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windows.c

/* windows.c: Routines to deal with register window management
 *            at the C-code level.
 *
 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>

#include <asm/uaccess.h>

/* Do save's until all user register windows are out of the cpu. */
void flush_user_windows(void)
{
      register int ctr asm("g5");

      ctr = 0;
      __asm__ __volatile__(
            "\n1:\n\t"
            "ld   [%%g6 + %2], %%g4\n\t"
            "orcc %%g0, %%g4, %%g0\n\t"
            "add  %0, 1, %0\n\t"
            "bne  1b\n\t"
            " save      %%sp, -64, %%sp\n"
            "2:\n\t"
            "subcc      %0, 1, %0\n\t"
            "bne  2b\n\t"
            " restore %%g0, %%g0, %%g0\n"
      : "=&r" (ctr)
      : "0" (ctr),
        "i" ((const unsigned long)TI_UWINMASK)
      : "g4", "cc");
}

static inline void shift_window_buffer(int first_win, int last_win, struct thread_info *tp)
{
      int i;

      for(i = first_win; i < last_win; i++) {
            tp->rwbuf_stkptrs[i] = tp->rwbuf_stkptrs[i+1];
            memcpy(&tp->reg_window[i], &tp->reg_window[i+1], sizeof(struct reg_window));
      }
}

/* Place as many of the user's current register windows 
 * on the stack that we can.  Even if the %sp is unaligned
 * we still copy the window there, the only case that we don't
 * succeed is if the %sp points to a bum mapping altogether.
 * setup_frame() and do_sigreturn() use this before shifting
 * the user stack around.  Future instruction and hardware
 * bug workaround routines will need this functionality as
 * well.
 */
void synchronize_user_stack(void)
{
      struct thread_info *tp = current_thread_info();
      int window;

      flush_user_windows();
      if(!tp->w_saved)
            return;

      /* Ok, there is some dirty work to do. */
      for(window = tp->w_saved - 1; window >= 0; window--) {
            unsigned long sp = tp->rwbuf_stkptrs[window];

            /* Ok, let it rip. */
            if (copy_to_user((char __user *) sp, &tp->reg_window[window],
                         sizeof(struct reg_window)))
                  continue;

            shift_window_buffer(window, tp->w_saved - 1, tp);
            tp->w_saved--;
      }
}

#if 0
/* An optimization. */
static inline void copy_aligned_window(void *dest, const void *src)
{
      __asm__ __volatile__("ldd [%1], %%g2\n\t"
                       "ldd [%1 + 0x8], %%g4\n\t"
                       "std %%g2, [%0]\n\t"
                       "std %%g4, [%0 + 0x8]\n\t"
                       "ldd [%1 + 0x10], %%g2\n\t"
                       "ldd [%1 + 0x18], %%g4\n\t"
                       "std %%g2, [%0 + 0x10]\n\t"
                       "std %%g4, [%0 + 0x18]\n\t"
                       "ldd [%1 + 0x20], %%g2\n\t"
                       "ldd [%1 + 0x28], %%g4\n\t"
                       "std %%g2, [%0 + 0x20]\n\t"
                       "std %%g4, [%0 + 0x28]\n\t"
                       "ldd [%1 + 0x30], %%g2\n\t"
                       "ldd [%1 + 0x38], %%g4\n\t"
                       "std %%g2, [%0 + 0x30]\n\t"
                       "std %%g4, [%0 + 0x38]\n\t" : :
                       "r" (dest), "r" (src) :
                       "g2", "g3", "g4", "g5");
}
#endif

/* Try to push the windows in a threads window buffer to the
 * user stack.  Unaligned %sp's are not allowed here.
 */

void try_to_clear_window_buffer(struct pt_regs *regs, int who)
{
      struct thread_info *tp = current_thread_info();
      int window;

      lock_kernel();
      flush_user_windows();
      for(window = 0; window < tp->w_saved; window++) {
            unsigned long sp = tp->rwbuf_stkptrs[window];

            if ((sp & 7) ||
                copy_to_user((char __user *) sp, &tp->reg_window[window],
                         sizeof(struct reg_window)))
                  do_exit(SIGILL);
      }
      tp->w_saved = 0;
      unlock_kernel();
}

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