ptrace.c revision 9b05a69e0534ec70bc94921936ffa05b330507cb
1/* 2 * Copyright (C) 2004-2006 Atmel Corporation 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License version 2 as 6 * published by the Free Software Foundation. 7 */ 8#undef DEBUG 9#include <linux/kernel.h> 10#include <linux/sched.h> 11#include <linux/mm.h> 12#include <linux/ptrace.h> 13#include <linux/errno.h> 14#include <linux/user.h> 15#include <linux/security.h> 16#include <linux/unistd.h> 17#include <linux/notifier.h> 18 19#include <asm/traps.h> 20#include <asm/uaccess.h> 21#include <asm/ocd.h> 22#include <asm/mmu_context.h> 23#include <linux/kdebug.h> 24 25static struct pt_regs *get_user_regs(struct task_struct *tsk) 26{ 27 return (struct pt_regs *)((unsigned long)task_stack_page(tsk) + 28 THREAD_SIZE - sizeof(struct pt_regs)); 29} 30 31void user_enable_single_step(struct task_struct *tsk) 32{ 33 pr_debug("user_enable_single_step: pid=%u, PC=0x%08lx, SR=0x%08lx\n", 34 tsk->pid, task_pt_regs(tsk)->pc, task_pt_regs(tsk)->sr); 35 36 /* 37 * We can't schedule in Debug mode, so when TIF_BREAKPOINT is 38 * set, the system call or exception handler will do a 39 * breakpoint to enter monitor mode before returning to 40 * userspace. 41 * 42 * The monitor code will then notice that TIF_SINGLE_STEP is 43 * set and return to userspace with single stepping enabled. 44 * The CPU will then enter monitor mode again after exactly 45 * one instruction has been executed, and the monitor code 46 * will then send a SIGTRAP to the process. 47 */ 48 set_tsk_thread_flag(tsk, TIF_BREAKPOINT); 49 set_tsk_thread_flag(tsk, TIF_SINGLE_STEP); 50} 51 52void user_disable_single_step(struct task_struct *child) 53{ 54 /* XXX(hch): a no-op here seems wrong.. */ 55} 56 57/* 58 * Called by kernel/ptrace.c when detaching 59 * 60 * Make sure any single step bits, etc. are not set 61 */ 62void ptrace_disable(struct task_struct *child) 63{ 64 clear_tsk_thread_flag(child, TIF_SINGLE_STEP); 65 clear_tsk_thread_flag(child, TIF_BREAKPOINT); 66 ocd_disable(child); 67} 68 69/* 70 * Read the word at offset "offset" into the task's "struct user". We 71 * actually access the pt_regs struct stored on the kernel stack. 72 */ 73static int ptrace_read_user(struct task_struct *tsk, unsigned long offset, 74 unsigned long __user *data) 75{ 76 unsigned long *regs; 77 unsigned long value; 78 79 if (offset & 3 || offset >= sizeof(struct user)) { 80 printk("ptrace_read_user: invalid offset 0x%08lx\n", offset); 81 return -EIO; 82 } 83 84 regs = (unsigned long *)get_user_regs(tsk); 85 86 value = 0; 87 if (offset < sizeof(struct pt_regs)) 88 value = regs[offset / sizeof(regs[0])]; 89 90 pr_debug("ptrace_read_user(%s[%u], %#lx, %p) -> %#lx\n", 91 tsk->comm, tsk->pid, offset, data, value); 92 93 return put_user(value, data); 94} 95 96/* 97 * Write the word "value" to offset "offset" into the task's "struct 98 * user". We actually access the pt_regs struct stored on the kernel 99 * stack. 