microblaze: Add stack unwinder

Implement intelligent backtracing by searching for stack frame creation,
and emitting only return addresses. Use print_hex_dump() to display the
entire binary kernel stack.

Limitation: MMU kernels are not currently able to trace beyond a system trap
(interrupt, syscall, etc.). It is the intent of this patch to provide
infrastructure that can be extended to add this capability later.

Changes from V1:
* Removed checks in find_frame_creation() that prevented location of the frame
  creation instruction in heavily optimized code
* Various formatting/commenting/file location tweaks per review comments
* Dropped Kconfig option to enable STACKTRACE as something logically separate

Signed-off-by: Steven J. Magnani <steve@digidescorp.com>

10 files changed, 454 insertions, 95 deletions

diff --git a/arch/microblaze/include/asm/exceptions.h b/arch/microblaze/include/asm/exceptions.h
index 4c7b5d037c88..fa0e36657fdd 100644
--- a/arch/microblaze/include/asm/exceptions.h
+++ b/arch/microblaze/include/asm/exceptions.h
@@ -14,6 +14,11 @@
 #define _ASM_MICROBLAZE_EXCEPTIONS_H
 
 #ifdef __KERNEL__
+
+#ifndef CONFIG_MMU
+#define EX_HANDLER_STACK_SIZ    (4*19)
+#endif
+
 #ifndef __ASSEMBLY__
 
 /* Macros to enable and disable HW exceptions in the MSR */
diff --git a/arch/microblaze/include/asm/system.h b/arch/microblaze/include/asm/system.h
index 48c4f0335e3f..4f8eaea21f88 100644
--- a/arch/microblaze/include/asm/system.h
+++ b/arch/microblaze/include/asm/system.h
@@ -45,7 +45,6 @@ extern struct task_struct *_switch_to(struct thread_info *prev,
 #define smp_rmb()               rmb()
 #define smp_wmb()               wmb()
 
-void show_trace(struct task_struct *task, unsigned long *stack);
 void __bad_xchg(volatile void *ptr, int size);
 
 static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
diff --git a/arch/microblaze/include/asm/unwind.h b/arch/microblaze/include/asm/unwind.h
new file mode 100644
index 000000000000..d248b7de4b13
--- /dev/null
+++ b/arch/microblaze/include/asm/unwind.h
@@ -0,0 +1,29 @@
+/*
+ * Backtrace support for Microblaze
+ *
+ * Copyright (C) 2010  Digital Design Corporation
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef __MICROBLAZE_UNWIND_H
+#define __MICROBLAZE_UNWIND_H
+
+struct stack_trace;
+
+struct trap_handler_info {
+        unsigned long start_addr;
+        unsigned long end_addr;
+        const char    *trap_name;
+};
+extern struct trap_handler_info microblaze_trap_handlers;
+
+extern const char _hw_exception_handler;
+extern const char ex_handler_unhandled;
+
+void microblaze_unwind(struct task_struct *task, struct stack_trace *trace);
+
+#endif  /* __MICROBLAZE_UNWIND_H */
+
diff --git a/arch/microblaze/kernel/Makefile b/arch/microblaze/kernel/Makefile
index e51bc1520825..d66ddef53c07 100644
--- a/arch/microblaze/kernel/Makefile
+++ b/arch/microblaze/kernel/Makefile
@@ -17,7 +17,7 @@ extra-y := head.o vmlinux.lds
 obj-y += dma.o exceptions.o \
         hw_exception_handler.o init_task.o intc.o irq.o of_device.o \
         of_platform.o process.o prom.o prom_parse.o ptrace.o \
-        setup.o signal.o sys_microblaze.o timer.o traps.o reset.o
+        reset.o setup.o signal.o sys_microblaze.o timer.o traps.o unwind.o
 
 obj-y += cpu/
 
diff --git a/arch/microblaze/kernel/entry-nommu.S b/arch/microblaze/kernel/entry-nommu.S
index 8cc18cd2cce6..ca84368570b6 100644
--- a/arch/microblaze/kernel/entry-nommu.S
+++ b/arch/microblaze/kernel/entry-nommu.S
@@ -588,3 +588,31 @@ sys_rt_sigsuspend_wrapper:
 #include "syscall_table.S"
 
