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 return 0; 45 } 46 47 /* 48 * arch_uprobe_pre_xol - prepare to execute out of line. 49 * @auprobe: the probepoint information. 50 * @regs: reflects the saved user state of current task. 51 */ 52 int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 53 { 54 struct arch_uprobe_task *autask = ¤t->utask->autask; 55 56 autask->saved_trap_nr = current->thread.trap_nr; 57 current->thread.trap_nr = UPROBE_TRAP_NR; 58 regs->nip = current->utask->xol_vaddr; 59 60 user_enable_single_step(current); 61 return 0; 62 } 63 64 /** 65 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs 66 * @regs: Reflects the saved state of the task after it has hit a breakpoint 67 * instruction. 68 * Return the address of the breakpoint instruction. 69 */ 70 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs) 71 { 72 return instruction_pointer(regs); 73 } 74 75 /* 76 * If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc), 77 * then detect the case where a singlestepped instruction jumps back to its 78 * own address. It is assumed that anything like do_page_fault/do_trap/etc 79 * sets thread.trap_nr != UINT_MAX. 80 * 81 * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr, 82 * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to 83 * UPROBE_TRAP_NR == UINT_MAX set by arch_uprobe_pre_xol(). 84 */ 85 bool arch_uprobe_xol_was_trapped(struct task_struct *t) 86 { 87 if (t->thread.trap_nr != UPROBE_TRAP_NR) 88 return true; 89 90 return false; 91 } 92 93 /* 94 * Called after single-stepping. To avoid the SMP problems that can 95 * occur when we temporarily put back the original opcode to 96 * single-step, we single-stepped a copy of the instruction. 97 * 98 * This function prepares to resume execution after the single-step. 99 */ 100 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 101 { 102 struct uprobe_task *utask = current->utask; 103 104 WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR); 105 106 current->thread.trap_nr = utask->autask.saved_trap_nr; 107 108 /* 109 * On powerpc, except for loads and stores, most instructions 110 * including ones that alter code flow (branches, calls, returns) 111 * are emulated in the kernel. We get here only if the emulation 112 * support doesn't exist and have to fix-up the next instruction 113 * to be executed. 114 */ 115 regs->nip = (unsigned long)ppc_inst_next((void *)utask->vaddr, &auprobe->insn); 116 117 user_disable_single_step(current); 118 return 0; 119 } 120 121 /* callback routine for handling exceptions. */ 122 int arch_uprobe_exception_notify(struct notifier_block *self, 123 unsigned long val, void *data) 124 { 125 struct die_args *args = data; 126 struct pt_regs *regs = args->regs; 127 128 /* regs == NULL is a kernel bug */ 129 if (WARN_ON(!regs)) 130 return NOTIFY_DONE; 131 132 /* We are only interested in userspace traps */ 133 if (!user_mode(regs)) 134 return NOTIFY_DONE; 135 136 switch (val) { 137 case DIE_BPT: 138 if (uprobe_pre_sstep_notifier(regs)) 139 return NOTIFY_STOP; 140 break; 141 case DIE_SSTEP: 142 if (uprobe_post_sstep_notifier(regs)) 143 return NOTIFY_STOP; 144 default: 145 break; 146 } 147 return NOTIFY_DONE; 148 } 149 150 /* 151 * This function gets called when XOL instruction either gets trapped or 152 * the thread has a fatal signal, so reset the instruction pointer to its 153 * probed address. 154 */ 155 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 156 { 157 struct uprobe_task *utask = current->utask; 158 159 current->thread.trap_nr = utask->autask.saved_trap_nr; 160 instruction_pointer_set(regs, utask->vaddr); 161 162 user_disable_single_step(current); 163 } 164 165 /* 166 * See if the instruction can be emulated. 167 * Returns true if instruction was emulated, false otherwise. 168 */ 169 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) 170 { 171 int ret; 172 173 /* 174 * emulate_step() returns 1 if the insn was successfully emulated. 175 * For all other cases, we need to single-step in hardware. 176 */ 177 ret = emulate_step(regs, ppc_inst_read(&auprobe->insn)); 178 if (ret > 0) 179 return true; 180 181 return false; 182 } 183 184 unsigned long 185 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs) 186 { 187 unsigned long orig_ret_vaddr; 188 189 orig_ret_vaddr = regs->link; 190 191 /* Replace the return addr with trampoline addr */ 192 regs->link = trampoline_vaddr; 193 194 return orig_ret_vaddr; 195 } 196 197 bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, 198 struct pt_regs *regs) 199 { 200 if (ctx == RP_CHECK_CHAIN_CALL) 201 return regs->gpr[1] <= ret->stack; 202 else 203 return regs->gpr[1] < ret->stack; 204 } 205