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Linux/arch/sh/kernel/kgdb.c

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  1 /*
  2  * SuperH KGDB support
  3  *
  4  * Copyright (C) 2008 - 2012  Paul Mundt
  5  *
  6  * Single stepping taken from the old stub by Henry Bell and Jeremy Siegel.
  7  *
  8  * This file is subject to the terms and conditions of the GNU General Public
  9  * License.  See the file "COPYING" in the main directory of this archive
 10  * for more details.
 11  */
 12 #include <linux/kgdb.h>
 13 #include <linux/kdebug.h>
 14 #include <linux/irq.h>
 15 #include <linux/io.h>
 16 #include <asm/cacheflush.h>
 17 #include <asm/traps.h>
 18 
 19 /* Macros for single step instruction identification */
 20 #define OPCODE_BT(op)           (((op) & 0xff00) == 0x8900)
 21 #define OPCODE_BF(op)           (((op) & 0xff00) == 0x8b00)
 22 #define OPCODE_BTF_DISP(op)     (((op) & 0x80) ? (((op) | 0xffffff80) << 1) : \
 23                                  (((op) & 0x7f ) << 1))
 24 #define OPCODE_BFS(op)          (((op) & 0xff00) == 0x8f00)
 25 #define OPCODE_BTS(op)          (((op) & 0xff00) == 0x8d00)
 26 #define OPCODE_BRA(op)          (((op) & 0xf000) == 0xa000)
 27 #define OPCODE_BRA_DISP(op)     (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
 28                                  (((op) & 0x7ff) << 1))
 29 #define OPCODE_BRAF(op)         (((op) & 0xf0ff) == 0x0023)
 30 #define OPCODE_BRAF_REG(op)     (((op) & 0x0f00) >> 8)
 31 #define OPCODE_BSR(op)          (((op) & 0xf000) == 0xb000)
 32 #define OPCODE_BSR_DISP(op)     (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
 33                                  (((op) & 0x7ff) << 1))
 34 #define OPCODE_BSRF(op)         (((op) & 0xf0ff) == 0x0003)
 35 #define OPCODE_BSRF_REG(op)     (((op) >> 8) & 0xf)
 36 #define OPCODE_JMP(op)          (((op) & 0xf0ff) == 0x402b)
 37 #define OPCODE_JMP_REG(op)      (((op) >> 8) & 0xf)
 38 #define OPCODE_JSR(op)          (((op) & 0xf0ff) == 0x400b)
 39 #define OPCODE_JSR_REG(op)      (((op) >> 8) & 0xf)
 40 #define OPCODE_RTS(op)          ((op) == 0xb)
 41 #define OPCODE_RTE(op)          ((op) == 0x2b)
 42 
 43 #define SR_T_BIT_MASK           0x1
 44 #define STEP_OPCODE             0xc33d
 45 
 46 /* Calculate the new address for after a step */
 47 static short *get_step_address(struct pt_regs *linux_regs)
 48 {
 49         insn_size_t op = __raw_readw(linux_regs->pc);
 50         long addr;
 51 
 52         /* BT */
 53         if (OPCODE_BT(op)) {
 54                 if (linux_regs->sr & SR_T_BIT_MASK)
 55                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
 56                 else
 57                         addr = linux_regs->pc + 2;
 58         }
 59 
 60         /* BTS */
 61         else if (OPCODE_BTS(op)) {
 62                 if (linux_regs->sr & SR_T_BIT_MASK)
 63                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
 64                 else
 65                         addr = linux_regs->pc + 4;      /* Not in delay slot */
 66         }
 67 
 68         /* BF */
 69         else if (OPCODE_BF(op)) {
 70                 if (!(linux_regs->sr & SR_T_BIT_MASK))
 71                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
 72                 else
 73                         addr = linux_regs->pc + 2;
 74         }
 75 
 76         /* BFS */
 77         else if (OPCODE_BFS(op)) {
 78                 if (!(linux_regs->sr & SR_T_BIT_MASK))
 79                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
 80                 else
 81                         addr = linux_regs->pc + 4;      /* Not in delay slot */
 82         }
 83 
 84         /* BRA */
 85         else if (OPCODE_BRA(op))
 86                 addr = linux_regs->pc + 4 + OPCODE_BRA_DISP(op);
 87 
 88         /* BRAF */
 89         else if (OPCODE_BRAF(op))
 90                 addr = linux_regs->pc + 4
 91                     + linux_regs->regs[OPCODE_BRAF_REG(op)];
 92 
 93         /* BSR */
 94         else if (OPCODE_BSR(op))
 95                 addr = linux_regs->pc + 4 + OPCODE_BSR_DISP(op);
 96 
 97         /* BSRF */
 98         else if (OPCODE_BSRF(op))
 99                 addr = linux_regs->pc + 4
100                     + linux_regs->regs[OPCODE_BSRF_REG(op)];
101 
102         /* JMP */
103         else if (OPCODE_JMP(op))
104                 addr = linux_regs->regs[OPCODE_JMP_REG(op)];
105 
106         /* JSR */
107         else if (OPCODE_JSR(op))
108                 addr = linux_regs->regs[OPCODE_JSR_REG(op)];
109 
110         /* RTS */
111         else if (OPCODE_RTS(op))
112                 addr = linux_regs->pr;
113 
114         /* RTE */
115         else if (OPCODE_RTE(op))
116                 addr = linux_regs->regs[15];
117 
118         /* Other */
119         else
120                 addr = linux_regs->pc + instruction_size(op);
121 
122         flush_icache_range(addr, addr + instruction_size(op));
123         return (short *)addr;
124 }
125 
126 /*
127  * Replace the instruction immediately after the current instruction
128  * (i.e. next in the expected flow of control) with a trap instruction,
129  * so that returning will cause only a single instruction to be executed.
