Linux 2.6.31.6
[linux/fpc-iii.git] / arch / powerpc / kernel / ftrace.c
blobce1f3e44c24fabf07408fd3e0ed70919a3828cb3
1 /*
2 * Code for replacing ftrace calls with jumps.
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
6 * Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
8 * Added function graph tracer code, taken from x86 that was written
9 * by Frederic Weisbecker, and ported to PPC by Steven Rostedt.
13 #include <linux/spinlock.h>
14 #include <linux/hardirq.h>
15 #include <linux/uaccess.h>
16 #include <linux/module.h>
17 #include <linux/ftrace.h>
18 #include <linux/percpu.h>
19 #include <linux/init.h>
20 #include <linux/list.h>
22 #include <asm/cacheflush.h>
23 #include <asm/code-patching.h>
24 #include <asm/ftrace.h>
27 #ifdef CONFIG_DYNAMIC_FTRACE
28 static unsigned int
29 ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
31 unsigned int op;
33 addr = ppc_function_entry((void *)addr);
35 /* if (link) set op to 'bl' else 'b' */
36 op = create_branch((unsigned int *)ip, addr, link ? 1 : 0);
38 return op;
41 static int
42 ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new)
44 unsigned int replaced;
47 * Note: Due to modules and __init, code can
48 * disappear and change, we need to protect against faulting
49 * as well as code changing. We do this by using the
50 * probe_kernel_* functions.
52 * No real locking needed, this code is run through
53 * kstop_machine, or before SMP starts.
56 /* read the text we want to modify */
57 if (probe_kernel_read(&replaced, (void *)ip, MCOUNT_INSN_SIZE))
58 return -EFAULT;
60 /* Make sure it is what we expect it to be */
61 if (replaced != old)
62 return -EINVAL;
64 /* replace the text with the new text */
65 if (probe_kernel_write((void *)ip, &new, MCOUNT_INSN_SIZE))
66 return -EPERM;
68 flush_icache_range(ip, ip + 8);
70 return 0;
74 * Helper functions that are the same for both PPC64 and PPC32.
76 static int test_24bit_addr(unsigned long ip, unsigned long addr)
79 /* use the create_branch to verify that this offset can be branched */
80 return create_branch((unsigned int *)ip, addr, 0);
83 #ifdef CONFIG_MODULES
85 static int is_bl_op(unsigned int op)
87 return (op & 0xfc000003) == 0x48000001;
90 static unsigned long find_bl_target(unsigned long ip, unsigned int op)
92 static int offset;
94 offset = (op & 0x03fffffc);
95 /* make it signed */
96 if (offset & 0x02000000)
97 offset |= 0xfe000000;
99 return ip + (long)offset;
102 #ifdef CONFIG_PPC64
103 static int
104 __ftrace_make_nop(struct module *mod,
105 struct dyn_ftrace *rec, unsigned long addr)
107 unsigned int op;
108 unsigned int jmp[5];
109 unsigned long ptr;
110 unsigned long ip = rec->ip;
111 unsigned long tramp;
112 int offset;
114 /* read where this goes */
115 if (probe_kernel_read(&op, (void *)ip, sizeof(int)))
116 return -EFAULT;
118 /* Make sure that that this is still a 24bit jump */
119 if (!is_bl_op(op)) {
120 printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
121 return -EINVAL;
124 /* lets find where the pointer goes */
125 tramp = find_bl_target(ip, op);
128 * On PPC64 the trampoline looks like:
129 * 0x3d, 0x82, 0x00, 0x00, addis r12,r2, <high>
130 * 0x39, 0x8c, 0x00, 0x00, addi r12,r12, <low>
131 * Where the bytes 2,3,6 and 7 make up the 32bit offset
132 * to the TOC that holds the pointer.
133 * to jump to.
134 * 0xf8, 0x41, 0x00, 0x28, std r2,40(r1)
135 * 0xe9, 0x6c, 0x00, 0x20, ld r11,32(r12)
136 * The actually address is 32 bytes from the offset
137 * into the TOC.
