unwind.c 9.9 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
/*
 * Kernel unwinding support
 *
 * (c) 2002-2004 Randolph Chung <tausq@debian.org>
 *
 * Derived partially from the IA64 implementation. The PA-RISC
 * Runtime Architecture Document is also a useful reference to
 * understand what is happening here
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/kallsyms.h>

#include <asm/uaccess.h>
#include <asm/assembly.h>

#include <asm/unwind.h>

/* #define DEBUG 1 */
#ifdef DEBUG
#define dbg(x...) printk(x)
#else
#define dbg(x...)
#endif

extern struct unwind_table_entry __start___unwind[];
extern struct unwind_table_entry __stop___unwind[];

static spinlock_t unwind_lock;
/*
 * the kernel unwind block is not dynamically allocated so that
 * we can call unwind_init as early in the bootup process as 
 * possible (before the slab allocator is initialized)
 */
37
static struct unwind_table kernel_unwind_table __read_mostly;
L
Linus Torvalds 已提交
38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392
static LIST_HEAD(unwind_tables);

static inline const struct unwind_table_entry *
find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
{
	const struct unwind_table_entry *e = NULL;
	unsigned long lo, hi, mid;

	lo = 0; 
	hi = table->length - 1; 
	
	while (lo <= hi) {
		mid = (hi - lo) / 2 + lo;
		e = &table->table[mid];
		if (addr < e->region_start)
			hi = mid - 1;
		else if (addr > e->region_end)
			lo = mid + 1;
		else
			return e;
	}

	return NULL;
}

static const struct unwind_table_entry *
find_unwind_entry(unsigned long addr)
{
	struct unwind_table *table;
	const struct unwind_table_entry *e = NULL;

	if (addr >= kernel_unwind_table.start && 
	    addr <= kernel_unwind_table.end)
		e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
	else 
		list_for_each_entry(table, &unwind_tables, list) {
			if (addr >= table->start && 
			    addr <= table->end)
				e = find_unwind_entry_in_table(table, addr);
			if (e)
				break;
		}

	return e;
}

static void
unwind_table_init(struct unwind_table *table, const char *name,
		  unsigned long base_addr, unsigned long gp,
		  void *table_start, void *table_end)
{
	struct unwind_table_entry *start = table_start;
	struct unwind_table_entry *end = 
		(struct unwind_table_entry *)table_end - 1;

	table->name = name;
	table->base_addr = base_addr;
	table->gp = gp;
	table->start = base_addr + start->region_start;
	table->end = base_addr + end->region_end;
	table->table = (struct unwind_table_entry *)table_start;
	table->length = end - start + 1;
	INIT_LIST_HEAD(&table->list);

	for (; start <= end; start++) {
		if (start < end && 
		    start->region_end > (start+1)->region_start) {
			printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1);
		}

		start->region_start += base_addr;
		start->region_end += base_addr;
	}
}

static void
unwind_table_sort(struct unwind_table_entry *start,
		  struct unwind_table_entry *finish)
{
	struct unwind_table_entry el, *p, *q;

	for (p = start + 1; p < finish; ++p) {
		if (p[0].region_start < p[-1].region_start) {
			el = *p;
			q = p;
			do {
				q[0] = q[-1];
				--q;
			} while (q > start && 
				 el.region_start < q[-1].region_start);
			*q = el;
		}
	}
}

struct unwind_table *
unwind_table_add(const char *name, unsigned long base_addr, 
		 unsigned long gp,
                 void *start, void *end)
{
	struct unwind_table *table;
	unsigned long flags;
	struct unwind_table_entry *s = (struct unwind_table_entry *)start;
	struct unwind_table_entry *e = (struct unwind_table_entry *)end;

	unwind_table_sort(s, e);

	table = kmalloc(sizeof(struct unwind_table), GFP_USER);
	if (table == NULL)
		return NULL;
	unwind_table_init(table, name, base_addr, gp, start, end);
	spin_lock_irqsave(&unwind_lock, flags);
	list_add_tail(&table->list, &unwind_tables);
	spin_unlock_irqrestore(&unwind_lock, flags);

	return table;
}

void unwind_table_remove(struct unwind_table *table)
{
	unsigned long flags;

	spin_lock_irqsave(&unwind_lock, flags);
	list_del(&table->list);
	spin_unlock_irqrestore(&unwind_lock, flags);

	kfree(table);
}

/* Called from setup_arch to import the kernel unwind info */
static int unwind_init(void)
{
	long start, stop;
	register unsigned long gp __asm__ ("r27");

	start = (long)&__start___unwind[0];
	stop = (long)&__stop___unwind[0];

	spin_lock_init(&unwind_lock);

	printk("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n", 
	    start, stop,
	    (stop - start) / sizeof(struct unwind_table_entry));

	unwind_table_init(&kernel_unwind_table, "kernel", KERNEL_START,
			  gp, 
			  &__start___unwind[0], &__stop___unwind[0]);
#if 0
	{
		int i;
		for (i = 0; i < 10; i++)
		{
			printk("region 0x%x-0x%x\n", 
				__start___unwind[i].region_start, 
				__start___unwind[i].region_end);
		}
	}
#endif
	return 0;
}

static void unwind_frame_regs(struct unwind_frame_info *info)
{
	const struct unwind_table_entry *e;
	unsigned long npc;
	unsigned int insn;
	long frame_size = 0;
	int looking_for_rp, rpoffset = 0;

	e = find_unwind_entry(info->ip);
	if (e == NULL) {
		unsigned long sp;
		extern char _stext[], _etext[];

		dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip);

