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