 syscall_table_size=(.-sys_call_table)
+
+type_SYSCALL:
+        .ascii "SYSCALL\0"
+type_IRQ:
+        .ascii "IRQ\0"
+type_IRQ_PREEMPT:
+        .ascii "IRQ (PREEMPTED)\0"
+type_SYSCALL_PREEMPT:
+        .ascii " SYSCALL (PREEMPTED)\0"
+
+        /*
+         * Trap decoding for stack unwinder
+         * Tuples are (start addr, end addr, string)
+         * If return address lies on [start addr, end addr],
+         * unwinder displays 'string'
+         */
+
+        .align 4
+.global microblaze_trap_handlers
+microblaze_trap_handlers:
+        /* Exact matches come first */
+        .word ret_to_user  ; .word ret_to_user    ; .word type_SYSCALL
+        .word ret_from_intr; .word ret_from_intr  ; .word type_IRQ
+        /* Fuzzy matches go here */
+        .word ret_from_intr; .word no_intr_resched; .word type_IRQ_PREEMPT
+        .word work_pending ; .word no_work_pending; .word type_SYSCALL_PREEMPT
+        /* End of table */
+        .word 0             ; .word 0               ; .word 0
diff --git a/arch/microblaze/kernel/entry.S b/arch/microblaze/kernel/entry.S
index 077377a5d0ca..7a19d8910e3b 100644
--- a/arch/microblaze/kernel/entry.S
+++ b/arch/microblaze/kernel/entry.S
@@ -1127,3 +1127,30 @@ ENTRY(_break)
 
 syscall_table_size=(.-sys_call_table)
 
+type_SYSCALL:
+        .ascii "SYSCALL\0"
+type_IRQ:
+        .ascii "IRQ\0"
+type_IRQ_PREEMPT:
+        .ascii "IRQ (PREEMPTED)\0"
+type_SYSCALL_PREEMPT:
+        .ascii " SYSCALL (PREEMPTED)\0"
+
+        /*
+         * Trap decoding for stack unwinder
+         * Tuples are (start addr, end addr, string)
+         * If return address lies on [start addr, end addr],
+         * unwinder displays 'string'
+         */
+
+        .align 4
+.global microblaze_trap_handlers
+microblaze_trap_handlers:
+        /* Exact matches come first */
+        .word ret_from_trap; .word ret_from_trap   ; .word type_SYSCALL
+        .word ret_from_irq ; .word ret_from_irq    ; .word type_IRQ
+        /* Fuzzy matches go here */
+        .word ret_from_irq ; .word no_intr_resched ; .word type_IRQ_PREEMPT
+        .word ret_from_trap; .word TRAP_return     ; .word type_SYSCALL_PREEMPT
+        /* End of table */
+        .word 0               ; .word 0               ; .word 0
diff --git a/arch/microblaze/kernel/hw_exception_handler.S b/arch/microblaze/kernel/hw_exception_handler.S
index 995a2123635b..781195438ee6 100644
--- a/arch/microblaze/kernel/hw_exception_handler.S
+++ b/arch/microblaze/kernel/hw_exception_handler.S
@@ -78,9 +78,6 @@
 #include <asm/asm-offsets.h>
 
 /* Helpful Macros */
-#ifndef CONFIG_MMU
-#define EX_HANDLER_STACK_SIZ    (4*19)
-#endif
 #define NUM_TO_REG(num)         r ## num
 
 #ifdef CONFIG_MMU
@@ -988,6 +985,7 @@ ex_unaligned_fixup:
 .end _unaligned_data_exception
 #endif /* CONFIG_MMU */
 
+.global ex_handler_unhandled
 ex_handler_unhandled:
 /* FIXME add handle function for unhandled exception - dump register */
         bri 0
diff --git a/arch/microblaze/kernel/stacktrace.c b/arch/microblaze/kernel/stacktrace.c
index 123692f22647..84bc6686102c 100644
--- a/arch/microblaze/kernel/stacktrace.c
+++ b/arch/microblaze/kernel/stacktrace.c
@@ -14,52 +14,18 @@
 #include <linux/thread_info.h>
 #include <linux/ptrace.h>
 #include <linux/module.h>
+#include <asm/unwind.h>
 
