1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * User-space Probes (UProbes) for powerpc 4 * 5 * Copyright IBM Corporation, 2007-2012 6 * 7 * Adapted from the x86 port by Ananth N Mavinakayanahalli <ananth@in.ibm.com> 8 */ 9 #include <linux/kernel.h> 10 #include <linux/sched.h> 11 #include <linux/ptrace.h> 12 #include <linux/uprobes.h> 13 #include <linux/uaccess.h> 14 #include <linux/kdebug.h> 15 16 #include <asm/sstep.h> 17 #include <asm/inst.h> 18 19 #define UPROBE_TRAP_NR UINT_MAX 20 21 /** 22 * is_trap_insn - check if the instruction is a trap variant 23 * @insn: instruction to be checked. 24 * Returns true if @insn is a trap variant. 25 */ 26 bool is_trap_insn(uprobe_opcode_t *insn) 27 { 28 return (is_trap(*insn)); 29 } 30 31 /** 32 * arch_uprobe_analyze_insn 33 * @mm: the probed address space. 34 * @arch_uprobe: the probepoint information. 35 * @addr: vaddr to probe. 36 * Return 0 on success or a -ve number on error. 37 */ 38 int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, 39 struct mm_struct *mm, unsigned long addr) 40 { 41 if (addr & 0x03) 42 return -EINVAL; 43 44 if (cpu_has_feature(CPU_FTR_ARCH_31) && 45 ppc_inst_prefixed(ppc_inst_read(auprobe->insn)) && 46 (addr & 0x3f) == 60) { 47 pr_info_ratelimited("Cannot register a uprobe on 64 byte unaligned prefixed instruction\n"); 48 return -EINVAL; 49 } 50 51 if (!can_single_step(ppc_inst_val(ppc_inst_read(auprobe->insn)))) { 52 pr_info_ratelimited("Cannot register a uprobe on instructions that can't be single stepped\n"); 53 return -ENOTSUPP; 54 } 55 56 return 0; 57 } 58 59 /* 60 * arch_uprobe_pre_xol - prepare to execute out of line. 61 * @auprobe: the probepoint information. 62 * @regs: reflects the saved user state of current task. 63 */ 64 int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 65 { 66 struct arch_uprobe_task *autask = ¤t->utask->autask; 67 68 autask->saved_trap_nr = current->thread.trap_nr; 69 current->thread.trap_nr = UPROBE_TRAP_NR; 70 regs_set_return_ip(regs, current->utask->xol_vaddr); 71 72 user_enable_single_step(current); 73 return 0; 74 } 75 76 /** 77 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs 78 * @regs: Reflects the saved state of the task after it has hit a breakpoint 79 * instruction. 80 * Return the address of the breakpoint instruction. 81 */ 82 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs) 83 { 84 return instruction_pointer(regs); 85 } 86 87 /* 88 * If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc), 89 * then detect the case where a singlestepped instruction jumps back to its 90 * own address. It is assumed that anything like do_page_fault/do_trap/etc 91 * sets thread.trap_nr != UINT_MAX. 92 * 93 * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr, 94 * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to 95 * UPROBE_TRAP_NR == UINT_MAX set by arch_uprobe_pre_xol(). 96 */ 97 bool arch_uprobe_xol_was_trapped(struct task_struct *t) 98 { 99 if (t->thread.trap_nr != UPROBE_TRAP_NR) 100 return true; 101 102 return false; 103 } 104 105 /* 106 * Called after single-stepping. To avoid the SMP problems that can 107 * occur when we temporarily put back the original opcode to 108 * single-step, we single-stepped a copy of the instruction. 109 * 110 * This function prepares to resume execution after the single-step. 111 */ 112 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 113 { 114 struct uprobe_task *utask = current->utask; 115 116 WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR); 117 118 current->thread.trap_nr = utask->autask.saved_trap_nr; 119 120 /* 121 * On powerpc, except for loads and stores, most instructions 122 * including ones that alter code flow (branches, calls, returns) 123 * are emulated in the kernel. We get here only if the emulation 124 * support doesn't exist and have to fix-up the next instruction 125 * to be executed. 126 */ 127 regs_set_return_ip(regs, (unsigned long)ppc_inst_next((void *)utask->vaddr, auprobe->insn)); 128 129 user_disable_single_step(current); 130 return 0; 131 } 132 133 /* callback routine for handling exceptions. */ 134 int arch_uprobe_exception_notify(struct notifier_block *self, 135 unsigned long val, void *data) 136 { 137 struct die_args *args = data; 138 struct pt_regs *regs = args->regs; 139 140 /* regs == NULL is a kernel bug */ 141 if (WARN_ON(!regs)) 142 return NOTIFY_DONE; 143 144 /* We are only interested in userspace traps */ 145 if (!user_mode(regs)) 146 return NOTIFY_DONE; 147 148 switch (val) { 149 case DIE_BPT: 150 if (uprobe_pre_sstep_notifier(regs)) 151 return NOTIFY_STOP; 152 break; 153 case DIE_SSTEP: 154 if (uprobe_post_sstep_notifier(regs)) 155 return NOTIFY_STOP; 156 break; 157 default: 158 break; 159 } 160 return NOTIFY_DONE; 161 } 162 163 /* 164 * This function gets called when XOL instruction either gets trapped or 165 * the thread has a fatal signal, so reset the instruction pointer to its 166 * probed address. 167 */ 168 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 169 { 170 struct uprobe_task *utask = current->utask; 171 172 current->thread.trap_nr = utask->autask.saved_trap_nr; 173 instruction_pointer_set(regs, utask->vaddr); 174 175 user_disable_single_step(current); 176 } 177 178 /* 179 * See if the instruction can be emulated. 180 * Returns true if instruction was emulated, false otherwise. 181 */ 182 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) 183 { 184 int ret; 185 186 /* 187 * emulate_step() returns 1 if the insn was successfully emulated. 188 * For all other cases, we need to single-step in hardware. 189 */ 190 ret = emulate_step(regs, ppc_inst_read(auprobe->insn)); 191 if (ret > 0) 192 return true; 193 194 return false; 195 } 196 197 unsigned long 198 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs) 199 { 200 unsigned long orig_ret_vaddr; 201 202 orig_ret_vaddr = regs->link; 203 204 /* Replace the return addr with trampoline addr */ 205 regs->link = trampoline_vaddr; 206 207 return orig_ret_vaddr; 208 } 209 210 bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, 211 struct pt_regs *regs) 212 { 213 if (ctx == RP_CHECK_CHAIN_CALL) 214 return regs->gpr[1] <= ret->stack; 215 else 216 return regs->gpr[1] < ret->stack; 217 } 218