arch/xtensa/kernel/stacktrace.c

   1 /*
   2  * Kernel and userspace stack tracing.
   3  *
   4  * This file is subject to the terms and conditions of the GNU General Public
   5  * License.  See the file "COPYING" in the main directory of this archive
   6  * for more details.
   7  *
   8  * Copyright (C) 2001 - 2013 Tensilica Inc.
   9  * Copyright (C) 2015 Cadence Design Systems Inc.
  10  */
  11 #include <linux/export.h>
  12 #include <linux/sched.h>
  13 #include <linux/stacktrace.h>
  14
  15 #include <asm/stacktrace.h>
  16 #include <asm/traps.h>
  17 #include <asm/uaccess.h>
  18
  19 #if IS_ENABLED(CONFIG_OPROFILE) || IS_ENABLED(CONFIG_PERF_EVENTS)
  20
  21 /* Address of common_exception_return, used to check the
  22  * transition from kernel to user space.
  23  */
  24 extern int common_exception_return;
  25
  26 /* A struct that maps to the part of the frame containing the a0 and
  27  * a1 registers.
  28  */
  29 struct frame_start {
  30         unsigned long a0;
  31         unsigned long a1;
  32 };
  33
  34 void xtensa_backtrace_user(struct pt_regs *regs, unsigned int depth,
  35                            int (*ufn)(struct stackframe *frame, void *data),
  36                            void *data)
  37 {
  38         unsigned long windowstart = regs->windowstart;
  39         unsigned long windowbase = regs->windowbase;
  40         unsigned long a0 = regs->areg[0];
  41         unsigned long a1 = regs->areg[1];
  42         unsigned long pc = regs->pc;
  43         struct stackframe frame;
  44         int index;
  45
  46         if (!depth--)
  47                 return;
  48
  49         frame.pc = pc;
  50         frame.sp = a1;
  51
  52         if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
  53                 return;
  54
  55         /* Two steps:
  56          *
  57          * 1. Look through the register window for the
  58          * previous PCs in the call trace.
  59          *
  60          * 2. Look on the stack.
  61          */
  62
  63         /* Step 1.  */
  64         /* Rotate WINDOWSTART to move the bit corresponding to
  65          * the current window to the bit #0.
  66          */
  67         windowstart = (windowstart << WSBITS | windowstart) >> windowbase;
  68
  69         /* Look for bits that are set, they correspond to
  70          * valid windows.
  71          */
  72         for (index = WSBITS - 1; (index > 0) && depth; depth--, index--)
  73                 if (windowstart & (1 << index)) {
  74                         /* Get the PC from a0 and a1. */
  75                         pc = MAKE_PC_FROM_RA(a0, pc);
  76                         /* Read a0 and a1 from the
  77                          * corresponding position in AREGs.
  78                          */
  79                         a0 = regs->areg[index * 4];
  80                         a1 = regs->areg[index * 4 + 1];
  81
  82                         frame.pc = pc;
  83                         frame.sp = a1;
  84
  85                         if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
  86                                 return;
  87                 }
  88
  89         /* Step 2. */
  90         /* We are done with the register window, we need to
  91          * look through the stack.
  92          */
  93         if (!depth)
  94                 return;
  95
  96         /* Start from the a1 register. */
  97         /* a1 = regs->areg[1]; */
  98         while (a0 != 0 && depth--) {
  99                 struct frame_start frame_start;
 100                 /* Get the location for a1, a0 for the
 101                  * previous frame from the current a1.
 102                  */
 103                 unsigned long *psp = (unsigned long *)a1;
 104
 105                 psp -= 4;
 106
 107                 /* Check if the region is OK to access. */
 108                 if (!access_ok(VERIFY_READ, psp, sizeof(frame_start)))
 109                         return;
 110                 /* Copy a1, a0 from user space stack frame. */
 111                 if (__copy_from_user_inatomic(&frame_start, psp,
 112                                               sizeof(frame_start)))
 113                         return;
 114
 115                 pc = MAKE_PC_FROM_RA(a0, pc);
 116                 a0 = frame_start.a0;
 117                 a1 = frame_start.a1;
 118
 119                 frame.pc = pc;
 120                 frame.sp = a1;
 121
 122                 if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
 123                         return;
 124         }
 125 }
 126 EXPORT_SYMBOL(xtensa_backtrace_user);
 127
 128 void xtensa_backtrace_kernel(struct pt_regs *regs, unsigned int depth,
 129                              int (*kfn)(struct stackframe *frame, void *data),
 130                              int (*ufn)(struct stackframe *frame, void *data),
 131                              void *data)
 132 {
 133         unsigned long pc = regs->depc > VALID_DOUBLE_EXCEPTION_ADDRESS ?
