ftrace.c

  1/*
  2 * Ftrace support for Microblaze.
  3 *
  4 * Copyright (C) 2009 Michal Simek <monstr@monstr.eu>
  5 * Copyright (C) 2009 PetaLogix
  6 *
  7 * Based on MIPS and PowerPC ftrace code
  8 *
  9 * This file is subject to the terms and conditions of the GNU General Public
 10 * License. See the file "COPYING" in the main directory of this archive
 11 * for more details.
 12 */
 13
 14#include <asm/cacheflush.h>
 15#include <linux/ftrace.h>
 16
 17#ifdef CONFIG_FUNCTION_GRAPH_TRACER
 18/*
 19 * Hook the return address and push it in the stack of return addrs
 20 * in current thread info.
 21 */
 22void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 23{
 24	unsigned long old;
 25	int faulted;
 26	unsigned long return_hooker = (unsigned long)
 27				&return_to_handler;
 28
 29	if (unlikely(ftrace_graph_is_dead()))
 30		return;
 31
 32	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 33		return;
 34
 35	/*
 36	 * Protect against fault, even if it shouldn't
 37	 * happen. This tool is too much intrusive to
 38	 * ignore such a protection.
 39	 */
 40	asm volatile("	1:	lwi	%0, %2, 0;"		\
 41			"2:	swi	%3, %2, 0;"		\
 42			"	addik	%1, r0, 0;"		\
 43			"3:"					\
 44			"	.section .fixup, \"ax\";"	\
 45			"4:	brid	3b;"			\
 46			"	addik	%1, r0, 1;"		\
 47			"	.previous;"			\
 48			"	.section __ex_table,\"a\";"	\
 49			"	.word	1b,4b;"			\
 50			"	.word	2b,4b;"			\
 51			"	.previous;"			\
 52			: "=&r" (old), "=r" (faulted)
 53			: "r" (parent), "r" (return_hooker)
 54	);
 55
 56	flush_dcache_range((u32)parent, (u32)parent + 4);
 57	flush_icache_range((u32)parent, (u32)parent + 4);
 58
 59	if (unlikely(faulted)) {
 60		ftrace_graph_stop();
 61		WARN_ON(1);
 62		return;
 63	}
 64
 65	if (function_graph_enter(old, self_addr, 0, NULL))
 66		*parent = old;
 67}
 68#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 69
 70#ifdef CONFIG_DYNAMIC_FTRACE
 71/* save value to addr - it is save to do it in asm */
 72static int ftrace_modify_code(unsigned long addr, unsigned int value)
 73{
 74	int faulted = 0;
 75
 76	__asm__ __volatile__("	1:	swi	%2, %1, 0;"		\
 77				"	addik	%0, r0, 0;"		\
 78				"2:"					\
 79				"	.section .fixup, \"ax\";"	\
 80				"3:	brid	2b;"			\
 81				"	addik	%0, r0, 1;"		\
 82				"	.previous;"			\
 83				"	.section __ex_table,\"a\";"	\
 84				"	.word	1b,3b;"			\
 85				"	.previous;"			\
 86				: "=r" (faulted)
 87				: "r" (addr), "r" (value)
 88	);
 89
 90	if (unlikely(faulted))
 91		return -EFAULT;
 92
 93	flush_dcache_range(addr, addr + 4);
 94	flush_icache_range(addr, addr + 4);
 95
 96	return 0;
 97}
 98
 99#define MICROBLAZE_NOP 0x80000000
100#define MICROBLAZE_BRI 0xb800000C
101
102static unsigned int recorded; /* if save was or not */
103static unsigned int imm; /* saving whole imm instruction */
104
105/* There are two approaches howto solve ftrace_make nop function - look below */
106#undef USE_FTRACE_NOP
107
108#ifdef USE_FTRACE_NOP
109static unsigned int bralid; /* saving whole bralid instruction */
110#endif
111
112int ftrace_make_nop(struct module *mod,
113			struct dyn_ftrace *rec, unsigned long addr)
114{
115	/* we have this part of code which we are working with
116	 * b000c000        imm     -16384
117	 * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
