// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/arch/arm/mm/alignment.c
*
* Copyright (C) 1995 Linus Torvalds
* Modifications for ARM processor (c) 1995-2001 Russell King
* Thumb alignment fault fixups (c) 2004 MontaVista Software, Inc.
* - Adapted from gdb/sim/arm/thumbemu.c -- Thumb instruction emulation.
* Copyright (C) 1996, Cygnus Software Technologies Ltd.
*/
#include <linux/moduleparam.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/sched/debug.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <asm/cp15.h>
#include <asm/system_info.h>
#include <asm/unaligned.h>
#include <asm/opcodes.h>
#include "fault.h"
#include "mm.h"
/*
* 32-bit misaligned trap handler (c) 1998 San Mehat (CCC) -July 1998
* /proc/sys/debug/alignment, modified and integrated into
* Linux 2.1 by Russell King
*
* Speed optimisations and better fault handling by Russell King.
*
* *** NOTE ***
* This code is not portable to processors with late data abort handling.
*/
#define CODING_BITS(i) (i & 0x0e000000)
#define COND_BITS(i) (i & 0xf0000000)
#define LDST_I_BIT(i) (i & (1 << 26)) /* Immediate constant */
#define LDST_P_BIT(i) (i & (1 << 24)) /* Preindex */
#define LDST_U_BIT(i) (i & (1 << 23)) /* Add offset */
#define LDST_W_BIT(i) (i & (1 << 21)) /* Writeback */
#define LDST_L_BIT(i) (i & (1 << 20)) /* Load */
#define LDST_P_EQ_U(i) ((((i) ^ ((i) >> 1)) & (1 << 23)) == 0)
#define LDSTHD_I_BIT(i) (i & (1 << 22)) /* double/half-word immed */
#define LDM_S_BIT(i) (i & (1 << 22)) /* write CPSR from SPSR */
#define RN_BITS(i) ((i >> 16) & 15) /* Rn */
#define RD_BITS(i) ((i >> 12) & 15) /* Rd */
#define RM_BITS(i) (i & 15) /* Rm */
#define REGMASK_BITS(i) (i & 0xffff)
#define OFFSET_BITS(i) (i & 0x0fff)
#define IS_SHIFT(i) (i & 0x0ff0)
#define SHIFT_BITS(i) ((i >> 7) & 0x1f)
#define SHIFT_TYPE(i) (i & 0x60)
#define SHIFT_LSL 0x00
#define SHIFT_LSR 0x20
#define SHIFT_ASR 0x40
#define SHIFT_RORRRX 0x60
#define BAD_INSTR 0xdeadc0de
/* Thumb-2 32 bit format per ARMv7 DDI0406A A6.3, either f800h,e800h,f800h */
#define IS_T32(hi16) \
(((hi16) & 0xe000) == 0xe000 && ((hi16) & 0x1800))
static unsigned long ai_user;
static unsigned long ai_sys;
static void *ai_sys_last_pc;
static unsigned long ai_skipped;
static unsigned long ai_half;
static unsigned long ai_word;
static unsigned long ai_dword;
static unsigned long ai_multi;
static int ai_usermode;
static unsigned long cr_no_alignment;
core_param(alignment, ai_usermode, int, 0600);
#define UM_WARN (1 << 0)
#define UM_FIXUP (1 << 1)
#define UM_SIGNAL (1 << 2)
/* Return true if and only if the ARMv6 unaligned access model is in use. */
static bool cpu_is_v6_unaligned(void)
{
return cpu_architecture() >= CPU_ARCH_ARMv6 && get_cr() & CR_U;
}
static int safe_usermode(int new_usermode, bool warn)
{
/*
* ARMv6 and later CPUs can perform unaligned accesses for
* most single load and store instructions up to word size.
* LDM, STM, LDRD and STRD still need to be handled.
*
* Ignoring the alignment fault is not an option on these
* CPUs since we spin re-faulting the instruction without
* making any progress.
*/
if (cpu_is_v6_unaligned() && !(new_usermode & (UM_FIXUP | UM_SIGNAL))) {
new_usermode |= UM_FIXUP;
if (warn)
pr_warn("alignment: ignoring faults is unsafe on this CPU. Defaulting to fixup mode.\n");
}
return new_usermode;
}
#ifdef CONFIG_PROC_FS
static const char *usermode_action[] = {
"ignored",
"warn",
"fixup",
"fixup+warn",
"signal",
"signal+warn"
};
static int alignment_proc_show(struct seq_file *m, void *v)
{
seq_printf(m, "User:\t\t%lu\n", ai_user);
seq_printf(m, "System:\t\t%lu (%pS)\n", ai_sys, ai_sys_last_pc);
seq_printf(m, "Skipped:\t%lu\n", ai_skipped);
seq_printf(m, "Half:\t\t%lu\n", ai_half);
seq_printf(m, "Word:\t\t%lu\n", ai_word);
if (cpu_architecture() >= CPU_ARCH_ARMv5TE)
seq_printf(m, "DWord:\t\t%lu\n", ai_dword);
seq_printf(m, "Multi:\t\t%lu\n", ai_multi);
seq_printf(m, "User faults:\t%i (%s)\n", ai_usermode,
usermode_action[ai_usermode]);
return 0;
}
static int alignment_proc_open(struct inode *inode, struct file *file)
{
return single_open(file, alignment_proc_show, NULL);
}
static ssize_t alignment_proc_write(struct file *file, const char __user *buffer,
size_t count, loff_t *pos)
{
char mode;
if (count > 0) {
if (get_user(mode, buffer))
return -EFAULT;
if (mode >= '0' && mode <= '5')
ai_usermode = safe_usermode(mode - '0', true);
}
return count;
}
static const struct file_operations alignment_proc_fops = {
.open