[mirror_ubuntu-artful-kernel.git] / arch / arm / kernel / swp_emulate.c

/*
 *  linux/arch/arm/kernel/swp_emulate.c
 *
 *  Copyright (C) 2009 ARM Limited
 *  __user_* functions adapted from include/asm/uaccess.h
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  Implements emulation of the SWP/SWPB instructions using load-exclusive and
 *  store-exclusive for processors that have them disabled (or future ones that
 *  might not implement them).
 *
 *  Syntax of SWP{B} instruction: SWP{B}<c> <Rt>, <Rt2>, [<Rn>]
 *  Where: Rt  = destination
 *	   Rt2 = source
 *	   Rn  = address
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/syscalls.h>
#include <linux/perf_event.h>

#include <asm/opcodes.h>
#include <asm/system_info.h>
#include <asm/traps.h>
#include <linux/uaccess.h>

/*
 * Error-checking SWP macros implemented using ldrex{b}/strex{b}
 */
#define __user_swpX_asm(data, addr, res, temp, B)		\
	__asm__ __volatile__(					\
	"0:	ldrex"B"	%2, [%3]\n"			\
	"1:	strex"B"	%0, %1, [%3]\n"			\
	"	cmp		%0, #0\n"			\
	"	moveq		%1, %2\n"			\
	"	movne		%0, %4\n"			\
	"2:\n"							\
	"	.section	 .text.fixup,\"ax\"\n"		\
	"	.align		2\n"				\
	"3:	mov		%0, %5\n"			\
	"	b		2b\n"				\
	"	.previous\n"					\
	"	.section	 __ex_table,\"a\"\n"		\
	"	.align		3\n"				\
	"	.long		0b, 3b\n"			\
	"	.long		1b, 3b\n"			\
	"	.previous"					\
	: "=&r" (res), "+r" (data), "=&r" (temp)		\
	: "r" (addr), "i" (-EAGAIN), "i" (-EFAULT)		\
	: "cc", "memory")

#define __user_swp_asm(data, addr, res, temp) \
	__user_swpX_asm(data, addr, res, temp, "")
#define __user_swpb_asm(data, addr, res, temp) \
	__user_swpX_asm(data, addr, res, temp, "b")

/*
 * Macros/defines for extracting register numbers from instruction.
 */
#define EXTRACT_REG_NUM(instruction, offset) \
	(((instruction) & (0xf << (offset))) >> (offset))
#define RN_OFFSET  16
#define RT_OFFSET  12
#define RT2_OFFSET  0
/*
 * Bit 22 of the instruction encoding distinguishes between
 * the SWP and SWPB variants (bit set means SWPB).
 */
#define TYPE_SWPB (1 << 22)

static unsigned long swpcounter;
static unsigned long swpbcounter;
static unsigned long abtcounter;
static pid_t         previous_pid;

#ifdef CONFIG_PROC_FS
static int proc_status_show(struct seq_file *m, void *v)
{
	seq_printf(m, "Emulated SWP:\t\t%lu\n", swpcounter);
	seq_printf(m, "Emulated SWPB:\t\t%lu\n", swpbcounter);
	seq_printf(m, "Aborted SWP{B}:\t\t%lu\n", abtcounter);
	if (previous_pid != 0)
		seq_printf(m, "Last process:\t\t%d\n", previous_pid);
	return 0;
}

static int proc_status_open(struct inode *inode, struct file *file)
{
	return single_open(file, proc_status_show, PDE_DATA(inode));
}

static const struct file_operations proc_status_fops = {
	.open		= proc_status_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};
#endif

