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>
25 #include <asm/syscall.h>
28 #ifdef CONFIG_DYNAMIC_FTRACE
30 ftrace_call_replace(unsigned long ip
, unsigned long addr
, int link
)
34 addr
= ppc_function_entry((void *)addr
);
36 /* if (link) set op to 'bl' else 'b' */
37 op
= create_branch((unsigned int *)ip
, addr
, link
? 1 : 0);
43 ftrace_modify_code(unsigned long ip
, unsigned int old
, unsigned int new)
45 unsigned int replaced
;
48 * Note: Due to modules and __init, code can
49 * disappear and change, we need to protect against faulting
50 * as well as code changing. We do this by using the
51 * probe_kernel_* functions.
53 * No real locking needed, this code is run through
54 * kstop_machine, or before SMP starts.
57 /* read the text we want to modify */
58 if (probe_kernel_read(&replaced
, (void *)ip
, MCOUNT_INSN_SIZE
))
61 /* Make sure it is what we expect it to be */
65 /* replace the text with the new text */
66 if (patch_instruction((unsigned int *)ip
, new))
73 * Helper functions that are the same for both PPC64 and PPC32.
75 static int test_24bit_addr(unsigned long ip
, unsigned long addr
)
78 /* use the create_branch to verify that this offset can be branched */
79 return create_branch((unsigned int *)ip
, addr
, 0);
84 static int is_bl_op(unsigned int op
)
86 return (op
& 0xfc000003) == 0x48000001;
89 static unsigned long find_bl_target(unsigned long ip
, unsigned int op
)
93 offset
= (op
& 0x03fffffc);
95 if (offset
& 0x02000000)
98 return ip
+ (long)offset
;
103 __ftrace_make_nop(struct module
*mod
,
104 struct dyn_ftrace
*rec
, unsigned long addr
)
109 unsigned long ip
= rec
->ip
;
113 /* read where this goes */
114 if (probe_kernel_read(&op
, (void *)ip
, sizeof(int)))
117 /* Make sure that that this is still a 24bit jump */
119 printk(KERN_ERR
"Not expected bl: opcode is %x\n", op
);
123 /* lets find where the pointer goes */
124 tramp
= find_bl_target(ip
, op
);
127 * On PPC64 the trampoline looks like:
128 * 0x3d, 0x82, 0x00, 0x00, addis r12,r2, <high>
129 * 0x39, 0x8c, 0x00, 0x00, addi r12,r12, <low>
130 * Where the bytes 2,3,6 and 7 make up the 32bit offset
131 * to the TOC that holds the pointer.
133 * 0xf8, 0x41, 0x00, 0x28, std r2,40(r1)
134 * 0xe9, 0x6c, 0x00, 0x20, ld r11,32(r12)
135 * The actually address is 32 bytes from the offset
137 * 0xe8, 0x4c, 0x00, 0x28, ld r2,40(r12)
140 pr_devel("ip:%lx jumps to %lx r2: %lx", ip
, tramp
, mod
->arch
.toc
);
142 /* Find where the trampoline jumps to */
143 if (probe_kernel_read(jmp
, (void *)tramp
, sizeof(jmp
))) {
144 printk(KERN_ERR
"Failed to read %lx\n", tramp
);
148 pr_devel(" %08x %08x", jmp
[0], jmp
[1]);
150 /* verify that this is what we expect it to be */
151 if (((jmp
[0] & 0xffff0000) != 0x3d820000) ||
152 ((jmp
[1] & 0xffff0000) != 0x398c0000) ||
153 (jmp
[2] != 0xf8410028) ||
154 (jmp
[3] != 0xe96c0020) ||
155 (jmp
[4] != 0xe84c0028)) {
156 printk(KERN_ERR
"Not a trampoline\n");
160 /* The bottom half is signed extended */
161 offset
= ((unsigned)((unsigned short)jmp
[0]) << 16) +
162 (int)((short)jmp
[1]);
164 pr_devel(" %x ", offset
);
166 /* get the address this jumps too */
167 tramp
= mod
->arch
.toc
+ offset
+ 32;
168 pr_devel("toc: %lx", tramp
);
170 if (probe_kernel_read(jmp
, (void *)tramp
, 8)) {
171 printk(KERN_ERR
"Failed to read %lx\n", tramp
);
175 pr_devel(" %08x %08x\n", jmp
[0], jmp
[1]);
177 #ifdef __LITTLE_ENDIAN__
178 ptr
= ((unsigned long)jmp
[1] << 32) + jmp
[0];
180 ptr
= ((unsigned long)jmp
[0] << 32) + jmp
[1];
183 /* This should match what was called */
184 if (ptr
!= ppc_function_entry((void *)addr
)) {
185 printk(KERN_ERR
"addr does not match %lx\n", ptr
);
190 * We want to nop the line, but the next line is
191 * 0xe8, 0x41, 0x00, 0x28 ld r2,40(r1)
192 * This needs to be turned to a nop too.
