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