ARM: Build fix after Tegra14 K3.4 merge
[linux-3.10.git] / arch / arm / kernel / swp_emulate.c
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>
24 #include <linux/seq_file.h>
25 #include <linux/sched.h>
26 #include <linux/syscalls.h>
27 #include <linux/perf_event.h>
28
29 #include <asm/opcodes.h>
30 #include <asm/traps.h>
31 #include <asm/uaccess.h>
32
33 /*
34  * Error-checking SWP macros implemented using ldrex{b}/strex{b}
35  */
36 #define __user_swpX_asm(data, addr, res, temp, B)               \
37         __asm__ __volatile__(                                   \
38         "       mov             %2, %1\n"                       \
39         "0:     ldrex"B"        %1, [%3]\n"                     \
40         "1:     strex"B"        %0, %2, [%3]\n"                 \
41         "       cmp             %0, #0\n"                       \
42         "       movne           %0, %4\n"                       \
43         "2:\n"                                                  \
44         "       .section         .fixup,\"ax\"\n"               \
45         "       .align          2\n"                            \
46         "3:     mov             %0, %5\n"                       \
47         "       b               2b\n"                           \
48         "       .previous\n"                                    \
49         "       .section         __ex_table,\"a\"\n"            \
50         "       .align          3\n"                            \
51         "       .long           0b, 3b\n"                       \
52         "       .long           1b, 3b\n"                       \
53         "       .previous"                                      \
54         : "=&r" (res), "+r" (data), "=&r" (temp)                \
55         : "r" (addr), "i" (-EAGAIN), "i" (-EFAULT)              \
56         : "cc", "memory")
57
58 #define __user_swp_asm(data, addr, res, temp) \
59         __user_swpX_asm(data, addr, res, temp, "")
60 #define __user_swpb_asm(data, addr, res, temp) \
61         __user_swpX_asm(data, addr, res, temp, "b")
62
63 /*
64  * Macros/defines for extracting register numbers from instruction.
65  */
66 #define EXTRACT_REG_NUM(instruction, offset) \
67         (((instruction) & (0xf << (offset))) >> (offset))
68 #define RN_OFFSET  16
69 #define RT_OFFSET  12
70 #define RT2_OFFSET  0
71 /*
72  * Bit 22 of the instruction encoding distinguishes between
73  * the SWP and SWPB variants (bit set means SWPB).
74  */
75 #define TYPE_SWPB (1 << 22)
76
77 static unsigned long swpcounter;
78 static unsigned long swpbcounter;
79 static unsigned long abtcounter;
80 static pid_t         previous_pid;
81
82 #ifdef CONFIG_PROC_FS
83 static int proc_status_show(struct seq_file *m, void *v)
84 {
85         seq_printf(m, "Emulated SWP:\t\t%lu\n", swpcounter);
86         seq_printf(m, "Emulated SWPB:\t\t%lu\n", swpbcounter);
87         seq_printf(m, "Aborted SWP{B}:\t\t%lu\n", abtcounter);
88         if (previous_pid != 0)
89                 seq_printf(m, "Last process:\t\t%d\n", previous_pid);
90         return 0;
91 }
92
93 static int proc_status_open(struct inode *inode, struct file *file)
94 {
95         return single_open(file, proc_status_show, PDE_DATA(inode));
96 }
97
98 static const struct file_operations proc_status_fops = {
99         .open           = proc_status_open,
100         .read           = seq_read,
101         .llseek         = seq_lseek,
102         .release        = single_release,
103 };
104 #endif
105
106 /*
107  * Set up process info to signal segmentation fault - called on access error.
108  */
109 static void set_segfault(struct pt_regs *regs, unsigned long addr)
110 {
111         siginfo_t info;
112
113         down_read(&current->mm->mmap_sem);
114         if (find_vma(current->mm, addr) == NULL)
115                 info.si_code = SEGV_MAPERR;
116         else
117                 info.si_code = SEGV_ACCERR;
118         up_read(&current->mm->mmap_sem);
119
120         info.si_signo = SIGSEGV;
121         info.si_errno = 0;
122         info.si_addr  = (void *) instruction_pointer(regs);
123
124         pr_debug("SWP{B} emulation: access caused memory abort!\n");
125         arm_notify_die("Illegal memory access", regs, &info, 0, 0);
126
127         abtcounter++;
128 }
129
130 static int emulate_swpX(unsigned int address, unsigned int *data,
131                         unsigned int type)
132 {
133         unsigned int res = 0;
134
135         if ((type != TYPE_SWPB) && (address & 0x3)) {
136                 /* SWP to unaligned address not permitted */
137                 pr_debug("SWP instruction on unaligned pointer!\n");
138                 return -EFAULT;
139         }
140
141         while (1) {
142                 unsigned long temp;
143
144                 /*
145                  * Barrier required between accessing protected resource and
146                  * releasing a lock for it. Legacy code might not have done
147                  * this, and we cannot determine that this is not the case
148                  * being emulated, so insert always.