130  * Note that this model is slightly broken for instructions with delay
131  * slots (e.g. B[TF]S, BSR, BRA etc), where both the branch and the
132  * instruction in the delay slot will be executed.
133  */
134 
135 static unsigned long stepped_address;
136 static insn_size_t stepped_opcode;
137 
138 static void do_single_step(struct pt_regs *linux_regs)
139 {
140         /* Determine where the target instruction will send us to */
141         unsigned short *addr = get_step_address(linux_regs);
142 
143         stepped_address = (int)addr;
144 
145         /* Replace it */
146         stepped_opcode = __raw_readw((long)addr);
147         *addr = STEP_OPCODE;
148 
149         /* Flush and return */
150         flush_icache_range((long)addr, (long)addr +
151                            instruction_size(stepped_opcode));
152 }
153 
154 /* Undo a single step */
155 static void undo_single_step(struct pt_regs *linux_regs)
156 {
157         /* If we have stepped, put back the old instruction */
158         /* Use stepped_address in case we stopped elsewhere */
159         if (stepped_opcode != 0) {
160                 __raw_writew(stepped_opcode, stepped_address);
161                 flush_icache_range(stepped_address, stepped_address + 2);
162         }
163 
164         stepped_opcode = 0;
165 }
166 
167 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
168         { "r0",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[0]) },
169         { "r1",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[1]) },
170         { "r2",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[2]) },
171         { "r3",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[3]) },
172         { "r4",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[4]) },
173         { "r5",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[5]) },
174         { "r6",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[6]) },
175         { "r7",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[7]) },
176         { "r8",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[8]) },
177         { "r9",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[9]) },
178         { "r10",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[10]) },
179         { "r11",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[11]) },
180         { "r12",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[12]) },
181         { "r13",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[13]) },
182         { "r14",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[14]) },
183         { "r15",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[15]) },
184         { "pc",         GDB_SIZEOF_REG, offsetof(struct pt_regs, pc) },
185         { "pr",         GDB_SIZEOF_REG, offsetof(struct pt_regs, pr) },
186         { "sr",         GDB_SIZEOF_REG, offsetof(struct pt_regs, sr) },
187         { "gbr",        GDB_SIZEOF_REG, offsetof(struct pt_regs, gbr) },
188         { "mach",       GDB_SIZEOF_REG, offsetof(struct pt_regs, mach) },
189         { "macl",       GDB_SIZEOF_REG, offsetof(struct pt_regs, macl) },
190         { "vbr",        GDB_SIZEOF_REG, -1 },
191 };
192 
193 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
194 {
195         if (regno < 0 || regno >= DBG_MAX_REG_NUM)
196                 return -EINVAL;
197 
198         if (dbg_reg_def[regno].offset != -1)
199                 memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
200                        dbg_reg_def[regno].size);
201 
202         return 0;
203 }
204 
205 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
206 {
207         if (regno >= DBG_MAX_REG_NUM || regno < 0)
208                 return NULL;
209 
210         if (dbg_reg_def[regno].size != -1)
211                 memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
212                        dbg_reg_def[regno].size);
213 
214         switch (regno) {
215         case GDB_VBR:
216                 __asm__ __volatile__ ("stc vbr, %0" : "=r" (mem));
217                 break;
218         }
219 
220         return dbg_reg_def[regno].name;
221 }
222 
223 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
224 {
225         struct pt_regs *thread_regs = task_pt_regs(p);
226         int reg;
227 
228         /* Initialize to zero */
229         for (reg = 0; reg < DBG_MAX_REG_NUM; reg++)
230                 gdb_regs[reg] = 0;
231 
232         /*
233          * Copy out GP regs 8 to 14.
