| 1 | |
| 2 | * Backtrace support for Microblaze
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| 3 | *
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| 4 | * Copyright (C) 2010 Digital Design Corporation
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| 5 | *
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| 6 | * Based on arch/sh/kernel/cpu/sh5/unwind.c code which is:
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| 7 | * Copyright (C) 2004 Paul Mundt
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| 8 | * Copyright (C) 2004 Richard Curnow
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| 9 | *
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| 10 | * This file is subject to the terms and conditions of the GNU General Public
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| 11 | * License. See the file "COPYING" in the main directory of this archive
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| 12 | * for more details.
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| 13 |
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| 14 |
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| 15 |
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| 16 | #include <linux/export.h>
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| 17 | #include <linux/kallsyms.h>
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| 18 | #include <linux/kernel.h>
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| 19 | #include <linux/sched.h>
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| 20 | #include <linux/sched/task_stack.h>
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| 21 | #include <linux/stacktrace.h>
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| 22 | #include <linux/types.h>
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| 23 | #include <linux/errno.h>
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| 24 | #include <linux/io.h>
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| 25 | #include <asm/sections.h>
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| 26 | #include <asm/exceptions.h>
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| 27 | #include <asm/unwind.h>
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| 28 | #include <asm/switch_to.h>
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| 29 |
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| 30 | struct stack_trace;
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| 31 |
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| 32 | |
| 33 | * On Microblaze, finding the previous stack frame is a little tricky.
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| 34 | * At this writing (3/2010), Microblaze does not support CONFIG_FRAME_POINTERS,
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| 35 | * and even if it did, gcc (4.1.2) does not store the frame pointer at
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| 36 | * a consistent offset within each frame. To determine frame size, it is
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| 37 | * necessary to search for the assembly instruction that creates or reclaims
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| 38 | * the frame and extract the size from it.
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| 39 | *
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| 40 | * Microblaze stores the stack pointer in r1, and creates a frame via
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| 41 | *
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| 42 | * addik r1, r1, -FRAME_SIZE
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| 43 | *
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| 44 | * The frame is reclaimed via
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| 45 | *
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| 46 | * addik r1, r1, FRAME_SIZE
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| 47 | *
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| 48 | * Frame creation occurs at or near the top of a function.
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| 49 | * Depending on the compiler, reclaim may occur at the end, or before
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| 50 | * a mid-function return.
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| 51 | *
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| 52 | * A stack frame is usually not created in a leaf function.
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| 53 | *
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| 54 |
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| 55 |
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| 56 | |
| 57 | * get_frame_size - Extract the stack adjustment from an
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| 58 | * "addik r1, r1, adjust" instruction
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| 59 | * @instr : Microblaze instruction
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| 60 | *
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| 61 | * Return - Number of stack bytes the instruction reserves or reclaims
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| 62 |
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| 63 | static inline long get_frame_size(unsigned long instr)
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| 64 | {
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| 65 | return abs((s16)(instr & 0xFFFF));
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| 66 | }
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| 67 |
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| 68 | |
| 69 | * find_frame_creation - Search backward to find the instruction that creates
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| 70 | * the stack frame (hopefully, for the same function the
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| 71 | * initial PC is in).
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| 72 | * @pc : Program counter at which to begin the search
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| 73 | *
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| 74 | * Return - PC at which stack frame creation occurs
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| 75 | * NULL if this cannot be found, i.e. a leaf function
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| 76 |
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| 77 | static unsigned long *find_frame_creation(unsigned long *pc)
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| 78 | {
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| 79 | int i;
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| 80 |
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| 81 | |
| 82 | * 250 works well for most things,
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| 83 | * 750 picks up things like tcp_recvmsg(),
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| 84 | * 1000 needed for fat_fill_super()
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| 85 |
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| 86 | for (i = 0; i < 1000; i++, pc--) {
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| 87 | unsigned long instr;
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| 88 | s16 frame_size;
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| 89 |
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| 90 | if (!kernel_text_address((unsigned long) pc))
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| 91 | return NULL;
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| 92 |
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| 93 | instr = *pc;
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| 94 |
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| 95 |
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| 96 | if ((instr & 0xFFFF0000) != 0x30210000)
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| 97 | continue;
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| 98 |
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| 99 | frame_size = get_frame_size(instr);
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| 100 | if ((frame_size < 8) || (frame_size & 3)) {
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| 101 | pr_debug(" Invalid frame size %d at 0x%p\n",
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| 102 | frame_size, pc);
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| 103 | return NULL;
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| 104 | }
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| 105 |
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| 106 | pr_debug(" Found frame creation at 0x%p, size %d\n", pc,
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| 107 | frame_size);
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| 108 | return pc;
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| 109 | }
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| 110 |
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| 111 | return NULL;
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| 112 | }
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| 113 |
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| 114 | |
| 115 | * lookup_prev_stack_frame - Find the stack frame of the previous function.
