Olivier Deprez | 157378f | 2022-04-04 15:47:50 +0200 | [diff] [blame^] | 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * Copyright (C) 2020 SiFive |
| 4 | */ |
| 5 | |
| 6 | #include <linux/spinlock.h> |
| 7 | #include <linux/mm.h> |
| 8 | #include <linux/memory.h> |
| 9 | #include <linux/uaccess.h> |
| 10 | #include <linux/stop_machine.h> |
| 11 | #include <asm/kprobes.h> |
| 12 | #include <asm/cacheflush.h> |
| 13 | #include <asm/fixmap.h> |
| 14 | #include <asm/patch.h> |
| 15 | |
| 16 | struct patch_insn { |
| 17 | void *addr; |
| 18 | u32 insn; |
| 19 | atomic_t cpu_count; |
| 20 | }; |
| 21 | |
| 22 | #ifdef CONFIG_MMU |
| 23 | static void *patch_map(void *addr, int fixmap) |
| 24 | { |
| 25 | uintptr_t uintaddr = (uintptr_t) addr; |
| 26 | struct page *page; |
| 27 | |
| 28 | if (core_kernel_text(uintaddr)) |
| 29 | page = phys_to_page(__pa_symbol(addr)); |
| 30 | else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) |
| 31 | page = vmalloc_to_page(addr); |
| 32 | else |
| 33 | return addr; |
| 34 | |
| 35 | BUG_ON(!page); |
| 36 | |
| 37 | return (void *)set_fixmap_offset(fixmap, page_to_phys(page) + |
| 38 | (uintaddr & ~PAGE_MASK)); |
| 39 | } |
| 40 | NOKPROBE_SYMBOL(patch_map); |
| 41 | |
| 42 | static void patch_unmap(int fixmap) |
| 43 | { |
| 44 | clear_fixmap(fixmap); |
| 45 | } |
| 46 | NOKPROBE_SYMBOL(patch_unmap); |
| 47 | |
| 48 | static int patch_insn_write(void *addr, const void *insn, size_t len) |
| 49 | { |
| 50 | void *waddr = addr; |
| 51 | bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE; |
| 52 | int ret; |
| 53 | |
| 54 | /* |
| 55 | * Before reaching here, it was expected to lock the text_mutex |
| 56 | * already, so we don't need to give another lock here and could |
| 57 | * ensure that it was safe between each cores. |
| 58 | */ |
| 59 | lockdep_assert_held(&text_mutex); |
| 60 | |
| 61 | if (across_pages) |
| 62 | patch_map(addr + len, FIX_TEXT_POKE1); |
| 63 | |
| 64 | waddr = patch_map(addr, FIX_TEXT_POKE0); |
| 65 | |
| 66 | ret = copy_to_kernel_nofault(waddr, insn, len); |
| 67 | |
| 68 | patch_unmap(FIX_TEXT_POKE0); |
| 69 | |
| 70 | if (across_pages) |
| 71 | patch_unmap(FIX_TEXT_POKE1); |
| 72 | |
| 73 | return ret; |
| 74 | } |
| 75 | NOKPROBE_SYMBOL(patch_insn_write); |
| 76 | #else |
| 77 | static int patch_insn_write(void *addr, const void *insn, size_t len) |
| 78 | { |
| 79 | return copy_to_kernel_nofault(addr, insn, len); |
| 80 | } |
| 81 | NOKPROBE_SYMBOL(patch_insn_write); |
| 82 | #endif /* CONFIG_MMU */ |
| 83 | |
| 84 | int patch_text_nosync(void *addr, const void *insns, size_t len) |
| 85 | { |
| 86 | u32 *tp = addr; |
| 87 | int ret; |
| 88 | |
| 89 | ret = patch_insn_write(tp, insns, len); |
| 90 | |
| 91 | if (!ret) |
| 92 | flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len); |
| 93 | |
| 94 | return ret; |
| 95 | } |
| 96 | NOKPROBE_SYMBOL(patch_text_nosync); |
| 97 | |
| 98 | static int patch_text_cb(void *data) |
| 99 | { |
| 100 | struct patch_insn *patch = data; |
| 101 | int ret = 0; |
| 102 | |
| 103 | if (atomic_inc_return(&patch->cpu_count) == 1) { |
| 104 | ret = |
| 105 | patch_text_nosync(patch->addr, &patch->insn, |
| 106 | GET_INSN_LENGTH(patch->insn)); |
| 107 | atomic_inc(&patch->cpu_count); |
| 108 | } else { |
| 109 | while (atomic_read(&patch->cpu_count) <= num_online_cpus()) |
| 110 | cpu_relax(); |
| 111 | smp_mb(); |
| 112 | } |
| 113 | |
| 114 | return ret; |
| 115 | } |
| 116 | NOKPROBE_SYMBOL(patch_text_cb); |
| 117 | |
| 118 | int patch_text(void *addr, u32 insn) |
| 119 | { |
| 120 | struct patch_insn patch = { |
| 121 | .addr = addr, |
| 122 | .insn = insn, |
| 123 | .cpu_count = ATOMIC_INIT(0), |
| 124 | }; |
| 125 | |
| 126 | return stop_machine_cpuslocked(patch_text_cb, |
| 127 | &patch, cpu_online_mask); |
| 128 | } |
| 129 | NOKPROBE_SYMBOL(patch_text); |