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unaligned.c

/* $Id: unaligned.c,v 1.23 2001/12/21 00:54:31 davem Exp $
 * unaligned.c: Unaligned load/store trap handling with special
 *              cases for the kernel to do them more quickly.
 *
 * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
 * Copyright (C) 1996 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
 */


#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <asm/ptrace.h>
#include <asm/processor.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>

/* #define DEBUG_MNA */

enum direction {
      load,    /* ld, ldd, ldh, ldsh */
      store,   /* st, std, sth, stsh */
      both,    /* Swap, ldstub, etc. */
      fpload,
      fpstore,
      invalid,
};

#ifdef DEBUG_MNA
static char *dirstrings[] = {
  "load", "store", "both", "fpload", "fpstore", "invalid"
};
#endif

static inline enum direction decode_direction(unsigned int insn)
{
      unsigned long tmp = (insn >> 21) & 1;

      if(!tmp)
            return load;
      else {
            if(((insn>>19)&0x3f) == 15)
                  return both;
            else
                  return store;
      }
}

/* 8 = double-word, 4 = word, 2 = half-word */
static inline int decode_access_size(unsigned int insn)
{
      insn = (insn >> 19) & 3;

      if(!insn)
            return 4;
      else if(insn == 3)
            return 8;
      else if(insn == 2)
            return 2;
      else {
            printk("Impossible unaligned trap. insn=%08x\n", insn);
            die_if_kernel("Byte sized unaligned access?!?!", current->thread.kregs);
            return 4; /* just to keep gcc happy. */
      }
}

/* 0x400000 = signed, 0 = unsigned */
static inline int decode_signedness(unsigned int insn)
{
      return (insn & 0x400000);
}

static inline void maybe_flush_windows(unsigned int rs1, unsigned int rs2,
                               unsigned int rd)
{
      if(rs2 >= 16 || rs1 >= 16 || rd >= 16) {
            /* Wheee... */
            __asm__ __volatile__("save %sp, -0x40, %sp\n\t"
                             "save %sp, -0x40, %sp\n\t"
                             "save %sp, -0x40, %sp\n\t"
                             "save %sp, -0x40, %sp\n\t"
                             "save %sp, -0x40, %sp\n\t"
                             "save %sp, -0x40, %sp\n\t"
                             "save %sp, -0x40, %sp\n\t"
                             "restore; restore; restore; restore;\n\t"
                             "restore; restore; restore;\n\t");
      }
}

static inline int sign_extend_imm13(int imm)
{
      return imm << 19 >> 19;
}

static inline unsigned long fetch_reg(unsigned int reg, struct pt_regs *regs)
{
      struct reg_window *win;

      if(reg < 16)
            return (!reg ? 0 : regs->u_regs[reg]);

      /* Ho hum, the slightly complicated case. */
      win = (struct reg_window *) regs->u_regs[UREG_FP];
      return win->locals[reg - 16]; /* yes, I know what this does... */
}

static inline unsigned long safe_fetch_reg(unsigned int reg, struct pt_regs *regs)
{
      struct reg_window __user *win;
      unsigned long ret;

      if (reg < 16)
            return (!reg ? 0 : regs->u_regs[reg]);

      /* Ho hum, the slightly complicated case. */
      win = (struct reg_window __user *) regs->u_regs[UREG_FP];

      if ((unsigned long)win & 3)
            return -1;

      if (get_user(ret, &win->locals[reg - 16]))
            return -1;

      return ret;
}

static inline unsigned long *fetch_reg_addr(unsigned int reg, struct pt_regs *regs)
{
      struct reg_window *win;

      if(reg < 16)
            return &regs->u_regs[reg];
      win = (struct reg_window *) regs->u_regs[UREG_FP];
      return &win->locals[reg - 16];
}

static unsigned long compute_effective_address(struct pt_regs *regs,
                                     unsigned int insn)
{
      unsigned int rs1 = (insn >> 14) & 0x1f;
      unsigned int rs2 = insn & 0x1f;
      unsigned int rd = (insn >> 25) & 0x1f;

      if(insn & 0x2000) {
            maybe_flush_windows(rs1, 0, rd);
            return (fetch_reg(rs1, regs) + sign_extend_imm13(insn));
      } else {
            maybe_flush_windows(rs1, rs2, rd);
            return (fetch_reg(rs1, regs) + fetch_reg(rs2, regs));
      }
}