-/* FIXME initial support */
 void save_stack_trace(struct stack_trace *trace)
 {
-        unsigned long *sp;
-        unsigned long addr;
-        asm("addik %0, r1, 0" : "=r" (sp));
-
-        while (!kstack_end(sp)) {
-                addr = *sp++;
-                if (__kernel_text_address(addr)) {
-                        if (trace->skip > 0)
-                                trace->skip--;
-                        else
-                                trace->entries[trace->nr_entries++] = addr;
-
-                        if (trace->nr_entries >= trace->max_entries)
-                                break;
-                }
-        }
+        /* Exclude our helper functions from the trace*/
+        trace->skip += 2;
+        microblaze_unwind(NULL, trace);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace);
 
 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 {
-        unsigned int *sp;
-        unsigned long addr;
-
-        struct thread_info *ti = task_thread_info(tsk);
-
-        if (tsk == current)
-                asm("addik %0, r1, 0" : "=r" (sp));
-        else
-                sp = (unsigned int *)ti->cpu_context.r1;
-
-        while (!kstack_end(sp)) {
-                addr = *sp++;
-                if (__kernel_text_address(addr)) {
-                        if (trace->skip > 0)
-                                trace->skip--;
-                        else
-                                trace->entries[trace->nr_entries++] = addr;
-
-                        if (trace->nr_entries >= trace->max_entries)
-                                break;
-                }
-        }
+        microblaze_unwind(tsk, trace);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
diff --git a/arch/microblaze/kernel/traps.c b/arch/microblaze/kernel/traps.c
index 75e49202a5ed..ba034d421ec2 100644
--- a/arch/microblaze/kernel/traps.c
+++ b/arch/microblaze/kernel/traps.c
@@ -16,13 +16,14 @@
 
 #include <asm/exceptions.h>
 #include <asm/system.h>
+#include <asm/unwind.h>
 
 void trap_init(void)
 {
         __enable_hw_exceptions();
 }
 
-static unsigned long kstack_depth_to_print = 24;
+static unsigned long kstack_depth_to_print;     /* 0 == entire stack */
 
 static int __init kstack_setup(char *s)
 {
@@ -30,31 +31,47 @@ static int __init kstack_setup(char *s)
 }
 __setup("kstack=", kstack_setup);
 
-void show_trace(struct task_struct *task, unsigned long *stack)
+void show_stack(struct task_struct *task, unsigned long *sp)
 {
-        unsigned long addr;
-
-        if (!stack)
-                stack = (unsigned long *)&stack;
+        unsigned long words_to_show;
+        u32 fp = (u32) sp;
+
+        if (fp == 0) {
+                if (task) {
+                        fp = ((struct thread_info *)
+                                (task->stack))->cpu_context.r1;
+                } else {
+                        /* Pick up caller of dump_stack() */
+                        fp = (u32)&sp - 8;
+                }
+        }
 
-        printk(KERN_NOTICE "Call Trace: ");
-#ifdef CONFIG_KALLSYMS
-        printk(KERN_NOTICE "\n");
-#endif
-        while (!kstack_end(stack)) {
-                addr = *stack++;
-                /*
-                 * If the address is either in the text segment of the
-                 * kernel, or in the region which contains vmalloc'ed
-                 * memory, it *may* be the address of a calling
-                 * routine; if so, print it so that someone tracing
-                 * down the cause of the crash will be able to figure
-                 * out the call path that was taken.
-                 */
-                if (kernel_text_address(addr))
-                        print_ip_sym(addr);
+        words_to_show = (THREAD_SIZE - (fp & (THREAD_SIZE - 1))) >> 2;
+        if (kstack_depth_to_print && (words_to_show > kstack_depth_to_print))
+                words_to_show = kstack_depth_to_print;
+
+        pr_info("Kernel Stack:\n");
+
+        /*
+         * Make the first line an 'odd' size if necessary to get
+         * remaining lines to start at an address multiple of 0x10
+         */
+        if (fp & 0xF) {
+                unsigned long line1_words = (0x10 - (fp & 0xF)) >> 2;
+                if (line1_words < words_to_show) {
+                        print_hex_dump(KERN_INFO, "", DUMP_PREFIX_ADDRESS, 32,
+                                       4, (void *)fp, line1_words << 2, 0);
+                        fp += line1_words << 2;
+                        words_to_show -= line1_words;
+                }
         }
-        printk(KERN_NOTICE "\n");
+        print_hex_dump(KERN_INFO, "", DUMP_PREFIX_ADDRESS, 32, 4, (void *)fp,
+                       words_to_show << 2, 0);
+        printk(KERN_INFO "\n\n");
+
+        pr_info("Call Trace:\n");
+        microblaze_unwind(task, NULL);
+        pr_info("\n");
 