/*
 * Set up process info to signal segmentation fault - called on access error.
 */
static void set_segfault(struct pt_regs *regs, unsigned long addr)
{
	siginfo_t info;

	down_read(&current->mm->mmap_sem);
	if (find_vma(current->mm, addr) == NULL)
		info.si_code = SEGV_MAPERR;
	else
		info.si_code = SEGV_ACCERR;
	up_read(&current->mm->mmap_sem);

	info.si_signo = SIGSEGV;
	info.si_errno = 0;
	info.si_addr  = (void *) instruction_pointer(regs);

	pr_debug("SWP{B} emulation: access caused memory abort!\n");
	arm_notify_die("Illegal memory access", regs, &info, 0, 0);

	abtcounter++;
}

static int emulate_swpX(unsigned int address, unsigned int *data,
			unsigned int type)
{
	unsigned int res = 0;

	if ((type != TYPE_SWPB) && (address & 0x3)) {
		/* SWP to unaligned address not permitted */
		pr_debug("SWP instruction on unaligned pointer!\n");
		return -EFAULT;
	}

	while (1) {
		unsigned long temp;
		unsigned int __ua_flags;

		__ua_flags = uaccess_save_and_enable();
		if (type == TYPE_SWPB)
			__user_swpb_asm(*data, address, res, temp);
		else
			__user_swp_asm(*data, address, res, temp);
		uaccess_restore(__ua_flags);

		if (likely(res != -EAGAIN) || signal_pending(current))
			break;

		cond_resched();
	}

	if (res == 0) {
		if (type == TYPE_SWPB)
			swpbcounter++;
		else
			swpcounter++;
	}

	return res;
}

/*
 * swp_handler logs the id of calling process, dissects the instruction, sanity
 * checks the memory location, calls emulate_swpX for the actual operation and
 * deals with fixup/error handling before returning
 */
static int swp_handler(struct pt_regs *regs, unsigned int instr)
{
	unsigned int address, destreg, data, type;
	unsigned int res = 0;

	perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc);

	res = arm_check_condition(instr, regs->ARM_cpsr);
	switch (res) {
	case ARM_OPCODE_CONDTEST_PASS:
		break;
	case ARM_OPCODE_CONDTEST_FAIL:
		/* Condition failed - return to next instruction */
		regs->ARM_pc += 4;
		return 0;
	case ARM_OPCODE_CONDTEST_UNCOND:
		/* If unconditional encoding - not a SWP, undef */
		return -EFAULT;
	default:
		return -EINVAL;
	}

	if (current->pid != previous_pid) {
		pr_debug("\"%s\" (%ld) uses deprecated SWP{B} instruction\n",
			 current->comm, (unsigned long)current->pid);
		previous_pid = current->pid;
	}

	address = regs->uregs[EXTRACT_REG_NUM(instr, RN_OFFSET)];
	data	= regs->uregs[EXTRACT_REG_NUM(instr, RT2_OFFSET)];
	destreg = EXTRACT_REG_NUM(instr, RT_OFFSET);

	type = instr & TYPE_SWPB;

	pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
		 EXTRACT_REG_NUM(instr, RN_OFFSET), address,
		 destreg, EXTRACT_REG_NUM(instr, RT2_OFFSET), data);

	/* Check access in reasonable access range for both SWP and SWPB */
	if (!access_ok(VERIFY_WRITE, (address & ~3), 4)) {
		pr_debug("SWP{B} emulation: access to %p not allowed!\n",
			 (void *)address);
		res = -EFAULT;
	} else {
		res = emulate_swpX(address, &data, type);
	}

	if (res == 0) {
		/*
		 * On successful emulation, revert the adjustment to the PC
		 * made in kernel/traps.c in order to resume execution at the
		 * instruction following the SWP{B}.
		 */
		regs->ARM_pc += 4;
		regs->uregs[destreg] = data;
	} else if (res == -EFAULT) {
		/*
		 * Memory errors do not mean emulation failed.
		 * Set up signal info to return SEGV, then return OK
		 */
		set_segfault(regs, address);
	}

	return 0;
}

/*
 * Only emulate SWP/SWPB executed in ARM state/User mode.
 * The kernel must be SWP free and SWP{B} does not exist in Thumb/ThumbEE.
 */
static struct undef_hook swp_hook = {
	.instr_mask = 0x0fb00ff0,
	.instr_val  = 0x01000090,
	.cpsr_mask  = MODE_MASK | PSR_T_BIT | PSR_J_BIT,
	.cpsr_val   = USR_MODE,
	.fn	    = swp_handler
};