100 */ 101static int ptrace_write_user(struct task_struct *tsk, unsigned long offset, 102 unsigned long value) 103{ 104 unsigned long *regs; 105 106 pr_debug("ptrace_write_user(%s[%u], %#lx, %#lx)\n", 107 tsk->comm, tsk->pid, offset, value); 108 109 if (offset & 3 || offset >= sizeof(struct user)) { 110 pr_debug(" invalid offset 0x%08lx\n", offset); 111 return -EIO; 112 } 113 114 if (offset >= sizeof(struct pt_regs)) 115 return 0; 116 117 regs = (unsigned long *)get_user_regs(tsk); 118 regs[offset / sizeof(regs[0])] = value; 119 120 return 0; 121} 122 123static int ptrace_getregs(struct task_struct *tsk, void __user *uregs) 124{ 125 struct pt_regs *regs = get_user_regs(tsk); 126 127 return copy_to_user(uregs, regs, sizeof(*regs)) ? -EFAULT : 0; 128} 129 130static int ptrace_setregs(struct task_struct *tsk, const void __user *uregs) 131{ 132 struct pt_regs newregs; 133 int ret; 134 135 ret = -EFAULT; 136 if (copy_from_user(&newregs, uregs, sizeof(newregs)) == 0) { 137 struct pt_regs *regs = get_user_regs(tsk); 138 139 ret = -EINVAL; 140 if (valid_user_regs(&newregs)) { 141 *regs = newregs; 142 ret = 0; 143 } 144 } 145 146 return ret; 147} 148 149long arch_ptrace(struct task_struct *child, long request, 150 unsigned long addr, unsigned long data) 151{ 152 int ret; 153 154 switch (request) { 155 /* Read the word at location addr in the child process */ 156 case PTRACE_PEEKTEXT: 157 case PTRACE_PEEKDATA: 158 ret = generic_ptrace_peekdata(child, addr, data); 159 break; 160 161 case PTRACE_PEEKUSR: 162 ret = ptrace_read_user(child, addr, 163 (unsigned long __user *)data); 164 break; 165 166 /* Write the word in data at location addr */ 167 case PTRACE_POKETEXT: 168 case PTRACE_POKEDATA: 169 ret = generic_ptrace_pokedata(child, addr, data); 170 break; 171 172 case PTRACE_POKEUSR: 173 ret = ptrace_write_user(child, addr, data); 174 break; 175 176 case PTRACE_GETREGS: 177 ret = ptrace_getregs(child, (void __user *)data); 178 break; 179 180 case PTRACE_SETREGS: 181 ret = ptrace_setregs(child, (const void __user *)data); 182 break; 183 184 default: 185 ret = ptrace_request(child, request, addr, data); 186 break; 187 } 188 189 return ret; 190} 191 192asmlinkage void syscall_trace(void) 193{ 194 if (!test_thread_flag(TIF_SYSCALL_TRACE)) 195 return; 196 if (!(current->ptrace & PT_PTRACED)) 197 return; 198 199 /* The 0x80 provides a way for the tracing parent to 200 * distinguish between a syscall stop and SIGTRAP delivery */ 201 ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD) 202 ? 0x80 : 0)); 203 204 /* 205 * this isn't the same as continuing with a signal, but it 206 * will do for normal use. strace only continues with a 207 * signal if the stopping signal is not SIGTRAP. -brl 208 */ 209 if (current->exit_code) { 210 pr_debug("syscall_trace: sending signal %d to PID %u\n", 211 current->exit_code, current->pid); 212 send_sig(current->exit_code, current, 1); 213 current->exit_code = 0; 214 } 215} 216 217/* 218 * debug_trampoline() is an assembly stub which will store all user 219 * registers on the stack and execute a breakpoint instruction. 220 * 221 * If we single-step into an exception handler which runs with 222 * interrupts disabled the whole time so it doesn't have to check for 223 * pending work, its return address will be modified so that it ends 224 * up returning to debug_trampoline. 225 * 226 * If the exception handler decides to store the user context and 227 * enable interrupts after all, it will restore the original return 228 * address and status register value. Before it returns, it will 229 * notice that TIF_BREAKPOINT is set and execute a breakpoint 230 * instruction. 