194 if (probe_kernel_read(&op
, (void *)(ip
+4), MCOUNT_INSN_SIZE
))
197 if (op
!= 0xe8410028) {
198 printk(KERN_ERR
"Next line is not ld! (%08x)\n", op
);
203 * Milton Miller pointed out that we can not blindly do nops.
204 * If a task was preempted when calling a trace function,
205 * the nops will remove the way to restore the TOC in r2
206 * and the r2 TOC will get corrupted.
211 * bl <tramp> <==== will be replaced with "b 1f"
215 op
= 0x48000008; /* b +8 */
217 if (patch_instruction((unsigned int *)ip
, op
))
225 __ftrace_make_nop(struct module
*mod
,
226 struct dyn_ftrace
*rec
, unsigned long addr
)
230 unsigned long ip
= rec
->ip
;
233 if (probe_kernel_read(&op
, (void *)ip
, MCOUNT_INSN_SIZE
))
236 /* Make sure that that this is still a 24bit jump */
238 printk(KERN_ERR
"Not expected bl: opcode is %x\n", op
);
242 /* lets find where the pointer goes */
243 tramp
= find_bl_target(ip
, op
);
246 * On PPC32 the trampoline looks like:
247 * 0x3d, 0x80, 0x00, 0x00 lis r12,sym@ha
248 * 0x39, 0x8c, 0x00, 0x00 addi r12,r12,sym@l
249 * 0x7d, 0x89, 0x03, 0xa6 mtctr r12
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
);
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) != 0x3d800000) ||
265 ((jmp
[1] & 0xffff0000) != 0x398c0000) ||
266 (jmp
[2] != 0x7d8903a6) ||
267 (jmp
[3] != 0x4e800420)) {
268 printk(KERN_ERR
"Not a trampoline\n");
272 tramp
= (jmp
[1] & 0xffff) |
273 ((jmp
[0] & 0xffff) << 16);
277 pr_devel(" %lx ", tramp
);
281 "Trampoline location %08lx does not match addr\n",
288 if (patch_instruction((unsigned int *)ip
, op
))
294 #endif /* CONFIG_MODULES */
296 int ftrace_make_nop(struct module
*mod
,
297 struct dyn_ftrace
*rec
, unsigned long addr
)
299 unsigned long ip
= rec
->ip
;
300 unsigned int old
, new;
303 * If the calling address is more that 24 bits away,
304 * then we had to use a trampoline to make the call.
305 * Otherwise just update the call site.
307 if (test_24bit_addr(ip
, addr
)) {
309 old
= ftrace_call_replace(ip
, addr
, 1);
311 return ftrace_modify_code(ip
, old
, new);
314 #ifdef CONFIG_MODULES
316 * Out of range jumps are called from modules.
317 * We should either already have a pointer to the module
318 * or it has been passed in.
