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 -EPERM; 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 static __ro_after_init DEFINE_STATIC_KEY_FALSE(poking_init_done); 83 84 /* 85 * Although BUG_ON() is rude, in this case it should only happen if ENOMEM, and 86 * we judge it as being preferable to a kernel that will crash later when 87 * someone tries to use patch_instruction(). 88 */ 89 void __init poking_init(void) 90 { 91 BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, 92 "powerpc/text_poke:online", text_area_cpu_up, 93 text_area_cpu_down)); 94 static_branch_enable(&poking_init_done); 95 } 96 97 static unsigned long get_patch_pfn(void *addr) 98 { 99 if (IS_ENABLED(CONFIG_MODULES) && is_vmalloc_or_module_addr(addr)) 100 return vmalloc_to_pfn(addr); 101 else 102 return __pa_symbol(addr) >> PAGE_SHIFT; 103 } 104 105 /* 106 * This can be called for kernel text or a module. 107 */ 108 static int map_patch_area(void *addr, unsigned long text_poke_addr) 109 { 110 unsigned long pfn = get_patch_pfn(addr); 111 112 return map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL); 113 } 114 115 static void unmap_patch_area(unsigned long addr) 116 { 117 pte_t *ptep; 118 pmd_t *pmdp; 119 pud_t *pudp; 120 p4d_t *p4dp; 121 pgd_t *pgdp; 122 123 pgdp = pgd_offset_k(addr); 124 if (WARN_ON(pgd_none(*pgdp))) 125 return; 126 127 p4dp = p4d_offset(pgdp, addr); 128 if (WARN_ON(p4d_none(*p4dp))) 129 return; 130 131 pudp = pud_offset(p4dp, addr); 132 if (WARN_ON(pud_none(*pudp))) 133 return; 134 135 pmdp = pmd_offset(pudp, addr); 136 if (WARN_ON(pmd_none(*pmdp))) 137 return; 138 139 ptep = pte_offset_kernel(pmdp, addr); 140 if (WARN_ON(pte_none(*ptep))) 141 return; 142 143 /* 144 * In hash, pte_clear flushes the tlb, in radix, we have to 145 */ 146 pte_clear(&init_mm, addr, ptep); 147 flush_tlb_kernel_range(addr, addr + PAGE_SIZE); 148 } 149 150 static int __do_patch_instruction(u32 *addr, ppc_inst_t instr) 151 { 152 int err; 153 u32 *patch_addr; 154 unsigned long text_poke_addr; 155 pte_t *pte; 156 unsigned long pfn = get_patch_pfn(addr); 157 158 text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr & PAGE_MASK; 159 patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr)); 160 161 pte = virt_to_kpte(text_poke_addr); 162 __set_pte_at(&init_mm, text_poke_addr, pte, pfn_pte(pfn, PAGE_KERNEL), 0); 163 /* See ptesync comment in radix__set_pte_at() */ 164 if (radix_enabled()) 165 asm volatile("ptesync": : :"memory"); 166 167 err = __patch_instruction(addr, instr, patch_addr); 168 169 pte_clear(&init_mm, text_poke_addr, pte); 170 flush_tlb_kernel_range(text_poke_addr, text_poke_addr + PAGE_SIZE); 171 172 return err; 173 } 174 175 static int do_patch_instruction(u32 *addr, ppc_inst_t instr) 176 { 177 int err; 178 unsigned long flags; 179 180 /* 181 * During early early boot patch_instruction is called 182 * when text_poke_area is not ready, but we still need 183 * to allow patching. We just do the plain old patching 184 */ 185 if (!static_branch_likely(&poking_init_done)) 186 return raw_patch_instruction(addr, instr); 187 188 local_irq_save(flags); 189 err = __do_patch_instruction(addr, instr); 190 local_irq_restore(flags); 191 192 return err; 193 } 194 #else /* !CONFIG_STRICT_KERNEL_RWX */ 195 196 static int do_patch_instruction(u32 *addr, ppc_inst_t instr) 197 { 198 return raw_patch_instruction(addr, instr); 199 } 200 201 #endif /* CONFIG_STRICT_KERNEL_RWX */ 202 203 __ro_after_init DEFINE_STATIC_KEY_FALSE(init_mem_is_free); 204 205 int patch_instruction(u32 *addr, ppc_inst_t instr) 206 { 207 /* Make sure we aren't patching a freed init section */ 208 if (static_branch_likely(&init_mem_is_free) && init_section_contains(addr, 4)) 209 return 0; 210 211 return do_patch_instruction(addr, instr); 212 } 213 NOKPROBE_SYMBOL(patch_instruction); 214 215 int patch_branch(u32 *addr, unsigned long target, int flags) 216 { 217 ppc_inst_t instr; 218 219 if (create_branch(&instr, addr, target, flags)) 220 return -ERANGE; 221 222 return patch_instruction(addr, instr); 223 } 224 225 /* 226 * Helper to check if a given instruction is a conditional branch 227 * Derived from the conditional checks in analyse_instr() 228 */ 229 bool is_conditional_branch(ppc_inst_t instr) 230 { 231 unsigned int opcode = ppc_inst_primary_opcode(instr); 232 233 if (opcode == 16) /* bc, bca, bcl, bcla */ 234 return true; 235 if (opcode == 19) { 236 switch ((ppc_inst_val(instr) >> 1) & 0x3ff) { 237 case 16: /* bclr, bclrl */ 238 case 528: /* bcctr, bcctrl */ 239 case 560: /* bctar, bctarl */ 240 return true; 241 } 242 } 243 return false; 244 } 245 NOKPROBE_SYMBOL(is_conditional_branch); 246 247 int create_cond_branch(ppc_inst_t *instr, const u32 *addr, 248 unsigned long target, int flags) 249 { 250 long offset; 251 252 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_cond_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(0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC)); 262 263 return 0; 264 } 265 266 int instr_is_relative_branch(ppc_inst_t instr) 267 { 268 if (ppc_inst_val(instr) & BRANCH_ABSOLUTE) 269 return 0; 270 271 return instr_is_branch_iform(instr) || instr_is_branch_bform(instr); 272 } 273 274 int instr_is_relative_link_branch(ppc_inst_t instr) 275 { 276 return instr_is_relative_branch(instr) && (ppc_inst_val(instr) & BRANCH_SET_LINK); 277 } 278 279 static unsigned long branch_iform_target(const u32 *instr) 280 { 281 signed long imm; 282 283 imm = ppc_inst_val(ppc_inst_read(instr)) & 0x3FFFFFC; 284 285 /* If the top bit of the immediate value is set this is negative */ 286 if (imm & 0x2000000) 287 imm -= 0x4000000; 288 289 if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0) 290 imm += (unsigned long)instr; 291 292 return (unsigned long)imm; 293 } 294 295 static unsigned long branch_bform_target(const u32 *instr) 296 { 297 signed long imm; 298 299 imm = ppc_inst_val(ppc_inst_read(instr)) & 0xFFFC; 300 301 /* If the top bit of the immediate value is set this is negative */ 302 if (imm & 0x8000) 303 imm -= 0x10000; 304 305 if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0) 306 imm += (unsigned long)instr; 307 308 return (unsigned long)imm; 309 } 310 311 unsigned long branch_target(const u32 *instr) 312 { 313 if (instr_is_branch_iform(ppc_inst_read(instr))) 314 return branch_iform_target(instr); 315 else if (instr_is_branch_bform(ppc_inst_read(instr))) 316 return branch_bform_target(instr); 317 318 return 0; 319 } 320 321 int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src) 322 { 323 unsigned long target; 324 target = branch_target(src); 325 326 if (instr_is_branch_iform(ppc_inst_read(src))) 327 return create_branch(instr, dest, target, 328 ppc_inst_val(ppc_inst_read(src))); 329 else if (instr_is_branch_bform(ppc_inst_read(src))) 330 return create_cond_branch(instr, dest, target, 331 ppc_inst_val(ppc_inst_read(src))); 332 333 return 1; 334 } 335