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 DECLARE_STATIC_KEY_FALSE(init_mem_is_free);
26 
27 /*
28  * Powerpc branch instruction is :
29  *
30  *  0         6                 30   31
31  *  +---------+----------------+---+---+
32  *  | opcode  |     LI         |AA |LK |
33  *  +---------+----------------+---+---+
34  *  Where AA = 0 and LK = 0
35  *
36  * LI is a signed 24 bits integer. The real branch offset is computed
37  * by: imm32 = SignExtend(LI:'0b00', 32);
38  *
39  * So the maximum forward branch should be:
40  *   (0x007fffff << 2) = 0x01fffffc =  0x1fffffc
41  * The maximum backward branch should be:
42  *   (0xff800000 << 2) = 0xfe000000 = -0x2000000
43  */
is_offset_in_branch_range(long offset)44 static inline bool is_offset_in_branch_range(long offset)
45 {
46 	return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
47 }
48 
is_offset_in_cond_branch_range(long offset)49 static inline bool is_offset_in_cond_branch_range(long offset)
50 {
51 	return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3);
52 }
53 
create_branch(ppc_inst_t * instr,const u32 * addr,unsigned long target,int flags)54 static inline int create_branch(ppc_inst_t *instr, const u32 *addr,
55 				unsigned long target, int flags)
56 {
57 	long offset;
58 
59 	*instr = ppc_inst(0);
60 	offset = target;
61 	if (! (flags & BRANCH_ABSOLUTE))
62 		offset = offset - (unsigned long)addr;
63 
64 	/* Check we can represent the target in the instruction format */
65 	if (!is_offset_in_branch_range(offset))
66 		return 1;
67 
68 	/* Mask out the flags and target, so they don't step on each other. */
69 	*instr = ppc_inst(0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC));
70 
71 	return 0;
72 }
73 
74 int create_cond_branch(ppc_inst_t *instr, const u32 *addr,
75 		       unsigned long target, int flags);
76 int patch_branch(u32 *addr, unsigned long target, int flags);
77 int patch_instruction(u32 *addr, ppc_inst_t instr);
78 int raw_patch_instruction(u32 *addr, ppc_inst_t instr);
79 
patch_site_addr(s32 * site)80 static inline unsigned long patch_site_addr(s32 *site)
81 {
82 	return (unsigned long)site + *site;
83 }
84 
patch_instruction_site(s32 * site,ppc_inst_t instr)85 static inline int patch_instruction_site(s32 *site, ppc_inst_t instr)
86 {
87 	return patch_instruction((u32 *)patch_site_addr(site), instr);
88 }
89 
patch_branch_site(s32 * site,unsigned long target,int flags)90 static inline int patch_branch_site(s32 *site, unsigned long target, int flags)
91 {
92 	return patch_branch((u32 *)patch_site_addr(site), target, flags);
93 }
94 
modify_instruction(unsigned int * addr,unsigned int clr,unsigned int set)95 static inline int modify_instruction(unsigned int *addr, unsigned int clr,
96 				     unsigned int set)
97 {
98 	return patch_instruction(addr, ppc_inst((*addr & ~clr) | set));
99 }
100 
modify_instruction_site(s32 * site,unsigned int clr,unsigned int set)101 static inline int modify_instruction_site(s32 *site, unsigned int clr, unsigned int set)
102 {
103 	return modify_instruction((unsigned int *)patch_site_addr(site), clr, set);
104 }
105 
branch_opcode(ppc_inst_t instr)106 static inline unsigned int branch_opcode(ppc_inst_t instr)
107 {
108 	return ppc_inst_primary_opcode(instr) & 0x3F;
109 }
110 
instr_is_branch_iform(ppc_inst_t instr)111 static inline int instr_is_branch_iform(ppc_inst_t instr)
112 {
113 	return branch_opcode(instr) == 18;
114 }
115 
instr_is_branch_bform(ppc_inst_t instr)116 static inline int instr_is_branch_bform(ppc_inst_t instr)
117 {
118 	return branch_opcode(instr) == 16;
119 }
120 
121 int instr_is_relative_branch(ppc_inst_t instr);
122 int instr_is_relative_link_branch(ppc_inst_t instr);
123 unsigned long branch_target(const u32 *instr);
124 int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src);
125 bool is_conditional_branch(ppc_inst_t instr);
126 
127 #define OP_RT_RA_MASK	0xffff0000UL
128 #define LIS_R2		(PPC_RAW_LIS(_R2, 0))
129 #define ADDIS_R2_R12	(PPC_RAW_ADDIS(_R2, _R12, 0))
130 #define ADDI_R2_R2	(PPC_RAW_ADDI(_R2, _R2, 0))
131 
132 
ppc_function_entry(void * func)133 static inline unsigned long ppc_function_entry(void *func)
134 {
135 #ifdef CONFIG_PPC64_ELF_ABI_V2
136 	u32 *insn = func;
137 
138 	/*
139 	 * A PPC64 ABIv2 function may have a local and a global entry
140 	 * point. We need to use the local entry point when patching
141 	 * functions, so identify and step over the global entry point
142 	 * sequence.
