAT(parse_start = ia64_get_itc());

	for (table = unw.tables; table; table = table->next) {
		if (ip >= table->start && ip < table->end) {
			e = lookup(table, ip - table->segment_base);
			break;
		}
	}
	if (!e) {
		/* no info, return default unwinder (leaf proc, no mem stack, no saved regs)  */
		UNW_DPRINT(1, "unwind.%s: no unwind info for ip=0x%lx (prev ip=0x%lx)\n",
			__FUNCTION__, ip, unw.cache[info->prev_script].ip);
		sr.curr.reg[UNW_REG_RP].where = UNW_WHERE_BR;
		sr.curr.reg[UNW_REG_RP].when = -1;
		sr.curr.reg[UNW_REG_RP].val = 0;
		compile_reg(&sr, UNW_REG_RP, script);
		script_finalize(script, &sr);
		STAT(unw.stat.script.parse_time += ia64_get_itc() - parse_start);
		STAT(unw.stat.script.build_time += ia64_get_itc() - start);
		return script;
	}

	sr.when_target = (3*((ip & ~0xfUL) - (table->segment_base + e->start_offset))/16
			  + (ip & 0xfUL));
	hdr = *(u64 *) (table->segment_base + e->info_offset);
	dp =   (u8 *)  (table->segment_base + e->info_offset + 8);
	desc_end = dp + 8*UNW_LENGTH(hdr);

	while (!sr.done && dp < desc_end)
		dp = unw_decode(dp, sr.in_body, &sr);

	if (sr.when_target > sr.epilogue_start) {
		/*
		 * sp has been restored and all values on the memory stack below
		 * psp also have been restored.
		 */
		sr.curr.reg[UNW_REG_PSP].val = 0;
		sr.curr.reg[UNW_REG_PSP].where = UNW_WHERE_NONE;
		sr.curr.reg[UNW_REG_PSP].when = UNW_WHEN_NEVER;
		for (r = sr.curr.reg; r < sr.curr.reg + UNW_NUM_REGS; ++r)
			if ((r->where == UNW_WHERE_PSPREL && r->val <= 0x10)
			    || r->where == UNW_WHERE_SPREL)
			{
				r->val = 0;
				r->where = UNW_WHERE_NONE;
				r->when = UNW_WHEN_NEVER;
			}
	}

	script->flags = sr.flags;

	/*
	 * If RP did't get saved, generate entry for the return link
	 * register.
	 */
	if (sr.curr.reg[UNW_REG_RP].when >= sr.when_target) {
		sr.curr.reg[UNW_REG_RP].where = UNW_WHERE_BR;
		sr.curr.reg[UNW_REG_RP].when = -1;
		sr.curr.reg[UNW_REG_RP].val = sr.return_link_reg;
		UNW_DPRINT(1, "unwind.%s: using default for rp at ip=0x%lx where=%d val=0x%lx\n",
			   __FUNCTION__, ip, sr.curr.reg[UNW_REG_RP].where,
			   sr.curr.reg[UNW_REG_RP].val);
	}

#ifdef UNW_DEBUG
	UNW_DPRINT(1, "unwind.%s: state record for func 0x%lx, t=%u:\n",
		__FUNCTION__, table->segment_base + e->start_offset, sr.when_target);
	for (r = sr.curr.reg; r < sr.curr.reg + UNW_NUM_REGS; ++r) {
		if (r->where != UNW_WHERE_NONE || r->when != UNW_WHEN_NEVER) {
			UNW_DPRINT(1, "  %s <- ", unw.preg_name[r - sr.curr.reg]);
			switch (r->where) {
			      case UNW_WHERE_GR:     UNW_DPRINT(1, "r%lu", r->val); break;
			      case UNW_WHERE_FR:     UNW_DPRINT(1, "f%lu", r->val); break;
			      case UNW_WHERE_BR:     UNW_DPRINT(1, "b%lu", r->val); break;
			      case UNW_WHERE_SPREL:  UNW_DPRINT(1, "[sp+0x%lx]", r->val); break;
			      case UNW_WHERE_PSPREL: UNW_DPRINT(1, "[psp+0x%lx]", r->val); break;
			      case UNW_WHERE_NONE:
				UNW_DPRINT(1, "%s+0x%lx", unw.preg_name[r - sr.curr.reg], r->val);
				break;

			      default:
				UNW_DPRINT(1, "BADWHERE(%d)", r->where);
				break;
			}
			UNW_DPRINT(1, "\t\t%d\n", r->when);
		}
	}
#endif