231 */ 232extern void debug_trampoline(void); 233 234asmlinkage struct pt_regs *do_debug(struct pt_regs *regs) 235{ 236 struct thread_info *ti; 237 unsigned long trampoline_addr; 238 u32 status; 239 u32 ctrl; 240 int code; 241 242 status = ocd_read(DS); 243 ti = current_thread_info(); 244 code = TRAP_BRKPT; 245 246 pr_debug("do_debug: status=0x%08x PC=0x%08lx SR=0x%08lx tif=0x%08lx\n", 247 status, regs->pc, regs->sr, ti->flags); 248 249 if (!user_mode(regs)) { 250 unsigned long die_val = DIE_BREAKPOINT; 251 252 if (status & (1 << OCD_DS_SSS_BIT)) 253 die_val = DIE_SSTEP; 254 255 if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP) 256 == NOTIFY_STOP) 257 return regs; 258 259 if ((status & (1 << OCD_DS_SWB_BIT)) 260 && test_and_clear_ti_thread_flag( 261 ti, TIF_BREAKPOINT)) { 262 /* 263 * Explicit breakpoint from trampoline or 264 * exception/syscall/interrupt handler. 265 * 266 * The real saved regs are on the stack right 267 * after the ones we saved on entry. 268 */ 269 regs++; 270 pr_debug(" -> TIF_BREAKPOINT done, adjusted regs:" 271 "PC=0x%08lx SR=0x%08lx\n", 272 regs->pc, regs->sr); 273 BUG_ON(!user_mode(regs)); 274 275 if (test_thread_flag(TIF_SINGLE_STEP)) { 276 pr_debug("Going to do single step...\n"); 277 return regs; 278 } 279 280 /* 281 * No TIF_SINGLE_STEP means we're done 282 * stepping over a syscall. Do the trap now. 283 */ 284 code = TRAP_TRACE; 285 } else if ((status & (1 << OCD_DS_SSS_BIT)) 286 && test_ti_thread_flag(ti, TIF_SINGLE_STEP)) { 287 288 pr_debug("Stepped into something, " 289 "setting TIF_BREAKPOINT...\n"); 290 set_ti_thread_flag(ti, TIF_BREAKPOINT); 291 292 /* 293 * We stepped into an exception, interrupt or 294 * syscall handler. Some exception handlers 295 * don't check for pending work, so we need to 296 * set up a trampoline just in case. 297 * 298 * The exception entry code will undo the 299 * trampoline stuff if it does a full context 300 * save (which also means that it'll check for 301 * pending work later.) 302 */ 303 if ((regs->sr & MODE_MASK) == MODE_EXCEPTION) { 304 trampoline_addr 305 = (unsigned long)&debug_trampoline; 306 307 pr_debug("Setting up trampoline...\n"); 308 ti->rar_saved = sysreg_read(RAR_EX); 309 ti->rsr_saved = sysreg_read(RSR_EX); 310 sysreg_write(RAR_EX, trampoline_addr); 311 sysreg_write(RSR_EX, (MODE_EXCEPTION 312 | SR_EM | SR_GM)); 313 BUG_ON(ti->rsr_saved & MODE_MASK); 314 } 315 316 /* 317 * If we stepped into a system call, we 318 * shouldn't do a single step after we return 319 * since the return address is right after the 320 * "scall" instruction we were told to step 321 * over. 322 */ 323 if ((regs->sr & MODE_MASK) == MODE_SUPERVISOR) { 324 pr_debug("Supervisor; no single step\n"); 325 clear_ti_thread_flag(ti, TIF_SINGLE_STEP); 326 } 327 328 ctrl = ocd_read(DC); 329 ctrl &= ~(1 << OCD_DC_SS_BIT); 330 ocd_write(DC, ctrl); 331 332 return regs; 333 } else { 334 printk(KERN_ERR "Unexpected OCD_DS value: 0x%08x\n", 335 status); 336 printk(KERN_ERR "Thread flags: 0x%08lx\n", ti->flags); 337 die("Unhandled debug trap in kernel mode", 338 regs, SIGTRAP); 339 } 340 } else if (status & (1 << OCD_DS_SSS_BIT)) { 341 /* Single step in user mode */ 342 code = TRAP_TRACE; 343 344 ctrl = ocd_read(DC); 345 ctrl &= ~(1 << OCD_DC_SS_BIT); 346 ocd_write(DC, ctrl); 347 } 348 349 pr_debug("Sending SIGTRAP: code=%d PC=0x%08lx SR=0x%08lx\n", 350 code, regs->pc, regs->sr); 351 352 clear_thread_flag(TIF_SINGLE_STEP); 353 _exception(SIGTRAP, regs, code, instruction_pointer(regs)); 354 355 return regs; 356} 357