1 files changed, 146 insertions, 111 deletions

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 7ab67f786bfe..2613a0dd4b82 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;
 }
-