 134                 regs->depc : regs->pc;
 135         unsigned long sp_start, sp_end;
 136         unsigned long a0 = regs->areg[0];
 137         unsigned long a1 = regs->areg[1];
 138
 139         sp_start = a1 & ~(THREAD_SIZE - 1);
 140         sp_end = sp_start + THREAD_SIZE;
 141
 142         /* Spill the register window to the stack first. */
 143         spill_registers();
 144
 145         /* Read the stack frames one by one and create the PC
 146          * from the a0 and a1 registers saved there.
 147          */
 148         while (a1 > sp_start && a1 < sp_end && depth--) {
 149                 struct stackframe frame;
 150                 unsigned long *psp = (unsigned long *)a1;
 151
 152                 frame.pc = pc;
 153                 frame.sp = a1;
 154
 155                 if (kernel_text_address(pc) && kfn(&frame, data))
 156                         return;
 157
 158                 if (pc == (unsigned long)&common_exception_return) {
 159                         regs = (struct pt_regs *)a1;
 160                         if (user_mode(regs)) {
 161                                 if (ufn == NULL)
 162                                         return;
 163                                 xtensa_backtrace_user(regs, depth, ufn, data);
 164                                 return;
 165                         }
 166                         a0 = regs->areg[0];
 167                         a1 = regs->areg[1];
 168                         continue;
 169                 }
 170
 171                 sp_start = a1;
 172
 173                 pc = MAKE_PC_FROM_RA(a0, pc);
 174                 a0 = *(psp - 4);
 175                 a1 = *(psp - 3);
 176         }
 177 }
 178 EXPORT_SYMBOL(xtensa_backtrace_kernel);
 179
 180 #endif
 181
 182 void walk_stackframe(unsigned long *sp,
 183                 int (*fn)(struct stackframe *frame, void *data),
 184                 void *data)
 185 {
 186         unsigned long a0, a1;
 187         unsigned long sp_end;
 188
 189         a1 = (unsigned long)sp;
 190         sp_end = ALIGN(a1, THREAD_SIZE);
 191
 192         spill_registers();
 193
 194         while (a1 < sp_end) {
 195                 struct stackframe frame;
 196
 197                 sp = (unsigned long *)a1;
 198
 199                 a0 = *(sp - 4);
 200                 a1 = *(sp - 3);
 201
 202                 if (a1 <= (unsigned long)sp)
 203                         break;
 204
 205                 frame.pc = MAKE_PC_FROM_RA(a0, a1);
 206                 frame.sp = a1;
 207
 208                 if (fn(&frame, data))
 209                         return;
 210         }
 211 }
 212
 213 #ifdef CONFIG_STACKTRACE
 214
 215 struct stack_trace_data {
 216         struct stack_trace *trace;
 217         unsigned skip;
 218 };
 219
 220 static int stack_trace_cb(struct stackframe *frame, void *data)
 221 {
 222         struct stack_trace_data *trace_data = data;
 223         struct stack_trace *trace = trace_data->trace;
 224
 225         if (trace_data->skip) {
 226                 --trace_data->skip;
 227                 return 0;
 228         }
 229         if (!kernel_text_address(frame->pc))
 230                 return 0;
 231
 232         trace->entries[trace->nr_entries++] = frame->pc;
 233         return trace->nr_entries >= trace->max_entries;
 234 }
 235
 236 void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
 237 {
 238         struct stack_trace_data trace_data = {
 239                 .trace = trace,
 240                 .skip = trace->skip,
 241         };
 242         walk_stackframe(stack_pointer(task), stack_trace_cb, &trace_data);
 243 }
 244 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
 245
 246 void save_stack_trace(struct stack_trace *trace)
 247 {
 248         save_stack_trace_tsk(current, trace);
 249 }
 250 EXPORT_SYMBOL_GPL(save_stack_trace);
 251
 252 #endif
 253
 254 #ifdef CONFIG_FRAME_POINTER
 255
 256 struct return_addr_data {
 257         unsigned long addr;
 258         unsigned skip;
 259 };
 260
 261 static int return_address_cb(struct stackframe *frame, void *data)
 262 {
 263         struct return_addr_data *r = data;
 264
 265         if (r->skip) {
 266                 --r->skip;
 267                 return 0;
 268         }
 269         if (!kernel_text_address(frame->pc))
 270                 return 0;
 271         r->addr = frame->pc;
 272         return 1;
 273 }
 274
 275 unsigned long return_address(unsigned level)
 276 {
 277         struct return_addr_data r = {
 278                 .skip = level + 1,
 279         };
 280         walk_stackframe(stack_pointer(NULL), return_address_cb, &r);
 281         return r.addr;
 282 }
 283 EXPORT_SYMBOL(return_address);
 284
 285 #endif