1/*
  2 * Copyright (C) 2008 Imagination Technologies Ltd.
  3 * Licensed under the GPL
  4 *
  5 * Dynamic ftrace support.
  6 */
  7
  8#include <linux/ftrace.h>
  9#include <linux/io.h>
 10#include <linux/uaccess.h>
 11
 12#include <asm/cacheflush.h>
 13
 14#define D04_MOVT_TEMPLATE	0x02200005
 15#define D04_CALL_TEMPLATE	0xAC200005
 16#define D1RTP_MOVT_TEMPLATE	0x03200005
 17#define D1RTP_CALL_TEMPLATE	0xAC200006
 18
 19static const unsigned long NOP[2] = {0xa0fffffe, 0xa0fffffe};
 20static unsigned long movt_and_call_insn[2];
 21
 22static unsigned char *ftrace_nop_replace(void)
 23{
 24	return (char *)&NOP[0];
 25}
 26
 27static unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr)
 28{
 29	unsigned long hi16, low16;
 30
 31	hi16 = (addr & 0xffff0000) >> 13;
 32	low16 = (addr & 0x0000ffff) << 3;
 33
 34	/*
 35	 * The compiler makes the call to mcount_wrapper()
 36	 * (Meta's wrapper around mcount()) through the register
 37	 * D0.4. So whenever we're patching one of those compiler-generated
 38	 * calls we also need to go through D0.4. Otherwise use D1RtP.
 39	 */
 40	if (pc == (unsigned long)&ftrace_call) {
 41		writel(D1RTP_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
 42		writel(D1RTP_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
 43	} else {
 44		writel(D04_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
 45		writel(D04_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
 46	}
 47
 48	return (unsigned char *)&movt_and_call_insn[0];
 49}
 50
 51static int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
 52			      unsigned char *new_code)
 53{
 54	unsigned char replaced[MCOUNT_INSN_SIZE];
 55
 56	/*
 57	 * Note: Due to modules and __init, code can
 58	 *  disappear and change, we need to protect against faulting
 59	 *  as well as code changing.
 60	 *
 61	 * No real locking needed, this code is run through
 62	 * kstop_machine.
 63	 */
 64
 65	/* read the text we want to modify */
 66	if (probe_kernel_read(replaced, (void *)pc, MCOUNT_INSN_SIZE))
 67		return -EFAULT;
 68
 69	/* Make sure it is what we expect it to be */
 70	if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
 71		return -EINVAL;
 72
 73	/* replace the text with the new text */
 74	if (probe_kernel_write((void *)pc, new_code, MCOUNT_INSN_SIZE))
 75		return -EPERM;
 76
 77	flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
 78
 79	return 0;
 80}
 81
 82int ftrace_update_ftrace_func(ftrace_func_t func)
 83{
 84	int ret;
 85	unsigned long pc;
 86	unsigned char old[MCOUNT_INSN_SIZE], *new;
 87
 88	pc = (unsigned long)&ftrace_call;
 89	memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
 90	new = ftrace_call_replace(pc, (unsigned long)func);
 91	ret = ftrace_modify_code(pc, old, new);
 92
 93	return ret;
 94}
 95
 96int ftrace_make_nop(struct module *mod,
 97		    struct dyn_ftrace *rec, unsigned long addr)
 98{
 99	unsigned char *new, *old;
100	unsigned long ip = rec->ip;
101
102	old = ftrace_call_replace(ip, addr);
103	new = ftrace_nop_replace();
104
105	return ftrace_modify_code(ip, old, new);
106}
107
108int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
109{
110	unsigned char *new, *old;
111	unsigned long ip = rec->ip;
112
113	old = ftrace_nop_replace();
114	new = ftrace_call_replace(ip, addr);
115
116	return ftrace_modify_code(ip, old, new);
117}
118
119/* run from kstop_machine */
120int __init ftrace_dyn_arch_init(void)
121{
122	return 0;
123}