1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/highmem.h> 3 #include <linux/kdebug.h> 4 #include <linux/types.h> 5 #include <linux/notifier.h> 6 #include <linux/sched.h> 7 #include <linux/uprobes.h> 8 9 #include <asm/branch.h> 10 #include <asm/cpu-features.h> 11 #include <asm/ptrace.h> 12 13 #include "probes-common.h" 14 15 static inline int insn_has_delay_slot(const union mips_instruction insn) 16 { 17 return __insn_has_delay_slot(insn); 18 } 19 20 /** 21 * arch_uprobe_analyze_insn - instruction analysis including validity and fixups. 22 * @mm: the probed address space. 23 * @arch_uprobe: the probepoint information. 24 * @addr: virtual address at which to install the probepoint 25 * Return 0 on success or a -ve number on error. 26 */ 27 int arch_uprobe_analyze_insn(struct arch_uprobe *aup, 28 struct mm_struct *mm, unsigned long addr) 29 { 30 union mips_instruction inst; 31 32 /* 33 * For the time being this also blocks attempts to use uprobes with 34 * MIPS16 and microMIPS. 35 */ 36 if (addr & 0x03) 37 return -EINVAL; 38 39 inst.word = aup->insn[0]; 40 41 if (__insn_is_compact_branch(inst)) { 42 pr_notice("Uprobes for compact branches are not supported\n"); 43 return -EINVAL; 44 } 45 46 aup->ixol[0] = aup->insn[insn_has_delay_slot(inst)]; 47 aup->ixol[1] = UPROBE_BRK_UPROBE_XOL; /* NOP */ 48 49 return 0; 50 } 51 52 /** 53 * is_trap_insn - check if the instruction is a trap variant 54 * @insn: instruction to be checked. 55 * Returns true if @insn is a trap variant. 56 * 57 * This definition overrides the weak definition in kernel/events/uprobes.c. 58 * and is needed for the case where an architecture has multiple trap 59 * instructions (like PowerPC or MIPS). We treat BREAK just like the more 60 * modern conditional trap instructions. 61 */ 62 bool is_trap_insn(uprobe_opcode_t *insn) 63 { 64 union mips_instruction inst; 65 66 inst.word = *insn; 67 68 switch (inst.i_format.opcode) { 69 case spec_op: 70 switch (inst.r_format.func) { 71 case break_op: 72 case teq_op: 73 case tge_op: 74 case tgeu_op: 75 case tlt_op: 76 case tltu_op: 77 case tne_op: 78 return true; 79 } 80 break; 81 82 case bcond_op: /* Yes, really ... */ 83 switch (inst.u_format.rt) { 84 case teqi_op: 85 case tgei_op: 86 case tgeiu_op: 87 case tlti_op: 88 case tltiu_op: 89 case tnei_op: 90 return true; 91 } 92 break; 93 } 94 95 return false; 96 } 97 98 #define UPROBE_TRAP_NR ULONG_MAX 99 100 /* 101 * arch_uprobe_pre_xol - prepare to execute out of line. 102 * @auprobe: the probepoint information. 103 * @regs: reflects the saved user state of current task. 104 */ 105 int arch_uprobe_pre_xol(struct arch_uprobe *aup, struct pt_regs *regs) 106 { 107 struct uprobe_task *utask = current->utask; 108 109 /* 110 * Now find the EPC where to resume after the breakpoint has been 111 * dealt with. This may require emulation of a branch. 112 */ 113 aup->resume_epc = regs->cp0_epc + 4; 114 if (insn_has_delay_slot((union mips_instruction) aup->insn[0])) { 115 __compute_return_epc_for_insn(regs, 116 (union mips_instruction) aup->insn[0]); 117 aup->resume_epc = regs->cp0_epc; 118 } 119 utask->autask.saved_trap_nr = current->thread.trap_nr; 120 current->thread.trap_nr = UPROBE_TRAP_NR; 121 regs->cp0_epc = current->utask->xol_vaddr; 122 123 return 0; 124 } 125 126 int arch_uprobe_post_xol(struct arch_uprobe *aup, struct pt_regs *regs) 127 { 128 struct uprobe_task *utask = current->utask; 129 130 current->thread.trap_nr = utask->autask.saved_trap_nr; 131 regs->cp0_epc = aup->resume_epc; 132 133 return 0; 134 } 135 136 /* 137 * If xol insn itself traps and generates a signal(Say, 138 * SIGILL/SIGSEGV/etc), then detect the case where a singlestepped 139 * instruction jumps back to its own address. It is assumed that anything 140 * like do_page_fault/do_trap/etc sets thread.trap_nr != -1. 