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 void __init poking_init(void) 85 { 86 int ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, 87 "powerpc/text_poke:online", 88 text_area_cpu_up, 89 text_area_cpu_down); 90 91 /* cpuhp_setup_state returns >= 0 on success */ 92 if (WARN_ON(ret < 0)) 93 return; 94 95 static_branch_enable(&poking_init_done); 96 } 97 98 static unsigned long get_patch_pfn(void *addr) 99 { 100 if (IS_ENABLED(CONFIG_MODULES) && is_vmalloc_or_module_addr(addr)) 101 return vmalloc_to_pfn(addr); 102 else 103 return __pa_symbol(addr) >> PAGE_SHIFT; 104 } 105 106 /* 107 * This can be called for kernel text or a module. 108 */ 109 static int map_patch_area(void *addr, unsigned long text_poke_addr) 110 { 111 unsigned long pfn = get_patch_pfn(addr); 112 113 return map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL); 114 } 115 116 static void unmap_patch_area(unsigned long addr) 117 { 118 pte_t *ptep; 119 pmd_t *pmdp; 120 pud_t *pudp; 121 p4d_t *p4dp; 122 pgd_t *pgdp; 123 124 pgdp = pgd_offset_k(addr); 125 if (WARN_ON(pgd_none(*pgdp))) 126 return; 127 128 p4dp = p4d_offset(pgdp, addr); 129 if (WARN_ON(p4d_none(*p4dp))) 130 return; 131 132 pudp = pud_offset(p4dp, addr); 133 if (WARN_ON(pud_none(*pudp))) 134 return; 135 136 pmdp = pmd_offset(pudp, addr); 137 if (WARN_ON(pmd_none(*pmdp))) 138 return; 139 140 ptep = pte_offset_kernel(pmdp, addr); 141 if (WARN_ON(pte_none(*ptep))) 142 return; 143 144 /* 145 * In hash, pte_clear flushes the tlb, in radix, we have to 146 */ 147 pte_clear(&init_mm, addr, ptep); 148 flush_tlb_kernel_range(addr, addr + PAGE_SIZE); 149 } 150 151 static int __do_patch_instruction(u32 *addr, ppc_inst_t instr) 152 { 153 int err; 154 u32 *patch_addr; 155 unsigned long text_poke_addr; 156 pte_t *pte; 157 unsigned long pfn = get_patch_pfn(addr); 158 159 text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr & PAGE_MASK; 160 patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr)); 161 162 pte = virt_to_kpte(text_poke_addr); 163 __set_pte_at(&init_mm, text_poke_addr, pte, pfn_pte(pfn, PAGE_KERNEL), 0); 164 /* See ptesync comment in radix__set_pte_at() */ 165 if (radix_enabled()) 166 asm volatile("ptesync": : :"memory"); 167 168 err = __patch_instruction(addr, instr, patch_addr); 169 170 pte_clear(&init_mm, text_poke_addr, pte); 171 flush_tlb_kernel_range(text_poke_addr, text_poke_addr + PAGE_SIZE); 172 173 return err; 174 } 175 176 static int do_patch_instruction(u32 *addr, ppc_inst_t instr) 177 { 178 int err; 179 unsigned long flags; 180 181 /* 182 * During early early boot patch_instruction is called 183 * when text_poke_area is not ready, but we still need 184 * to allow patching. We just do the plain old patching 185 */ 186 if (!static_branch_likely(&poking_init_done)) 187 return raw_patch_instruction(addr, instr); 188 189 local_irq_save(flags); 190 err = __do_patch_instruction(addr, instr); 191 local_irq_restore(flags); 192 193 return err; 194 } 195 #else /* !CONFIG_STRICT_KERNEL_RWX */ 196 197 static int do_patch_instruction(u32 *addr, ppc_inst_t instr) 198 { 199 return raw_patch_instruction(addr, instr); 200 } 201 202 #endif /* CONFIG_STRICT_KERNEL_RWX */ 203 204 __ro_after_init DEFINE_STATIC_KEY_FALSE(init_mem_is_free); 205 206 int patch_instruction(u32 *addr, ppc_inst_t instr) 207 { 208 /* Make sure we aren't patching a freed init section */ 209 if (static_branch_likely(&init_mem_is_free) && init_section_contains(addr, 