1 files changed, 146 insertions, 111 deletions

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 7ab67f7..2613a0d 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -273,104 +273,107 @@ long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 }
 
-static struct mips_frame_info {
-	void *func;
-	unsigned long func_size;
-	int frame_size;
-	int pc_offset;
-} *schedule_frame, mfinfo[64];
-static int mfinfo_num;
-
-static int __init get_frame_info(struct mips_frame_info *info)
+/*
+ *
+ */
+struct mips_frame_info {
+	void		*func;
+	unsigned long	func_size;
+	int		frame_size;
+	int		pc_offset;
+};
+
+static inline int is_ra_save_ins(union mips_instruction *ip)
 {
-	int i;
-	void *func = info->func;
-	union mips_instruction *ip = (union mips_instruction *)func;
+	/* sw / sd $ra, offset($sp) */
+	return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
+		ip->i_format.rs == 29 &&
+		ip->i_format.rt == 31;
+}
+
+static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
+{
+	if (ip->j_format.opcode == jal_op)
+		return 1;
+	if (ip->r_format.opcode != spec_op)
+		return 0;
+	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
+}
+
+static inline int is_sp_move_ins(union mips_instruction *ip)
+{
+	/* addiu/daddiu sp,sp,-imm */
+	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
+		return 0;
+	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
+		return 1;
+	return 0;
+}
+
+static int get_frame_info(struct mips_frame_info *info)
+{
+	union mips_instruction *ip = info->func;
+	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
+	unsigned i;
+
 	info->pc_offset = -1;
 	info->frame_size = 0;
-	for (i = 0; i < 128; i++, ip++) {
-		/* if jal, jalr, jr, stop. */
-		if (ip->j_format.opcode == jal_op ||
-		    (ip->r_format.opcode == spec_op &&
-		     (ip->r_format.func == jalr_op ||
-		      ip->r_format.func == jr_op)))
-			break;
 
-		if (info->func_size && i >= info->func_size / 4)
+	if (!ip)
+		goto err;
+
+	if (max_insns == 0)
+		max_insns = 128U;	/* unknown function size */
+	max_insns = min(128U, max_insns);
+
+	for (i = 0; i < max_insns; i++, ip++) {
+
+		if (is_jal_jalr_jr_ins(ip))
 			break;
-		if (
-#ifdef CONFIG_32BIT
-		    ip->i_format.opcode == addiu_op &&
-#endif
-#ifdef CONFIG_64BIT
-		    ip->i_format.opcode == daddiu_op &&
-#endif
-		    ip->i_format.rs == 29 &&
-		    ip->i_format.rt == 29) {
-			/* addiu/daddiu sp,sp,-imm */
-			if (info->frame_size)
-				continue;
-			info->frame_size = - ip->i_format.simmediate;
+		if (!info->frame_size) {
+			if (is_sp_move_ins(ip))
+				info->frame_size = - ip->i_format.simmediate;
+			continue;
 		}
-
-		if (
-#ifdef CONFIG_32BIT
-		    ip->i_format.opcode == sw_op &&
-#endif
-#ifdef CONFIG_64BIT
-		    ip->i_format.opcode == sd_op &&
-#endif
-		    ip->i_format.rs == 29 &&
-		    ip->i_format.rt == 31) {
-			/* sw / sd $ra, offset($sp) */
-			if (info->pc_offset != -1)
-				continue;
+		if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 			info->pc_offset =
 				ip->i_format.simmediate / sizeof(long);
+			break;
 		}
 	}
-	if (info->pc_offset == -1 || info->frame_size == 0) {
-		if (func == schedule)
-			printk("Can't analyze prologue code at %p\n", func);
-		info->pc_offset = -1;
-		info->frame_size = 0;
-	}
-
-	return 0;
+	if (info->frame_size && info->pc_offset >= 0) /* nested */
+		return 0;
+	if (info->pc_offset < 0) /* leaf */
+		return 1;
+	/* prologue seems boggus... */
+err:
+	return -1;
 }
 
