[ARM] 5383/2: unwind: Add core support for ARM stack unwinding

This patch adds the main functionality for parsing the stack unwinding
information generated by the ARM EABI toolchains. The unwinding
information consists of an index with a pair of words per function and a
table with unwinding instructions. For more information, see "Exception
Handling ABI for the ARM Architecture" at:

http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/boot/compressed/vmlinux.lds.in

@@ -11,6 +11,11 @@ OUTPUT_ARCH(arm)
 ENTRY(_start)
 SECTIONS
 {
+  /DISCARD/ : {
+    *(.ARM.exidx*)
+    *(.ARM.extab*)
+  }
+
   . = TEXT_START;
   _text = .;
 

arch/arm/include/asm/unwind.h

@@ -0,0 +1,69 @@
+/*
+ * arch/arm/include/asm/unwind.h
+ *
+ * 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
+ */
+
+#ifndef __ASM_UNWIND_H
+#define __ASM_UNWIND_H
+
+#ifndef __ASSEMBLY__
+
+/* Unwind reason code according the the ARM EABI documents */
+enum unwind_reason_code {
+	URC_OK = 0,			/* operation completed successfully */
+	URC_CONTINUE_UNWIND = 8,
+	URC_FAILURE = 9			/* unspecified failure of some kind */
+};
+
+struct unwind_idx {
+	unsigned long addr;
+	unsigned long insn;
+};
+
+struct unwind_table {
+	struct list_head list;
+	struct unwind_idx *start;
+	struct unwind_idx *stop;
+	unsigned long begin_addr;
+	unsigned long end_addr;
+};
+
+extern struct unwind_table *unwind_table_add(unsigned long start,
+					     unsigned long size,
+					     unsigned long text_addr,
+					     unsigned long text_size);
+extern void unwind_table_del(struct unwind_table *tab);
+extern void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk);
+
+#ifdef CONFIG_ARM_UNWIND
+extern int __init unwind_init(void);
+#else
+static inline int __init unwind_init(void)
+{
+	return 0;
+}
+#endif
+
+#endif	/* !__ASSEMBLY__ */
+
+#ifdef CONFIG_ARM_UNWIND
+#define UNWIND(code...)		code
+#else
+#define UNWIND(code...)
+#endif
+
+#endif	/* __ASM_UNWIND_H */

arch/arm/kernel/setup.c

@@ -40,6 +40,7 @@
 #include <asm/mach/irq.h>
 #include <asm/mach/time.h>
 #include <asm/traps.h>
+#include <asm/unwind.h>
 
 #include "compat.h"
 #include "atags.h"
@@ -684,6 +685,8 @@ void __init setup_arch(char **cmdline_p)
 	struct machine_desc *mdesc;
 	char *from = default_command_line;
 
+	unwind_init();
+
 	setup_processor();
 	mdesc = setup_machine(machine_arch_type);
 	machine_name = mdesc->name;

arch/arm/kernel/traps.c

@@ -27,6 +27,7 @@
 #include <asm/system.h>
 #include <asm/unistd.h>
 #include <asm/traps.h>
+#include <asm/unwind.h>
 
 #include "ptrace.h"
 #include "signal.h"
@@ -61,6 +62,7 @@ void dump_backtrace_entry(unsigned long where, unsigned long from, unsigned long
 		dump_mem("Exception stack", frame + 4, frame + 4 + sizeof(struct pt_regs));
 }
 
+#ifndef CONFIG_ARM_UNWIND
 /*
  * Stack pointers should always be within the kernels view of
  * physical memory.  If it is not there, then we can't dump
@@ -74,6 +76,7 @@ static int verify_stack(unsigned long sp)
 
 	return 0;
 }
+#endif
 
 /*
  * Dump out the contents of some memory nicely...
@@ -150,6 +153,12 @@ static void dump_instr(struct pt_regs *regs)
 	set_fs(fs);
 }
 
+#ifdef CONFIG_ARM_UNWIND
+static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
+{
+	unwind_backtrace(regs, tsk);
+}
+#else
 static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 {
 	unsigned int fp, mode;
@@ -184,6 +193,7 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 	if (ok)
 		c_backtrace(fp, mode);
 }
+#endif
 
 void dump_stack(void)
 {