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 unsigned int insn; 21 }; 22 23 static void __kprobes *patch_map(void *addr, int fixmap) 24 { 25 unsigned long uintaddr = (uintptr_t) addr; 26 bool module = !core_kernel_text(uintaddr); 27 struct page *page; 28 29 if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) 30 page = vmalloc_to_page(addr); 31 else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) 32 page = virt_to_page(addr); 33 else 34 return addr; 35 36 set_fixmap(fixmap, page_to_phys(page)); 37 38 return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK)); 39 } 40 41 static void __kprobes patch_unmap(int fixmap) 42 { 43 clear_fixmap(fixmap); 44 } 45 46 void __kprobes __patch_text(void *addr, unsigned int insn) 47 { 48 void *waddr = addr; 49 int size; 50 51 waddr = patch_map(addr, FIX_TEXT_POKE0); 52 *(u32 *)waddr = insn; 53 size = sizeof(u32); 54 flush_kernel_vmap_range(waddr, size); 55 patch_unmap(FIX_TEXT_POKE0); 56 flush_icache_range((uintptr_t)(addr), 57 (uintptr_t)(addr) + size); 58 } 59 60 static int __kprobes patch_text_stop_machine(void *data) 61 { 62 struct patch *patch = data; 63 64 __patch_text(patch->addr, patch->insn); 65 66 return 0; 67 } 68 69 void __kprobes patch_text(void *addr, unsigned int insn) 70 { 71 struct patch patch = { 72 .addr = addr, 73 .insn = insn, 74 }; 75 76 stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL); 77 } 78