/*
 * Register handler and create status file in /proc/cpu
 * Invoked as late_initcall, since not needed before init spawned.
 */
static int __init swp_emulation_init(void)
{
	if (cpu_architecture() < CPU_ARCH_ARMv7)
		return 0;

#ifdef CONFIG_PROC_FS
	if (!proc_create("cpu/swp_emulation", S_IRUGO, NULL, &proc_status_fops))
		return -ENOMEM;
#endif /* CONFIG_PROC_FS */

	pr_notice("Registering SWP/SWPB emulation handler\n");
	register_undef_hook(&swp_hook);

	return 0;
}

late_initcall(swp_emulation_init);
Commit	Line	Data
64d2dc38 LL	1	/*
	2	* linux/arch/arm/kernel/swp_emulate.c
	3	*
	4	* Copyright (C) 2009 ARM Limited
	5	* __user_* functions adapted from include/asm/uaccess.h
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License version 2 as
	9	* published by the Free Software Foundation.
	10	*
	11	* Implements emulation of the SWP/SWPB instructions using load-exclusive and
	12	* store-exclusive for processors that have them disabled (or future ones that
	13	* might not implement them).
	14	*
	15	* Syntax of SWP{B} instruction: SWP{B}<c> <Rt>, <Rt2>, [<Rn>]
	16	* Where: Rt = destination
	17	* Rt2 = source
	18	* Rn = address
	19	*/
	20
	21	#include <linux/init.h>
	22	#include <linux/kernel.h>
	23	#include <linux/proc_fs.h>
526c5978	24	#include <linux/seq_file.h>
64d2dc38	25	#include <linux/sched.h>
589ee628	26	#include <linux/sched/mm.h>
64d2dc38 LL	27	#include <linux/syscalls.h>
	28	#include <linux/perf_event.h>
	29
c245dcd3	30	#include <asm/opcodes.h>
7397aa48	31	#include <asm/system_info.h>
64d2dc38	32	#include <asm/traps.h>
7c0f6ba6	33	#include <linux/uaccess.h>
64d2dc38 LL	34
	35	/*
	36	* Error-checking SWP macros implemented using ldrex{b}/strex{b}
	37	*/
	38	#define __user_swpX_asm(data, addr, res, temp, B) \
	39	__asm__ __volatile__( \
34bfbae3 SW	40	"0: ldrex"B" %2, [%3]\n" \
34bfbae3 SW	41	"1: strex"B" %0, %1, [%3]\n" \
64d2dc38	42	" cmp %0, #0\n" \
34bfbae3	43	" moveq %1, %2\n" \
64d2dc38 LL	44	" movne %0, %4\n" \
64d2dc38 LL	45	"2:\n" \
c4a84ae3	46	" .section .text.fixup,\"ax\"\n" \
64d2dc38 LL	47	" .align 2\n" \
	48	"3: mov %0, %5\n" \
	49	" b 2b\n" \
	50	" .previous\n" \
	51	" .section __ex_table,\"a\"\n" \
	52	" .align 3\n" \
	53	" .long 0b, 3b\n" \
	54	" .long 1b, 3b\n" \
	55	" .previous" \
	56	: "=&r" (res), "+r" (data), "=&r" (temp) \
	57	: "r" (addr), "i" (-EAGAIN), "i" (-EFAULT) \
	58	: "cc", "memory")
	59
	60	#define __user_swp_asm(data, addr, res, temp) \
	61	__user_swpX_asm(data, addr, res, temp, "")
	62	#define __user_swpb_asm(data, addr, res, temp) \
	63	__user_swpX_asm(data, addr, res, temp, "b")
	64
	65	/*
	66	* Macros/defines for extracting register numbers from instruction.
	67	*/
	68	#define EXTRACT_REG_NUM(instruction, offset) \
	69	(((instruction) & (0xf << (offset))) >> (offset))
	70	#define RN_OFFSET 16
	71	#define RT_OFFSET 12
	72	#define RT2_OFFSET 0
	73	/*
	74	* Bit 22 of the instruction encoding distinguishes between
	75	* the SWP and SWPB variants (bit set means SWPB).
	76	*/
	77	#define TYPE_SWPB (1 << 22)
	78
