// SPDX-License-Identifier: GPL-2.0/* * Code for replacing ftrace calls with jumps. * * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> * 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. */ #include <linux/uaccess.h>#include <linux/init.h>#include <linux/ftrace.h>#include <linux/syscalls.h> #include <asm/asm.h>#include <asm/asm-offsets.h>#include <asm/cacheflush.h>#include <asm/syscall.h>#include <asm/uasm.h>#include <asm/unistd.h> #include <asm-generic/sections.h> #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)#define MCOUNT_OFFSET_INSNS 5#else#define MCOUNT_OFFSET_INSNS 4#endif #ifdef CONFIG_DYNAMIC_FTRACE /* Arch override because MIPS doesn't need to run this from stop_machine() */void arch_ftrace_update_code(int command){	ftrace_modify_all_code(command);} #define JAL 0x0c000000		/* jump & link: ip --> ra, jump to target */#define ADDR_MASK 0x03ffffff	/*  op_code|addr : 31...26|25 ....0 */#define JUMP_RANGE_MASK ((1UL << 28) - 1) #define INSN_NOP 0x00000000	/* nop */#define INSN_JAL(addr)	\	((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK))) static unsigned int insn_jal_ftrace_caller __read_mostly;static unsigned int insn_la_mcount[2] __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; 	/* If we are not in compat space, the number of generated	 * instructions will exceed the maximum expected limit of 2.	 * To prevent buffer overflow, we avoid generating them.	 * insn_la_mcount will not be used later in ftrace_make_call.	 */	if (uasm_in_compat_space_p(MCOUNT_ADDR)) {		/* la v1, _mcount */		v1 = 3;		buf = (u32 *)&insn_la_mcount[0];		UASM_i_LA(&buf, v1, MCOUNT_ADDR);	} else {		pr_warn("ftrace: mcount address beyond 32 bits is not supported (%lX)\n",			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) & JUMP_RANGE_MASK); #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 & JUMP_RANGE_MASK);#endif} static int ftrace_modify_code(unsigned long ip, unsigned int new_code){	int faulted; 	/* *(unsigned int *)ip = new_code; */	safe_store_code(new_code, ip, faulted); 	if (unlikely(faulted))		return -EFAULT; 	flush_icache_range(ip, ip + 8); 	return 0;} #ifndef CONFIG_64BITstatic int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,				unsigned int new_code2){	int faulted; 	safe_store_code(new_code1, ip, faulted);	if (unlikely(faulted))		return -EFAULT; 	ip += 4;	safe_store_code(new_code2, ip, faulted);	if (unlikely(faulted))		return -EFAULT; 	ip -= 4;	flush_icache_range(ip, ip + 8); 	return 0;} static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,				 unsigned int new_code2){	int faulted; 	ip += 4;	safe_store_code(new_code2, ip, faulted);	if (unlikely(faulted))		return -EFAULT; 	ip -= 4;	safe_store_code(new_code1, ip, faulted);	if (unlikely(faulted))		return -EFAULT; 	flush_icache_range(ip, ip + 8); 	return 0;}#endif /* * The details about the calling site of mcount on MIPS * * 1. For kernel: * * move at, ra * jal _mcount		--> nop *  sub sp, sp, 8	--> nop  (CONFIG_32BIT) * * 2. For modules: * * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT * * lui v1, hi_16bit_of_mcount	     --> b 1f (0x10000005) * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT) * move at, ra * move $12, ra_address * jalr v1 *  sub sp, sp, 8 *				    1: offset = 5 instructions * 2.2 For the Other situations * * lui v1, hi_16bit_of_mcount	     --> b 1f (0x10000004) * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT) * move at, ra * jalr v1 *  nop | move $12, ra_address | sub sp, sp, 8 *				    1: offset = 4 instructions */ #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS) int ftrace_make_nop(struct module *mod,		    struct dyn_ftrace *rec, unsigned long addr){	unsigned int new;	unsigned long ip = rec->ip; 	/*	 * If ip is in kernel space, no long call, otherwise, long call is	 * needed.	 */	new = core_kernel_text(ip) ? INSN_NOP : INSN_B_1F;#ifdef CONFIG_64BIT	return ftrace_modify_code(ip, new);#else	/*	 * On 32 bit MIPS platforms, gcc adds a stack adjust	 * instruction in the delay slot after the branch to	 * mcount and expects mcount to restore the sp on return.	 * This is based on a legacy API and does nothing but	 * waste instructions so it's being removed at runtime.	 */	return ftrace_modify_code_2(ip, new, INSN_NOP);#endif} int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr){	unsigned int new;	unsigned long ip = rec->ip; 	/* When the code to patch does not belong to the kernel code	 * space, we must use insn_la_mcount. However, if MCOUNT_ADDR	 * is not in compat space, insn_la_mcount is not usable.	 */	if (!core_kernel_text(ip) && !uasm_in_compat_space_p(MCOUNT_ADDR))		return -EFAULT; 	new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0]; #ifdef CONFIG_64BIT	return ftrace_modify_code(ip, new);#else	return ftrace_modify_code_2r(ip, new, core_kernel_text(ip) ?						INSN_NOP : insn_la_mcount[1]);#endif} #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call)) int ftrace_update_ftrace_func(ftrace_func_t func){	unsigned int new; 	new = INSN_JAL((unsigned long)func); 	return ftrace_modify_code(FTRACE_CALL_IP, new);} int __init ftrace_dyn_arch_init(void){	/* 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); 	return 0;}#endif	/* CONFIG_DYNAMIC_FTRACE */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER #ifdef CONFIG_DYNAMIC_FTRACE extern void ftrace_graph_call(void);#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,			insn_j_ftrace_graph_caller);} int ftrace_disable_ftrace_graph_caller(void){	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);} #endif	/* CONFIG_DYNAMIC_FTRACE */ #ifndef KBUILD_MCOUNT_RA_ADDRESS #define S_RA_SP (0xafbf << 16)	/* s{d,w} ra, offset(sp) */#define S_R_SP	(0xafb0 << 16)	/* s{d,w} R, offset(sp) */#define OFFSET_MASK	0xffff	/* stack offset range: 0 ~ PT_SIZE */ static unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long		old_parent_ra, unsigned long parent_ra_addr, unsigned long fp){	unsigned long sp, ip, tmp;	unsigned int code;	int faulted; 	/*	 * For module, move the ip from the return address after the	 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for	 * kernel, move after the instruction "move ra, at"(offset is 16)	 */	ip = self_ra - (core_kernel_text(self_ra) ? 16 : 24); 	/*	 * search the text until finding the non-store instruction or "s{d,w}	 * ra, offset(sp)" instruction	 */	do {		/* get the code at "ip": code = *(unsigned int *)ip; */		safe_load_code(code, ip, faulted); 		if (unlikely(faulted))			return 0;		/*		 * If we hit the non-store instruction before finding where the		 * ra is stored, then this is a leaf function and it does not		 * store the ra on the stack		 */		if ((code & S_R_SP) != S_R_SP)			return parent_ra_addr; 		/* Move to the next instruction */		ip -= 4;	} while ((code & S_RA_SP) != S_RA_SP); 	sp = fp + (code & OFFSET_MASK); 	/* tmp = *(unsigned long *)sp; */	safe_load_stack(tmp, sp, faulted);	if (unlikely(faulted))		return 0; 	if (tmp == old_parent_ra)		return sp;	return 0;} #endif	/* !KBUILD_MCOUNT_RA_ADDRESS */ /* * Hook the return address and push it in the stack of return addrs * in current thread info. */void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,			   unsigned long fp){	unsigned long old_parent_ra;	unsigned long return_hooker = (unsigned long)	    &return_to_handler;	int faulted, insns; 	if (unlikely(ftrace_graph_is_dead()))		return; 	if (unlikely(atomic_read(&current->tracing_graph_pause)))		return; 	/*	 * "parent_ra_addr" is the stack address where the return address of	 * the caller of _mcount is saved.	 *	 * If gcc < 4.5, a leaf function does not save the return address	 * in the stack address, so we "emulate" one in _mcount's stack space,	 * and hijack it directly.	 * For a non-leaf function, it does save the return address to its own	 * stack space, so we can not hijack it directly, but need to find the	 * real stack address, which is done by ftrace_get_parent_addr().	 *	 * If gcc >= 4.5, with the new -mmcount-ra-address option, for a	 * non-leaf function, the location of the return address will be saved	 * to $12 for us.	 * For a leaf function, it just puts a zero into $12, so we handle	 * it in ftrace_graph_caller() of mcount.S.	 */ 	/* old_parent_ra = *parent_ra_addr; */	safe_load_stack(old_parent_ra, parent_ra_addr, faulted);	if (unlikely(faulted))		goto out;#ifndef KBUILD_MCOUNT_RA_ADDRESS	parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,			old_parent_ra, (unsigned long)parent_ra_addr, fp);	/*	 * If fails when getting the stack address of the non-leaf function's	 * ra, stop function graph tracer and return	 */	if (parent_ra_addr == NULL)		goto out;#endif	/* *parent_ra_addr = return_hooker; */	safe_store_stack(return_hooker, parent_ra_addr, faulted);	if (unlikely(faulted))		goto out; 	/*	 * Get the recorded ip of the current mcount calling site in the	 * __mcount_loc section, which will be used to filter the function	 * entries configured through the tracing/set_graph_function interface.	 */ 	insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;	self_ra -= (MCOUNT_INSN_SIZE * insns); 	if (function_graph_enter(old_parent_ra, self_ra, fp, NULL))		*parent_ra_addr = old_parent_ra;	return;out:	ftrace_graph_stop();	WARN_ON(1);}#endif	/* CONFIG_FUNCTION_GRAPH_TRACER */ #ifdef CONFIG_FTRACE_SYSCALLS #ifdef CONFIG_32BITunsigned long __init arch_syscall_addr(int nr){	return (unsigned long)sys_call_table[nr - __NR_O32_Linux];}#endif #ifdef CONFIG_64BIT unsigned long __init arch_syscall_addr(int nr){#ifdef CONFIG_MIPS32_N32	if (nr >= __NR_N32_Linux && nr < __NR_N32_Linux + __NR_N32_Linux_syscalls)		return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];#endif	if (nr >= __NR_64_Linux  && nr < __NR_64_Linux + __NR_64_Linux_syscalls)		return (unsigned long)sys_call_table[nr - __NR_64_Linux];#ifdef CONFIG_MIPS32_O32	if (nr >= __NR_O32_Linux && nr < __NR_O32_Linux + __NR_O32_Linux_syscalls)		return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];#endif 	return (unsigned long) &sys_ni_syscall;}#endif #endif /* CONFIG_FTRACE_SYSCALLS */