ptrace.c revision 9e584fbbd9fd4f0f10b8aafc9982df8d0b553e35
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, long addr, long data) 150{ 151 int ret; 152 153 switch (request) { 154 /* Read the word at location addr in the child process */ 155 case PTRACE_PEEKTEXT: 156 case PTRACE_PEEKDATA: 157 ret = generic_ptrace_peekdata(child, addr, data); 158 break; 159 160 case PTRACE_PEEKUSR: 161 ret = ptrace_read_user(child, addr, 162 (unsigned long __user *)data); 163 break; 164 165 /* Write the word in data at location addr */ 166 case PTRACE_POKETEXT: 167 case PTRACE_POKEDATA: 168 ret = generic_ptrace_pokedata(child, addr, data); 169 break; 170 171 case PTRACE_POKEUSR: 172 ret = ptrace_write_user(child, addr, data); 173 break; 174 175 case PTRACE_GETREGS: 176 ret = ptrace_getregs(child, (void __user *)data); 177 break; 178 179 case PTRACE_SETREGS: 180 ret = ptrace_setregs(child, (const void __user *)data); 181 break; 182 183 default: 184 ret = ptrace_request(child, request, addr, data); 185 break; 186 } 187 188 return ret; 189} 190 191asmlinkage void syscall_trace(void) 192{ 193 if (!test_thread_flag(TIF_SYSCALL_TRACE)) 194 return; 195 if (!(current->ptrace & PT_PTRACED)) 196 return; 197 198 /* The 0x80 provides a way for the tracing parent to 199 * distinguish between a syscall stop and SIGTRAP delivery */ 200 ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD) 201 ? 0x80 : 0)); 202 203 /* 204 * this isn't the same as continuing with a signal, but it 205 * will do for normal use. strace only continues with a 206 * signal if the stopping signal is not SIGTRAP. -brl 207 */ 208 if (current->exit_code) { 209 pr_debug("syscall_trace: sending signal %d to PID %u\n", 210 current->exit_code, current->pid); 211 send_sig(current->exit_code, current, 1); 212 current->exit_code = 0; 213 } 214} 215 216/* 217 * debug_trampoline() is an assembly stub which will store all user 218 * registers on the stack and execute a breakpoint instruction. 219 * 220 * If we single-step into an exception handler which runs with 221 * interrupts disabled the whole time so it doesn't have to check for 222 * pending work, its return address will be modified so that it ends 223 * up returning to debug_trampoline. 224 * 225 * If the exception handler decides to store the user context and 226 * enable interrupts after all, it will restore the original return 227 * address and status register value. Before it returns, it will 228 * notice that TIF_BREAKPOINT is set and execute a breakpoint 229 * instruction. 230 */ 231extern void debug_trampoline(void); 232 233asmlinkage struct pt_regs *do_debug(struct pt_regs *regs) 234{ 235 struct thread_info *ti; 236 unsigned long trampoline_addr; 237 u32 status; 238 u32 ctrl; 239 int code; 240 241 status = ocd_read(DS); 242 ti = current_thread_info(); 243 code = TRAP_BRKPT; 244 245 pr_debug("do_debug: status=0x%08x PC=0x%08lx SR=0x%08lx tif=0x%08lx\n", 246 status, regs->pc, regs->sr, ti->flags); 247 248 if (!user_mode(regs)) { 249 unsigned long die_val = DIE_BREAKPOINT; 250 251 if (status & (1 << OCD_DS_SSS_BIT)) 252 die_val = DIE_SSTEP; 253 254 if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP) 255 == NOTIFY_STOP) 256 return regs; 257 258 if ((status & (1 << OCD_DS_SWB_BIT)) 259 && test_and_clear_ti_thread_flag( 260 ti, TIF_BREAKPOINT)) { 261 /* 262 * Explicit breakpoint from trampoline or 263 * exception/syscall/interrupt handler. 264 * 265 * The real saved regs are on the stack right 266 * after the ones we saved on entry. 267 */ 268 regs++; 269 pr_debug(" -> TIF_BREAKPOINT done, adjusted regs:" 270 "PC=0x%08lx SR=0x%08lx\n", 271 regs->pc, regs->sr); 272 BUG_ON(!user_mode(regs)); 273 274 if (test_thread_flag(TIF_SINGLE_STEP)) { 275 pr_debug("Going to do single step...\n"); 276 return regs; 277 } 278 279 /* 280 * No TIF_SINGLE_STEP means we're done 281 * stepping over a syscall. Do the trap now. 282 */ 283 code = TRAP_TRACE; 284 } else if ((status & (1 << OCD_DS_SSS_BIT)) 285 && test_ti_thread_flag(ti, TIF_SINGLE_STEP)) { 286 287 pr_debug("Stepped into something, " 288 "setting TIF_BREAKPOINT...\n"); 289 set_ti_thread_flag(ti, TIF_BREAKPOINT); 290 291 /* 292 * We stepped into an exception, interrupt or 293 * syscall handler. Some exception handlers 294 * don't check for pending work, so we need to 295 * set up a trampoline just in case. 296 * 297 * The exception entry code will undo the 298 * trampoline stuff if it does a full context 299 * save (which also means that it'll check for 300 * pending work later.) 301 */ 302 if ((regs->sr & MODE_MASK) == MODE_EXCEPTION) { 303 trampoline_addr 304 = (unsigned long)&debug_trampoline; 305 306 pr_debug("Setting up trampoline...\n"); 307 ti->rar_saved = sysreg_read(RAR_EX); 308 ti->rsr_saved = sysreg_read(RSR_EX); 309 sysreg_write(RAR_EX, trampoline_addr); 310 sysreg_write(RSR_EX, (MODE_EXCEPTION 311 | SR_EM | SR_GM)); 312 BUG_ON(ti->rsr_saved & MODE_MASK); 313 } 314 315 /* 316 * If we stepped into a system call, we 317 * shouldn't do a single step after we return 318 * since the return address is right after the 319 * "scall" instruction we were told to step 320 * over. 321 */ 322 if ((regs->sr & MODE_MASK) == MODE_SUPERVISOR) { 323 pr_debug("Supervisor; no single step\n"); 324 clear_ti_thread_flag(ti, TIF_SINGLE_STEP); 325 } 326 327 ctrl = ocd_read(DC); 328 ctrl &= ~(1 << OCD_DC_SS_BIT); 329 ocd_write(DC, ctrl); 330 331 return regs; 332 } else { 333 printk(KERN_ERR "Unexpected OCD_DS value: 0x%08x\n", 334 status); 335 printk(KERN_ERR "Thread flags: 0x%08lx\n", ti->flags); 336 die("Unhandled debug trap in kernel mode", 337 regs, SIGTRAP); 338 } 339 } else if (status & (1 << OCD_DS_SSS_BIT)) { 340 /* Single step in user mode */ 341 code = TRAP_TRACE; 342 343 ctrl = ocd_read(DC); 344 ctrl &= ~(1 << OCD_DC_SS_BIT); 345 ocd_write(DC, ctrl); 346 } 347 348 pr_debug("Sending SIGTRAP: code=%d PC=0x%08lx SR=0x%08lx\n", 349 code, regs->pc, regs->sr); 350 351 clear_thread_flag(TIF_SINGLE_STEP); 352 _exception(SIGTRAP, regs, code, instruction_pointer(regs)); 353 354 return regs; 355} 356