	79	static unsigned long swpcounter;
	80	static unsigned long swpbcounter;
	81	static unsigned long abtcounter;
	82	static pid_t previous_pid;
	83
	84	#ifdef CONFIG_PROC_FS
526c5978	85	static int proc_status_show(struct seq_file m, void v)
64d2dc38	86	{
526c5978 DH	87	seq_printf(m, "Emulated SWP:\t\t%lu\n", swpcounter);
	88	seq_printf(m, "Emulated SWPB:\t\t%lu\n", swpbcounter);
	89	seq_printf(m, "Aborted SWP{B}:\t\t%lu\n", abtcounter);
64d2dc38	90	if (previous_pid != 0)
526c5978 DH	91	seq_printf(m, "Last process:\t\t%d\n", previous_pid);
	92	return 0;
	93	}
64d2dc38	94
526c5978 DH	95	static int proc_status_open(struct inode inode, struct file file)
	96	{
	97	return single_open(file, proc_status_show, PDE_DATA(inode));
64d2dc38	98	}
526c5978 DH	99
	100	static const struct file_operations proc_status_fops = {
	101	.open = proc_status_open,
	102	.read = seq_read,
	103	.llseek = seq_lseek,
b11ac20e	104	.release = single_release,
526c5978	105	};
64d2dc38 LL	106	#endif
	107
	108	/*
	109	* Set up process info to signal segmentation fault - called on access error.
	110	*/
	111	static void set_segfault(struct pt_regs *regs, unsigned long addr)
	112	{
	113	siginfo_t info;
	114
7bf9b7be	115	down_read(&current->mm->mmap_sem);
64d2dc38 LL	116	if (find_vma(current->mm, addr) == NULL)
	117	info.si_code = SEGV_MAPERR;
	118	else
	119	info.si_code = SEGV_ACCERR;
7bf9b7be	120	up_read(&current->mm->mmap_sem);
64d2dc38 LL	121
	122	info.si_signo = SIGSEGV;
	123	info.si_errno = 0;
	124	info.si_addr = (void *) instruction_pointer(regs);
	125
	126	pr_debug("SWP{B} emulation: access caused memory abort!\n");
	127	arm_notify_die("Illegal memory access", regs, &info, 0, 0);
	128
	129	abtcounter++;
	130	}
	131
	132	static int emulate_swpX(unsigned int address, unsigned int *data,
	133	unsigned int type)
	134	{
	135	unsigned int res = 0;
	136
	137	if ((type != TYPE_SWPB) && (address & 0x3)) {
	138	/* SWP to unaligned address not permitted */
	139	pr_debug("SWP instruction on unaligned pointer!\n");
	140	return -EFAULT;
	141	}
	142
	143	while (1) {
	144	unsigned long temp;
a5e090ac	145	unsigned int __ua_flags;
64d2dc38	146
a5e090ac	147	__ua_flags = uaccess_save_and_enable();
64d2dc38 LL	148	if (type == TYPE_SWPB)
	149	__user_swpb_asm(*data, address, res, temp);
	150	else
	151	__user_swp_asm(*data, address, res, temp);
a5e090ac	152	uaccess_restore(__ua_flags);
64d2dc38 LL	153
	154	if (likely(res != -EAGAIN) \|\| signal_pending(current))
	155	break;
	156
	157	cond_resched();
	158	}
	159
	160	if (res == 0) {
64d2dc38 LL	161	if (type == TYPE_SWPB)
	162	swpbcounter++;
	163	else
	164	swpcounter++;
	165	}
	166
	167	return res;
	168	}
	169
	170	/*
	171	* swp_handler logs the id of calling process, dissects the instruction, sanity
	172	* checks the memory location, calls emulate_swpX for the actual operation and
	173	* deals with fixup/error handling before returning
	174	*/
	175	static int swp_handler(struct pt_regs *regs, unsigned int instr)
	176	{
	177	unsigned int address, destreg, data, type;
