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 return 0; 52 } 53 54 /* 55 * arch_uprobe_pre_xol - prepare to execute out of line. 56 * @auprobe: the probepoint information. 57 * @regs: reflects the saved user state of current task. 58 */ 59 int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 60 { 61 struct arch_uprobe_task *autask = ¤t->utask->autask; 62 63 autask->saved_trap_nr = current->thread.trap_nr; 64 current->thread.trap_nr = UPROBE_TRAP_NR; 65 regs_set_return_ip(regs, current->utask->xol_vaddr); 66 67 user_enable_single_step(current); 68 return 0; 69 } 70 71 /** 72 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs 73 * @regs: Reflects the saved state of the task after it has hit a breakpoint 74 * instruction. 75 * Return the address of the breakpoint instruction. 76 */ 77 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs) 78 { 79 return instruction_pointer(regs); 80 } 81 82 /* 83 * If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc), 84 * then detect the case where a singlestepped instruction jumps back to its 85 * own address. It is assumed that anything like do_page_fault/do_trap/etc 86 * sets thread.trap_nr != UINT_MAX. 87 * 88 * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr, 89 * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to 90 * UPROBE_TRAP_NR == UINT_MAX set by arch_uprobe_pre_xol(). 91 */ 92 bool arch_uprobe_xol_was_trapped(struct task_struct *t) 93 { 94 if (t->thread.trap_nr != UPROBE_TRAP_NR) 95 return true; 96 97 return false; 98 } 99 100 /* 101 * Called after single-stepping. To avoid the SMP problems that can 102 * occur when we temporarily put back the original opcode to 103 * single-step, we single-stepped a copy of the instruction. 104 * 105 * This function prepares to resume execution after the single-step. 106 */ 107 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 108 { 109 struct uprobe_task *utask = current->utask; 110 111 WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR); 112 113 current->thread.trap_nr = utask->autask.saved_trap_nr; 114 115 /* 116 * On powerpc, except for loads and stores, most instructions 117 * including ones that alter code flow (branches, calls, returns) 118 * are emulated in the kernel. We get here only if the emulation 119 * support doesn't exist and have to fix-up the next instruction 120 * to be executed. 121 */ 122 regs_set_return_ip(regs, (unsigned long)ppc_inst_next((void *)utask->vaddr, auprobe->insn)); 123 124 user_disable_single_step(current); 125 return 0; 126 } 127 128 /* callback routine for handling exceptions. */ 129 int arch_uprobe_exception_notify(struct notifier_block *self, 130 unsigned long val, void *data) 131 { 132 struct die_args *args = data; 133 struct pt_regs *regs = args->regs; 134 135 /* regs == NULL is a kernel bug */ 136 if (WARN_ON(!regs)) 137 return NOTIFY_DONE; 138 139 /* We are only interested in userspace traps */ 140 if (!user_mode(regs)) 141 return NOTIFY_DONE; 142 143 switch (val) { 144 case DIE_BPT: 145 if (uprobe_pre_sstep_notifier(regs)) 146 return NOTIFY_STOP; 147 break; 148 case DIE_SSTEP: 149 if (uprobe_post_sstep_notifier(regs)) 150 return NOTIFY_STOP; 151 break; 152 default: 153 break; 154 } 155 return NOTIFY_DONE; 156 } 157 158 /* 159 * This function gets called when XOL instruction either gets trapped or 160 * the thread has a fatal signal, so reset the instruction pointer to its 161 * probed address. 162 */ 163 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 164 { 165 struct uprobe_task *utask = current->utask; 166 167 current->thread.trap_nr = utask->autask.saved_trap_nr; 168 instruction_pointer_set(regs, utask->vaddr); 169 170 user_disable_single_step(current); 171 } 172 173 /* 174 * See if the instruction can be emulated. 175 * Returns true if instruction was emulated, false otherwise. 176 */ 177 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) 178 { 179 int ret; 180 181 /* 182 * emulate_step() returns 1 if the insn was successfully emulated. 183 * For all other cases, we need to single-step in hardware. 184 */ 185 ret = emulate_step(regs, ppc_inst_read(auprobe->insn)); 186 if (ret > 0) 187 return true; 188 189 return false; 190 } 191 192 unsigned long 193 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs) 194 { 195 unsigned long orig_ret_vaddr; 196 197 orig_ret_vaddr = regs->link; 198 199 /* Replace the return addr with trampoline addr */ 200 regs->link = trampoline_vaddr; 201 202 return orig_ret_vaddr; 203 } 204 205 bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, 206 struct pt_regs *regs) 207 { 208 if (ctx == RP_CHECK_CHAIN_CALL) 209 return regs->gpr[1] <= ret->stack; 210 else 211 return regs->gpr[1] < ret->stack; 212 } 213