4)) 210 return 0; 211 212 return do_patch_instruction(addr, instr); 213 } 214 NOKPROBE_SYMBOL(patch_instruction); 215 216 int patch_branch(u32 *addr, unsigned long target, int flags) 217 { 218 ppc_inst_t instr; 219 220 if (create_branch(&instr, addr, target, flags)) 221 return -ERANGE; 222 223 return patch_instruction(addr, instr); 224 } 225 226 /* 227 * Helper to check if a given instruction is a conditional branch 228 * Derived from the conditional checks in analyse_instr() 229 */ 230 bool is_conditional_branch(ppc_inst_t instr) 231 { 232 unsigned int opcode = ppc_inst_primary_opcode(instr); 233 234 if (opcode == 16) /* bc, bca, bcl, bcla */ 235 return true; 236 if (opcode == 19) { 237 switch ((ppc_inst_val(instr) >> 1) & 0x3ff) { 238 case 16: /* bclr, bclrl */ 239 case 528: /* bcctr, bcctrl */ 240 case 560: /* bctar, bctarl */ 241 return true; 242 } 243 } 244 return false; 245 } 246 NOKPROBE_SYMBOL(is_conditional_branch); 247 248 int create_cond_branch(ppc_inst_t *instr, const u32 *addr, 249 unsigned long target, int flags) 250 { 251 long offset; 252 253 offset = target; 254 if (! (flags & BRANCH_ABSOLUTE)) 255 offset = offset - (unsigned long)addr; 256 257 /* Check we can represent the target in the instruction format */ 258 if (!is_offset_in_cond_branch_range(offset)) 259 return 1; 260 261 /* Mask out the flags and target, so they don't step on each other. */ 262 *instr = ppc_inst(0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC)); 263 264 return 0; 265 } 266 267 int instr_is_relative_branch(ppc_inst_t instr) 268 { 269 if (ppc_inst_val(instr) & BRANCH_ABSOLUTE) 270 return 0; 271 272 return instr_is_branch_iform(instr) || instr_is_branch_bform(instr); 273 } 274 275 int instr_is_relative_link_branch(ppc_inst_t instr) 276 { 277 return instr_is_relative_branch(instr) && (ppc_inst_val(instr) & BRANCH_SET_LINK); 278 } 279 280 static unsigned long branch_iform_target(const u32 *instr) 281 { 282 signed long imm; 283 284 imm = ppc_inst_val(ppc_inst_read(instr)) & 0x3FFFFFC; 285 286 /* If the top bit of the immediate value is set this is negative */ 287 if (imm & 0x2000000) 288 imm -= 0x4000000; 289 290 if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0) 291 imm += (unsigned long)instr; 292 293 return (unsigned long)imm; 294 } 295 296 static unsigned long branch_bform_target(const u32 *instr) 297 { 298 signed long imm; 299 300 imm = ppc_inst_val(ppc_inst_read(instr)) & 0xFFFC; 301 302 /* If the top bit of the immediate value is set this is negative */ 303 if (imm & 0x8000) 304 imm -= 0x10000; 305 306 if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0) 307 imm += (unsigned long)instr; 308 309 return (unsigned long)imm; 310 } 311 312 unsigned long branch_target(const u32 *instr) 313 { 314 if (instr_is_branch_iform(ppc_inst_read(instr))) 315 return branch_iform_target(instr); 316 else if (instr_is_branch_bform(ppc_inst_read(instr))) 317 return branch_bform_target(instr); 318 319 return 0; 320 } 321 322 int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src) 323 { 324 unsigned long target; 325 target = branch_target(src); 326 327 if (instr_is_branch_iform(ppc_inst_read(src))) 328 return create_branch(instr, dest, target, 329 ppc_inst_val(ppc_inst_read(src))); 330 else if (instr_is_branch_bform(ppc_inst_read(src))) 331 return create_cond_branch(instr, dest, target, 332 ppc_inst_val(ppc_inst_read(src))); 333 334 return 1; 335 } 336