         if (!task)
                 task = current;
@@ -62,34 +79,6 @@ void show_trace(struct task_struct *task, unsigned long *stack)
         debug_show_held_locks(task);
 }
 
-void show_stack(struct task_struct *task, unsigned long *sp)
-{
-        unsigned long *stack;
-        int i;
-
-        if (sp == NULL) {
-                if (task)
-                        sp = (unsigned long *) ((struct thread_info *)
-                                                (task->stack))->cpu_context.r1;
-                else
-                        sp = (unsigned long *)&sp;
-        }
-
-        stack = sp;
-
-        printk(KERN_INFO "\nStack:\n  ");
-
-        for (i = 0; i < kstack_depth_to_print; i++) {
-                if (kstack_end(sp))
-                        break;
-                if (i && ((i % 8) == 0))
-                        printk("\n  ");
-                printk("%08lx ", *sp++);
-        }
-        printk("\n");
-        show_trace(task, stack);
-}
-
 void dump_stack(void)
 {
         show_stack(NULL, NULL);
diff --git a/arch/microblaze/kernel/unwind.c b/arch/microblaze/kernel/unwind.c
new file mode 100644
index 000000000000..fefac5c33586
--- /dev/null
+++ b/arch/microblaze/kernel/unwind.c
@@ -0,0 +1,318 @@
+/*
+ * Backtrace support for Microblaze
+ *
+ * Copyright (C) 2010  Digital Design Corporation
+ *
+ * Based on arch/sh/kernel/cpu/sh5/unwind.c code which is:
+ * Copyright (C) 2004  Paul Mundt
+ * Copyright (C) 2004  Richard Curnow
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+/* #define DEBUG 1 */
+#include <linux/kallsyms.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <asm/sections.h>
+#include <asm/exceptions.h>
+#include <asm/unwind.h>
+
+struct stack_trace;
+
+/*
+ * On Microblaze, finding the previous stack frame is a little tricky.
+ * At this writing (3/2010), Microblaze does not support CONFIG_FRAME_POINTERS,
+ * and even if it did, gcc (4.1.2) does not store the frame pointer at
+ * a consistent offset within each frame. To determine frame size, it is
+ * necessary to search for the assembly instruction that creates or reclaims
+ * the frame and extract the size from it.
+ *
+ * Microblaze stores the stack pointer in r1, and creates a frame via
+ *
+ *     addik r1, r1, -FRAME_SIZE
+ *
+ * The frame is reclaimed via
+ *
+ *     addik r1, r1, FRAME_SIZE
+ *
+ * Frame creation occurs at or near the top of a function.
+ * Depending on the compiler, reclaim may occur at the end, or before
+ * a mid-function return.
+ *
+ * A stack frame is usually not created in a leaf function.
+ *
+ */
+
+/**
+ * get_frame_size - Extract the stack adjustment from an
+ *                  "addik r1, r1, adjust" instruction
+ * @instr : Microblaze instruction
+ *
+ * Return - Number of stack bytes the instruction reserves or reclaims
+ */
+inline long get_frame_size(unsigned long instr)
+{
+        return abs((s16)(instr & 0xFFFF));
+}
+
+/**
+ * find_frame_creation - Search backward to find the instruction that creates
+ *                       the stack frame (hopefully, for the same function the
+ *                       initial PC is in).
+ * @pc : Program counter at which to begin the search
+ *
+ * Return - PC at which stack frame creation occurs
+ *          NULL if this cannot be found, i.e. a leaf function
+ */
+static unsigned long *find_frame_creation(unsigned long *pc)
+{
+        int i;
+
+        /* NOTE: Distance to search is arbitrary
+         *       250 works well for most things,
+         *       750 picks up things like tcp_recvmsg(),
+         *      1000 needed for fat_fill_super()
+         */
+        for (i = 0; i < 1000; i++, pc--) {
+                unsigned long instr;
+                s16 frame_size;
+
+                if (!kernel_text_address((unsigned long) pc))
+                        return NULL;
+
+                instr = *pc;
+
+                /* addik r1, r1, foo ? */
+                if ((instr & 0xFFFF0000) != 0x30210000)
+                        continue;       /* No */
+
+                frame_size = get_frame_size(instr);
+                if ((frame_size < 8) || (frame_size & 3)) {
+                        pr_debug("    Invalid frame size %d at 0x%p\n",
+                                 frame_size, pc);
+                        return NULL;
+                }
+
+                pr_debug("    Found frame creation at 0x%p, size %d\n", pc,