	178	unsigned int res = 0;
	179
a8b0ca17	180	perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc);
64d2dc38	181
c245dcd3 LL	182	res = arm_check_condition(instr, regs->ARM_cpsr);
	183	switch (res) {
	184	case ARM_OPCODE_CONDTEST_PASS:
	185	break;
	186	case ARM_OPCODE_CONDTEST_FAIL:
	187	/* Condition failed - return to next instruction */
	188	regs->ARM_pc += 4;
	189	return 0;
	190	case ARM_OPCODE_CONDTEST_UNCOND:
	191	/* If unconditional encoding - not a SWP, undef */
	192	return -EFAULT;
	193	default:
	194	return -EINVAL;
	195	}
	196
64d2dc38 LL	197	if (current->pid != previous_pid) {
	198	pr_debug("\"%s\" (%ld) uses deprecated SWP{B} instruction\n",
	199	current->comm, (unsigned long)current->pid);
	200	previous_pid = current->pid;
	201	}
	202
	203	address = regs->uregs[EXTRACT_REG_NUM(instr, RN_OFFSET)];
	204	data = regs->uregs[EXTRACT_REG_NUM(instr, RT2_OFFSET)];
	205	destreg = EXTRACT_REG_NUM(instr, RT_OFFSET);
	206
	207	type = instr & TYPE_SWPB;
	208
	209	pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
	210	EXTRACT_REG_NUM(instr, RN_OFFSET), address,
	211	destreg, EXTRACT_REG_NUM(instr, RT2_OFFSET), data);
	212
	213	/* Check access in reasonable access range for both SWP and SWPB */
	214	if (!access_ok(VERIFY_WRITE, (address & ~3), 4)) {
	215	pr_debug("SWP{B} emulation: access to %p not allowed!\n",
	216	(void *)address);
	217	res = -EFAULT;
	218	} else {
	219	res = emulate_swpX(address, &data, type);
	220	}
	221
	222	if (res == 0) {
	223	/*
	224	* On successful emulation, revert the adjustment to the PC
	225	* made in kernel/traps.c in order to resume execution at the
	226	* instruction following the SWP{B}.
	227	*/
	228	regs->ARM_pc += 4;
	229	regs->uregs[destreg] = data;
	230	} else if (res == -EFAULT) {
	231	/*
	232	* Memory errors do not mean emulation failed.
	233	* Set up signal info to return SEGV, then return OK
	234	*/
	235	set_segfault(regs, address);
	236	}
	237
	238	return 0;
	239	}
	240
	241	/*
	242	* Only emulate SWP/SWPB executed in ARM state/User mode.
	243	* The kernel must be SWP free and SWP{B} does not exist in Thumb/ThumbEE.
	244	*/
	245	static struct undef_hook swp_hook = {
	246	.instr_mask = 0x0fb00ff0,
	247	.instr_val = 0x01000090,
	248	.cpsr_mask = MODE_MASK \| PSR_T_BIT \| PSR_J_BIT,
	249	.cpsr_val = USR_MODE,
	250	.fn = swp_handler
	251	};
	252
	253	/*
	254	* Register handler and create status file in /proc/cpu
	255	* Invoked as late_initcall, since not needed before init spawned.
	256	*/
	257	static int __init swp_emulation_init(void)
	258	{
7397aa48 RK	259	if (cpu_architecture() < CPU_ARCH_ARMv7)
	260	return 0;
	261
64d2dc38	262	#ifdef CONFIG_PROC_FS
526c5978	263	if (!proc_create("cpu/swp_emulation", S_IRUGO, NULL, &proc_status_fops))
64d2dc38	264	return -ENOMEM;
64d2dc38 LL	265	#endif /* CONFIG_PROC_FS */
64d2dc38 LL	266
4ed89f22	267	pr_notice("Registering SWP/SWPB emulation handler\n");
64d2dc38 LL	268	register_undef_hook(&swp_hook);
	269
	270	return 0;
	271	}
	272
	273	late_initcall(swp_emulation_init);