Add linux-next specific files for 20110831
[linux-2.6/next.git] / arch / arm / kernel / swp_emulate.c
blob5f452f8fde0569d140e0d6055220f29be08396f1
1 /*
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
17 * Rt2 = source
18 * Rn = address
21 #include <linux/init.h>
22 #include <linux/kernel.h>
23 #include <linux/proc_fs.h>
24 #include <linux/sched.h>
25 #include <linux/syscalls.h>
26 #include <linux/perf_event.h>
28 #include <asm/traps.h>
29 #include <asm/uaccess.h>
32 * Error-checking SWP macros implemented using ldrex{b}/strex{b}
34 #define __user_swpX_asm(data, addr, res, temp, B) \
35 __asm__ __volatile__( \
36 " mov %2, %1\n" \
37 "0: ldrex"B" %1, [%3]\n" \
38 "1: strex"B" %0, %2, [%3]\n" \
39 " cmp %0, #0\n" \
40 " movne %0, %4\n" \
41 "2:\n" \
42 " .section .fixup,\"ax\"\n" \
43 " .align 2\n" \
44 "3: mov %0, %5\n" \
45 " b 2b\n" \
46 " .previous\n" \
47 " .section __ex_table,\"a\"\n" \
48 " .align 3\n" \
49 " .long 0b, 3b\n" \
50 " .long 1b, 3b\n" \
51 " .previous" \
52 : "=&r" (res), "+r" (data), "=&r" (temp) \
53 : "r" (addr), "i" (-EAGAIN), "i" (-EFAULT) \
54 : "cc", "memory")
56 #define __user_swp_asm(data, addr, res, temp) \
57 __user_swpX_asm(data, addr, res, temp, "")
58 #define __user_swpb_asm(data, addr, res, temp) \
59 __user_swpX_asm(data, addr, res, temp, "b")
62 * Macros/defines for extracting register numbers from instruction.
64 #define EXTRACT_REG_NUM(instruction, offset) \
65 (((instruction) & (0xf << (offset))) >> (offset))
66 #define RN_OFFSET 16
67 #define RT_OFFSET 12
68 #define RT2_OFFSET 0
70 * Bit 22 of the instruction encoding distinguishes between
71 * the SWP and SWPB variants (bit set means SWPB).
73 #define TYPE_SWPB (1 << 22)
75 static unsigned long swpcounter;
76 static unsigned long swpbcounter;
77 static unsigned long abtcounter;
78 static pid_t previous_pid;
80 #ifdef CONFIG_PROC_FS
81 static int proc_read_status(char *page, char **start, off_t off, int count,
82 int *eof, void *data)
84 char *p = page;
85 int len;
87 p += sprintf(p, "Emulated SWP:\t\t%lu\n", swpcounter);
88 p += sprintf(p, "Emulated SWPB:\t\t%lu\n", swpbcounter);
89 p += sprintf(p, "Aborted SWP{B}:\t\t%lu\n", abtcounter);
90 if (previous_pid != 0)
91 p += sprintf(p, "Last process:\t\t%d\n", previous_pid);
93 len = (p - page) - off;
94 if (len < 0)
95 len = 0;
97 *eof = (len <= count) ? 1 : 0;
98 *start = page + off;
100 return len;
102 #endif
105 * Set up process info to signal segmentation fault - called on access error.
107 static void set_segfault(struct pt_regs *regs, unsigned long addr)
109 siginfo_t info;
111 if (find_vma(current->mm, addr) == NULL)
112 info.si_code = SEGV_MAPERR;
113 else
114 info.si_code = SEGV_ACCERR;
116 info.si_signo = SIGSEGV;
117 info.si_errno = 0;
118 info.si_addr = (void *) instruction_pointer(regs);
120 pr_debug("SWP{B} emulation: access caused memory abort!\n");
121 arm_notify_die("Illegal memory access", regs, &info, 0, 0);
123 abtcounter++;
126 static int emulate_swpX(unsigned int address, unsigned int *data,
127 unsigned int type)
129 unsigned int res = 0;
131 if ((type != TYPE_SWPB) && (address & 0x3)) {
132 /* SWP to unaligned address not permitted */
133 pr_debug("SWP instruction on unaligned pointer!\n");
134 return -EFAULT;
137 while (1) {
138 unsigned long temp;
141 * Barrier required between accessing protected resource and
142 * releasing a lock for it. Legacy code might not have done
143 * this, and we cannot determine that this is not the case
144 * being emulated, so insert always.