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| 116 | * @fp : Frame (stack) pointer for current function
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| 117 | * @pc : Program counter within current function
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| 118 | * @leaf_return : r15 value within current function. If the current function
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| 119 | * is a leaf, this is the caller's return address.
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| 120 | * @pprev_fp : On exit, set to frame (stack) pointer for previous function
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| 121 | * @pprev_pc : On exit, set to current function caller's return address
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| 122 | *
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| 123 | * Return - 0 on success, -EINVAL if the previous frame cannot be found
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| 124 |
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| 125 | static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc,
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| 126 | unsigned long leaf_return,
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| 127 | unsigned long *pprev_fp,
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| 128 | unsigned long *pprev_pc)
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| 129 | {
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| 130 | unsigned long *prologue = NULL;
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| 131 |
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| 132 |
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| 133 | if (pc != (unsigned long) &_switch_to)
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| 134 | prologue = find_frame_creation((unsigned long *)pc);
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| 135 |
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| 136 | if (prologue) {
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| 137 | long frame_size = get_frame_size(*prologue);
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| 138 |
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| 139 | *pprev_fp = fp + frame_size;
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| 140 | *pprev_pc = *(unsigned long *)fp;
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| 141 | } else {
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| 142 | if (!leaf_return)
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| 143 | return -EINVAL;
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| 144 | *pprev_pc = leaf_return;
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| 145 | *pprev_fp = fp;
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| 146 | }
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| 147 |
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| 148 | |
| 149 | * of userland return address
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| 150 |
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| 151 | return (!*pprev_pc || (*pprev_pc & 3)) ? -EINVAL : 0;
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| 152 | }
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| 153 |
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| 154 | static void microblaze_unwind_inner(struct task_struct *task,
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| 155 | unsigned long pc, unsigned long fp,
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| 156 | unsigned long leaf_return,
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| 157 | struct stack_trace *trace,
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| 158 | const char *loglvl);
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| 159 |
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| 160 | |
| 161 | * unwind_trap - Unwind through a system trap, that stored previous state
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| 162 | * on the stack.
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| 163 |
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| 164 | static inline void unwind_trap(struct task_struct *task, unsigned long pc,
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| 165 | unsigned long fp, struct stack_trace *trace,
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| 166 | const char *loglvl)
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| 167 | {
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| 168 |
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| 169 | }
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| 170 |
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| 171 | |
| 172 | * microblaze_unwind_inner - Unwind the stack from the specified point
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| 173 | * @task : Task whose stack we are to unwind (may be NULL)
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| 174 | * @pc : Program counter from which we start unwinding
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| 175 | * @fp : Frame (stack) pointer from which we start unwinding
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| 176 | * @leaf_return : Value of r15 at pc. If the function is a leaf, this is
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| 177 | * the caller's return address.
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| 178 | * @trace : Where to store stack backtrace (PC values).
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| 179 | * NULL == print backtrace to kernel log
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| 180 | * @loglvl : Used for printk log level if (trace == NULL).
