unaligned.c

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/* $Id: unaligned.c,v 1.24 2002/02/09 19:49:31 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 ([e-mail])
 * Copyright (C) 1996,1997 Jakub Jelinek ([e-mail])
 */


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

/* #define DEBUG_MNA */

enum direction {
	load,    /* ld, ldd, ldh, ldsh */
	store,   /* st, std, sth, stsh */
	both,    /* Swap, ldstub, cas, ... */
	fpld,
	fpst,
	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 {
		switch ((insn>>19)&0xf) {
		case 15: /* swap* */
			return both;
		default:
			return store;
		}
	}
}

/* 16 = double-word, 8 = extra-word, 4 = word, 2 = half-word */
static inline int decode_access_size(unsigned int insn)
{
	unsigned int tmp;

	tmp = ((insn >> 19) & 0xf);
	if (tmp == 11 || tmp == 14) /* ldx/stx */
		return 8;
	tmp &= 3;
	if (!tmp)
		return 4;
	else if (tmp == 3)
		return 16;	/* ldd/std - Although it is actually 8 */
	else if (tmp == 2)
		return 2;
	else {
		printk("Impossible unaligned trap. insn=%08x\n", insn);
		die_if_kernel("Byte sized unaligned access?!?!", current_thread_info()->kregs);

		/* GCC should never warn that control reaches the end
		 * of this function without returning a value because
		 * die_if_kernel() is marked with attribute 'noreturn'.
		 * Alas, some versions do...
		 */

		return 0;
	}
}

static inline int decode_asi(unsigned int insn, struct pt_regs *regs)
{
	if (insn & 0x800000) {
		if (insn & 0x2000)
			return (unsigned char)(regs->tstate >> 24);	/* %asi */
		else
			return (unsigned char)(insn >> 5);		/* imm_asi */
	} else
		return ASI_P;
}

/* 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, int from_kernel)
{
	if (rs2 >= 16 || rs1 >= 16 || rd >= 16) {
		if (from_kernel != 0)
			__asm__ __volatile__("flushw");
		else
			flushw_user();
	}
}

static inline long sign_extend_imm13(long imm)
{
	return imm << 51 >> 51;
}

static unsigned long fetch_reg(unsigned int reg, struct pt_regs *regs)
{
	unsigned long value;
	
	if (reg < 16)
		return (!reg ? 0 : regs->u_regs[reg]);
	if (regs->tstate & TSTATE_PRIV) {
		struct reg_window *win;
		win = (struct reg_window *)(regs->u_regs[UREG_FP] + STACK_BIAS);
		value = win->locals[reg - 16];
	} else if (test_thread_flag(TIF_32BIT)) {
		struct reg_window32 __user *win32;
		win32 = (struct reg_window32 __user *)((unsigned long)((u32)regs->u_regs[UREG_FP]));
		get_user(value, &win32->locals[reg - 16]);
	} else {
		struct reg_window __user *win;
		win = (struct reg_window __user *)(regs->u_regs[UREG_FP] + STACK_BIAS);
		get_user(value, &win->locals[reg - 16]);
	}
	return value;
}

static unsigned long *fetch_reg_addr(unsigned int reg, struct pt_regs *regs)
{
	if (reg < 16)
		return &regs->u_regs[reg];
	if (regs->tstate & TSTATE_PRIV) {
		struct reg_window *win;
		win = (struct reg_window *)(regs->u_regs[UREG_FP] + STACK_BIAS);
		return &win->locals[reg - 16];
	} else if (test_thread_flag(TIF_32BIT)) {
		struct reg_window32 *win32;
		win32 = (struct reg_window32 *)((unsigned long)((u32)regs->u_regs[UREG_FP]));
		return (unsigned long *)&win32->locals[reg - 16];
	} else {
		struct reg_window *win;
		win = (struct reg_window *)(regs->u_regs[UREG_FP] + STACK_BIAS);
		return &win->locals[reg - 16];
	}
}

unsigned long compute_effective_address(struct pt_regs *regs,
					unsigned int insn, unsigned int rd)
{
	unsigned int rs1 = (insn >> 14) & 0x1f;
	unsigned int rs2 = insn & 0x1f;
	int from_kernel = (regs->tstate & TSTATE_PRIV) != 0;

