1 files changed, 434 insertions, 0 deletions

diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
new file mode 100644
index 000000000000..1dedc2c7ff49
--- /dev/null
+++ b/arch/arm/kernel/unwind.c
@@ -0,0 +1,434 @@
+/*
+ * 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
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.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 */
+	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 {
+	FP = 11,
+	SP = 13,
+	LR = 14,
+	PC = 15
+};
+
+extern struct unwind_idx __start_unwind_idx[];
+extern 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 entries are
+ * guaranteed to be sorted in ascending order by the linker.
+ */
+static struct unwind_idx *search_index(unsigned long addr,
+				       struct unwind_idx *first,
+				       struct unwind_idx *last)
+{
+	pr_debug("%s(%08lx, %p, %p)\n", __func__, addr, first, last);
+
+	if (addr < first->addr) {
+		pr_warning("unwind: Unknown symbol address %08lx\n", addr);
+		return NULL;
+	} else if (addr >= last->addr)
+		return last;
+
+	while (first < last - 1) {
+		struct unwind_idx *mid = first + ((last - first + 1) >> 1);
+
+		if (addr < mid->addr)
+			last = mid;
+		else
+			first = mid;
+	}
+
+	return first;
+}
+
+static struct unwind_idx *unwind_find_idx(unsigned long addr)
+{
+	struct unwind_idx *idx = NULL;
+	unsigned long flags;
+
+	pr_debug("%s(%08lx)\n", __func__, addr);
+
+	if (core_kernel_text(addr))
+		/* main unwind table */
+		idx = search_index(addr, __start_unwind_idx,
+				   __stop_unwind_idx - 1);
+	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->stop - 1);
+				break;
+			}
+		}
+		spin_unlock_irqrestore(&unwind_lock, flags);
+	}
+
+	pr_debug("%s: idx = %p\n", __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\n");
+		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\n", __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\n",
+				   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) {
+		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\n",
+			       (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\n", insn);
+		return -URC_FAILURE;
+	}
+
+	pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __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;
+	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) + THREAD_SIZE;
+
+	pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __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\n", 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\n",
+			   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\n",
+			   *ctrl.insn, ctrl.insn);
+		return -URC_FAILURE;
+	}
+
+	while (ctrl.entries > 0) {
+		int urc;
+
+		if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
+			return -URC_FAILURE;
+		urc = unwind_exec_insn(&ctrl);
+		if (urc < 0)
+			return urc;
+	}
+
+	if (ctrl.vrs[PC] == 0)
+		ctrl.vrs[PC] = ctrl.vrs[LR];
+
+	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;
+	unsigned long high, low;
+	register unsigned long current_sp asm ("sp");
+
+	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
+
+	if (!tsk)
+		tsk = current;
+
+	if (regs) {
+		frame.fp = regs->ARM_fp;
+		frame.sp = regs->ARM_sp;
+		frame.lr = regs->ARM_lr;
+		frame.pc = regs->ARM_pc;
+	} 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);
+	}
+
+	low = frame.sp & ~(THREAD_SIZE - 1);
+	high = low + THREAD_SIZE;
+
+	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_idx *idx;
+	struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
+
+	pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
+		 text_addr, text_size);
+
+	if (!tab)
+		return tab;
+
+	tab->start = (struct unwind_idx *)start;
+	tab->stop = (struct unwind_idx *)(start + size);
+	tab->begin_addr = text_addr;
+	tab->end_addr = text_addr + text_size;
+
+	/* Convert the symbol addresses to absolute values */
+	for (idx = tab->start; idx < tab->stop; idx++)
+		idx->addr = prel31_to_addr(&idx->addr);
+
+	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);
+}
+
+int __init unwind_init(void)
+{
+	struct unwind_idx *idx;
+
+	/* Convert the symbol addresses to absolute values */
+	for (idx = __start_unwind_idx; idx < __stop_unwind_idx; idx++)
+		idx->addr = prel31_to_addr(&idx->addr);
+
+	pr_debug("unwind: ARM stack unwinding initialised\n");
+
+	return 0;
+}