2 * linux/arch/arm/kernel/swp_emulate.c
4 * Copyright (C) 2009 ARM Limited
5 * __user_* functions adapted from include/asm/uaccess.h
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.
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).
15 * Syntax of SWP{B} instruction: SWP{B}<c> <Rt>, <Rt2>, [<Rn>]
16 * Where: Rt = destination
21 #include <linux/init.h>
22 #include <linux/kernel.h>
23 #include <linux/proc_fs.h>
24 #include <linux/seq_file.h>
25 #include <linux/sched.h>
26 #include <linux/syscalls.h>
27 #include <linux/perf_event.h>
29 #include <asm/opcodes.h>
30 #include <asm/system_info.h>
31 #include <asm/traps.h>
32 #include <asm/uaccess.h>
35 * Error-checking SWP macros implemented using ldrex{b}/strex{b}
37 #define __user_swpX_asm(data, addr, res, temp, B) \
38 __asm__ __volatile__( \
40 "0: ldrex"B" %1, [%3]\n" \
41 "1: strex"B" %0, %2, [%3]\n" \
45 " .section .fixup,\"ax\"\n" \
50 " .section __ex_table,\"a\"\n" \
55 : "=&r" (res), "+r" (data), "=&r" (temp) \
56 : "r" (addr), "i" (-EAGAIN), "i" (-EFAULT) \
59 #define __user_swp_asm(data, addr, res, temp) \
60 __user_swpX_asm(data, addr, res, temp, "")
61 #define __user_swpb_asm(data, addr, res, temp) \
62 __user_swpX_asm(data, addr, res, temp, "b")
65 * Macros/defines for extracting register numbers from instruction.
67 #define EXTRACT_REG_NUM(instruction, offset) \
68 (((instruction) & (0xf << (offset))) >> (offset))
73 * Bit 22 of the instruction encoding distinguishes between
74 * the SWP and SWPB variants (bit set means SWPB).
76 #define TYPE_SWPB (1 << 22)
78 static unsigned long swpcounter
;
79 static unsigned long swpbcounter
;
80 static unsigned long abtcounter
;
81 static pid_t previous_pid
;
84 static int proc_status_show(struct seq_file
*m
, void *v
)
86 seq_printf(m
, "Emulated SWP:\t\t%lu\n", swpcounter
);
87 seq_printf(m
, "Emulated SWPB:\t\t%lu\n", swpbcounter
);
88 seq_printf(m
, "Aborted SWP{B}:\t\t%lu\n", abtcounter
);
89 if (previous_pid
!= 0)
90 seq_printf(m
, "Last process:\t\t%d\n", previous_pid
);
94 static int proc_status_open(struct inode
*inode
, struct file
*file
)
96 return single_open(file
, proc_status_show
, PDE_DATA(inode
));
99 static const struct file_operations proc_status_fops
= {
100 .open
= proc_status_open
,
103 .release
= single_release
,
108 * Set up process info to signal segmentation fault - called on access error.
110 static void set_segfault(struct pt_regs
*regs
, unsigned long addr
)
114 down_read(¤t
->mm
->mmap_sem
);
115 if (find_vma(current
->mm
, addr
) == NULL
)
116 info
.si_code
= SEGV_MAPERR
;
118 info
.si_code
= SEGV_ACCERR
;
119 up_read(¤t
->mm
->mmap_sem
);
121 info
.si_signo
= SIGSEGV
;
123 info
.si_addr
= (void *) instruction_pointer(regs
);
125 pr_debug("SWP{B} emulation: access caused memory abort!\n");
126 arm_notify_die("Illegal memory access", regs
, &info
, 0, 0);
131 static int emulate_swpX(unsigned int address
, unsigned int *data
,
134 unsigned int res
= 0;
136 if ((type
!= TYPE_SWPB
) && (address
& 0x3)) {
137 /* SWP to unaligned address not permitted */
138 pr_debug("SWP instruction on unaligned pointer!\n");
145 if (type
== TYPE_SWPB
)
146 __user_swpb_asm(*data
, address
, res
, temp
);
148 __user_swp_asm(*data
, address
, res
, temp
);
150 if (likely(res
!= -EAGAIN
) || signal_pending(current
))
157 if (type
== TYPE_SWPB
)
167 * swp_handler logs the id of calling process, dissects the instruction, sanity
168 * checks the memory location, calls emulate_swpX for the actual operation and
169 * deals with fixup/error handling before returning
171 static int swp_handler(struct pt_regs
*regs
, unsigned int instr
)
173 unsigned int address
, destreg
, data
, type
;
174 unsigned int res
= 0;
176 perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS
, 1, regs
, regs
->ARM_pc
);
178 res
= arm_check_condition(instr
, regs
->ARM_cpsr
);
180 case ARM_OPCODE_CONDTEST_PASS
:
182 case ARM_OPCODE_CONDTEST_FAIL
:
183 /* Condition failed - return to next instruction */
186 case ARM_OPCODE_CONDTEST_UNCOND
:
187 /* If unconditional encoding - not a SWP, undef */
193 if (current
->pid
!= previous_pid
) {
194 pr_debug("\"%s\" (%ld) uses deprecated SWP{B} instruction\n",
195 current
->comm
, (unsigned long)current
->pid
);
196 previous_pid
= current
->pid
;
199 address
= regs
->uregs
[EXTRACT_REG_NUM(instr
, RN_OFFSET
)];
200 data
= regs
->uregs
[EXTRACT_REG_NUM(instr
, RT2_OFFSET
)];
201 destreg
= EXTRACT_REG_NUM(instr
, RT_OFFSET
);
203 type
= instr
& TYPE_SWPB
;
205 pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
206 EXTRACT_REG_NUM(instr
, RN_OFFSET
), address
,
207 destreg
, EXTRACT_REG_NUM(instr
, RT2_OFFSET
), data
);
209 /* Check access in reasonable access range for both SWP and SWPB */
210 if (!access_ok(VERIFY_WRITE
, (address
& ~3), 4)) {
211 pr_debug("SWP{B} emulation: access to %p not allowed!\n",
215 res
= emulate_swpX(address
, &data
, type
);
220 * On successful emulation, revert the adjustment to the PC
221 * made in kernel/traps.c in order to resume execution at the
222 * instruction following the SWP{B}.
225 regs
->uregs
[destreg
] = data
;
226 } else if (res
== -EFAULT
) {
228 * Memory errors do not mean emulation failed.
229 * Set up signal info to return SEGV, then return OK
231 set_segfault(regs
, address
);
238 * Only emulate SWP/SWPB executed in ARM state/User mode.
239 * The kernel must be SWP free and SWP{B} does not exist in Thumb/ThumbEE.
241 static struct undef_hook swp_hook
= {
242 .instr_mask
= 0x0fb00ff0,
243 .instr_val
= 0x01000090,
244 .cpsr_mask
= MODE_MASK
| PSR_T_BIT
| PSR_J_BIT
,
245 .cpsr_val
= USR_MODE
,
250 * Register handler and create status file in /proc/cpu
251 * Invoked as late_initcall, since not needed before init spawned.
253 static int __init
swp_emulation_init(void)
255 if (cpu_architecture() < CPU_ARCH_ARMv7
)
258 #ifdef CONFIG_PROC_FS
259 if (!proc_create("cpu/swp_emulation", S_IRUGO
, NULL
, &proc_status_fops
))
261 #endif /* CONFIG_PROC_FS */
263 pr_notice("Registering SWP/SWPB emulation handler\n");
264 register_undef_hook(&swp_hook
);
269 late_initcall(swp_emulation_init
);