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 #include <linux/jump_label.h> 12 13 #include <asm/tlbflush.h> 14 #include <asm/page.h> 15 #include <asm/code-patching.h> 16 #include <asm/inst.h> 17 18 static int __patch_instruction(u32 *exec_addr, ppc_inst_t instr, u32 *patch_addr) 19 { 20 if (!ppc_inst_prefixed(instr)) { 21 u32 val = ppc_inst_val(instr); 22 23 __put_kernel_nofault(patch_addr, &val, u32, failed); 24 } else { 25 u64 val = ppc_inst_as_ulong(instr); 26 27 __put_kernel_nofault(patch_addr, &val, u64, failed); 28 } 29 30 asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr), 31 "r" (exec_addr)); 32 33 return 0; 34 35 failed: 36 return -EFAULT; 37 } 38 39 int raw_patch_instruction(u32 *addr, ppc_inst_t instr) 40 { 41 return __patch_instruction(addr, instr, addr); 42 } 43 44 #ifdef CONFIG_STRICT_KERNEL_RWX 45 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area); 46 47 static int map_patch_area(void *addr, unsigned long text_poke_addr); 48 static void unmap_patch_area(unsigned long addr); 49 50 static int text_area_cpu_up(unsigned int cpu) 51 { 52 struct vm_struct *area; 53 unsigned long addr; 54 int err; 55 56 area = get_vm_area(PAGE_SIZE, VM_ALLOC); 57 if (!area) { 58 WARN_ONCE(1, "Failed to create text area for cpu %d\n", 59 cpu); 60 return -1; 61 } 62 63 // Map/unmap the area to ensure all page tables are pre-allocated 64 addr = (unsigned long)area->addr; 65 err = map_patch_area(empty_zero_page, addr); 66 if (err) 67 return err; 68 69 unmap_patch_area(addr); 70 71 this_cpu_write(text_poke_area, area); 72 73 return 0; 74 } 75 76 static int text_area_cpu_down(unsigned int cpu) 77 { 78 free_vm_area(this_cpu_read(text_poke_area)); 79 return 0; 80 } 81 82 /* 83 * Although BUG_ON() is rude, in this case it should only happen if ENOMEM, and 84 * we judge it as being preferable to a kernel that will crash later when 85 * someone tries to use patch_instruction(). 86 */ 87 void __init poking_init(void) 88 { 89 BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, 90 "powerpc/text_poke:online", text_area_cpu_up, 91 text_area_cpu_down)); 92 } 93 94 /* 95 * This can be called for kernel text or a module. 96 */ 97 static int map_patch_area(void *addr, unsigned long text_poke_addr) 98 { 99 unsigned long pfn; 100 101 if (IS_ENABLED(CONFIG_MODULES) && is_vmalloc_or_module_addr(addr)) 102 pfn = vmalloc_to_pfn(addr); 103 else 104 pfn = __pa_symbol(addr) >> PAGE_SHIFT; 105 106 return map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL); 107 } 108 109 static void unmap_patch_area(unsigned long addr) 110 { 111 pte_t *ptep; 112 pmd_t *pmdp; 113 pud_t *pudp; 114 p4d_t *p4dp; 115 pgd_t *pgdp; 116 117 pgdp = pgd_offset_k(addr); 118 if (WARN_ON(pgd_none(*pgdp))) 119 return; 120 121 p4dp = p4d_offset(pgdp, addr); 122 if (WARN_ON(p4d_none(*p4dp))) 123 return; 124 125 pudp = pud_offset(p4dp, addr); 126 if (WARN_ON(pud_none(*pudp))) 127 return; 128 129 pmdp = pmd_offset(pudp, addr); 130 if (WARN_ON(pmd_none(*pmdp))) 131 return; 132 133 ptep = pte_offset_kernel(pmdp, addr); 134 if (WARN_ON(pte_none(*ptep))) 135 return; 136 137 /* 138 * In hash, pte_clear flushes the tlb, in radix, we have to 139 */ 140 pte_clear(&init_mm, addr, ptep); 141 flush_tlb_kernel_range(addr, addr + PAGE_SIZE); 142 } 143 144 static int __do_patch_instruction(u32 *addr, ppc_inst_t instr) 145 { 146 int err; 147 u32 *patch_addr; 148 unsigned long text_poke_addr; 149 150 text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr; 151 patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr)); 152 153 err = map_patch_area(addr, text_poke_addr); 154 if (err) 155 return err; 156 157 err = __patch_instruction(addr, instr, patch_addr); 158 159 unmap_patch_area(text_poke_addr); 160 161 return err; 162 } 163 164 static int do_patch_instruction(u32 *addr, ppc_inst_t instr) 165 { 166 int err; 167 unsigned long flags; 168 169 /* 170 * During early early boot patch_instruction is called 171 * when text_poke_area is not ready, but we still need 172 * to allow patching. We just do the plain old patching 173 */ 174 if (!this_cpu_read(text_poke_area)) 175 return raw_patch_instruction(addr, instr); 176 177 local_irq_save(flags); 178 err = __do_patch_instruction(addr, instr); 179 local_irq_restore(flags); 180 181 return err; 182 } 183 #else /* !CONFIG_STRICT_KERNEL_RWX */ 184 185 static int do_patch_instruction(u32 *addr, ppc_inst_t instr) 186 { 187 return raw_patch_instruction(addr, instr); 188 } 189 190 #endif /* CONFIG_STRICT_KERNEL_RWX */ 191 192 __ro_after_init DEFINE_STATIC_KEY_FALSE(init_mem_is_free); 193 194 int patch_instruction(u32 *addr, ppc_inst_t instr) 195 { 196 /* Make sure we aren't patching a freed init section */ 197 if (static_branch_likely(&init_mem_is_free) && init_section_contains(addr, 4)) 198 return 0; 199 200 return do_patch_instruction(addr, instr); 201 } 202 NOKPROBE_SYMBOL(patch_instruction); 203 204 int patch_branch(u32 *addr, unsigned long target, int flags) 205 { 206 ppc_inst_t instr; 207 208 if (create_branch(&instr, addr, target, flags)) 209 return -ERANGE; 210 211 return patch_instruction(addr, instr); 212 } 213 214 bool is_offset_in_branch_range(long offset) 215 { 216 /* 217 * Powerpc branch instruction is : 218 * 219 * 0 6 30 31 220 * +---------+----------------+---+---+ 221 * | opcode | LI |AA |LK | 222 * +---------+----------------+---+---+ 223 * Where AA = 0 and LK = 0 224 * 225 * LI is a signed 24 bits integer. The real branch offset is computed 226 * by: imm32 = SignExtend(LI:'0b00', 32); 227 * 228 * So the maximum forward branch should be: 229 * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc 230 * The maximum backward branch should be: 231 * (0xff800000 << 2) = 0xfe000000 = -0x2000000 232 */ 233 return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3)); 234 } 235 236 bool is_offset_in_cond_branch_range(long offset) 237 { 238 return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3); 239 } 240 241 /* 242 * Helper to check if a given instruction is a conditional branch 243 * Derived from the conditional checks in analyse_instr() 244 */ 245 bool is_conditional_branch(ppc_inst_t instr) 246 { 247 unsigned int opcode = ppc_inst_primary_opcode(instr); 248 249 if (opcode == 16) /* bc, bca, bcl, bcla */ 250 return true; 251 if (opcode == 19) { 252 switch ((ppc_inst_val(instr) >> 1) & 0x3ff) { 253 case 16: /* bclr, bclrl */ 254 case 528: /* bcctr, bcctrl */ 255 case 560: /* bctar, bctarl */ 256 return true; 257 } 258 } 259 return false; 260 } 261 NOKPROBE_SYMBOL(is_conditional_branch); 262 263 int create_branch(ppc_inst_t *instr, const u32 *addr, 264 unsigned long target, int flags) 265 { 266 long offset; 267 268 *instr = ppc_inst(0); 269 offset = target; 270 if (! (flags & BRANCH_ABSOLUTE)) 271 offset = offset - (unsigned long)addr; 272 273 /* Check we can represent the target in the instruction format */ 274 if (!is_offset_in_branch_range(offset)) 275 return 1; 276 277 /* Mask out the flags and target, so they don't step on each other. */ 278 *instr = ppc_inst(0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC)); 279 280 return 0; 281 } 282 283 int create_cond_branch(ppc_inst_t *instr, const u32 *addr, 284 unsigned long target, int flags) 285 { 286 long offset; 287 288 offset = target; 289 if (! (flags & BRANCH_ABSOLUTE)) 290 offset = offset - (unsigned long)addr; 291 292 /* Check we can represent the target in the instruction format */ 293 if (!is_offset_in_cond_branch_range(offset)) 294 return 1; 295 296 /* Mask out the flags and target, so they don't step on each other. */ 297 *instr = ppc_inst(0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC)); 298 299 return 0; 300 } 301 302 int instr_is_relative_branch(ppc_inst_t instr) 303 { 304 if (ppc_inst_val(instr) & BRANCH_ABSOLUTE) 305 return 0; 306 307 return instr_is_branch_iform(instr) || instr_is_branch_bform(instr); 308 } 309 310 int instr_is_relative_link_branch(ppc_inst_t instr) 311 { 312 return instr_is_relative_branch(instr) && (ppc_inst_val(instr) & BRANCH_SET_LINK); 313 } 314 315 static unsigned long branch_iform_target(const u32 *instr) 316 { 317 signed long imm; 318 319 imm = ppc_inst_val(ppc_inst_read(instr)) & 0x3FFFFFC; 320 321 /* If the top bit of the immediate value is set this is negative */ 322 if (imm & 0x2000000) 323 imm -= 0x4000000; 324 325 if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0) 326 imm += (unsigned long)instr; 327 328 return (unsigned long)imm; 329 } 330 331 static unsigned long branch_bform_target(const u32 *instr) 332 { 333 signed long imm; 334 335 imm = ppc_inst_val(ppc_inst_read(instr)) & 0xFFFC; 336 337 /* If the top bit of the immediate value is set this is negative */ 338 if (imm & 0x8000) 339 imm -= 0x10000; 340 341 if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0) 342 imm += (unsigned long)instr; 343 344 return (unsigned long)imm; 345 } 346 347 unsigned long branch_target(const u32 *instr) 348 { 349 if (instr_is_branch_iform(ppc_inst_read(instr))) 350 return branch_iform_target(instr); 351 else if (instr_is_branch_bform(ppc_inst_read(instr))) 352 return branch_bform_target(instr); 353 354 return 0; 355 } 356 357 int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src) 358 { 359 unsigned long target; 360 target = branch_target(src); 361 362 if (instr_is_branch_iform(ppc_inst_read(src))) 363 return create_branch(instr, dest, target, 364 ppc_inst_val(ppc_inst_read(src))); 365 else if (instr_is_branch_bform(ppc_inst_read(src))) 366 return create_cond_branch(instr, dest, target, 367 ppc_inst_val(ppc_inst_read(src))); 368 369 return 1; 370 } 371