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

/* This is just to make gcc think die_if_kernel does return... */
static void __attribute_used__ unaligned_panic(char *str, struct pt_regs *regs)
{
	die_if_kernel(str, regs);
}

extern int do_int_load(unsigned long *dest_reg, int size,
		       unsigned long *saddr, int is_signed, int asi);
	
extern int __do_int_store(unsigned long *dst_addr, int size,
			  unsigned long src_val, int asi);

static inline int do_int_store(int reg_num, int size, unsigned long *dst_addr,
			       struct pt_regs *regs, int asi, int orig_asi)
{
	unsigned long zero = 0;
	unsigned long *src_val_p = &zero;
	unsigned long src_val;

	if (size == 16) {
		size = 8;
		zero = (((long)(reg_num ?
		        (unsigned)fetch_reg(reg_num, regs) : 0)) << 32) |
			(unsigned)fetch_reg(reg_num + 1, regs);
	} else if (reg_num) {
		src_val_p = fetch_reg_addr(reg_num, regs);
	}
	src_val = *src_val_p;
	if (unlikely(asi != orig_asi)) {
		switch (size) {
		case 2:
			src_val = swab16(src_val);
			break;
		case 4:
			src_val = swab32(src_val);
			break;
		case 8:
			src_val = swab64(src_val);
			break;
		case 16:
		default:
			BUG();
			break;
		};
	}
	return __do_int_store(dst_addr, size, src_val, asi);
}

static inline void advance(struct pt_regs *regs)
{
	regs->tpc   = regs->tnpc;
	regs->tnpc += 4;
	if (test_thread_flag(TIF_32BIT)) {
		regs->tpc &= 0xffffffff;
		regs->tnpc &= 0xffffffff;
	}
}

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);
}

static void kernel_mna_trap_fault(void)
{
	struct pt_regs *regs = current_thread_info()->kern_una_regs;
	unsigned int insn = current_thread_info()->kern_una_insn;
	const struct exception_table_entry *entry;

	entry = search_exception_tables(regs->tpc);
	if (!entry) {
		unsigned long address;

		address = compute_effective_address(regs, insn,
						    ((insn >> 25) & 0x1f));
        	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 %016lx\n",address);
		printk(KERN_ALERT "current->{active_,}mm->context = %016lx\n",
			(current->mm ? CTX_HWBITS(current->mm->context) :
			CTX_HWBITS(current->active_mm->context)));
		printk(KERN_ALERT "current->{active_,}mm->pgd = %016lx\n",
			(current->mm ? (unsigned long) current->mm->pgd :
			(unsigned long) current->active_mm->pgd));
	        die_if_kernel("Oops", regs);
		/* Not reached */
	}
	regs->tpc = entry->fixup;
	regs->tnpc = regs->tpc + 4;

	regs->tstate &= ~TSTATE_ASI;
	regs->tstate |= (ASI_AIUS << 24UL);
}

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

	current_thread_info()->kern_una_regs = regs;
	current_thread_info()->kern_una_insn = insn;

	if (!ok_for_kernel(insn) || dir == both) {
		printk("Unsupported unaligned load/store trap for kernel "
		       "at <%016lx>.\n", regs->tpc);
		unaligned_panic("Kernel does fpu/atomic "
				"unaligned load/store.", regs);

		kernel_mna_trap_fault();
	} else {
		unsigned long addr, *reg_addr;
		int orig_asi, asi, err;

		addr = compute_effective_address(regs, insn,
						 ((insn >> 25) & 0x1f));
#ifdef DEBUG_MNA
		printk("KMNA: pc=%016lx [dir=%s addr=%016lx size=%d] "
		       "retpc[%016lx]\n",
		       regs->tpc, dirstrings[dir], addr, size,
		       regs->u_regs[UREG_RETPC]);
#endif
		orig_asi = asi = decode_asi(insn, regs);
		switch (asi) {
		case ASI_NL:
		case ASI_AIUPL:
		case ASI_AIUSL:
		case ASI_PL:
		case ASI_SL:
		case ASI_PNFL:
		case ASI_SNFL:
			asi &= ~0x08;
			break;
		};
		switch (dir) {
		case load: