1 // SPDX-License-Identifier: GPL-2.0 2 3 #ifndef pr_fmt 4 #define pr_fmt(fmt) "alt: " fmt 5 #endif 6 7 #include <linux/hex.h> 8 #include <linux/uaccess.h> 9 #include <linux/printk.h> 10 #include <asm/nospec-branch.h> 11 #include <asm/abs_lowcore.h> 12 #include <asm/alternative.h> 13 #include <asm/facility.h> 14 #include <asm/sections.h> 15 #include <asm/machine.h> 16 17 #ifndef a_debug 18 #define a_debug pr_debug 19 #endif 20 21 #ifndef __kernel_va 22 #define __kernel_va(x) (void *)(x) 23 #endif 24 25 unsigned long __bootdata_preserved(machine_features[1]); 26 27 struct alt_debug { 28 unsigned long facilities[MAX_FACILITY_BIT / BITS_PER_LONG]; 29 unsigned long mfeatures[MAX_MFEATURE_BIT / BITS_PER_LONG]; 30 int spec; 31 }; 32 33 static struct alt_debug __bootdata_preserved(alt_debug); 34 35 static void alternative_dump(u8 *old, u8 *new, unsigned int len, unsigned int type, unsigned int data) 36 { 37 char oinsn[33], ninsn[33]; 38 unsigned long kptr; 39 unsigned int pos; 40 41 for (pos = 0; pos < len && 2 * pos < sizeof(oinsn) - 3; pos++) 42 hex_byte_pack(&oinsn[2 * pos], old[pos]); 43 oinsn[2 * pos] = 0; 44 for (pos = 0; pos < len && 2 * pos < sizeof(ninsn) - 3; pos++) 45 hex_byte_pack(&ninsn[2 * pos], new[pos]); 46 ninsn[2 * pos] = 0; 47 kptr = (unsigned long)__kernel_va(old); 48 a_debug("[%d/%3d] %016lx: %s -> %s\n", type, data, kptr, oinsn, ninsn); 49 } 50 51 void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx) 52 { 53 struct alt_debug *d; 54 struct alt_instr *a; 55 bool debug, replace; 56 u8 *old, *new; 57 58 /* 59 * The scan order should be from start to end. A later scanned 60 * alternative code can overwrite previously scanned alternative code. 61 */ 62 d = &alt_debug; 63 for (a = start; a < end; a++) { 64 if (!(a->ctx & ctx)) 65 continue; 66 switch (a->type) { 67 case ALT_TYPE_FACILITY: 68 replace = test_facility(a->data); 69 debug = __test_facility(a->data, d->facilities); 70 break; 71 case ALT_TYPE_FEATURE: 72 replace = test_machine_feature(a->data); 73 debug = __test_machine_feature(a->data, d->mfeatures); 74 break; 75 case ALT_TYPE_SPEC: 76 replace = nobp_enabled(); 77 debug = d->spec; 78 break; 79 default: 80 replace = false; 81 debug = false; 82 } 83 if (!replace) 84 continue; 85 old = (u8 *)&a->instr_offset + a->instr_offset; 86 new = (u8 *)&a->repl_offset + a->repl_offset; 87 if (debug) 88 alternative_dump(old, new, a->instrlen, a->type, a->data); 89 s390_kernel_write(old, new, a->instrlen); 90 } 91 } 92