138 * 0xe8, 0x4c, 0x00, 0x28, ld r2,40(r12)
141 pr_devel("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);
143 /* Find where the trampoline jumps to */
144 if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
145 printk(KERN_ERR "Failed to read %lx\n", tramp);
146 return -EFAULT;
149 pr_devel(" %08x %08x", jmp[0], jmp[1]);
151 /* verify that this is what we expect it to be */
152 if (((jmp[0] & 0xffff0000) != 0x3d820000) ||
153 ((jmp[1] & 0xffff0000) != 0x398c0000) ||
154 (jmp[2] != 0xf8410028) ||
155 (jmp[3] != 0xe96c0020) ||
156 (jmp[4] != 0xe84c0028)) {
157 printk(KERN_ERR "Not a trampoline\n");
158 return -EINVAL;
161 /* The bottom half is signed extended */
162 offset = ((unsigned)((unsigned short)jmp[0]) << 16) +
163 (int)((short)jmp[1]);
165 pr_devel(" %x ", offset);
167 /* get the address this jumps too */
168 tramp = mod->arch.toc + offset + 32;
169 pr_devel("toc: %lx", tramp);
171 if (probe_kernel_read(jmp, (void *)tramp, 8)) {
172 printk(KERN_ERR "Failed to read %lx\n", tramp);
173 return -EFAULT;
176 pr_devel(" %08x %08x\n", jmp[0], jmp[1]);
178 ptr = ((unsigned long)jmp[0] << 32) + jmp[1];
180 /* This should match what was called */
181 if (ptr != ppc_function_entry((void *)addr)) {
182 printk(KERN_ERR "addr does not match %lx\n", ptr);
183 return -EINVAL;
187 * We want to nop the line, but the next line is
188 * 0xe8, 0x41, 0x00, 0x28 ld r2,40(r1)
189 * This needs to be turned to a nop too.
191 if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE))
192 return -EFAULT;
194 if (op != 0xe8410028) {
195 printk(KERN_ERR "Next line is not ld! (%08x)\n", op);
196 return -EINVAL;
200 * Milton Miller pointed out that we can not blindly do nops.
201 * If a task was preempted when calling a trace function,
202 * the nops will remove the way to restore the TOC in r2
203 * and the r2 TOC will get corrupted.
207 * Replace:
208 * bl <tramp> <==== will be replaced with "b 1f"
209 * ld r2,40(r1)
210 * 1:
212 op = 0x48000008; /* b +8 */
214 if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
215 return -EPERM;
218 flush_icache_range(ip, ip + 8);
220 return 0;
223 #else /* !PPC64 */
224 static int
225 __ftrace_make_nop(struct module *mod,
226 struct dyn_ftrace *rec, unsigned long addr)
228 unsigned int op;
229 unsigned int jmp[4];
230 unsigned long ip = rec->ip;
231 unsigned long tramp;
233 if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
234 return -EFAULT;
236 /* Make sure that that this is still a 24bit jump */
237 if (!is_bl_op(op)) {
238 printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
239 return -EINVAL;
242 /* lets find where the pointer goes */
243 tramp = find_bl_target(ip, op);
246 * On PPC32 the trampoline looks like:
247 * 0x3d, 0x60, 0x00, 0x00 lis r11,sym@ha
248 * 0x39, 0x6b, 0x00, 0x00 addi r11,r11,sym@l
249 * 0x7d, 0x69, 0x03, 0xa6 mtctr r11
250 * 0x4e, 0x80, 0x04, 0x20 bctr
253 pr_devel("ip:%lx jumps to %lx", ip, tramp);
255 /* Find where the trampoline jumps to */
256 if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
257 printk(KERN_ERR "Failed to read %lx\n", tramp);
258 return -EFAULT;
261 pr_devel(" %08x %08x ", jmp[0], jmp[1]);
263 /* verify that this is what we expect it to be */
264 if (((jmp[0] & 0xffff0000) != 0x3d600000) ||
265 ((jmp[1] & 0xffff0000) != 0x396b0000) ||
266 (jmp[2] != 0x7d6903a6) ||
267 (jmp[3] != 0x4e800420)) {
268 printk(KERN_ERR "Not a trampoline\n");
269 return -EINVAL;
272 tramp = (jmp[1] & 0xffff) |
273 ((jmp[0] & 0xffff) << 16);
274 if (tramp & 0x8000)
275 tramp -= 0x10000;
277 pr_devel(" %lx ", tramp);
279 if (tramp != addr) {
280 printk(KERN_ERR
281 "Trampoline location %08lx does not match addr\n",
282 tramp);
283 return -EINVAL;
286 op = PPC_INST_NOP;
288 if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
289 return -EPERM;
291 flush_icache_range(ip, ip + 8);
293 return 0;
295 #endif /* PPC64 */
296 #endif /* CONFIG_MODULES */
298 int ftrace_make_nop(struct module *mod,
299 struct dyn_ftrace *rec, unsigned long addr)
301 unsigned long ip = rec->ip;
302 unsigned int old, new;
305 * If the calling address is more that 24 bits away,
306 * then we had to use a trampoline to make the call.
307 * Otherwise just update the call site.
309 if (test_24bit_addr(ip, addr)) {
310 /* within range */
311 old = ftrace_call_replace(ip, addr, 1);
312 new = PPC_INST_NOP;
313 return ftrace_modify_code(ip, old, new);
316 #ifdef CONFIG_MODULES
318 * Out of range jumps are called from modules.
319 * We should either already have a pointer to the module
320 * or it has been passed in.
322 if (!rec->arch.mod) {
323 if (!mod) {
324 printk(KERN_ERR "No module loaded addr=%lx\n",
325 addr);
326 return -EFAULT;
328 rec->arch.mod = mod;
329 } else if (mod) {
330 if (mod != rec->arch.mod) {
331 printk(KERN_ERR
332 "Record mod %p not equal to passed in mod %p\n",
333 rec->arch.mod, mod);
334 return -EINVAL;
336 /* nothing to do if mod == rec->arch.mod */
337 } else
338 mod = rec->arch.mod;
340 return __ftrace_make_nop(mod, rec, addr);
341 #else
342 /* We should not get here without modules */
343 return -EINVAL;
344 #endif /* CONFIG_MODULES */
347 #ifdef CONFIG_MODULES
348 #ifdef CONFIG_PPC64
349 static int
350 __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
352 unsigned int op[2];
353 unsigned long ip = rec->ip;
355 /* read where this goes */
356 if (probe_kernel_read(op, (void *)ip, MCOUNT_INSN_SIZE * 2))
357 return -EFAULT;
360 * It should be pointing to two nops or
361 * b +8; ld r2,40(r1)
363 if (((op[0] != 0x48000008) || (op[1] != 0xe8410028)) &&
364 ((op[0] != PPC_INST_NOP) || (op[1] != PPC_INST_NOP))) {
365 printk(KERN_ERR "Expected NOPs but have %x %x\n", op[0], op[1]);
366 return -EINVAL;
369 /* If we never set up a trampoline to ftrace_caller, then bail */
370 if (!rec->arch.mod->arch.tramp) {
371 printk(KERN_ERR "No ftrace trampoline\n");
372 return -EINVAL;
375 /* create the branch to the trampoline */
376 op[0] = create_branch((unsigned int *)ip,
377 rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
378 if (!op[0]) {
379 printk(KERN_ERR "REL24 out of range!\n");
380 return -EINVAL;
383 /* ld r2,40(r1) */
384 op[1] = 0xe8410028;
386 pr_devel("write to %lx\n", rec->ip);
388 if (probe_kernel_write((void *)ip, op, MCOUNT_INSN_SIZE * 2))
389 return -EPERM;
391 flush_icache_range(ip, ip + 8);
393 return 0;
395 #else
396 static int
397 __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
399 unsigned int op;
400 unsigned long ip = rec->ip;
402 /* read where this goes */
403 if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
404 return -EFAULT;
406 /* It should be pointing to a nop */
407 if (op != PPC_INST_NOP) {
408 printk(KERN_ERR "Expected NOP but have %x\n", op);
409 return -EINVAL;
412 /* If we never set up a trampoline to ftrace_caller, then bail */
413 if (!rec->arch.mod->arch.tramp) {
414 printk(KERN_ERR "No ftrace trampoline\n");
415 return -EINVAL;
418 /* create the branch to the trampoline */
419 op = create_branch((unsigned int *)ip,
420 rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
421 if (!op) {
422 printk(KERN_ERR "REL24 out of range!\n");
423 return -EINVAL;
426 pr_devel("write to %lx\n", rec->ip);
428 if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
429 return -EPERM;
431 flush_icache_range(ip, ip + 8);
433 return 0;
435 #endif /* CONFIG_PPC64 */
436 #endif /* CONFIG_MODULES */
438 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
440 unsigned long ip = rec->ip;
441 unsigned int old, new;
444 * If the calling address is more that 24 bits away,
445 * then we had to use a trampoline to make the call.
446 * Otherwise just update the call site.
448 if (test_24bit_addr(ip, addr)) {
449 /* within range */
450 old = PPC_INST_NOP;
451 new = ftrace_call_replace(ip, addr, 1);
452 return ftrace_modify_code(ip, old, new);
455 #ifdef CONFIG_MODULES
457 * Out of range jumps are called from modules.
