1 /* 2 * User-space Probes (UProbes) for powerpc 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation; either version 2 of the License, or 7 * (at your option) any later version. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, write to the Free Software 16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 17 * 18 * Copyright IBM Corporation, 2007-2012 19 * 20 * Adapted from the x86 port by Ananth N Mavinakayanahalli <ananth@in.ibm.com> 21 */ 22 #include <linux/kernel.h> 23 #include <linux/sched.h> 24 #include <linux/ptrace.h> 25 #include <linux/uprobes.h> 26 #include <linux/uaccess.h> 27 #include <linux/kdebug.h> 28 29 #include <asm/sstep.h> 30 31 #define UPROBE_TRAP_NR UINT_MAX 32 33 /** 34 * is_trap_insn - check if the instruction is a trap variant 35 * @insn: instruction to be checked. 36 * Returns true if @insn is a trap variant. 37 */ 38 bool is_trap_insn(uprobe_opcode_t *insn) 39 { 40 return (is_trap(*insn)); 41 } 42 43 /** 44 * arch_uprobe_analyze_insn 45 * @mm: the probed address space. 46 * @arch_uprobe: the probepoint information. 47 * @addr: vaddr to probe. 48 * Return 0 on success or a -ve number on error. 49 */ 50 int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, 51 struct mm_struct *mm, unsigned long addr) 52 { 53 if (addr & 0x03) 54 return -EINVAL; 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->nip = 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->nip = utask->vaddr + MAX_UINSN_BYTES; 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 default: 157 break; 158 } 159 return NOTIFY_DONE; 160 } 161 162 /* 163 * This function gets called when XOL instruction either gets trapped or 164 * the thread has a fatal signal, so reset the instruction pointer to its 165 * probed address. 166 */ 167 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 168 { 169 struct uprobe_task *utask = current->utask; 170 171 current->thread.trap_nr = utask->autask.saved_trap_nr; 172 instruction_pointer_set(regs, utask->vaddr); 173 174 user_disable_single_step(current); 175 } 176 177 /* 178 * See if the instruction can be emulated. 179 * Returns true if instruction was emulated, false otherwise. 180 */ 181 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) 182 { 183 int ret; 184 185 /* 186 * emulate_step() returns 1 if the insn was successfully emulated. 187 * For all other cases, we need to single-step in hardware. 188 */ 189 ret = emulate_step(regs, auprobe->ainsn); 190 if (ret > 0) 191 return true; 192 193 return false; 194 } 195 196 unsigned long 197 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs) 198 { 199 unsigned long orig_ret_vaddr; 200 201 orig_ret_vaddr = regs->link; 202 203 /* Replace the return addr with trampoline addr */ 204 regs->link = trampoline_vaddr; 205 206 return orig_ret_vaddr; 207 } 208