arch/sh/kernel/cpu/sh5/unwind.c

   1 /*
   2  * arch/sh/kernel/cpu/sh5/unwind.c
   3  *
   4  * Copyright (C) 2004  Paul Mundt
   5  * Copyright (C) 2004  Richard Curnow
   6  *
   7  * This file is subject to the terms and conditions of the GNU General Public
   8  * License.  See the file "COPYING" in the main directory of this archive
   9  * for more details.
  10  */
  11 #include <linux/kallsyms.h>
  12 #include <linux/kernel.h>
  13 #include <linux/types.h>
  14 #include <linux/errno.h>
  15 #include <asm/page.h>
  16 #include <asm/ptrace.h>
  17 #include <asm/processor.h>
  18 #include <asm/io.h>
  19
  20 static u8 regcache[63];
  21
  22 /*
  23  * Finding the previous stack frame isn't horribly straightforward as it is
  24  * on some other platforms. In the sh64 case, we don't have "linked" stack
  25  * frames, so we need to do a bit of work to determine the previous frame,
  26  * and in turn, the previous r14/r18 pair.
  27  *
  28  * There are generally a few cases which determine where we can find out
  29  * the r14/r18 values. In the general case, this can be determined by poking
  30  * around the prologue of the symbol PC is in (note that we absolutely must
  31  * have frame pointer support as well as the kernel symbol table mapped,
  32  * otherwise we can't even get this far).
  33  *
  34  * In other cases, such as the interrupt/exception path, we can poke around
  35  * the sp/fp.
  36  *
  37  * Notably, this entire approach is somewhat error prone, and in the event
  38  * that the previous frame cannot be determined, that's all we can do.
  39  * Either way, this still leaves us with a more correct backtrace then what
  40  * we would be able to come up with by walking the stack (which is garbage
  41  * for anything beyond the first frame).
  42  *                                              -- PFM.
  43  */
  44 static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc,
  45                       unsigned long *pprev_fp, unsigned long *pprev_pc,
  46                       struct pt_regs *regs)
  47 {
  48         const char *sym;
  49         char namebuf[128];
  50         unsigned long offset;
  51         unsigned long prologue = 0;
  52         unsigned long fp_displacement = 0;
  53         unsigned long fp_prev = 0;
  54         unsigned long offset_r14 = 0, offset_r18 = 0;
  55         int i, found_prologue_end = 0;
  56
  57         sym = kallsyms_lookup(pc, NULL, &offset, NULL, namebuf);
  58         if (!sym)
  59                 return -EINVAL;
  60
  61         prologue = pc - offset;
  62         if (!prologue)
  63                 return -EINVAL;
  64
  65         /* Validate fp, to avoid risk of dereferencing a bad pointer later.
  66            Assume 128Mb since that's the amount of RAM on a Cayman.  Modify
  67            when there is an SH-5 board with more. */
  68         if ((fp < (unsigned long) phys_to_virt(__MEMORY_START)) ||
  69             (fp >= (unsigned long)(phys_to_virt(__MEMORY_START)) + 128*1024*1024) ||
  70             ((fp & 7) != 0)) {
  71                 return -EINVAL;
  72         }
  73
  74         /*
  75          * Depth to walk, depth is completely arbitrary.