unsigned long safe_compute_effective_address(struct pt_regs *regs,
                                   unsigned int insn)
{
      unsigned int rs1 = (insn >> 14) & 0x1f;
      unsigned int rs2 = insn & 0x1f;
      unsigned int rd = (insn >> 25) & 0x1f;

      if(insn & 0x2000) {
            maybe_flush_windows(rs1, 0, rd);
            return (safe_fetch_reg(rs1, regs) + sign_extend_imm13(insn));
      } else {
            maybe_flush_windows(rs1, rs2, rd);
            return (safe_fetch_reg(rs1, regs) + safe_fetch_reg(rs2, regs));
      }
}

/* This is just to make gcc think panic does return... */
static void unaligned_panic(char *str)
{
      panic(str);
}

#define do_integer_load(dest_reg, size, saddr, is_signed, errh) ({            \
__asm__ __volatile__ (                                            \
      "cmp  %1, 8\n\t"                                      \
      "be   9f\n\t"                                               \
      " cmp %1, 4\n\t"                                      \
      "be   6f\n"                                           \
"4:\t"      " ldub      [%2], %%l1\n"                                         \
"5:\t"      "ldub [%2 + 1], %%l2\n\t"                                   \
      "sll  %%l1, 8, %%l1\n\t"                                    \
      "tst  %3\n\t"                                               \
      "be   3f\n\t"                                               \
      " add %%l1, %%l2, %%l1\n\t"                                 \
      "sll  %%l1, 16, %%l1\n\t"                                   \
      "sra  %%l1, 16, %%l1\n"                               \
"3:\t"      "b    0f\n\t"                                               \
      " st  %%l1, [%0]\n"                                         \
"6:\t"      "ldub [%2 + 1], %%l2\n\t"                                   \
      "sll  %%l1, 24, %%l1\n"                               \
"7:\t"      "ldub [%2 + 2], %%g7\n\t"                                   \
      "sll  %%l2, 16, %%l2\n"                               \
"8:\t"      "ldub [%2 + 3], %%g1\n\t"                                   \
      "sll  %%g7, 8, %%g7\n\t"                                    \
      "or   %%l1, %%l2, %%l1\n\t"                                 \
      "or   %%g7, %%g1, %%g7\n\t"                                 \
      "or   %%l1, %%g7, %%l1\n\t"                                 \
      "b    0f\n\t"                                               \
      " st  %%l1, [%0]\n"                                         \
"9:\t"      "ldub [%2], %%l1\n"                                         \
"10:\t"     "ldub [%2 + 1], %%l2\n\t"                                   \
      "sll  %%l1, 24, %%l1\n"                               \
"11:\t"     "ldub [%2 + 2], %%g7\n\t"                                   \
      "sll  %%l2, 16, %%l2\n"                               \
"12:\t"     "ldub [%2 + 3], %%g1\n\t"                                   \
      "sll  %%g7, 8, %%g7\n\t"                                    \
      "or   %%l1, %%l2, %%l1\n\t"                                 \
      "or   %%g7, %%g1, %%g7\n\t"                                 \
      "or   %%l1, %%g7, %%g7\n"                                   \
"13:\t"     "ldub [%2 + 4], %%l1\n\t"                                   \
      "st   %%g7, [%0]\n"                                         \
"14:\t"     "ldub [%2 + 5], %%l2\n\t"                                   \
      "sll  %%l1, 24, %%l1\n"                               \
"15:\t"     "ldub [%2 + 6], %%g7\n\t"                                   \
      "sll  %%l2, 16, %%l2\n"                               \
"16:\t"     "ldub [%2 + 7], %%g1\n\t"                                   \
      "sll  %%g7, 8, %%g7\n\t"                                    \
      "or   %%l1, %%l2, %%l1\n\t"                                 \
      "or   %%g7, %%g1, %%g7\n\t"                                 \
      "or   %%l1, %%g7, %%g7\n\t"                                 \
      "st   %%g7, [%0 + 4]\n"                               \
"0:\n\n\t"                                                  \
      ".section __ex_table,#alloc\n\t"                            \
      ".word      4b, " #errh "\n\t"                                    \
      ".word      5b, " #errh "\n\t"                                    \
      ".word      6b, " #errh "\n\t"                                    \
      ".word      7b, " #errh "\n\t"                                    \
      ".word      8b, " #errh "\n\t"                                    \
      ".word      9b, " #errh "\n\t"                                    \
      ".word      10b, " #errh "\n\t"                                   \
      ".word      11b, " #errh "\n\t"                                   \
      ".word      12b, " #errh "\n\t"                                   \
      ".word      13b, " #errh "\n\t"                                   \
      ".word      14b, " #errh "\n\t"                                   \
      ".word      15b, " #errh "\n\t"                                   \
      ".word      16b, " #errh "\n\n\t"                                 \
      ".previous\n\t"                                             \
      : : "r" (dest_reg), "r" (size), "r" (saddr), "r" (is_signed)            \
      : "l1", "l2", "g7", "g1", "cc");                            \
})
      