320 if (!rec
->arch
.mod
) {
322 printk(KERN_ERR
"No module loaded addr=%lx\n",
328 if (mod
!= rec
->arch
.mod
) {
330 "Record mod %p not equal to passed in mod %p\n",
334 /* nothing to do if mod == rec->arch.mod */
338 return __ftrace_make_nop(mod
, rec
, addr
);
340 /* We should not get here without modules */
342 #endif /* CONFIG_MODULES */
345 #ifdef CONFIG_MODULES
348 __ftrace_make_call(struct dyn_ftrace
*rec
, unsigned long addr
)
351 unsigned long ip
= rec
->ip
;
353 /* read where this goes */
354 if (probe_kernel_read(op
, (void *)ip
, MCOUNT_INSN_SIZE
* 2))
358 * It should be pointing to two nops or
361 if (((op
[0] != 0x48000008) || (op
[1] != 0xe8410028)) &&
362 ((op
[0] != PPC_INST_NOP
) || (op
[1] != PPC_INST_NOP
))) {
363 printk(KERN_ERR
"Expected NOPs but have %x %x\n", op
[0], op
[1]);
367 /* If we never set up a trampoline to ftrace_caller, then bail */
368 if (!rec
->arch
.mod
->arch
.tramp
) {
369 printk(KERN_ERR
"No ftrace trampoline\n");
373 /* create the branch to the trampoline */
374 op
[0] = create_branch((unsigned int *)ip
,
375 rec
->arch
.mod
->arch
.tramp
, BRANCH_SET_LINK
);
377 printk(KERN_ERR
"REL24 out of range!\n");
384 pr_devel("write to %lx\n", rec
->ip
);
386 if (probe_kernel_write((void *)ip
, op
, MCOUNT_INSN_SIZE
* 2))
389 flush_icache_range(ip
, ip
+ 8);
395 __ftrace_make_call(struct dyn_ftrace
*rec
, unsigned long addr
)
398 unsigned long ip
= rec
->ip
;
400 /* read where this goes */
401 if (probe_kernel_read(&op
, (void *)ip
, MCOUNT_INSN_SIZE
))
404 /* It should be pointing to a nop */
405 if (op
!= PPC_INST_NOP
) {
406 printk(KERN_ERR
"Expected NOP but have %x\n", op
);
410 /* If we never set up a trampoline to ftrace_caller, then bail */
411 if (!rec
->arch
.mod
->arch
.tramp
) {
412 printk(KERN_ERR
"No ftrace trampoline\n");
416 /* create the branch to the trampoline */
417 op
= create_branch((unsigned int *)ip
,
418 rec
->arch
.mod
->arch
.tramp
, BRANCH_SET_LINK
);
420 printk(KERN_ERR
"REL24 out of range!\n");
424 pr_devel("write to %lx\n", rec
->ip
);
426 if (patch_instruction((unsigned int *)ip
, op
))
431 #endif /* CONFIG_PPC64 */
432 #endif /* CONFIG_MODULES */
434 int ftrace_make_call(struct dyn_ftrace
*rec
, unsigned long addr
)
436 unsigned long ip
= rec
->ip
;
437 unsigned int old
, new;
440 * If the calling address is more that 24 bits away,
441 * then we had to use a trampoline to make the call.
442 * Otherwise just update the call site.
444 if (test_24bit_addr(ip
, addr
)) {
447 new = ftrace_call_replace(ip
, addr
, 1);
448 return ftrace_modify_code(ip
, old
, new);
451 #ifdef CONFIG_MODULES
453 * Out of range jumps are called from modules.
454 * Being that we are converting from nop, it had better
455 * already have a module defined.
457 if (!rec
->arch
.mod
) {
458 printk(KERN_ERR
"No module loaded\n");
462 return __ftrace_make_call(rec
, addr
);
464 /* We should not get here without modules */
466 #endif /* CONFIG_MODULES */
469 int ftrace_update_ftrace_func(ftrace_func_t func
)
471 unsigned long ip
= (unsigned long)(&ftrace_call
);
472 unsigned int old
, new;
475 old
= *(unsigned int *)&ftrace_call
;
476 new = ftrace_call_replace(ip
, (unsigned long)func
, 1);
477 ret
= ftrace_modify_code(ip
, old
, new);
482 static int __ftrace_replace_code(struct dyn_ftrace
*rec
, int enable
)
484 unsigned long ftrace_addr
= (unsigned long)FTRACE_ADDR
;
487 ret
= ftrace_update_record(rec
, enable
);
490 case FTRACE_UPDATE_IGNORE
:
492 case FTRACE_UPDATE_MAKE_CALL
:
493 return ftrace_make_call(rec
, ftrace_addr
);
494 case FTRACE_UPDATE_MAKE_NOP
:
495 return ftrace_make_nop(NULL
, rec
, ftrace_addr
);
501 void ftrace_replace_code(int enable