  76          */
  77         for (i = 0; i < 100; i++, prologue += sizeof(unsigned long)) {
  78                 unsigned long op;
  79                 u8 major, minor;
  80                 u8 src, dest, disp;
  81
  82                 op = *(unsigned long *)prologue;
  83
  84                 major = (op >> 26) & 0x3f;
  85                 src   = (op >> 20) & 0x3f;
  86                 minor = (op >> 16) & 0xf;
  87                 disp  = (op >> 10) & 0x3f;
  88                 dest  = (op >>  4) & 0x3f;
  89
  90                 /*
  91                  * Stack frame creation happens in a number of ways.. in the
  92                  * general case when the stack frame is less than 511 bytes,
  93                  * it's generally created by an addi or addi.l:
  94                  *
  95                  *      addi/addi.l r15, -FRAME_SIZE, r15
  96                  *
  97                  * in the event that the frame size is bigger than this, it's
  98                  * typically created using a movi/sub pair as follows:
  99                  *
 100                  *      movi    FRAME_SIZE, rX
 101                  *      sub     r15, rX, r15
 102                  */
 103
 104                 switch (major) {
 105                 case (0x00 >> 2):
 106                         switch (minor) {
 107                         case 0x8: /* add.l */
 108                         case 0x9: /* add */
 109                                 /* Look for r15, r63, r14 */
 110                                 if (src == 15 && disp == 63 && dest == 14)
 111                                         found_prologue_end = 1;
 112
 113                                 break;
 114                         case 0xa: /* sub.l */
 115                         case 0xb: /* sub */
 116                                 if (src != 15 || dest != 15)
 117                                         continue;
 118
 119                                 fp_displacement -= regcache[disp];
 120                                 fp_prev = fp - fp_displacement;
 121                                 break;
 122                         }
 123                         break;
 124                 case (0xa8 >> 2): /* st.l */
 125                         if (src != 15)
 126                                 continue;
 127
 128                         switch (dest) {
 129                         case 14:
 130                                 if (offset_r14 || fp_displacement == 0)
 131                                         continue;
 132
 133                                 offset_r14 = (u64)(((((s64)op >> 10) & 0x3ff) << 54) >> 54);
 134                                 offset_r14 *= sizeof(unsigned long);
 135                                 offset_r14 += fp_displacement;
 136                                 break;
 137                         case 18:
 138                                 if (offset_r18 || fp_displacement == 0)
 139                                         continue;
 140
 141                                 offset_r18 = (u64)(((((s64)op >> 10) & 0x3ff) << 54) >> 54);
 142                                 offset_r18 *= sizeof(unsigned long);
 143                                 offset_r18 += fp_displacement;
 144                                 break;
 145                         }
 146
 147                         break;
 148                 case (0xcc >> 2): /* movi */
 149                         if (dest >= 63) {
 150                                 printk(KERN_NOTICE "%s: Invalid dest reg %d "
 151                                        "specified in movi handler. Failed "
 152                                        "opcode was 0x%lx: ", __func__,
 153                                        dest, op);
 154
 155                                 continue;
 156                         }
 157
 158                         /* Sign extend */
 159                         regcache[dest] =
 160                                 ((((s64)(u64)op >> 10) & 0xffff) << 54) >> 54;
 161                         break;
 162                 case (0xd0 >> 2): /* addi */
 163                 case (0xd4 >> 2): /* addi.l */
 164                         /* Look for r15, -FRAME_SIZE, r15 */
 165                         if (src != 15 || dest != 15)
 166                                 continue;
 167
 168                         /* Sign extended frame size.. */
 169                         fp_displacement +=
 170                                 (u64)(((((s64)op >> 10) & 0x3ff) << 54) >> 54);
 171                         fp_prev = fp - fp_displacement;
 172                         break;
 173                 }
 174
 175                 if (found_prologue_end && offset_r14 && (offset_r18 || *pprev_pc) && fp_prev)
 176                         break;
 177         }
 178
 179         if (offset_r14 == 0 || fp_prev == 0) {
 180                 if (!offset_r14)
 181                         pr_debug("Unable to find r14 offset\n");
 182                 if (!fp_prev)
 183                         pr_debug("Unable to find previous fp\n");
 184
 185                 return -EINVAL;
 186         }
 187
 188         /* For innermost leaf function, there might not be a offset_r18 */
 189         if (!*pprev_pc && (offset_r18 == 0))
