// SPDX-License-Identifier: GPL-2.0
/* 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 <asm/cacheflush.h>
#include <linux/uaccess.h>

#include "kernel.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_window32));
        }
}

/* 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_window32)))
                        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;

        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_window32))) {
                        force_exit_sig(SIGILL);
                        return;
                }
        }
        tp->w_saved = 0;
}