1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Copyright 2008 Michael Ellerman, IBM Corporation. 4 */ 5 6 #include <linux/kprobes.h> 7 #include <linux/vmalloc.h> 8 #include <linux/init.h> 9 #include <linux/cpuhotplug.h> 10 #include <linux/uaccess.h> 11 12 #include <asm/tlbflush.h> 13 #include <asm/page.h> 14 #include <asm/code-patching.h> 15 #include <asm/inst.h> 16 17 static int __patch_instruction(u32 *exec_addr, ppc_inst_t instr, u32 *patch_addr) 18 { 19 if (!ppc_inst_prefixed(instr)) { 20 u32 val = ppc_inst_val(instr); 21 22 __put_kernel_nofault(patch_addr, &val, u32, failed); 23 } else { 24 u64 val = ppc_inst_as_ulong(instr); 25 26 __put_kernel_nofault(patch_addr, &val, u64, failed); 27 } 28 29 asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr), 30 "r" (exec_addr)); 31 32 return 0; 33 34 failed: 35 return -EFAULT; 36 } 37 38 int raw_patch_instruction(u32 *addr, ppc_inst_t instr) 39 { 40 return __patch_instruction(addr, instr, addr); 41 } 42 43 #ifdef CONFIG_STRICT_KERNEL_RWX 44 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area); 45 46 static int text_area_cpu_up(unsigned int cpu) 47 { 48 struct vm_struct *area; 49 50 area = get_vm_area(PAGE_SIZE, VM_ALLOC); 51 if (!area) { 52 WARN_ONCE(1, "Failed to create text area for cpu %d\n", 53 cpu); 54 return -1; 55 } 56 this_cpu_write(text_poke_area, area); 57 58 return 0; 59 } 60 61 static int text_area_cpu_down(unsigned int cpu) 62 { 63 free_vm_area(this_cpu_read(text_poke_area)); 64 return 0; 65 } 66 67 /* 68 * Although BUG_ON() is rude, in this case it should only happen if ENOMEM, and 69 * we judge it as being preferable to a kernel that will crash later when 70 * someone tries to use patch_instruction(). 71 */ 72 void __init poking_init(void) 73 { 74 BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, 75 "powerpc/text_poke:online", text_area_cpu_up, 76 text_area_cpu_down)); 77 } 78 79 /* 80 * This can be called for kernel text or a module. 81 */ 82 static int map_patch_area(void *addr, unsigned long text_poke_addr) 83 { 84 unsigned long pfn; 85 86 if (is_vmalloc_or_module_addr(addr)) 87 pfn = vmalloc_to_pfn(addr); 88 else 89 pfn = __pa_symbol(addr) >> PAGE_SHIFT; 90 91 return map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL); 92 } 93 94 static void unmap_patch_area(unsigned long addr) 95 { 96 pte_t *ptep; 97 pmd_t *pmdp; 98 pud_t *pudp; 99 p4d_t *p4dp; 100 pgd_t *pgdp; 101 102 pgdp = pgd_offset_k(addr); 103 if (WARN_ON(pgd_none(*pgdp))) 104 return; 105 106 p4dp = p4d_offset(pgdp, addr); 107 if (WARN_ON(p4d_none(*p4dp))) 108 return; 109 110 pudp = pud_offset(p4dp, addr); 111 if (WARN_ON(pud_none(*pudp))) 112 return; 113 114 pmdp = pmd_offset(pudp, addr); 115 if (WARN_ON(pmd_none(*pmdp))) 116 return; 117 118 ptep = pte_offset_kernel(pmdp, addr); 119 if (WARN_ON(pte_none(*ptep))) 120 return; 121 122 /* 123 * In hash, pte_clear flushes the tlb, in radix, we have to 124 */ 125 pte_clear(&init_mm, addr, ptep); 126 flush_tlb_kernel_range(addr, addr + PAGE_SIZE); 127 } 128 129 static int __do_patch_instruction(u32 *addr, ppc_inst_t instr) 130 { 131 int err; 132 u32 *patch_addr; 133 unsigned long text_poke_addr; 134 135 text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr; 136 patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr)); 137 138 err = map_patch_area(addr, text_poke_addr); 139 if (err) 140 return err; 141 142 err = __patch_instruction(addr, instr, patch_addr); 143 144 unmap_patch_area(text_poke_addr); 145 146 return err; 147 } 148 149 static int do_patch_instruction(u32 *addr, ppc_inst_t instr) 150 { 151 int err; 152 unsigned long flags; 153 154 /* 155 * During early early boot patch_instruction is called 156 * when text_poke_area is not ready, but we still need 157 * to allow patching. We just do the plain old patching 158 */ 159 if (!this_cpu_read(text_poke_area)) 160 return raw_patch_instruction(addr, instr); 161 162 local_irq_save(flags); 163 err = __do_patch_instruction(addr, instr); 164 local_irq_restore(flags); 165 166 return err; 167 } 168 #else /* !CONFIG_STRICT_KERNEL_RWX */ 169 170 static int do_patch_instruction(u32 *addr, ppc_inst_t instr) 171 { 172 return raw_patch_instruction(addr, instr); 173 } 174 175 #endif /* CONFIG_STRICT_KERNEL_RWX */ 176 177 int patch_instruction(u32 *addr, ppc_inst_t instr) 178 { 179 /* Make sure we aren't patching a freed init section */ 180 if (system_state >= SYSTEM_FREEING_INITMEM && init_section_contains(addr, 4)) 181 return 0; 182 183 return do_patch_instruction(addr, instr); 184 } 185 NOKPROBE_SYMBOL(patch_instruction); 186 187 int patch_branch(u32 *addr, unsigned long target, int flags) 