MIPS: Tracing: Reduce the overhead of dynamic Function Tracer (e4240540) · Commits · 戴 / test

arch/mips/kernel/ftrace.c

+49 −44

Original line number	Diff line number	Diff line
		@@ -2,7 +2,7 @@
		* Code for replacing ftrace calls with jumps.
		*
		* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
		* Copyright (C) 2009 DSLab, Lanzhou University, China
		* Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
		* Author: Wu Zhangjin <wuzhangjin@gmail.com>
		*
		* Thanks goes to Steven Rostedt for writing the original x86 version.
		@@ -12,21 +12,46 @@
		#include <linux/init.h>
		#include <linux/ftrace.h>

		#include <asm/cacheflush.h>
		#include <asm/asm.h>
		#include <asm/asm-offsets.h>
		#include <asm/cacheflush.h>
		#include <asm/uasm.h>

		#ifdef CONFIG_DYNAMIC_FTRACE

		#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
		#define ADDR_MASK 0x03ffffff /* op_code\|addr : 31...26\|25 ....0 */
		#define jump_insn_encode(op_code, addr) \
		((unsigned int)((op_code) \| (((addr) >> 2) & ADDR_MASK)))

		#define INSN_B_1F_4 0x10000004 /* b 1f; offset = 4 */
		#define INSN_B_1F_5 0x10000005 /* b 1f; offset = 5 */
		#define INSN_NOP 0x00000000 /* nop */
		#define INSN_JAL(addr) jump_insn_encode(JAL, addr)
		#define INSN_JAL(addr) \
		((unsigned int)(JAL \| (((addr) >> 2) & ADDR_MASK)))

		static unsigned int insn_jal_ftrace_caller __read_mostly;
		static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
		static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;

		static inline void ftrace_dyn_arch_init_insns(void)
		{
		u32 *buf;
		unsigned int v1;

		/* lui v1, hi16_mcount */
		v1 = 3;
		buf = (u32 *)&insn_lui_v1_hi16_mcount;
		UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);

		/* jal (ftrace_caller + 8), jump over the first two instruction */
		buf = (u32 *)&insn_jal_ftrace_caller;
		uasm_i_jal(&buf, (FTRACE_ADDR + 8));

		#ifdef CONFIG_FUNCTION_GRAPH_TRACER
		/* j ftrace_graph_caller */
		buf = (u32 *)&insn_j_ftrace_graph_caller;
		uasm_i_j(&buf, (unsigned long)ftrace_graph_caller);
		#endif
		}

		static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
		{
		@@ -43,30 +68,20 @@ static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
		return 0;
		}

		static int lui_v1;
		static int jal_mcount;

		int ftrace_make_nop(struct module *mod,
		struct dyn_ftrace *rec, unsigned long addr)
		{
		unsigned int new;
		int faulted;
		unsigned long ip = rec->ip;

		/* We have compiled module with -mlong-calls, but compiled the kernel
		* without it, we need to cope with them respectively. */
		/*
		* We have compiled module with -mlong-calls, but compiled the kernel
		* without it, we need to cope with them respectively.
		*/
		if (ip & 0x40000000) {
		/* record it for ftrace_make_call */
		if (lui_v1 == 0) {
		/* lui_v1 = (unsigned int )ip; */
		safe_load_code(lui_v1, ip, faulted);

		if (unlikely(faulted))
		return -EFAULT;
		}

		#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
		/* lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
		/*
		* lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
		* addiu v1, v1, low_16bit_of_mcount
		* move at, ra
		* move $12, ra_address
		@@ -76,7 +91,8 @@ int ftrace_make_nop(struct module *mod,
		*/
		new = INSN_B_1F_5;
		#else
		/* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
		/*
		* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
		* addiu v1, v1, low_16bit_of_mcount
		* move at, ra
		* jalr v1
		@@ -86,36 +102,22 @@ int ftrace_make_nop(struct module *mod,
		new = INSN_B_1F_4;
		#endif
		} else {
		/* record/calculate it for ftrace_make_call */
		if (jal_mcount == 0) {
		/* We can record it directly like this:
		* jal_mcount = (unsigned int )ip;
		* Herein, jump over the first two nop instructions */
		jal_mcount = INSN_JAL(MCOUNT_ADDR + 8);
		}

		/* move at, ra
		* jalr v1 --> nop
		/*
		* move at, ra
		* jal _mcount --> nop
		*/
		new = INSN_NOP;
		}
		return ftrace_modify_code(ip, new);
		}

		static int modified; /* initialized as 0 by default */

		int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
		{
		unsigned int new;
		unsigned long ip = rec->ip;

		/* We just need to remove the "b ftrace_stub" at the fist time! */
		if (modified == 0) {
		modified = 1;
		ftrace_modify_code(addr, INSN_NOP);
		}
		/* ip, module: 0xc0000000, kernel: 0x80000000 */
		new = (ip & 0x40000000) ? lui_v1 : jal_mcount;
		new = (ip & 0x40000000) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller;

		return ftrace_modify_code(ip, new);
		}
		@@ -133,6 +135,12 @@ int ftrace_update_ftrace_func(ftrace_func_t func)

		int __init ftrace_dyn_arch_init(void *data)
		{
		/* Encode the instructions when booting */
		ftrace_dyn_arch_init_insns();

		/* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
		ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);

		/* The return code is retured via data */
		(unsigned long )data = 0;

		@@ -145,15 +153,12 @@ int __init ftrace_dyn_arch_init(void *data)
		#ifdef CONFIG_DYNAMIC_FTRACE

		extern void ftrace_graph_call(void);
		#define JMP 0x08000000 /* jump to target directly */
		#define CALL_FTRACE_GRAPH_CALLER \
		jump_insn_encode(JMP, (unsigned long)(&ftrace_graph_caller))
		#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))

		int ftrace_enable_ftrace_graph_caller(void)
		{
		return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
		CALL_FTRACE_GRAPH_CALLER);
		insn_j_ftrace_graph_caller);
		}

		int ftrace_disable_ftrace_graph_caller(void)

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