 190                 return -EINVAL;
 191
 192         *pprev_fp = *(unsigned long *)(fp_prev + offset_r14);
 193
 194         if (offset_r18)
 195                 *pprev_pc = *(unsigned long *)(fp_prev + offset_r18);
 196
 197         *pprev_pc &= ~1;
 198
 199         return 0;
 200 }
 201
 202 /* Don't put this on the stack since we'll want to call sh64_unwind
 203  * when we're close to underflowing the stack anyway. */
 204 static struct pt_regs here_regs;
 205
 206 extern const char syscall_ret;
 207 extern const char ret_from_syscall;
 208 extern const char ret_from_exception;
 209 extern const char ret_from_irq;
 210
 211 static void sh64_unwind_inner(struct pt_regs *regs);
 212
 213 static void unwind_nested (unsigned long pc, unsigned long fp)
 214 {
 215         if ((fp >= __MEMORY_START) &&
 216             ((fp & 7) == 0)) {
 217                 sh64_unwind_inner((struct pt_regs *) fp);
 218         }
 219 }
 220
 221 static void sh64_unwind_inner(struct pt_regs *regs)
 222 {
 223         unsigned long pc, fp;
 224         int ofs = 0;
 225         int first_pass;
 226
 227         pc = regs->pc & ~1;
 228         fp = regs->regs[14];
 229
 230         first_pass = 1;
 231         for (;;) {
 232                 int cond;
 233                 unsigned long next_fp, next_pc;
 234
 235                 if (pc == ((unsigned long) &syscall_ret & ~1)) {
 236                         printk("SYSCALL\n");
 237                         unwind_nested(pc,fp);
 238                         return;
 239                 }
 240
 241                 if (pc == ((unsigned long) &ret_from_syscall & ~1)) {
 242                         printk("SYSCALL (PREEMPTED)\n");
 243                         unwind_nested(pc,fp);
 244                         return;
 245                 }
 246
 247                 /* In this case, the PC is discovered by lookup_prev_stack_frame but
 248                    it has 4 taken off it to look like the 'caller' */
 249                 if (pc == ((unsigned long) &ret_from_exception & ~1)) {
 250                         printk("EXCEPTION\n");
 251                         unwind_nested(pc,fp);
 252                         return;
 253                 }
 254
 255                 if (pc == ((unsigned long) &ret_from_irq & ~1)) {
 256                         printk("IRQ\n");
 257                         unwind_nested(pc,fp);
 258                         return;
 259                 }
 260
 261                 cond = ((pc >= __MEMORY_START) && (fp >= __MEMORY_START) &&
 262                         ((pc & 3) == 0) && ((fp & 7) == 0));
 263
 264                 pc -= ofs;
 265
 266                 printk("[<%08lx>] ", pc);
 267                 print_symbol("%s\n", pc);
 268
 269                 if (first_pass) {
 270                         /* If the innermost frame is a leaf function, it's
 271                          * possible that r18 is never saved out to the stack.
 272                          */
 273                         next_pc = regs->regs[18];
 274                 } else {
 275                         next_pc = 0;
 276                 }
 277
 278                 if (lookup_prev_stack_frame(fp, pc, &next_fp, &next_pc, regs) == 0) {
 279                         ofs = sizeof(unsigned long);
 280                         pc = next_pc & ~1;
 281                         fp = next_fp;
 282                 } else {
 283                         printk("Unable to lookup previous stack frame\n");
 284                         break;
 285                 }
 286                 first_pass = 0;
 287         }
 288
 289         printk("\n");
 290
 291 }
 292
 293 void sh64_unwind(struct pt_regs *regs)
 294 {
 295         if (!regs) {
 296                 /*
 297                  * Fetch current regs if we have no other saved state to back
 298                  * trace from.
 299                  */
 300                 regs = &here_regs;
 301
 302                 __asm__ __volatile__ ("ori r14, 0, %0" : "=r" (regs->regs[14]));
 303                 __asm__ __volatile__ ("ori r15, 0, %0" : "=r" (regs->regs[15]));
 304                 __asm__ __volatile__ ("ori r18, 0, %0" : "=r" (regs->regs[18]));
 305
 306                 __asm__ __volatile__ ("gettr tr0, %0" : "=r" (regs->tregs[0]));
 307                 __asm__ __volatile__ ("gettr tr1, %0" : "=r" (regs->tregs[1]));
 308                 __asm__ __volatile__ ("gettr tr2, %0" : "=r" (regs->tregs[2]));
 309                 __asm__ __volatile__ ("gettr tr3, %0" : "=r" (regs->tregs[3]));
 310                 __asm__ __volatile__ ("gettr tr4, %0" : "=r" (regs->tregs[4]));
 311                 __asm__ __volatile__ ("gettr tr5, %0" : "=r" (regs->tregs[5]));
 312                 __asm__ __volatile__ ("gettr tr6, %0" : "=r" (regs->tregs[6]));
 313                 __asm__ __volatile__ ("gettr tr7, %0" : "=r" (regs->tregs[7]));
 314
 315                 __asm__ __volatile__ (
 316                         "pta 0f, tr0\n\t"
 317                         "blink tr0, %0\n\t"
 318                         "0: nop"
 319                         : "=r" (regs->pc)
 320                 );
 321         }
 322
 323         printk("\nCall Trace:\n");
 324         sh64_unwind_inner(regs);
 325 }
 326