143 	 *
144 	 * The global entry point sequence is always of the form:
145 	 *
146 	 * addis r2,r12,XXXX
147 	 * addi  r2,r2,XXXX
148 	 *
149 	 * A linker optimisation may convert the addis to lis:
150 	 *
151 	 * lis   r2,XXXX
152 	 * addi  r2,r2,XXXX
153 	 */
154 	if ((((*insn & OP_RT_RA_MASK) == ADDIS_R2_R12) ||
155 	     ((*insn & OP_RT_RA_MASK) == LIS_R2)) &&
156 	    ((*(insn+1) & OP_RT_RA_MASK) == ADDI_R2_R2))
157 		return (unsigned long)(insn + 2);
158 	else
159 		return (unsigned long)func;
160 #elif defined(CONFIG_PPC64_ELF_ABI_V1)
161 	/*
162 	 * On PPC64 ABIv1 the function pointer actually points to the
163 	 * function's descriptor. The first entry in the descriptor is the
164 	 * address of the function text.
165 	 */
166 	return ((struct func_desc *)func)->addr;
167 #else
168 	return (unsigned long)func;
169 #endif
170 }
171 
ppc_global_function_entry(void * func)172 static inline unsigned long ppc_global_function_entry(void *func)
173 {
174 #ifdef CONFIG_PPC64_ELF_ABI_V2
175 	/* PPC64 ABIv2 the global entry point is at the address */
176 	return (unsigned long)func;
177 #else
178 	/* All other cases there is no change vs ppc_function_entry() */
179 	return ppc_function_entry(func);
180 #endif
181 }
182 
183 /*
184  * Wrapper around kallsyms_lookup() to return function entry address:
185  * - For ABIv1, we lookup the dot variant.
186  * - For ABIv2, we return the local entry point.
187  */
ppc_kallsyms_lookup_name(const char * name)188 static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
189 {
190 	unsigned long addr;
191 #ifdef CONFIG_PPC64_ELF_ABI_V1
192 	/* check for dot variant */
193 	char dot_name[1 + KSYM_NAME_LEN];
194 	bool dot_appended = false;
195 
196 	if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
197 		return 0;
198 
199 	if (name[0] != '.') {
200 		dot_name[0] = '.';
201 		dot_name[1] = '\0';
202 		strlcat(dot_name, name, sizeof(dot_name));
203 		dot_appended = true;
204 	} else {
205 		dot_name[0] = '\0';
206 		strlcat(dot_name, name, sizeof(dot_name));
207 	}
208 	addr = kallsyms_lookup_name(dot_name);
209 	if (!addr && dot_appended)
210 		/* Let's try the original non-dot symbol lookup	*/
211 		addr = kallsyms_lookup_name(name);
212 #elif defined(CONFIG_PPC64_ELF_ABI_V2)
213 	addr = kallsyms_lookup_name(name);
214 	if (addr)
215 		addr = ppc_function_entry((void *)addr);
216 #else
217 	addr = kallsyms_lookup_name(name);
218 #endif
219 	return addr;
220 }
221 
222 /*
223  * Some instruction encodings commonly used in dynamic ftracing
224  * and function live patching.
225  */
226 
227 /* This must match the definition of STK_GOT in <asm/ppc_asm.h> */
228 #ifdef CONFIG_PPC64_ELF_ABI_V2
229 #define R2_STACK_OFFSET         24
230 #else
231 #define R2_STACK_OFFSET         40
232 #endif
233 
234 #define PPC_INST_LD_TOC		PPC_RAW_LD(_R2, _R1, R2_STACK_OFFSET)
235 
236 /* usually preceded by a mflr r0 */
237 #define PPC_INST_STD_LR		PPC_RAW_STD(_R0, _R1, PPC_LR_STKOFF)
238 
239 #endif /* _ASM_POWERPC_CODE_PATCHING_H */
240