+                         frame_size);
+                return pc;
+        }
+
+        return NULL;
+}
+
+/**
+ * lookup_prev_stack_frame - Find the stack frame of the previous function.
+ * @fp          : Frame (stack) pointer for current function
+ * @pc          : Program counter within current function
+ * @leaf_return : r15 value within current function. If the current function
+ *                is a leaf, this is the caller's return address.
+ * @pprev_fp    : On exit, set to frame (stack) pointer for previous function
+ * @pprev_pc    : On exit, set to current function caller's return address
+ *
+ * Return - 0 on success, -EINVAL if the previous frame cannot be found
+ */
+static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc,
+                                   unsigned long leaf_return,
+                                   unsigned long *pprev_fp,
+                                   unsigned long *pprev_pc)
+{
+        unsigned long *prologue = NULL;
+
+        /* _switch_to is a special leaf function */
+        if (pc != (unsigned long) &_switch_to)
+                prologue = find_frame_creation((unsigned long *)pc);
+
+        if (prologue) {
+                long frame_size = get_frame_size(*prologue);
+
+                *pprev_fp = fp + frame_size;
+                *pprev_pc = *(unsigned long *)fp;
+        } else {
+                if (!leaf_return)
+                        return -EINVAL;
+                *pprev_pc = leaf_return;
+                *pprev_fp = fp;
+        }
+
+        /* NOTE: don't check kernel_text_address here, to allow display
+         *       of userland return address
+         */
+        return (!*pprev_pc || (*pprev_pc & 3)) ? -EINVAL : 0;
+}
+
+static void microblaze_unwind_inner(struct task_struct *task,
+                                    unsigned long pc, unsigned long fp,
+                                    unsigned long leaf_return,
+                                    struct stack_trace *trace);
+
+/**
+ * unwind_trap - Unwind through a system trap, that stored previous state
+ *               on the stack.
+ */
+#ifdef CONFIG_MMU
+static inline void unwind_trap(struct task_struct *task, unsigned long pc,
+                                unsigned long fp, struct stack_trace *trace)
+{
+        /* To be implemented */
+}
+#else
+static inline void unwind_trap(struct task_struct *task, unsigned long pc,
+                                unsigned long fp, struct stack_trace *trace)
+{
+        const struct pt_regs *regs = (const struct pt_regs *) fp;
+        microblaze_unwind_inner(task, regs->pc, regs->r1, regs->r15, trace);
+}
+#endif
+
+/**
+ * microblaze_unwind_inner - Unwind the stack from the specified point
+ * @task  : Task whose stack we are to unwind (may be NULL)
+ * @pc    : Program counter from which we start unwinding
+ * @fp    : Frame (stack) pointer from which we start unwinding
+ * @leaf_return : Value of r15 at pc. If the function is a leaf, this is
+ *                                the caller's return address.
+ * @trace : Where to store stack backtrace (PC values).
+ *          NULL == print backtrace to kernel log
+ */
+void microblaze_unwind_inner(struct task_struct *task,
+                             unsigned long pc, unsigned long fp,
+                             unsigned long leaf_return,
+                             struct stack_trace *trace)
+{
+        int ofs = 0;
+
+        pr_debug("    Unwinding with PC=%p, FP=%p\n", (void *)pc, (void *)fp);
+        if (!pc || !fp || (pc & 3) || (fp & 3)) {
+                pr_debug("    Invalid state for unwind, aborting\n");
+                return;
+        }
+        for (; pc != 0;) {
+                unsigned long next_fp, next_pc = 0;
+                unsigned long return_to = pc +  2 * sizeof(unsigned long);
+                const struct trap_handler_info *handler =
+                        &microblaze_trap_handlers;
+
+                /* Is previous function the HW exception handler? */
+                if ((return_to >= (unsigned long)&_hw_exception_handler)
+                    &&(return_to < (unsigned long)&ex_handler_unhandled)) {
+                        /*
+                         * HW exception handler doesn't save all registers,
+                         * so we open-code a special case of unwind_trap()
+                         */
+#ifndef CONFIG_MMU