#ifdef CONFIG_KALLSYMS
		/* Handle some frequent special cases.... */
		{
			char symname[KSYM_NAME_LEN+1];
			char *modname;
			unsigned long symsize, offset;

			kallsyms_lookup(info->ip, &symsize, &offset,
					&modname, symname);

			dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname);

			if (strcmp(symname, "_switch_to_ret") == 0) {
				info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
				info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
				dbg("_switch_to_ret @ %lx - setting "
				    "prev_sp=%lx prev_ip=%lx\n", 
				    info->ip, info->prev_sp, 
				    info->prev_ip);
				return;
			} else if (strcmp(symname, "ret_from_kernel_thread") == 0 ||
				   strcmp(symname, "syscall_exit") == 0) {
				info->prev_ip = info->prev_sp = 0;
				return;
			}
		}
#endif

		/* Since we are doing the unwinding blind, we don't know if
		   we are adjusting the stack correctly or extracting the rp
		   correctly. The rp is checked to see if it belongs to the
		   kernel text section, if not we assume we don't have a 
		   correct stack frame and we continue to unwind the stack.
		   This is not quite correct, and will fail for loadable
		   modules. */
		sp = info->sp & ~63;
		do {
			unsigned long tmp;

			info->prev_sp = sp - 64;
			info->prev_ip = 0;
			if (get_user(tmp, (unsigned long *)(info->prev_sp - RP_OFFSET))) 
				break;
			info->prev_ip = tmp;
			sp = info->prev_sp;
		} while (info->prev_ip < (unsigned long)_stext ||
			 info->prev_ip > (unsigned long)_etext);

		info->rp = 0;

		dbg("analyzing func @ %lx with no unwind info, setting "
		    "prev_sp=%lx prev_ip=%lx\n", info->ip, 
		    info->prev_sp, info->prev_ip);
	} else {
		dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, "
		    "Save_RP = %d, Millicode = %d size = %u\n", 
		    e->region_start, e->region_end, e->Save_SP, e->Save_RP, 
		    e->Millicode, e->Total_frame_size);

		looking_for_rp = e->Save_RP;

		for (npc = e->region_start; 
		     (frame_size < (e->Total_frame_size << 3) || 
		      looking_for_rp) && 
		     npc < info->ip; 
		     npc += 4) {

			insn = *(unsigned int *)npc;

			if ((insn & 0xffffc000) == 0x37de0000 ||
			    (insn & 0xffe00000) == 0x6fc00000) {
				/* ldo X(sp), sp, or stwm X,D(sp) */
				frame_size += (insn & 0x1 ? -1 << 13 : 0) | 
					((insn & 0x3fff) >> 1);
				dbg("analyzing func @ %lx, insn=%08x @ "
				    "%lx, frame_size = %ld\n", info->ip,
				    insn, npc, frame_size);
			} else if ((insn & 0xffe00008) == 0x73c00008) {
				/* std,ma X,D(sp) */
				frame_size += (insn & 0x1 ? -1 << 13 : 0) | 
					(((insn >> 4) & 0x3ff) << 3);
				dbg("analyzing func @ %lx, insn=%08x @ "
				    "%lx, frame_size = %ld\n", info->ip,
				    insn, npc, frame_size);
			} else if (insn == 0x6bc23fd9) { 
				/* stw rp,-20(sp) */
				rpoffset = 20;
				looking_for_rp = 0;
				dbg("analyzing func @ %lx, insn=stw rp,"
				    "-20(sp) @ %lx\n", info->ip, npc);
			} else if (insn == 0x0fc212c1) {
				/* std rp,-16(sr0,sp) */
				rpoffset = 16;
				looking_for_rp = 0;
				dbg("analyzing func @ %lx, insn=std rp,"
				    "-16(sp) @ %lx\n", info->ip, npc);
			}
		}

		info->prev_sp = info->sp - frame_size;
		if (e->Millicode)
			info->rp = info->r31;
		else if (rpoffset)
			info->rp = *(unsigned long *)(info->prev_sp - rpoffset);
		info->prev_ip = info->rp;
		info->rp = 0;

		dbg("analyzing func @ %lx, setting prev_sp=%lx "
		    "prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp, 
		    info->prev_ip, npc);
	}
}

void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t, 
		       struct pt_regs *regs)
{
	memset(info, 0, sizeof(struct unwind_frame_info));
	info->t = t;
	info->sp = regs->gr[30];
	info->ip = regs->iaoq[0];
	info->rp = regs->gr[2];
	info->r31 = regs->gr[31];

	dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n", 
	    t ? (int)t->pid : -1, info->sp, info->ip);
}

void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t)
{
	struct pt_regs *r = &t->thread.regs;
	struct pt_regs *r2;

	r2 = (struct pt_regs *)kmalloc(sizeof(struct pt_regs), GFP_KERNEL);
	if (!r2)
		return;
	*r2 = *r;
	r2->gr[30] = r->ksp;
	r2->iaoq[0] = r->kpc;
	unwind_frame_init(info, t, r2);
	kfree(r2);
}

void unwind_frame_init_running(struct unwind_frame_info *info, struct pt_regs *regs)
{
	unwind_frame_init(info, current, regs);
}

int unwind_once(struct unwind_frame_info *next_frame)
{
	unwind_frame_regs(next_frame);

	if (next_frame->prev_sp == 0 ||
	    next_frame->prev_ip == 0)
		return -1;

	next_frame->sp = next_frame->prev_sp;
	next_frame->ip = next_frame->prev_ip;
	next_frame->prev_sp = 0;
	next_frame->prev_ip = 0;

	dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n", 
	    next_frame->t ? (int)next_frame->t->pid : -1, 
	    next_frame->sp, next_frame->ip);

	return 0;
}

int unwind_to_user(struct unwind_frame_info *info)
{
	int ret;
	
	do {
		ret = unwind_once(info);
	} while (!ret && !(info->ip & 3));

	return ret;
}

module_init(unwind_init);