149                  */
150                 smp_mb();
151
152                 if (type == TYPE_SWPB)
153                         __user_swpb_asm(*data, address, res, temp);
154                 else
155                         __user_swp_asm(*data, address, res, temp);
156
157                 if (likely(res != -EAGAIN) || signal_pending(current))
158                         break;
159
160                 cond_resched();
161         }
162
163         if (res == 0) {
164                 /*
165                  * Barrier also required between acquiring a lock for a
166                  * protected resource and accessing the resource. Inserted for
167                  * same reason as above.
168                  */
169                 smp_mb();
170
171                 if (type == TYPE_SWPB)
172                         swpbcounter++;
173                 else
174                         swpcounter++;
175         }
176
177         return res;
178 }
179
180 /*
181  * swp_handler logs the id of calling process, dissects the instruction, sanity
182  * checks the memory location, calls emulate_swpX for the actual operation and
183  * deals with fixup/error handling before returning
184  */
185 static int swp_handler(struct pt_regs *regs, unsigned int instr)
186 {
187         unsigned int address, destreg, data, type;
188         unsigned int res = 0;
189
190         perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc);
191
192         res = arm_check_condition(instr, regs->ARM_cpsr);
193         switch (res) {
194         case ARM_OPCODE_CONDTEST_PASS:
195                 break;
196         case ARM_OPCODE_CONDTEST_FAIL:
197                 /* Condition failed - return to next instruction */
198                 regs->ARM_pc += 4;
199                 return 0;
200         case ARM_OPCODE_CONDTEST_UNCOND:
201                 /* If unconditional encoding - not a SWP, undef */
202                 return -EFAULT;
203         default:
204                 return -EINVAL;
205         }
206
207         if (current->pid != previous_pid) {
208                 pr_debug("\"%s\" (%ld) uses deprecated SWP{B} instruction\n",
209                          current->comm, (unsigned long)current->pid);
210                 previous_pid = current->pid;
211         }
212
213         address = regs->uregs[EXTRACT_REG_NUM(instr, RN_OFFSET)];
214         data    = regs->uregs[EXTRACT_REG_NUM(instr, RT2_OFFSET)];
215         destreg = EXTRACT_REG_NUM(instr, RT_OFFSET);
216
217         type = instr & TYPE_SWPB;
218
219         pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
220                  EXTRACT_REG_NUM(instr, RN_OFFSET), address,
221                  destreg, EXTRACT_REG_NUM(instr, RT2_OFFSET), data);
222
223         /* Check access in reasonable access range for both SWP and SWPB */
224         if (!access_ok(VERIFY_WRITE, (address & ~3), 4)) {
225                 pr_debug("SWP{B} emulation: access to %p not allowed!\n",
226                          (void *)address);
227                 res = -EFAULT;
228         } else {
229                 res = emulate_swpX(address, &data, type);
230         }
231
232         if (res == 0) {
233                 /*
234                  * On successful emulation, revert the adjustment to the PC
235                  * made in kernel/traps.c in order to resume execution at the
236                  * instruction following the SWP{B}.
237                  */
238                 regs->ARM_pc += 4;
239                 regs->uregs[destreg] = data;
240         } else if (res == -EFAULT) {
241                 /*
242                  * Memory errors do not mean emulation failed.
243                  * Set up signal info to return SEGV, then return OK
244                  */
245                 set_segfault(regs, address);
246         }
247
248         return 0;
249 }
250
251 /*
252  * Only emulate SWP/SWPB executed in ARM state/User mode.
253  * The kernel must be SWP free and SWP{B} does not exist in Thumb/ThumbEE.
254  */
255 static struct undef_hook swp_hook = {
256         .instr_mask = 0x0fb00ff0,
257         .instr_val  = 0x01000090,
258         .cpsr_mask  = MODE_MASK | PSR_T_BIT | PSR_J_BIT,
259         .cpsr_val   = USR_MODE,
260         .fn         = swp_handler
261 };
262
263 /*
264  * Register handler and create status file in /proc/cpu
265  * Invoked as late_initcall, since not needed before init spawned.
266  */
267 static int __init swp_emulation_init(void)
268 {
269 #ifdef CONFIG_PROC_FS
270         if (!proc_create("cpu/swp_emulation", S_IRUGO, NULL, &proc_status_fops))
271                 return -ENOMEM;
272 #endif /* CONFIG_PROC_FS */
273
274         printk(KERN_NOTICE "Registering SWP/SWPB emulation handler\n");
275         register_undef_hook(&swp_hook);
276
277         return 0;
278 }
279
280 late_initcall(swp_emulation_init);