+                        const struct pt_regs *regs =
+                                (const struct pt_regs *) fp;
+#endif
+                        pr_info("HW EXCEPTION\n");
+#ifndef CONFIG_MMU
+                        microblaze_unwind_inner(task, regs->r17 - 4,
+                                                fp + EX_HANDLER_STACK_SIZ,
+                                                regs->r15, trace);
+#endif
+                        return;
+                }
+
+                /* Is previous function a trap handler? */
+                for (; handler->start_addr; ++handler) {
+                        if ((return_to >= handler->start_addr)
+                            && (return_to <= handler->end_addr)) {
+                                if (!trace)
+                                        pr_info("%s\n", handler->trap_name);
+                                unwind_trap(task, pc, fp, trace);
+                                return;
+                        }
+                }
+                pc -= ofs;
+
+                if (trace) {
+#ifdef CONFIG_STACKTRACE
+                        if (trace->skip > 0)
+                                trace->skip--;
+                        else
+                                trace->entries[trace->nr_entries++] = pc;
+
+                        if (trace->nr_entries >= trace->max_entries)
+                                break;
+#endif
+                } else {
+                        /* Have we reached userland? */
+                        if (unlikely(pc == task_pt_regs(task)->pc)) {
+                                pr_info("[<%p>] PID %lu [%s]\n",
+                                        (void *) pc,
+                                        (unsigned long) task->pid,
+                                        task->comm);
+                                break;
+                        } else
+                                print_ip_sym(pc);
+                }
+
+                /* Stop when we reach anything not part of the kernel */
+                if (!kernel_text_address(pc))
+                        break;
+
+                if (lookup_prev_stack_frame(fp, pc, leaf_return, &next_fp,
+                                            &next_pc) == 0) {
+                        ofs = sizeof(unsigned long);
+                        pc = next_pc & ~3;
+                        fp = next_fp;
+                        leaf_return = 0;
+                } else {
+                        pr_debug("    Failed to find previous stack frame\n");
+                        break;
+                }
+
+                pr_debug("    Next PC=%p, next FP=%p\n",
+                         (void *)next_pc, (void *)next_fp);
+        }
+}
+
+/**
+ * microblaze_unwind - Stack unwinder for Microblaze (external entry point)
+ * @task  : Task whose stack we are to unwind (NULL == current)
+ * @trace : Where to store stack backtrace (PC values).
+ *          NULL == print backtrace to kernel log
+ */
+void microblaze_unwind(struct task_struct *task, struct stack_trace *trace)
+{
+        if (task) {
+                if (task == current) {
+                        const struct pt_regs *regs = task_pt_regs(task);
+                        microblaze_unwind_inner(task, regs->pc, regs->r1,
+                                                regs->r15, trace);
+                } else {
+                        struct thread_info *thread_info =
+                                (struct thread_info *)(task->stack);
+                        const struct cpu_context *cpu_context =
+                                &thread_info->cpu_context;
+
+                        microblaze_unwind_inner(task,
+                                                (unsigned long) &_switch_to,
+                                                cpu_context->r1,
+                                                cpu_context->r15, trace);
+                }
+        } else {
+                unsigned long pc, fp;
+
+                __asm__ __volatile__ ("or %0, r1, r0" : "=r" (fp));
+
+                __asm__ __volatile__ (
+                        "brlid %0, 0f;"
+                        "nop;"
+                        "0:"
+                        : "=r" (pc)
+                );
+
+                /* Since we are not a leaf function, use leaf_return = 0 */
+                microblaze_unwind_inner(current, pc, fp, 0, trace);
+        }
+}
+