118	 * 80000000        or      r0, r0, r0
119	 *
120	 * The first solution (!USE_FTRACE_NOP-could be called branch solution)
121	 * b000c000        bri	12 (0xC - jump to any other instruction)
122	 * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
123	 * 80000000        or      r0, r0, r0
124	 * any other instruction
125	 *
126	 * The second solution (USE_FTRACE_NOP) - no jump just nops
127	 * 80000000        or      r0, r0, r0
128	 * 80000000        or      r0, r0, r0
129	 * 80000000        or      r0, r0, r0
130	 */
131	int ret = 0;
132
133	if (recorded == 0) {
134		recorded = 1;
135		imm = *(unsigned int *)rec->ip;
136		pr_debug("%s: imm:0x%x\n", __func__, imm);
137#ifdef USE_FTRACE_NOP
138		bralid = *(unsigned int *)(rec->ip + 4);
139		pr_debug("%s: bralid 0x%x\n", __func__, bralid);
140#endif /* USE_FTRACE_NOP */
141	}
142
143#ifdef USE_FTRACE_NOP
144	ret = ftrace_modify_code(rec->ip, MICROBLAZE_NOP);
145	ret += ftrace_modify_code(rec->ip + 4, MICROBLAZE_NOP);
146#else /* USE_FTRACE_NOP */
147	ret = ftrace_modify_code(rec->ip, MICROBLAZE_BRI);
148#endif /* USE_FTRACE_NOP */
149	return ret;
150}
151
152/* I believe that first is called ftrace_make_nop before this function */
153int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
154{
155	int ret;
156	pr_debug("%s: addr:0x%x, rec->ip: 0x%x, imm:0x%x\n",
157		__func__, (unsigned int)addr, (unsigned int)rec->ip, imm);
158	ret = ftrace_modify_code(rec->ip, imm);
159#ifdef USE_FTRACE_NOP
160	pr_debug("%s: bralid:0x%x\n", __func__, bralid);
161	ret += ftrace_modify_code(rec->ip + 4, bralid);
162#endif /* USE_FTRACE_NOP */
163	return ret;
164}
165
166int ftrace_update_ftrace_func(ftrace_func_t func)
167{
168	unsigned long ip = (unsigned long)(&ftrace_call);
169	unsigned int upper = (unsigned int)func;
170	unsigned int lower = (unsigned int)func;
171	int ret = 0;
172
173	/* create proper saving to ftrace_call poll */
174	upper = 0xb0000000 + (upper >> 16); /* imm func_upper */
175	lower = 0x32800000 + (lower & 0xFFFF); /* addik r20, r0, func_lower */
176
177	pr_debug("%s: func=0x%x, ip=0x%x, upper=0x%x, lower=0x%x\n",
178		__func__, (unsigned int)func, (unsigned int)ip, upper, lower);
179
180	/* save upper and lower code */
181	ret = ftrace_modify_code(ip, upper);
182	ret += ftrace_modify_code(ip + 4, lower);
183
184	/* We just need to replace the rtsd r15, 8 with NOP */
185	ret += ftrace_modify_code((unsigned long)&ftrace_caller,
186				  MICROBLAZE_NOP);
187
188	return ret;
189}
190
191#ifdef CONFIG_FUNCTION_GRAPH_TRACER
192unsigned int old_jump; /* saving place for jump instruction */
193
194int ftrace_enable_ftrace_graph_caller(void)
195{
196	unsigned int ret;
197	unsigned long ip = (unsigned long)(&ftrace_call_graph);
198
199	old_jump = *(unsigned int *)ip; /* save jump over instruction */
200	ret = ftrace_modify_code(ip, MICROBLAZE_NOP);
201
202	pr_debug("%s: Replace instruction: 0x%x\n", __func__, old_jump);
203	return ret;
204}
205
206int ftrace_disable_ftrace_graph_caller(void)
207{
208	unsigned int ret;
209	unsigned long ip = (unsigned long)(&ftrace_call_graph);
210
211	ret = ftrace_modify_code(ip, old_jump);
212
213	pr_debug("%s\n", __func__);
214	return ret;
215}
216#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
217#endif /* CONFIG_DYNAMIC_FTRACE */