234          *
235          * switch_to() relies on SR.RB toggling, so regs 0->7 are banked
236          * and need privileged instructions to get to. The r15 value we
237          * fetch from the thread info directly.
238          */
239         for (reg = GDB_R8; reg < GDB_R15; reg++)
240                 gdb_regs[reg] = thread_regs->regs[reg];
241 
242         gdb_regs[GDB_R15] = p->thread.sp;
243         gdb_regs[GDB_PC] = p->thread.pc;
244 
245         /*
246          * Additional registers we have context for
247          */
248         gdb_regs[GDB_PR] = thread_regs->pr;
249         gdb_regs[GDB_GBR] = thread_regs->gbr;
250 }
251 
252 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
253                                char *remcomInBuffer, char *remcomOutBuffer,
254                                struct pt_regs *linux_regs)
255 {
256         unsigned long addr;
257         char *ptr;
258 
259         /* Undo any stepping we may have done */
260         undo_single_step(linux_regs);
261 
262         switch (remcomInBuffer[0]) {
263         case 'c':
264         case 's':
265                 /* try to read optional parameter, pc unchanged if no parm */
266                 ptr = &remcomInBuffer[1];
267                 if (kgdb_hex2long(&ptr, &addr))
268                         linux_regs->pc = addr;
269         case 'D':
270         case 'k':
271                 atomic_set(&kgdb_cpu_doing_single_step, -1);
272 
273                 if (remcomInBuffer[0] == 's') {
274                         do_single_step(linux_regs);
275                         kgdb_single_step = 1;
276 
277                         atomic_set(&kgdb_cpu_doing_single_step,
278                                    raw_smp_processor_id());
279                 }
280 
281                 return 0;
282         }
283 
284         /* this means that we do not want to exit from the handler: */
285         return -1;
286 }
287 
288 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
289 {
290         if (exception == 60)
291                 return instruction_pointer(regs) - 2;
292         return instruction_pointer(regs);
293 }
294 
295 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
296 {
297         regs->pc = ip;
298 }
299 
300 /*
301  * The primary entry points for the kgdb debug trap table entries.
302  */
303 BUILD_TRAP_HANDLER(singlestep)
304 {
305         unsigned long flags;
306         TRAP_HANDLER_DECL;
307 
308         local_irq_save(flags);
309         regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
310         kgdb_handle_exception(0, SIGTRAP, 0, regs);
311         local_irq_restore(flags);
312 }
313 
314 static void kgdb_call_nmi_hook(void *ignored)
315 {
316         kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
317 }
318 
319 void kgdb_roundup_cpus(unsigned long flags)
320 {
321         local_irq_enable();
322         smp_call_function(kgdb_call_nmi_hook, NULL, 0);
323         local_irq_disable();
324 }
325 
326 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
327 {
328         int ret;
329 
330         switch (cmd) {
331         case DIE_BREAKPOINT:
332                 /*
333                  * This means a user thread is single stepping
334                  * a system call which should be ignored
335                  */
336                 if (test_thread_flag(TIF_SINGLESTEP))
337                         return NOTIFY_DONE;
338 
339                 ret = kgdb_handle_exception(args->trapnr & 0xff, args->signr,
340                                             args->err, args->regs);
341                 if (ret)
342                         return NOTIFY_DONE;
343 
344                 break;
345         }
346 
347         return NOTIFY_STOP;
348 }
349 
350 static int
351 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
352 {
353         unsigned long flags;
354         int ret;
355 
356         local_irq_save(flags);
357         ret = __kgdb_notify(ptr, cmd);
358         local_irq_restore(flags);
359 
360         return ret;
361 }
362 
363 static struct notifier_block kgdb_notifier = {
364         .notifier_call  = kgdb_notify,
365 
366         /*
367          * Lowest-prio notifier priority, we want to be notified last:
368          */
369         .priority       = -INT_MAX,
370 };
371 
372 int kgdb_arch_init(void)
373 {
374         return register_die_notifier(&kgdb_notifier);
375 }
376 
377 void kgdb_arch_exit(void)
378 {
379         unregister_die_notifier(&kgdb_notifier);
380 }
381 
382 struct kgdb_arch arch_kgdb_ops = {
383         /* Breakpoint instruction: trapa #0x3c */
384 #ifdef CONFIG_CPU_LITTLE_ENDIAN
385         .gdb_bpt_instr          = { 0x3c, 0xc3 },
386 #else
387         .gdb_bpt_instr          = { 0xc3, 0x3c },
388 #endif
389 };
390 

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