#define store_common(dst_addr, size, src_val, errh) ({                        \
__asm__ __volatile__ (                                            \
      "ld   [%2], %%l1\n"                                         \
      "cmp  %1, 2\n\t"                                      \
      "be   2f\n\t"                                               \
      " cmp %1, 4\n\t"                                      \
      "be   1f\n\t"                                               \
      " srl %%l1, 24, %%l2\n\t"                                   \
      "srl  %%l1, 16, %%g7\n"                               \
"4:\t"      "stb  %%l2, [%0]\n\t"                                       \
      "srl  %%l1, 8, %%l2\n"                                \
"5:\t"      "stb  %%g7, [%0 + 1]\n\t"                                   \
      "ld   [%2 + 4], %%g7\n"                               \
"6:\t"      "stb  %%l2, [%0 + 2]\n\t"                                   \
      "srl  %%g7, 24, %%l2\n"                               \
"7:\t"      "stb  %%l1, [%0 + 3]\n\t"                                   \
      "srl  %%g7, 16, %%l1\n"                               \
"8:\t"      "stb  %%l2, [%0 + 4]\n\t"                                   \
      "srl  %%g7, 8, %%l2\n"                                \
"9:\t"      "stb  %%l1, [%0 + 5]\n"                               \
"10:\t"     "stb  %%l2, [%0 + 6]\n\t"                                   \
      "b    0f\n"                                           \
"11:\t"     " stb %%g7, [%0 + 7]\n"                               \
"1:\t"      "srl  %%l1, 16, %%g7\n"                               \
"12:\t"     "stb  %%l2, [%0]\n\t"                                       \
      "srl  %%l1, 8, %%l2\n"                                \
"13:\t"     "stb  %%g7, [%0 + 1]\n"                               \
"14:\t"     "stb  %%l2, [%0 + 2]\n\t"                                   \
      "b    0f\n"                                           \
"15:\t"     " stb %%l1, [%0 + 3]\n"                               \
"2:\t"      "srl  %%l1, 8, %%l2\n"                                \
"16:\t"     "stb  %%l2, [%0]\n"                                         \
"17:\t"     "stb  %%l1, [%0 + 1]\n"                               \
"0:\n\n\t"                                                  \
      ".section __ex_table,#alloc\n\t"                            \
      ".word      4b, " #errh "\n\t"                                    \
      ".word      5b, " #errh "\n\t"                                    \
      ".word      6b, " #errh "\n\t"                                    \
      ".word      7b, " #errh "\n\t"                                    \
      ".word      8b, " #errh "\n\t"                                    \
      ".word      9b, " #errh "\n\t"                                    \
      ".word      10b, " #errh "\n\t"                                   \
      ".word      11b, " #errh "\n\t"                                   \
      ".word      12b, " #errh "\n\t"                                   \
      ".word      13b, " #errh "\n\t"                                   \
      ".word      14b, " #errh "\n\t"                                   \
      ".word      15b, " #errh "\n\t"                                   \
      ".word      16b, " #errh "\n\t"                                   \
      ".word      17b, " #errh "\n\n\t"                                 \
      ".previous\n\t"                                             \
      : : "r" (dst_addr), "r" (size), "r" (src_val)                     \
      : "l1", "l2", "g7", "g1", "cc");                            \
})