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| 181 |
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| 182 | static void microblaze_unwind_inner(struct task_struct *task,
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| 183 | unsigned long pc, unsigned long fp,
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| 184 | unsigned long leaf_return,
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| 185 | struct stack_trace *trace,
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| 186 | const char *loglvl)
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| 187 | {
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| 188 | int ofs = 0;
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| 189 |
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| 190 | pr_debug(" Unwinding with PC=%p, FP=%p\n", (void *)pc, (void *)fp);
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| 191 | if (!pc || !fp || (pc & 3) || (fp & 3)) {
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| 192 | pr_debug(" Invalid state for unwind, aborting\n");
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| 193 | return;
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| 194 | }
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| 195 | for (; pc != 0;) {
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| 196 | unsigned long next_fp, next_pc = 0;
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| 197 | unsigned long return_to = pc + 2 * sizeof(unsigned long);
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| 198 | const struct trap_handler_info *handler =
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| 199 | µblaze_trap_handlers;
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| 200 |
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| 201 |
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| 202 | if ((return_to >= (unsigned long)&_hw_exception_handler)
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| 203 | &&(return_to < (unsigned long)&ex_handler_unhandled)) {
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| 204 | |
| 205 | * HW exception handler doesn't save all registers,
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| 206 | * so we open-code a special case of unwind_trap()
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| 207 |
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| 208 | printk("%sHW EXCEPTION\n", loglvl);
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| 209 | return;
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| 210 | }
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| 211 |
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| 212 |
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| 213 | for (; handler->start_addr; ++handler) {
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| 214 | if ((return_to >= handler->start_addr)
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| 215 | && (return_to <= handler->end_addr)) {
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| 216 | if (!trace)
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| 217 | printk("%s%s\n", loglvl, handler->trap_name);
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| 218 | unwind_trap(task, pc, fp, trace, loglvl);
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| 219 | return;
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| 220 | }
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| 221 | }
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| 222 | pc -= ofs;
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| 223 |
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| 224 | if (trace) {
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| 225 | #ifdef CONFIG_STACKTRACE
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| 226 | if (trace->skip > 0)
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| 227 | trace->skip--;
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| 228 | else
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| 229 | trace->entries[trace->nr_entries++] = pc;
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| 230 |
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| 231 | if (trace->nr_entries >= trace->max_entries)
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| 232 | break;
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| 233 | #endif
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| 234 | } else {
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| 235 |
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| 236 | if (unlikely(pc == task_pt_regs(task)->pc)) {
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| 237 | printk("%s[<%p>] PID %lu [%s]\n",
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| 238 | loglvl, (void *) pc,
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| 239 | (unsigned long) task->pid,
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| 240 | task->comm);
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| 241 | break;
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| 242 | } else
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| 243 | print_ip_sym(loglvl, pc);
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| 244 | }
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| 245 |
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| 246 |
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| 247 | if (!kernel_text_address(pc))
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| 248 | break;
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| 249 |
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| 250 | if (lookup_prev_stack_frame(fp, pc, leaf_return, &next_fp,
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| 251 | &next_pc) == 0) {
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| 252 | ofs = sizeof(unsigned long);
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| 253 | pc = next_pc & ~3;
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| 254 | fp = next_fp;
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| 255 | leaf_return = 0;
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| 256 | } else {
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| 257 | pr_debug(" Failed to find previous stack frame\n");
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| 258 | break;
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| 259 | }
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| 260 |
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| 261 | pr_debug(" Next PC=%p, next FP=%p\n",
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| 262 | (void *)next_pc, (void *)next_fp);
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| 263 | }
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| 264 | }
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| 265 |
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| 266 | |
| 267 | * microblaze_unwind - Stack unwinder for Microblaze (external entry point)
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| 268 | * @task : Task whose stack we are to unwind (NULL == current)
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| 269 | * @trace : Where to store stack backtrace (PC values).
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| 270 | * NULL == print backtrace to kernel log
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| 271 | * @loglvl : Used for printk log level if (trace == NULL).
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| 272 |
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| 273 | void microblaze_unwind(struct task_struct *task, struct stack_trace *trace,
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| 274 | const char *loglvl)
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| 275 | {
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| 276 | if (task) {
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| 277 | if (task == current) {
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| 278 | const struct pt_regs *regs = task_pt_regs(task);
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| 279 | microblaze_unwind_inner(task, regs->pc, regs->r1,
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| 280 | regs->r15, trace, loglvl);
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| 281 | } else {
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| 282 | struct thread_info *thread_info =
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| 283 | (struct thread_info *)(task->stack);
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| 284 | const struct cpu_context *cpu_context =
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| 285 | &thread_info->cpu_context;
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| 286 |
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| 287 | microblaze_unwind_inner(task,
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| 288 | (unsigned long) &_switch_to,
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| 289 | cpu_context->r1,
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| 290 | cpu_context->r15,
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| 291 | trace, loglvl);
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| 292 | }
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| 293 | } else {
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| 294 | unsigned long pc, fp;
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| 295 |
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| 296 | __asm__ __volatile__ ("or %0, r1, r0" : "=r" (fp));
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| 297 |
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| 298 | __asm__ __volatile__ (
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| 299 | "brlid %0, 0f;"
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| 300 | "nop;"
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| 301 | "0:"
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| 302 | : "=r" (pc)
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| 303 | );
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| 304 |
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| 305 |
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| 306 | microblaze_unwind_inner(current, pc, fp, 0, trace, loglvl);
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| 307 | }
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| 308 | }
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| 309 |
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