+static struct mips_frame_info schedule_mfi __read_mostly;
+
 static int __init frame_info_init(void)
 {
-	int i;
+	unsigned long size = 0;
 #ifdef CONFIG_KALLSYMS
+	unsigned long ofs;
 	char *modname;
 	char namebuf[KSYM_NAME_LEN + 1];
-	unsigned long start, size, ofs;
-	extern char __sched_text_start[], __sched_text_end[];
-	extern char __lock_text_start[], __lock_text_end[];
-
-	start = (unsigned long)__sched_text_start;
-	for (i = 0; i < ARRAY_SIZE(mfinfo); i++) {
-		if (start == (unsigned long)schedule)
-			schedule_frame = &mfinfo[i];
-		if (!kallsyms_lookup(start, &size, &ofs, &modname, namebuf))
-			break;
-		mfinfo[i].func = (void *)(start + ofs);
-		mfinfo[i].func_size = size;
-		start += size - ofs;
-		if (start >= (unsigned long)__lock_text_end)
-			break;
-		if (start == (unsigned long)__sched_text_end)
-			start = (unsigned long)__lock_text_start;
-	}
-#else
-	mfinfo[0].func = schedule;
-	schedule_frame = &mfinfo[0];
+
+	kallsyms_lookup((unsigned long)schedule, &size, &ofs, &modname, namebuf);
 #endif
-	for (i = 0; i < ARRAY_SIZE(mfinfo) && mfinfo[i].func; i++)
-		get_frame_info(&mfinfo[i]);
+	schedule_mfi.func = schedule;
+	schedule_mfi.func_size = size;
+
+	get_frame_info(&schedule_mfi);
+
+	/*
+	 * Without schedule() frame info, result given by
+	 * thread_saved_pc() and get_wchan() are not reliable.
+	 */
+	if (schedule_mfi.pc_offset < 0)
+		printk("Can't analyze schedule() prologue at %p\n", schedule);
 
-	mfinfo_num = i;
 	return 0;
 }
 
@@ -386,54 +389,86 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
 	/* New born processes are a special case */
 	if (t->reg31 == (unsigned long) ret_from_fork)
 		return t->reg31;
-
-	if (!schedule_frame || schedule_frame->pc_offset < 0)
+	if (schedule_mfi.pc_offset < 0)
 		return 0;
-	return ((unsigned long *)t->reg29)[schedule_frame->pc_offset];
+	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 }
 
-/* get_wchan - a maintenance nightmare^W^Wpain in the ass ...  */
-unsigned long get_wchan(struct task_struct *p)
+
+#ifdef CONFIG_KALLSYMS
+/* used by show_backtrace() */
+unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
+			   unsigned long pc, unsigned long ra)
 {
 	unsigned long stack_page;
-	unsigned long pc;
-#ifdef CONFIG_KALLSYMS
-	unsigned long frame;
-#endif
+	struct mips_frame_info info;
+	char *modname;
+	char namebuf[KSYM_NAME_LEN + 1];
+	unsigned long size, ofs;
+	int leaf;
 
-	if (!p || p == current || p->state == TASK_RUNNING)
+	stack_page = (unsigned long)task_stack_page(task);
+	if (!stack_page)
 		return 0;
 
-	stack_page = (unsigned long)task_stack_page(p);
-	if (!stack_page || !mfinfo_num)
+	if (!kallsyms_lookup(pc, &size, &ofs, &modname, namebuf))
+		return 0;
+	/*
+	 * Return ra if an exception occured at the first instruction
+	 */
+	if (unlikely(ofs == 0))
+		return ra;
+
+	info.func = (void *)(pc - ofs);
+	info.func_size = ofs;	/* analyze from start to ofs */
+	leaf = get_frame_info(&info);
+	if (leaf < 0)
+		return 0;
+
+	if (*sp < stack_page ||
+	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 		return 0;
 
-	pc = thread_saved_pc(p);
+	if (leaf)
+		/*
+		 * For some extreme cases, get_frame_info() can
+		 * consider wrongly a nested function as a leaf
+		 * one. In that cases avoid to return always the
+		 * same value.
+		 */
+		pc = pc != ra ? ra : 0;
+	else
+		pc = ((unsigned long *)(*sp))[info.pc_offset];
+
+	*sp += info.frame_size;
+	return __kernel_text_address(pc) ? pc : 0;
+}
+#endif
+
+/*
+ * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
+ */
+unsigned long get_wchan(struct task_struct *task)
+{
+	unsigned long pc = 0;
 #ifdef CONFIG_KALLSYMS
-	if (!in_sched_functions(pc))
-		return pc;
+	unsigned long sp;
+#endif
 
-	frame = p->thread.reg29 + schedule_frame->frame_size;
-	do {
-		int i;
+	if (!task || task == current || task->state == TASK_RUNNING)
+		goto out;
+	if (!task_stack_page(task))
+		goto out;
 
-		if (frame < stack_page || frame > stack_page + THREAD_SIZE - 32)
-			return 0;
+	pc = thread_saved_pc(task);
 
-		for (i = mfinfo_num - 1; i >= 0; i--) {
-			if (pc >= (unsigned long) mfinfo[i].func)
-				break;
-		}
-		if (i < 0)
-			break;
+#ifdef CONFIG_KALLSYMS
+	sp = task->thread.reg29 + schedule_mfi.frame_size;
 
-		pc = ((unsigned long *)frame)[mfinfo[i].pc_offset];
-		if (!mfinfo[i].frame_size)
-			break;
-		frame += mfinfo[i].frame_size;
-	} while (in_sched_functions(pc));
+	while (in_sched_functions(pc))
+		pc = unwind_stack(task, &sp, pc, 0);
 #endif
 
+out:
 	return pc;
 }
-