188 { 189 ppc_inst_t instr; 190 191 if (create_branch(&instr, addr, target, flags)) 192 return -ERANGE; 193 194 return patch_instruction(addr, instr); 195 } 196 197 bool is_offset_in_branch_range(long offset) 198 { 199 /* 200 * Powerpc branch instruction is : 201 * 202 * 0 6 30 31 203 * +---------+----------------+---+---+ 204 * | opcode | LI |AA |LK | 205 * +---------+----------------+---+---+ 206 * Where AA = 0 and LK = 0 207 * 208 * LI is a signed 24 bits integer. The real branch offset is computed 209 * by: imm32 = SignExtend(LI:'0b00', 32); 210 * 211 * So the maximum forward branch should be: 212 * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc 213 * The maximum backward branch should be: 214 * (0xff800000 << 2) = 0xfe000000 = -0x2000000 215 */ 216 return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3)); 217 } 218 219 bool is_offset_in_cond_branch_range(long offset) 220 { 221 return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3); 222 } 223 224 /* 225 * Helper to check if a given instruction is a conditional branch 226 * Derived from the conditional checks in analyse_instr() 227 */ 228 bool is_conditional_branch(ppc_inst_t instr) 229 { 230 unsigned int opcode = ppc_inst_primary_opcode(instr); 231 232 if (opcode == 16) /* bc, bca, bcl, bcla */ 233 return true; 234 if (opcode == 19) { 235 switch ((ppc_inst_val(instr) >> 1) & 0x3ff) { 236 case 16: /* bclr, bclrl */ 237 case 528: /* bcctr, bcctrl */ 238 case 560: /* bctar, bctarl */ 239 return true; 240 } 241 } 242 return false; 243 } 244 NOKPROBE_SYMBOL(is_conditional_branch); 245 246 int create_branch(ppc_inst_t *instr, const u32 *addr, 247 unsigned long target, int flags) 248 { 249 long offset; 250 251 *instr = ppc_inst(0); 252 offset = target; 253 if (! (flags & BRANCH_ABSOLUTE)) 254 offset = offset - (unsigned long)addr; 255 256 /* Check we can represent the target in the instruction format */ 257 if (!is_offset_in_branch_range(offset)) 258 return 1; 259 260 /* Mask out the flags and target, so they don't step on each other. */ 261 *instr = ppc_inst(0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC)); 262 263 return 0; 264 } 265 266 int create_cond_branch(ppc_inst_t *instr, const u32 *addr, 267 unsigned long target, int flags) 268 { 269 long offset; 270 271 offset = target; 272 if (! (flags & BRANCH_ABSOLUTE)) 273 offset = offset - (unsigned long)addr; 274 275 /* Check we can represent the target in the instruction format */ 276 if (!is_offset_in_cond_branch_range(offset)) 277 return 1; 278 279 /* Mask out the flags and target, so they don't step on each other. */ 280 *instr = ppc_inst(0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC)); 281 282 return 0; 283 } 284 285 int instr_is_relative_branch(ppc_inst_t instr) 286 { 287 if (ppc_inst_val(instr) & BRANCH_ABSOLUTE) 288 return 0; 289 290 return instr_is_branch_iform(instr) || instr_is_branch_bform(instr); 291 } 292 293 int instr_is_relative_link_branch(ppc_inst_t instr) 294 { 295 return instr_is_relative_branch(instr) && (ppc_inst_val(instr) & BRANCH_SET_LINK); 296 } 297 298 static unsigned long branch_iform_target(const u32 *instr) 299 { 300 signed long imm; 301 302 imm = ppc_inst_val(ppc_inst_read(instr)) & 0x3FFFFFC; 303 304 /* If the top bit of the immediate value is set this is negative */ 305 if (imm & 0x2000000) 306 imm -= 0x4000000; 307 308 if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0) 309 imm += (unsigned long)instr; 310 311 return (unsigned long)imm; 312 } 313 314 static unsigned long branch_bform_target(const u32 *instr) 315 { 316 signed long imm; 317 318 imm = ppc_inst_val(ppc_inst_read(instr)) & 0xFFFC; 319 320 /* If the top bit of the immediate value is set this is negative */ 321 if (imm & 0x8000) 322 imm -= 0x10000; 323 324 if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0) 325 imm += (unsigned long)instr; 326 327 return (unsigned long)imm; 328 } 329 330 unsigned long branch_target(const u32 *instr) 331 { 332 if (instr_is_branch_iform(ppc_inst_read(instr))) 333 return branch_iform_target(instr); 334 else if (instr_is_branch_bform(ppc_inst_read(instr))) 335 return branch_bform_target(instr); 336 337 return 0; 338 } 339 340 int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src) 341 { 342 unsigned long target; 343 target = branch_target(src); 344 345 if (instr_is_branch_iform(ppc_inst_read(src))) 346 return create_branch(instr, dest, target, 347 ppc_inst_val(ppc_inst_read(src))); 348 else if (instr_is_branch_bform(ppc_inst_read(src))) 349 return create_cond_branch(instr, dest, target, 350 ppc_inst_val(ppc_inst_read(src))); 351 352 return 1; 353 } 354