#define do_integer_store(reg_num, size, dst_addr, regs, errh) ({        \
      unsigned long *src_val;                                     \
      static unsigned long zero[2] = { 0, };                            \
                                                            \
      if (reg_num) src_val = fetch_reg_addr(reg_num, regs);             \
      else {                                                      \
            src_val = &zero[0];                                   \
            if (size == 8)                                        \
                  zero[1] = fetch_reg(1, regs);                   \
      }                                                     \
      store_common(dst_addr, size, src_val, errh);                      \
})

extern void smp_capture(void);
extern void smp_release(void);

#define do_atomic(srcdest_reg, mem, errh) ({                            \
      unsigned long flags, tmp;                                   \
                                                            \
      smp_capture();                                              \
      local_irq_save(flags);                                      \
      tmp = *srcdest_reg;                                         \
      do_integer_load(srcdest_reg, 4, mem, 0, errh);                    \
      store_common(mem, 4, &tmp, errh);                           \
      local_irq_restore(flags);                                   \
      smp_release();                                              \
})

static inline void advance(struct pt_regs *regs)
{
      regs->pc   = regs->npc;
      regs->npc += 4;
}

static inline int floating_point_load_or_store_p(unsigned int insn)
{
      return (insn >> 24) & 1;
}

static inline int ok_for_kernel(unsigned int insn)
{
      return !floating_point_load_or_store_p(insn);
}

void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn) __asm__ ("kernel_mna_trap_fault");

void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
{
      unsigned long g2 = regs->u_regs [UREG_G2];
      unsigned long fixup = search_extables_range(regs->pc, &g2);

      if (!fixup) {
            unsigned long address = compute_effective_address(regs, insn);
            if(address < PAGE_SIZE) {
                  printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference in mna handler");
            } else
                  printk(KERN_ALERT "Unable to handle kernel paging request in mna handler");
              printk(KERN_ALERT " at virtual address %08lx\n",address);
            printk(KERN_ALERT "current->{mm,active_mm}->context = %08lx\n",
                  (current->mm ? current->mm->context :
                  current->active_mm->context));
            printk(KERN_ALERT "current->{mm,active_mm}->pgd = %08lx\n",
                  (current->mm ? (unsigned long) current->mm->pgd :
                  (unsigned long) current->active_mm->pgd));
              die_if_kernel("Oops", regs);
            /* Not reached */
      }
      regs->pc = fixup;
      regs->npc = regs->pc + 4;
      regs->u_regs [UREG_G2] = g2;
}

asmlinkage void kernel_unaligned_trap(struct pt_regs *regs, unsigned int insn)
{
      enum direction dir = decode_direction(insn);
      int size = decode_access_size(insn);

      if(!ok_for_kernel(insn) || dir == both) {
            printk("Unsupported unaligned load/store trap for kernel at <%08lx>.\n",
                   regs->pc);
            unaligned_panic("Wheee. Kernel does fpu/atomic unaligned load/store.");

            __asm__ __volatile__ ("\n"
"kernel_unaligned_trap_fault:\n\t"
            "mov  %0, %%o0\n\t"
            "call kernel_mna_trap_fault\n\t"
            " mov %1, %%o1\n\t"
            :
            : "r" (regs), "r" (insn)
            : "o0", "o1", "o2", "o3", "o4", "o5", "o7",
              "g1", "g2", "g3", "g4", "g5", "g7", "cc");
      } else {
            unsigned long addr = compute_effective_address(regs, insn);

#ifdef DEBUG_MNA
            printk("KMNA: pc=%08lx [dir=%s addr=%08lx size=%d] retpc[%08lx]\n",
                   regs->pc, dirstrings[dir], addr, size, regs->u_regs[UREG_RETPC]);
#endif
            switch(dir) {
            case load:
                  do_integer_load(fetch_reg_addr(((insn>>25)&0x1f), regs),
                              size, (unsigned long *) addr,
                              decode_signedness(insn),
                              kernel_unaligned_trap_fault);
                  break;