	STAT(unw.stat.script.parse_time += ia64_get_itc() - parse_start);

	/* translate state record into unwinder instructions: */

	/*
	 * First, set psp if we're dealing with a fixed-size frame;
	 * subsequent instructions may depend on this value.
	 */
	if (sr.when_target > sr.curr.reg[UNW_REG_PSP].when
	    && (sr.curr.reg[UNW_REG_PSP].where == UNW_WHERE_NONE)
	    && sr.curr.reg[UNW_REG_PSP].val != 0) {
		/* new psp is sp plus frame size */
		insn.opc = UNW_INSN_ADD;
		insn.dst = offsetof(struct unw_frame_info, psp)/8;
		insn.val = sr.curr.reg[UNW_REG_PSP].val;	/* frame size */
		script_emit(script, insn);
	}

	/* determine where the primary UNaT is: */
	if (sr.when_target < sr.curr.reg[UNW_REG_PRI_UNAT_GR].when)
		i = UNW_REG_PRI_UNAT_MEM;
	else if (sr.when_target < sr.curr.reg[UNW_REG_PRI_UNAT_MEM].when)
		i = UNW_REG_PRI_UNAT_GR;
	else if (sr.curr.reg[UNW_REG_PRI_UNAT_MEM].when > sr.curr.reg[UNW_REG_PRI_UNAT_GR].when)
		i = UNW_REG_PRI_UNAT_MEM;
	else
		i = UNW_REG_PRI_UNAT_GR;

	compile_reg(&sr, i, script);

	for (i = UNW_REG_BSP; i < UNW_NUM_REGS; ++i)
		compile_reg(&sr, i, script);

	/* free labeled register states & stack: */

	STAT(parse_start = ia64_get_itc());
	for (ls = sr.labeled_states; ls; ls = next) {
		next = ls->next;
		free_state_stack(&ls->saved_state);
		free_labeled_state(ls);
	}
	free_state_stack(&sr.curr);
	STAT(unw.stat.script.parse_time += ia64_get_itc() - parse_start);

	script_finalize(script, &sr);
	STAT(unw.stat.script.build_time += ia64_get_itc() - start);
	return script;
}

/*
 * Apply the unwinding actions represented by OPS and update SR to
 * reflect the state that existed upon entry to the function that this
 * unwinder represents.
 */
static inline void
run_script (struct unw_script *script, struct unw_frame_info *state)
{
	struct unw_insn *ip, *limit, next_insn;
	unsigned long opc, dst, val, off;
	unsigned long *s = (unsigned long *) state;
	STAT(unsigned long start;)

	STAT(++unw.stat.script.runs; start = ia64_get_itc());
	state->flags = script->flags;
	ip = script->insn;
	limit = script->insn + script->count;
	next_insn = *ip;

	while (ip++ < limit) {
		opc = next_insn.opc;
		dst = next_insn.dst;
		val = next_insn.val;
		next_insn = *ip;

	  redo:
		switch (opc) {
		      case UNW_INSN_ADD:
			s[dst] += val;
			break;

		      case UNW_INSN_MOVE2:
			if (!s[val])
				goto lazy_init;
			s[dst+1] = s[val+1];
			s[dst] = s[val];
			break;

		      case UNW_INSN_MOVE:
			if (!s[val])
				goto lazy_init;
			s[dst] = s[val];
			break;

		      case UNW_INSN_MOVE_SCRATCH:
			if (state->pt) {
				s[dst] = (unsigned long) get_scratch_regs(state) + val;
			} else {
				s[dst] = 0;
				UNW_DPRINT(0, "unwind.%s: no state->pt, dst=%ld, val=%ld\n",
					   __FUNCTION__, dst, val);
			}
			break;

		      case UNW_INSN_MOVE_CONST:
			if (val == 0)
				s[dst] = (unsigned long) &unw.r0;
			else {
				s[dst] = 0;
				UNW_DPRINT(0, "unwind.%s: UNW_INSN_MOVE_CONST bad val=%ld\n",
					   __FUNCTION__, val);
			}
			break;