)
503 struct ftrace_rec_iter
*iter
;
504 struct dyn_ftrace
*rec
;
507 for (iter
= ftrace_rec_iter_start(); iter
;
508 iter
= ftrace_rec_iter_next(iter
)) {
509 rec
= ftrace_rec_iter_record(iter
);
510 ret
= __ftrace_replace_code(rec
, enable
);
512 ftrace_bug(ret
, rec
->ip
);
518 void arch_ftrace_update_code(int command
)
520 if (command
& FTRACE_UPDATE_CALLS
)
521 ftrace_replace_code(1);
522 else if (command
& FTRACE_DISABLE_CALLS
)
523 ftrace_replace_code(0);
525 if (command
& FTRACE_UPDATE_TRACE_FUNC
)
526 ftrace_update_ftrace_func(ftrace_trace_function
);
528 if (command
& FTRACE_START_FUNC_RET
)
529 ftrace_enable_ftrace_graph_caller();
530 else if (command
& FTRACE_STOP_FUNC_RET
)
531 ftrace_disable_ftrace_graph_caller();
534 int __init
ftrace_dyn_arch_init(void *data
)
536 /* caller expects data to be zero */
537 unsigned long *p
= data
;
543 #endif /* CONFIG_DYNAMIC_FTRACE */
545 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
547 #ifdef CONFIG_DYNAMIC_FTRACE
548 extern void ftrace_graph_call(void);
549 extern void ftrace_graph_stub(void);
551 int ftrace_enable_ftrace_graph_caller(void)
553 unsigned long ip
= (unsigned long)(&ftrace_graph_call
);
554 unsigned long addr
= (unsigned long)(&ftrace_graph_caller
);
555 unsigned long stub
= (unsigned long)(&ftrace_graph_stub
);
556 unsigned int old
, new;
558 old
= ftrace_call_replace(ip
, stub
, 0);
559 new = ftrace_call_replace(ip
, addr
, 0);
561 return ftrace_modify_code(ip
, old
, new);
564 int ftrace_disable_ftrace_graph_caller(void)
566 unsigned long ip
= (unsigned long)(&ftrace_graph_call
);
567 unsigned long addr
= (unsigned long)(&ftrace_graph_caller
);
568 unsigned long stub
= (unsigned long)(&ftrace_graph_stub
);
569 unsigned int old
, new;
571 old
= ftrace_call_replace(ip
, addr
, 0);
572 new = ftrace_call_replace(ip
, stub
, 0);
574 return ftrace_modify_code(ip
, old
, new);
576 #endif /* CONFIG_DYNAMIC_FTRACE */
579 extern void mod_return_to_handler(void);
583 * Hook the return address and push it in the stack of return addrs
584 * in current thread info.
586 void prepare_ftrace_return(unsigned long *parent
, unsigned long self_addr
)
590 struct ftrace_graph_ent trace
;
591 unsigned long return_hooker
= (unsigned long)&return_to_handler
;
593 if (unlikely(atomic_read(¤t
->tracing_graph_pause
)))
597 /* non core kernel code needs to save and restore the TOC */
598 if (REGION_ID(self_addr
) != KERNEL_REGION_ID
)
599 return_hooker
= (unsigned long)&mod_return_to_handler
;
602 return_hooker
= ppc_function_entry((void *)return_hooker
);
605 * Protect against fault, even if it shouldn't
606 * happen. This tool is too much intrusive to
607 * ignore such a protection.
610 "1: " PPC_LL
"%[old], 0(%[parent])\n"
611 "2: " PPC_STL
"%[return_hooker], 0(%[parent])\n"
612 " li %[faulted], 0\n"
615 ".section .fixup, \"ax\"\n"
616 "4: li %[faulted], 1\n"
620 ".section __ex_table,\"a\"\n"
626 : [old
] "=&r" (old
), [faulted
] "=r" (faulted
)
627 : [parent
] "r" (parent
), [return_hooker
] "r" (return_hooker
)
631 if (unlikely(faulted
)) {
637 trace
.func
= self_addr
;
638 trace
.depth
= current
->curr_ret_stack
+ 1;
640 /* Only trace if the calling function expects to */
641 if (!ftrace_graph_entry(&trace
)) {
646 if (ftrace_push_return_trace(old
, self_addr
, &trace
.depth
, 0) == -EBUSY
)
649 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
651 #if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64)
652 unsigned long __init
arch_syscall_addr(int nr
)
654 return sys_call_table
[nr
*2];
656 #endif /* CONFIG_FTRACE_SYSCALLS && CONFIG_PPC64 */
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