            case store:
                  do_integer_store(((insn>>25)&0x1f), size,
                               (unsigned long *) addr, regs,
                               kernel_unaligned_trap_fault);
                  break;
#if 0 /* unsupported */
            case both:
                  do_atomic(fetch_reg_addr(((insn>>25)&0x1f), regs),
                          (unsigned long *) addr,
                          kernel_unaligned_trap_fault);
                  break;
#endif
            default:
                  panic("Impossible kernel unaligned trap.");
                  /* Not reached... */
            }
            advance(regs);
      }
}

static inline int ok_for_user(struct pt_regs *regs, unsigned int insn,
                        enum direction dir)
{
      unsigned int reg;
      int check = (dir == load) ? VERIFY_READ : VERIFY_WRITE;
      int size = ((insn >> 19) & 3) == 3 ? 8 : 4;

      if ((regs->pc | regs->npc) & 3)
            return 0;

      /* Must access_ok() in all the necessary places. */
#define WINREG_ADDR(regnum) \
      ((void __user *)(((unsigned long *)regs->u_regs[UREG_FP])+(regnum)))

      reg = (insn >> 25) & 0x1f;
      if (reg >= 16) {
            if (!access_ok(check, WINREG_ADDR(reg - 16), size))
                  return -EFAULT;
      }
      reg = (insn >> 14) & 0x1f;
      if (reg >= 16) {
            if (!access_ok(check, WINREG_ADDR(reg - 16), size))
                  return -EFAULT;
      }
      if (!(insn & 0x2000)) {
            reg = (insn & 0x1f);
            if (reg >= 16) {
                  if (!access_ok(check, WINREG_ADDR(reg - 16), size))
                        return -EFAULT;
            }
      }
#undef WINREG_ADDR
      return 0;
}

void user_mna_trap_fault(struct pt_regs *regs, unsigned int insn) __asm__ ("user_mna_trap_fault");

void user_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
{
      siginfo_t info;

      info.si_signo = SIGBUS;
      info.si_errno = 0;
      info.si_code = BUS_ADRALN;
      info.si_addr = (void __user *)safe_compute_effective_address(regs, insn);
      info.si_trapno = 0;
      send_sig_info(SIGBUS, &info, current);
}

asmlinkage void user_unaligned_trap(struct pt_regs *regs, unsigned int insn)
{
      enum direction dir;

      lock_kernel();
      if(!(current->thread.flags & SPARC_FLAG_UNALIGNED) ||
         (((insn >> 30) & 3) != 3))
            goto kill_user;
      dir = decode_direction(insn);
      if(!ok_for_user(regs, insn, dir)) {
            goto kill_user;
      } else {
            int size = decode_access_size(insn);
            unsigned long addr;

            if(floating_point_load_or_store_p(insn)) {
                  printk("User FPU load/store unaligned unsupported.\n");
                  goto kill_user;
            }

            addr = compute_effective_address(regs, insn);
            switch(dir) {
            case load:
                  do_integer_load(fetch_reg_addr(((insn>>25)&0x1f), regs),
                              size, (unsigned long *) addr,
                              decode_signedness(insn),
                              user_unaligned_trap_fault);
                  break;

            case store:
                  do_integer_store(((insn>>25)&0x1f), size,
                               (unsigned long *) addr, regs,
                               user_unaligned_trap_fault);
                  break;

            case both:
#if 0 /* unsupported */
                  do_atomic(fetch_reg_addr(((insn>>25)&0x1f), regs),
                          (unsigned long *) addr,
                          user_unaligned_trap_fault);
#else
                  /*
                   * This was supported in 2.4. However, we question
                   * the value of SWAP instruction across word boundaries.
                   */
                  printk("Unaligned SWAP unsupported.\n");
                  goto kill_user;
#endif
                  break;

            default:
                  unaligned_panic("Impossible user unaligned trap.");

                  __asm__ __volatile__ ("\n"
"user_unaligned_trap_fault:\n\t"
                  "mov  %0, %%o0\n\t"
                  "call user_mna_trap_fault\n\t"
                  " mov %1, %%o1\n\t"
                  :
                  : "r" (regs), "r" (insn)
                  : "o0", "o1", "o2", "o3", "o4", "o5", "o7",
                    "g1", "g2", "g3", "g4", "g5", "g7", "cc");
                  goto out;
            }
            advance(regs);
            goto out;
      }

kill_user:
      user_mna_trap_fault(regs, insn);
out:
      unlock_kernel();
}

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