458 * Being that we are converting from nop, it had better
459 * already have a module defined.
461 if (!rec->arch.mod) {
462 printk(KERN_ERR "No module loaded\n");
463 return -EINVAL;
466 return __ftrace_make_call(rec, addr);
467 #else
468 /* We should not get here without modules */
469 return -EINVAL;
470 #endif /* CONFIG_MODULES */
473 int ftrace_update_ftrace_func(ftrace_func_t func)
475 unsigned long ip = (unsigned long)(&ftrace_call);
476 unsigned int old, new;
477 int ret;
479 old = *(unsigned int *)&ftrace_call;
480 new = ftrace_call_replace(ip, (unsigned long)func, 1);
481 ret = ftrace_modify_code(ip, old, new);
483 return ret;
486 int __init ftrace_dyn_arch_init(void *data)
488 /* caller expects data to be zero */
489 unsigned long *p = data;
491 *p = 0;
493 return 0;
495 #endif /* CONFIG_DYNAMIC_FTRACE */
497 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
499 #ifdef CONFIG_DYNAMIC_FTRACE
500 extern void ftrace_graph_call(void);
501 extern void ftrace_graph_stub(void);
503 int ftrace_enable_ftrace_graph_caller(void)
505 unsigned long ip = (unsigned long)(&ftrace_graph_call);
506 unsigned long addr = (unsigned long)(&ftrace_graph_caller);
507 unsigned long stub = (unsigned long)(&ftrace_graph_stub);
508 unsigned int old, new;
510 old = ftrace_call_replace(ip, stub, 0);
511 new = ftrace_call_replace(ip, addr, 0);
513 return ftrace_modify_code(ip, old, new);
516 int ftrace_disable_ftrace_graph_caller(void)
518 unsigned long ip = (unsigned long)(&ftrace_graph_call);
519 unsigned long addr = (unsigned long)(&ftrace_graph_caller);
520 unsigned long stub = (unsigned long)(&ftrace_graph_stub);
521 unsigned int old, new;
523 old = ftrace_call_replace(ip, addr, 0);
524 new = ftrace_call_replace(ip, stub, 0);
526 return ftrace_modify_code(ip, old, new);
528 #endif /* CONFIG_DYNAMIC_FTRACE */
530 #ifdef CONFIG_PPC64
531 extern void mod_return_to_handler(void);
532 #endif
535 * Hook the return address and push it in the stack of return addrs
536 * in current thread info.
538 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
540 unsigned long old;
541 int faulted;
542 struct ftrace_graph_ent trace;
543 unsigned long return_hooker = (unsigned long)&return_to_handler;
545 if (unlikely(atomic_read(&current->tracing_graph_pause)))
546 return;
548 #ifdef CONFIG_PPC64
549 /* non core kernel code needs to save and restore the TOC */
550 if (REGION_ID(self_addr) != KERNEL_REGION_ID)
551 return_hooker = (unsigned long)&mod_return_to_handler;
552 #endif
554 return_hooker = ppc_function_entry((void *)return_hooker);
557 * Protect against fault, even if it shouldn't
558 * happen. This tool is too much intrusive to
559 * ignore such a protection.
561 asm volatile(
562 "1: " PPC_LL "%[old], 0(%[parent])\n"
563 "2: " PPC_STL "%[return_hooker], 0(%[parent])\n"
564 " li %[faulted], 0\n"
565 "3:\n"
567 ".section .fixup, \"ax\"\n"
568 "4: li %[faulted], 1\n"
569 " b 3b\n"
570 ".previous\n"
572 ".section __ex_table,\"a\"\n"
573 PPC_LONG_ALIGN "\n"
574 PPC_LONG "1b,4b\n"
575 PPC_LONG "2b,4b\n"
576 ".previous"
578 : [old] "=&r" (old), [faulted] "=r" (faulted)
579 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
580 : "memory"
583 if (unlikely(faulted)) {
584 ftrace_graph_stop();
585 WARN_ON(1);
586 return;
589 if (ftrace_push_return_trace(old, self_addr, &trace.depth, 0) == -EBUSY) {
590 *parent = old;
591 return;
594 trace.func = self_addr;
596 /* Only trace if the calling function expects to */
597 if (!ftrace_graph_entry(&trace)) {
598 current->curr_ret_stack--;
599 *parent = old;
602 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */