1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 #ifndef _ASM_POWERPC_CODE_PATCHING_H
3 #define _ASM_POWERPC_CODE_PATCHING_H
4 
5 /*
6  * Copyright 2008, Michael Ellerman, IBM Corporation.
7  */
8 
9 #include <asm/types.h>
10 #include <asm/ppc-opcode.h>
11 #include <linux/string.h>
12 #include <linux/kallsyms.h>
13 #include <asm/asm-compat.h>
14 #include <asm/inst.h>
15 
16 /* Flags for create_branch:
17  * "b"   == create_branch(addr, target, 0);
18  * "ba"  == create_branch(addr, target, BRANCH_ABSOLUTE);
19  * "bl"  == create_branch(addr, target, BRANCH_SET_LINK);
20  * "bla" == create_branch(addr, target, BRANCH_ABSOLUTE | BRANCH_SET_LINK);
21  */
22 #define BRANCH_SET_LINK	0x1
23 #define BRANCH_ABSOLUTE	0x2
24 
25 /*
26  * Powerpc branch instruction is :
27  *
28  *  0         6                 30   31
29  *  +---------+----------------+---+---+
30  *  | opcode  |     LI         |AA |LK |
31  *  +---------+----------------+---+---+
32  *  Where AA = 0 and LK = 0
33  *
34  * LI is a signed 24 bits integer. The real branch offset is computed
35  * by: imm32 = SignExtend(LI:'0b00', 32);
36  *
37  * So the maximum forward branch should be:
38  *   (0x007fffff << 2) = 0x01fffffc =  0x1fffffc
39  * The maximum backward branch should be:
40  *   (0xff800000 << 2) = 0xfe000000 = -0x2000000
41  */
is_offset_in_branch_range(long offset)42 static inline bool is_offset_in_branch_range(long offset)
43 {
44 	return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
45 }
46 
is_offset_in_cond_branch_range(long offset)47 static inline bool is_offset_in_cond_branch_range(long offset)
48 {
49 	return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3);
50 }
51 
create_branch(ppc_inst_t * instr,const u32 * addr,unsigned long target,int flags)52 static inline int create_branch(ppc_inst_t *instr, const u32 *addr,
53 				unsigned long target, int flags)
54 {
55 	long offset;
56 
57 	*instr = ppc_inst(0);
58 	offset = target;
59 	if (! (flags & BRANCH_ABSOLUTE))
60 		offset = offset - (unsigned long)addr;
61 
62 	/* Check we can represent the target in the instruction format */
63 	if (!is_offset_in_branch_range(offset))
64 		return 1;
65 
66 	/* Mask out the flags and target, so they don't step on each other. */
67 	*instr = ppc_inst(0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC));
68 
69 	return 0;
70 }
71 
72 int create_cond_branch(ppc_inst_t *instr, const u32 *addr,
73 		       unsigned long target, int flags);
74 int patch_branch(u32 *addr, unsigned long target, int flags);
75 int patch_instruction(u32 *addr, ppc_inst_t instr);
76 int raw_patch_instruction(u32 *addr, ppc_inst_t instr);
77 
patch_site_addr(s32 * site)78 static inline unsigned long patch_site_addr(s32 *site)
79 {
80 	return (unsigned long)site + *site;
81 }
82 
patch_instruction_site(s32 * site,ppc_inst_t instr)83 static inline int patch_instruction_site(s32 *site, ppc_inst_t instr)
84 {
85 	return patch_instruction((u32 *)patch_site_addr(site), instr);
86 }
87 
patch_branch_site(s32 * site,unsigned long target,int flags)88 static inline int patch_branch_site(s32 *site, unsigned long target, int flags)
89 {
90 	return patch_branch((u32 *)patch_site_addr(site), target, flags);
91 }
92 
modify_instruction(unsigned int * addr,unsigned int clr,unsigned int set)93 static inline int modify_instruction(unsigned int *addr, unsigned int clr,
94 				     unsigned int set)
95 {
96 	return patch_instruction(addr, ppc_inst((*addr & ~clr) | set));
97 }
98 
modify_instruction_site(s32 * site,unsigned int clr,unsigned int set)99 static inline int modify_instruction_site(s32 *site, unsigned int clr, unsigned int set)
100 {
101 	return modify_instruction((unsigned int *)patch_site_addr(site), clr, set);
102 }
103 
branch_opcode(ppc_inst_t instr)104 static inline unsigned int branch_opcode(ppc_inst_t instr)
105 {
106 	return ppc_inst_primary_opcode(instr) & 0x3F;
107 }
108 
instr_is_branch_iform(ppc_inst_t instr)109 static inline int instr_is_branch_iform(ppc_inst_t instr)
110 {
111 	return branch_opcode(instr) == 18;
112 }
113 
instr_is_branch_bform(ppc_inst_t instr)114 static inline int instr_is_branch_bform(ppc_inst_t instr)
115 {
116 	return branch_opcode(instr) == 16;
117 }
118 
119 int instr_is_relative_branch(ppc_inst_t instr);
120 int instr_is_relative_link_branch(ppc_inst_t instr);
121 unsigned long branch_target(const u32 *instr);
122 int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src);
123 bool is_conditional_branch(ppc_inst_t instr);
124 
125 #define OP_RT_RA_MASK	0xffff0000UL
126 #define LIS_R2		(PPC_RAW_LIS(_R2, 0))
127 #define ADDIS_R2_R12	(PPC_RAW_ADDIS(_R2, _R12, 0))
128 #define ADDI_R2_R2	(PPC_RAW_ADDI(_R2, _R2, 0))
129 
130 
ppc_function_entry(void * func)131 static inline unsigned long ppc_function_entry(void *func)
132 {
133 #ifdef CONFIG_PPC64_ELF_ABI_V2
134 	u32 *insn = func;
135 
136 	/*
137 	 * A PPC64 ABIv2 function may have a local and a global entry
138 	 * point. We need to use the local entry point when patching
139 	 * functions, so identify and step over the global entry point
140 	 * sequence.
141 	 *
142 	 * The global entry point sequence is always of the form:
143 	 *
144 	 * addis r2,r12,XXXX
145 	 * addi  r2,r2,XXXX
146 	 *
147 	 * A linker optimisation may convert the addis to lis:
148 	 *
149 	 * lis   r2,XXXX
150 	 * addi  r2,r2,XXXX
151 	 */
152 	if ((((*insn & OP_RT_RA_MASK) == ADDIS_R2_R12) ||
153 	     ((*insn & OP_RT_RA_MASK) == LIS_R2)) &&
154 	    ((*(insn+1) & OP_RT_RA_MASK) == ADDI_R2_R2))
155 		return (unsigned long)(insn + 2);
156 	else
157 		return (unsigned long)func;
158 #elif defined(CONFIG_PPC64_ELF_ABI_V1)
159 	/*
160 	 * On PPC64 ABIv1 the function pointer actually points to the
161 	 * function's descriptor. The first entry in the descriptor is the
162 	 * address of the function text.
163 	 */
164 	return ((struct func_desc *)func)->addr;
165 #else
166 	return (unsigned long)func;
167 #endif
168 }
169 
ppc_global_function_entry(void * func)170 static inline unsigned long ppc_global_function_entry(void *func)
171 {
172 #ifdef CONFIG_PPC64_ELF_ABI_V2
173 	/* PPC64 ABIv2 the global entry point is at the address */
174 	return (unsigned long)func;
175 #else
176 	/* All other cases there is no change vs ppc_function_entry() */
177 	return ppc_function_entry(func);
178 #endif
179 }
180 
181 /*
182  * Wrapper around kallsyms_lookup() to return function entry address:
183  * - For ABIv1, we lookup the dot variant.
184  * - For ABIv2, we return the local entry point.
185  */
ppc_kallsyms_lookup_name(const char * name)186 static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
187 {
188 	unsigned long addr;
189 #ifdef CONFIG_PPC64_ELF_ABI_V1
190 	/* check for dot variant */
191 	char dot_name[1 + KSYM_NAME_LEN];
192 	bool dot_appended = false;
193 
194 	if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
195 		return 0;
196 
197 	if (name[0] != '.') {
198 		dot_name[0] = '.';
199 		dot_name[1] = '\0';
200 		strlcat(dot_name, name, sizeof(dot_name));
201 		dot_appended = true;
202 	} else {
203 		dot_name[0] = '\0';
204 		strlcat(dot_name, name, sizeof(dot_name));
205 	}
206 	addr = kallsyms_lookup_name(dot_name);
207 	if (!addr && dot_appended)
208 		/* Let's try the original non-dot symbol lookup	*/
209 		addr = kallsyms_lookup_name(name);
210 #elif defined(CONFIG_PPC64_ELF_ABI_V2)
211 	addr = kallsyms_lookup_name(name);
212 	if (addr)
213 		addr = ppc_function_entry((void *)addr);
214 #else
215 	addr = kallsyms_lookup_name(name);
216 #endif
217 	return addr;
218 }
219 
220 /*
221  * Some instruction encodings commonly used in dynamic ftracing
222  * and function live patching.
223  */
224 
225 /* This must match the definition of STK_GOT in <asm/ppc_asm.h> */
226 #ifdef CONFIG_PPC64_ELF_ABI_V2
227 #define R2_STACK_OFFSET         24
228 #else
229 #define R2_STACK_OFFSET         40
230 #endif
231 
232 #define PPC_INST_LD_TOC		PPC_RAW_LD(_R2, _R1, R2_STACK_OFFSET)
233 
234 /* usually preceded by a mflr r0 */
235 #define PPC_INST_STD_LR		PPC_RAW_STD(_R0, _R1, PPC_LR_STKOFF)
236 
237 #endif /* _ASM_POWERPC_CODE_PATCHING_H */
238