		      case UNW_INSN_MOVE_STACKED:
			s[dst] = (unsigned long) ia64_rse_skip_regs((unsigned long *)state->bsp,
								    val);
			break;

		      case UNW_INSN_ADD_PSP:
			s[dst] = state->psp + val;
			break;

		      case UNW_INSN_ADD_SP:
			s[dst] = state->sp + val;
			break;

		      case UNW_INSN_SETNAT_MEMSTK:
			if (!state->pri_unat_loc)
				state->pri_unat_loc = &state->sw->caller_unat;
			/* register off. is a multiple of 8, so the least 3 bits (type) are 0 */
			s[dst+1] = ((unsigned long) state->pri_unat_loc - s[dst]) | UNW_NAT_MEMSTK;
			break;

		      case UNW_INSN_SETNAT_TYPE:
			s[dst+1] = val;
			break;

		      case UNW_INSN_LOAD:
#ifdef UNW_DEBUG
			if ((s[val] & (local_cpu_data->unimpl_va_mask | 0x7)) != 0
#ifndef XEN
			    || s[val] < TASK_SIZE
#endif
				)
			{
				UNW_DPRINT(0, "unwind.%s: rejecting bad psp=0x%lx\n",
					   __FUNCTION__, s[val]);
				break;
			}
#endif
			s[dst] = *(unsigned long *) s[val];
			break;
		}
	}
	STAT(unw.stat.script.run_time += ia64_get_itc() - start);
	return;

  lazy_init:
	off = unw.sw_off[val];
	s[val] = (unsigned long) state->sw + off;
	if (off >= offsetof(struct switch_stack, r4) && off <= offsetof(struct switch_stack, r7))
		/*
		 * We're initializing a general register: init NaT info, too.  Note that
		 * the offset is a multiple of 8 which gives us the 3 bits needed for
		 * the type field.
		 */
		s[val+1] = (offsetof(struct switch_stack, ar_unat) - off) | UNW_NAT_MEMSTK;
	goto redo;
}

#ifdef XEN
static inline int
is_hypervisor_virt(unsigned long addr)
{
	return IS_VMM_ADDRESS(addr) &&
		(HYPERVISOR_VIRT_START <= addr) &&
		(addr < HYPERVISOR_VIRT_END);
}
#endif

static int
find_save_locs (struct unw_frame_info *info)
{
	int have_write_lock = 0;
	struct unw_script *scr;
	unsigned long flags = 0;

	if ((info->ip & (local_cpu_data->unimpl_va_mask | 0xf))
#ifndef XEN
	    || info->ip < TASK_SIZE
#else
	    || !is_hypervisor_virt(info->ip)
#endif
		) {
		/* don't let obviously bad addresses pollute the cache */
		/* FIXME: should really be level 0 but it occurs too often. KAO */
		UNW_DPRINT(1, "unwind.%s: rejecting bad ip=0x%lx\n", __FUNCTION__, info->ip);
		info->rp_loc = NULL;
		return -1;
	}

	scr = script_lookup(info);
	if (!scr) {
		spin_lock_irqsave(&unw.lock, flags);
		scr = build_script(info);
		if (!scr) {
			spin_unlock_irqrestore(&unw.lock, flags);
			UNW_DPRINT(0,
				   "unwind.%s: failed to locate/build unwind script for ip %lx\n",
				   __FUNCTION__, info->ip);
			return -1;
		}
		have_write_lock = 1;
	}
	info->hint = scr->hint;
	info->prev_script = scr - unw.cache;

	run_script(scr, info);

	if (have_write_lock) {
		write_unlock(&scr->lock);
		spin_unlock_irqrestore(&unw.lock, flags);
	} else
		read_unlock(&scr->lock);
	return 0;
}

int
unw_unwind (struct unw_frame_info *info)
{
	unsigned long prev_ip, prev_sp, prev_bsp;
	unsigned long ip, pr, num_regs;
	STAT(unsigned long start, flags;)
	int retval;

	STAT(local_irq_save(flags); ++unw.stat.api.unwinds; start = ia64_get_itc());