146 smp_mb();
148 if (type == TYPE_SWPB)
149 __user_swpb_asm(*data, address, res, temp);
150 else
151 __user_swp_asm(*data, address, res, temp);
153 if (likely(res != -EAGAIN) || signal_pending(current))
154 break;
156 cond_resched();
159 if (res == 0) {
161 * Barrier also required between acquiring a lock for a
162 * protected resource and accessing the resource. Inserted for
163 * same reason as above.
165 smp_mb();
167 if (type == TYPE_SWPB)
168 swpbcounter++;
169 else
170 swpcounter++;
173 return res;
177 * swp_handler logs the id of calling process, dissects the instruction, sanity
178 * checks the memory location, calls emulate_swpX for the actual operation and
179 * deals with fixup/error handling before returning
181 static int swp_handler(struct pt_regs *regs, unsigned int instr)
183 unsigned int address, destreg, data, type;
184 unsigned int res = 0;
186 perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc);
188 if (current->pid != previous_pid) {
189 pr_debug("\"%s\" (%ld) uses deprecated SWP{B} instruction\n",
190 current->comm, (unsigned long)current->pid);
191 previous_pid = current->pid;
194 address = regs->uregs[EXTRACT_REG_NUM(instr, RN_OFFSET)];
195 data = regs->uregs[EXTRACT_REG_NUM(instr, RT2_OFFSET)];
196 destreg = EXTRACT_REG_NUM(instr, RT_OFFSET);
198 type = instr & TYPE_SWPB;
200 pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
201 EXTRACT_REG_NUM(instr, RN_OFFSET), address,
202 destreg, EXTRACT_REG_NUM(instr, RT2_OFFSET), data);
204 /* Check access in reasonable access range for both SWP and SWPB */
205 if (!access_ok(VERIFY_WRITE, (address & ~3), 4)) {
206 pr_debug("SWP{B} emulation: access to %p not allowed!\n",
207 (void *)address);
208 res = -EFAULT;
209 } else {
210 res = emulate_swpX(address, &data, type);
213 if (res == 0) {
215 * On successful emulation, revert the adjustment to the PC
216 * made in kernel/traps.c in order to resume execution at the
217 * instruction following the SWP{B}.
219 regs->ARM_pc += 4;
220 regs->uregs[destreg] = data;
221 } else if (res == -EFAULT) {
223 * Memory errors do not mean emulation failed.
224 * Set up signal info to return SEGV, then return OK
226 set_segfault(regs, address);
229 return 0;
233 * Only emulate SWP/SWPB executed in ARM state/User mode.
234 * The kernel must be SWP free and SWP{B} does not exist in Thumb/ThumbEE.
236 static struct undef_hook swp_hook = {
237 .instr_mask = 0x0fb00ff0,
238 .instr_val = 0x01000090,
239 .cpsr_mask = MODE_MASK | PSR_T_BIT | PSR_J_BIT,
240 .cpsr_val = USR_MODE,
241 .fn = swp_handler
245 * Register handler and create status file in /proc/cpu
246 * Invoked as late_initcall, since not needed before init spawned.
248 static int __init swp_emulation_init(void)
250 #ifdef CONFIG_PROC_FS
251 struct proc_dir_entry *res;
253 res = create_proc_entry("cpu/swp_emulation", S_IRUGO, NULL);
255 if (!res)
256 return -ENOMEM;
258 res->read_proc = proc_read_status;
259 #endif /* CONFIG_PROC_FS */
261 printk(KERN_NOTICE "Registering SWP/SWPB emulation handler\n");
262 register_undef_hook(&swp_hook);
264 return 0;
267 late_initcall(swp_emulation_init);