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/*
* linux/arch/nios2/kernel/misaligned.c
*
* basic emulation for mis-aligned accesses on the NIOS II cpu
* modelled after the version for arm in arm/alignment.c
*
* Brad Parker <brad@heeltoe.com>
* Copyright (C) 2010 Ambient Corporation
* Copyright (c) 2010 Altera Corporation, San Jose, California, USA.
* Copyright (c) 2010 Arrow Electronics, Inc.
*
* This file is subject to the terms and conditions of the GNU General
* Public License. See the file COPYING in the main directory of
* this archive for more details.
*/
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/uaccess.h>
#include <linux/seq_file.h>
#include <asm/traps.h>
#include <asm/unaligned.h>
/* instructions we emulate */
#define INST_LDHU 0x0b
#define INST_STH 0x0d
#define INST_LDH 0x0f
#define INST_STW 0x15
#define INST_LDW 0x17
static unsigned int ma_usermode;
#define UM_WARN 0x01
#define UM_FIXUP 0x02
#define UM_SIGNAL 0x04
#define KM_WARN 0x08
/* see arch/nios2/include/asm/ptrace.h */
static u8 sys_stack_frame_reg_offset[] = {
/* struct pt_regs */
8, 9, 10, 11, 12, 13, 14, 15, 1, 2, 3, 4, 5, 6, 7, 0,
/* struct switch_stack */
16, 17, 18, 19, 20, 21, 22, 23, 0, 0, 0, 0, 0, 0, 0, 0
};
static int reg_offsets[32];
static inline u32 get_reg_val(struct pt_regs *fp, int reg)
{
u8 *p = ((u8 *)fp) + reg_offsets[reg];
return *(u32 *)p;
}
static inline void put_reg_val(struct pt_regs *fp, int reg, u32 val)
{
u8 *p = ((u8 *)fp) + reg_offsets[reg];
*(u32 *)p = val;
}
/*
* (mis)alignment handler
*/
asmlinkage void handle_unaligned_c(struct pt_regs *fp, int cause)
{
u32 isn, addr, val;
int in_kernel;
u8 a, b, d0, d1, d2, d3;
s16 imm16;
unsigned int fault;
/* back up one instruction */
fp->ea -= 4;
if (fixup_exception(fp)) {
return;
}
in_kernel = !user_mode(fp);
isn = *(unsigned long *)(fp->ea);
fault = 0;
/* do fixup if in kernel or mode turned on */
if (in_kernel || (ma_usermode & UM_FIXUP)) {
/* decompose instruction */
a = (isn >> 27) & 0x1f;
b = (isn >> 22) & 0x1f;
imm16 = (isn >> 6) & 0xffff;
addr = get_reg_val(fp, a) + imm16;
/* do fixup to saved registers */
switch (isn & 0x3f) {
case INST_LDHU:
fault |= __get_user(d0, (u8 *)(addr+0));
fault |= __get_user(d1, (u8 *)(addr+1));
val = (d1 << 8) | d0;
put_reg_val(fp, b, val);
break;
case INST_STH:
val = get_reg_val(fp, b);
d1 = val >> 8;
d0 = val >> 0;
if (in_kernel) {
*(u8 *)(addr+0) = d0;
*(u8 *)(addr+1) = d1;
} else {
fault |= __put_user(d0, (u8 *)(addr+0));
fault |= __put_user(d1, (u8 *)(addr+1));
}
break;
case INST_LDH:
fault |= __get_user(d0, (u8 *)(addr+0));
fault |= __get_user(d1, (u8 *)(addr+1));
val = (short)((d1 << 8) | d0);
put_reg_val(fp, b, val);
break;
case INST_STW:
val = get_reg_val(fp, b);
d3 = val >> 24;
d2 = val >> 16;
d1 = val >> 8;
d0 = val >> 0;
if (in_kernel) {
*(u8 *)(addr+0) = d0;
*(u8 *)(addr+1) = d1;
*(u8 *)(addr+2) = d2;
*(u8 *)(addr+3) = d3;
} else {
fault |= __put_user(d0, (u8 *)(addr+0));
fault |= __put_user(d1, (u8 *)(addr+1));
fault |= __put_user(d2, (u8 *)(addr+2));
fault |= __put_user(d3, (u8 *)(addr+3));
}
break;
case INST_LDW:
fault |= __get_user(d0, (u8 *)(addr+0));
fault |= __get_user(d1, (u8 *)(addr+1));
fault |= __get_user(d2, (u8 *)(addr+2));
fault |= __get_user(d3, (u8 *)(addr+3));
val = (d3 << 24) | (d2 << 16) | (d1 << 8) | d0;
put_reg_val(fp, b, val);
break;
}
}
addr = RDCTL(CTL_BADADDR);
cause >>= 2;
if (fault) {
if (in_kernel) {
pr_err("fault during kernel misaligned fixup @ %#lx; addr 0x%08x; isn=0x%08x\n",
fp->ea, (unsigned int)addr,
(unsigned int)isn);
} else {
pr_err("fault during user misaligned fixup @ %#lx; isn=%08x addr=0x%08x sp=0x%08lx pid=%d\n",
fp->ea,
(unsigned int)isn, addr, fp->sp,
current->pid);
_exception(SIGSEGV, fp, SEGV_MAPERR, fp->ea);
return;
}
}
/*
* kernel mode -
* note exception and skip bad instruction (return)
*/
if (in_kernel) {
fp->ea += 4;
if (ma_usermode & KM_WARN) {
pr_err("kernel unaligned access @ %#lx; BADADDR 0x%08x; cause=%d, isn=0x%08x\n",
fp->ea,
(unsigned int)addr, cause,
(unsigned int)isn);
/* show_regs(fp); */
}
return;
}
/*
* user mode -
* possibly warn,
* possibly send SIGBUS signal to process
*/
if (ma_usermode & UM_WARN) {
pr_err("user unaligned access @ %#lx; isn=0x%08lx ea=0x%08lx ra=0x%08lx sp=0x%08lx\n",
(unsigned long)addr, (unsigned long)isn,
fp->ea, fp->ra, fp->sp);
}
if (ma_usermode & UM_SIGNAL)
_exception(SIGBUS, fp, BUS_ADRALN, fp->ea);
else
fp->ea += 4; /* else advance */
}
static void __init misaligned_calc_reg_offsets(void)
{
int i, r, offset;
/* pre-calc offsets of registers on sys call stack frame */
offset = 0;
/* struct pt_regs */
for (i = 0; i < 16; i++) {
r = sys_stack_frame_reg_offset[i];
reg_offsets[r] = offset;
offset += 4;
}
/* struct switch_stack */
offset = -sizeof(struct switch_stack);
for (i = 16; i < 32; i++) {
r = sys_stack_frame_reg_offset[i];
reg_offsets[r] = offset;
offset += 4;
}
}
static int __init misaligned_init(void)
{
/* default mode - silent fix */
ma_usermode = UM_FIXUP | KM_WARN;
misaligned_calc_reg_offsets();
return 0;
}
fs_initcall(misaligned_init);
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