1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * functions to patch RO kernel text during runtime 4 * 5 * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org> 6 */ 7 8 #include <linux/kernel.h> 9 #include <linux/spinlock.h> 10 #include <linux/kprobes.h> 11 #include <linux/mm.h> 12 #include <linux/stop_machine.h> 13 14 #include <asm/cacheflush.h> 15 #include <asm/fixmap.h> 16 #include <asm/patch.h> 17 18 struct patch { 19 void *addr; 20 u32 *insn; 21 unsigned int len; 22 }; 23 24 static DEFINE_RAW_SPINLOCK(patch_lock); 25 26 static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags, 27 int *need_unmap) 28 { 29 unsigned long uintaddr = (uintptr_t) addr; 30 bool module = !core_kernel_text(uintaddr); 31 struct page *page; 32 33 *need_unmap = 0; 34 if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) 35 page = vmalloc_to_page(addr); 36 else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) 37 page = virt_to_page(addr); 38 else 39 return addr; 40 41 *need_unmap = 1; 42 set_fixmap(fixmap, page_to_phys(page)); 43 if (flags) 44 raw_spin_lock_irqsave(&patch_lock, *flags); 45 else 46 __acquire(&patch_lock); 47 48 return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK)); 49 } 50 51 static void __kprobes patch_unmap(int fixmap, unsigned long *flags) 52 { 53 clear_fixmap(fixmap); 54 55 if (flags) 56 raw_spin_unlock_irqrestore(&patch_lock, *flags); 57 else 58 __release(&patch_lock); 59 } 60 61 void __kprobes __patch_text_multiple(void *addr, u32 *insn, unsigned int len) 62 { 63 unsigned long start = (unsigned long)addr; 64 unsigned long end = (unsigned long)addr + len; 65 unsigned long flags; 66 u32 *p, *fixmap; 67 int mapped; 68 69 /* Make sure we don't have any aliases in cache */ 70 flush_kernel_vmap_range(addr, len); 71 flush_icache_range(start, end); 72 73 p = fixmap = patch_map(addr, FIX_TEXT_POKE0, &flags, &mapped); 74 75 while (len >= 4) { 76 *p++ = *insn++; 77 addr += sizeof(u32); 78 len -= sizeof(u32); 79 if (len && offset_in_page(addr) == 0) { 80 /* 81 * We're crossing a page boundary, so 82 * need to remap 83 */ 84 flush_kernel_vmap_range((void *)fixmap, 85 (p-fixmap) * sizeof(*p)); 86 if (mapped) 87 patch_unmap(FIX_TEXT_POKE0, &flags); 88 p = fixmap = patch_map(addr, FIX_TEXT_POKE0, &flags, 89 &mapped); 90 } 91 } 92 93 flush_kernel_vmap_range((void *)fixmap, (p-fixmap) * sizeof(*p)); 94 if (mapped) 95 patch_unmap(FIX_TEXT_POKE0, &flags); 96 flush_icache_range(start, end); 97 } 98 99 void __kprobes __patch_text(void *addr, u32 insn) 100 { 101 __patch_text_multiple(addr, &insn, sizeof(insn)); 102 } 103 104 static int __kprobes patch_text_stop_machine(void *data) 105 { 106 struct patch *patch = data; 107 108 __patch_text_multiple(patch->addr, patch->insn, patch->len); 109 return 0; 110 } 111 112 void __kprobes patch_text(void *addr, unsigned int insn) 113 { 114 struct patch patch = { 115 .addr = addr, 116 .insn = &insn, 117 .len = sizeof(insn), 118 }; 119 120 stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL); 121 } 122 123 void __kprobes patch_text_multiple(void *addr, u32 *insn, unsigned int len) 124 { 125 126 struct patch patch = { 127 .addr = addr, 128 .insn = insn, 129 .len = len 130 }; 131 132 stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL); 133 } 134