1 // SPDX-License-Identifier: GPL-2.0-only
3 * Copyright (C) 2020 SiFive
6 #include <linux/spinlock.h>
8 #include <linux/memory.h>
9 #include <linux/string.h>
10 #include <linux/uaccess.h>
11 #include <linux/stop_machine.h>
12 #include <asm/kprobes.h>
13 #include <asm/cacheflush.h>
14 #include <asm/fixmap.h>
15 #include <asm/ftrace.h>
16 #include <asm/patch.h>
17 #include <asm/sections.h>
26 int riscv_patch_in_stop_machine = false;
30 static inline bool is_kernel_exittext(uintptr_t addr)
32 return system_state < SYSTEM_RUNNING &&
33 addr >= (uintptr_t)__exittext_begin &&
34 addr < (uintptr_t)__exittext_end;
38 * The fix_to_virt(, idx) needs a const value (not a dynamic variable of
39 * reg-a0) or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".
40 * So use '__always_inline' and 'const unsigned int fixmap' here.
42 static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
44 uintptr_t uintaddr = (uintptr_t) addr;
47 if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr))
48 page = phys_to_page(__pa_symbol(addr));
49 else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
50 page = vmalloc_to_page(addr);
56 return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
57 (uintaddr & ~PAGE_MASK));
60 static void patch_unmap(int fixmap)
64 NOKPROBE_SYMBOL(patch_unmap);
66 static int __patch_insn_set(void *addr, u8 c, size_t len)
69 bool across_pages = (((uintptr_t)addr & ~PAGE_MASK) + len) > PAGE_SIZE;
72 * Only two pages can be mapped at a time for writing.
74 if (len + offset_in_page(addr) > 2 * PAGE_SIZE)
77 * Before reaching here, it was expected to lock the text_mutex
78 * already, so we don't need to give another lock here and could
79 * ensure that it was safe between each cores.
81 lockdep_assert_held(&text_mutex);
84 patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1);
86 waddr = patch_map(addr, FIX_TEXT_POKE0);
88 memset(waddr, c, len);
90 patch_unmap(FIX_TEXT_POKE0);
93 patch_unmap(FIX_TEXT_POKE1);
97 NOKPROBE_SYMBOL(__patch_insn_set);
99 static int __patch_insn_write(void *addr, const void *insn, size_t len)
102 bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE;
106 * Only two pages can be mapped at a time for writing.
108 if (len + offset_in_page(addr) > 2 * PAGE_SIZE)
112 * Before reaching here, it was expected to lock the text_mutex
113 * already, so we don't need to give another lock here and could
114 * ensure that it was safe between each cores.
116 * We're currently using stop_machine() for ftrace & kprobes, and while
117 * that ensures text_mutex is held before installing the mappings it
118 * does not ensure text_mutex is held by the calling thread. That's
119 * safe but triggers a lockdep failure, so just elide it for that
122 if (!riscv_patch_in_stop_machine)
123 lockdep_assert_held(&text_mutex);
126 patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1);
128 waddr = patch_map(addr, FIX_TEXT_POKE0);
130 ret = copy_to_kernel_nofault(waddr, insn, len);
132 patch_unmap(FIX_TEXT_POKE0);
135 patch_unmap(FIX_TEXT_POKE1);
139 NOKPROBE_SYMBOL(__patch_insn_write);
141 static int __patch_insn_set(void *addr, u8 c, size_t len)
143 memset(addr, c, len);
147 NOKPROBE_SYMBOL(__patch_insn_set);
149 static int __patch_insn_write(void *addr, const void *insn, size_t len)
151 return copy_to_kernel_nofault(addr, insn, len);
153 NOKPROBE_SYMBOL(__patch_insn_write);
154 #endif /* CONFIG_MMU */
156 static int patch_insn_set(void *addr, u8 c, size_t len)
163 * __patch_insn_set() can only work on 2 pages at a time so call it in a
164 * loop with len <= 2 * PAGE_SIZE.
166 while (patched < len && !ret) {
167 size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched);
168 ret = __patch_insn_set(addr + patched, c, size);
175 NOKPROBE_SYMBOL(patch_insn_set);
177 int patch_text_set_nosync(void *addr, u8 c, size_t len)
182 ret = patch_insn_set(tp, c, len);
185 flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len);
189 NOKPROBE_SYMBOL(patch_text_set_nosync);
191 static int patch_insn_write(void *addr, const void *insn, size_t len)
198 * Copy the instructions to the destination address, two pages at a time
199 * because __patch_insn_write() can only handle len <= 2 * PAGE_SIZE.
201 while (patched < len && !ret) {
202 size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched);
203 ret = __patch_insn_write(addr + patched, insn + patched, size);
210 NOKPROBE_SYMBOL(patch_insn_write);
212 int patch_text_nosync(void *addr, const void *insns, size_t len)
217 ret = patch_insn_write(tp, insns, len);
220 flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len);
224 NOKPROBE_SYMBOL(patch_text_nosync);
226 static int patch_text_cb(void *data)
228 struct patch_insn *patch = data;
232 if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
233 for (i = 0; ret == 0 && i < patch->ninsns; i++) {
234 len = GET_INSN_LENGTH(patch->insns[i]);
235 ret = patch_text_nosync(patch->addr + i * len,
236 &patch->insns[i], len);
238 atomic_inc(&patch->cpu_count);
240 while (atomic_read(&patch->cpu_count) <= num_online_cpus())
247 NOKPROBE_SYMBOL(patch_text_cb);
249 int patch_text(void *addr, u32 *insns, int ninsns)
252 struct patch_insn patch = {
256 .cpu_count = ATOMIC_INIT(0),
260 * kprobes takes text_mutex, before calling patch_text(), but as we call
261 * calls stop_machine(), the lockdep assertion in patch_insn_write()
262 * gets confused by the context in which the lock is taken.
263 * Instead, ensure the lock is held before calling stop_machine(), and
264 * set riscv_patch_in_stop_machine to skip the check in
265 * patch_insn_write().
267 lockdep_assert_held(&text_mutex);
268 riscv_patch_in_stop_machine = true;
269 ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask);
270 riscv_patch_in_stop_machine = false;
273 NOKPROBE_SYMBOL(patch_text);