141 * 142 * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr, 143 * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to 144 * UPROBE_TRAP_NR == -1 set by arch_uprobe_pre_xol(). 145 */ 146 bool arch_uprobe_xol_was_trapped(struct task_struct *tsk) 147 { 148 if (tsk->thread.trap_nr != UPROBE_TRAP_NR) 149 return true; 150 151 return false; 152 } 153 154 int arch_uprobe_exception_notify(struct notifier_block *self, 155 unsigned long val, void *data) 156 { 157 struct die_args *args = data; 158 struct pt_regs *regs = args->regs; 159 160 /* regs == NULL is a kernel bug */ 161 if (WARN_ON(!regs)) 162 return NOTIFY_DONE; 163 164 /* We are only interested in userspace traps */ 165 if (!user_mode(regs)) 166 return NOTIFY_DONE; 167 168 switch (val) { 169 case DIE_UPROBE: 170 if (uprobe_pre_sstep_notifier(regs)) 171 return NOTIFY_STOP; 172 break; 173 case DIE_UPROBE_XOL: 174 if (uprobe_post_sstep_notifier(regs)) 175 return NOTIFY_STOP; 176 break; 177 default: 178 break; 179 } 180 181 return 0; 182 } 183 184 /* 185 * This function gets called when XOL instruction either gets trapped or 186 * the thread has a fatal signal. Reset the instruction pointer to its 187 * probed address for the potential restart or for post mortem analysis. 188 */ 189 void arch_uprobe_abort_xol(struct arch_uprobe *aup, 190 struct pt_regs *regs) 191 { 192 struct uprobe_task *utask = current->utask; 193 194 current->thread.trap_nr = utask->autask.saved_trap_nr; 195 instruction_pointer_set(regs, utask->vaddr); 196 } 197 198 unsigned long arch_uretprobe_hijack_return_addr( 199 unsigned long trampoline_vaddr, struct pt_regs *regs) 200 { 201 unsigned long ra; 202 203 ra = regs->regs[31]; 204 205 /* Replace the return address with the trampoline address */ 206 regs->regs[31] = trampoline_vaddr; 207 208 return ra; 209 } 210 211 void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr, 212 void *src, unsigned long len) 213 { 214 unsigned long kaddr, kstart; 215 216 /* Initialize the slot */ 217 kaddr = (unsigned long)kmap_atomic(page); 218 kstart = kaddr + (vaddr & ~PAGE_MASK); 219 memcpy((void *)kstart, src, len); 220 flush_icache_range(kstart, kstart + len); 221 kunmap_atomic((void *)kaddr); 222 } 223 224 /** 225 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs 226 * @regs: Reflects the saved state of the task after it has hit a breakpoint 227 * instruction. 228 * Return the address of the breakpoint instruction. 229 * 230 * This overrides the weak version in kernel/events/uprobes.c. 231 */ 232 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs) 233 { 234 return instruction_pointer(regs); 235 } 236 237 /* 238 * See if the instruction can be emulated. 239 * Returns true if instruction was emulated, false otherwise. 240 * 241 * For now we always emulate so this function just returns false. 242 */ 243 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) 244 { 245 return false; 246 } 247