Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 1 | /* |
| 2 | * x86 single-step support code, common to 32-bit and 64-bit. |
| 3 | */ |
| 4 | #include <linux/sched.h> |
| 5 | #include <linux/mm.h> |
| 6 | #include <linux/ptrace.h> |
| 7 | |
Harvey Harrison | 37cd9cf | 2008-01-30 13:33:12 +0100 | [diff] [blame] | 8 | unsigned long convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs) |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 9 | { |
| 10 | unsigned long addr, seg; |
| 11 | |
H. Peter Anvin | 65ea5b0 | 2008-01-30 13:30:56 +0100 | [diff] [blame] | 12 | addr = regs->ip; |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 13 | seg = regs->cs & 0xffff; |
H. Peter Anvin | 65ea5b0 | 2008-01-30 13:30:56 +0100 | [diff] [blame] | 14 | if (v8086_mode(regs)) { |
Roland McGrath | 7122ec8 | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 15 | addr = (addr & 0xffff) + (seg << 4); |
| 16 | return addr; |
| 17 | } |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 18 | |
| 19 | /* |
| 20 | * We'll assume that the code segments in the GDT |
| 21 | * are all zero-based. That is largely true: the |
| 22 | * TLS segments are used for data, and the PNPBIOS |
| 23 | * and APM bios ones we just ignore here. |
| 24 | */ |
Roland McGrath | 3f80c1a | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 25 | if ((seg & SEGMENT_TI_MASK) == SEGMENT_LDT) { |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 26 | u32 *desc; |
| 27 | unsigned long base; |
| 28 | |
| 29 | seg &= ~7UL; |
| 30 | |
| 31 | mutex_lock(&child->mm->context.lock); |
| 32 | if (unlikely((seg >> 3) >= child->mm->context.size)) |
| 33 | addr = -1L; /* bogus selector, access would fault */ |
| 34 | else { |
| 35 | desc = child->mm->context.ldt + seg; |
| 36 | base = ((desc[0] >> 16) | |
| 37 | ((desc[1] & 0xff) << 16) | |
| 38 | (desc[1] & 0xff000000)); |
| 39 | |
| 40 | /* 16-bit code segment? */ |
| 41 | if (!((desc[1] >> 22) & 1)) |
| 42 | addr &= 0xffff; |
| 43 | addr += base; |
| 44 | } |
| 45 | mutex_unlock(&child->mm->context.lock); |
| 46 | } |
| 47 | |
| 48 | return addr; |
| 49 | } |
| 50 | |
| 51 | static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs) |
| 52 | { |
| 53 | int i, copied; |
| 54 | unsigned char opcode[15]; |
Harvey Harrison | 37cd9cf | 2008-01-30 13:33:12 +0100 | [diff] [blame] | 55 | unsigned long addr = convert_ip_to_linear(child, regs); |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 56 | |
| 57 | copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0); |
| 58 | for (i = 0; i < copied; i++) { |
| 59 | switch (opcode[i]) { |
| 60 | /* popf and iret */ |
| 61 | case 0x9d: case 0xcf: |
| 62 | return 1; |
| 63 | |
| 64 | /* CHECKME: 64 65 */ |
| 65 | |
| 66 | /* opcode and address size prefixes */ |
| 67 | case 0x66: case 0x67: |
| 68 | continue; |
| 69 | /* irrelevant prefixes (segment overrides and repeats) */ |
| 70 | case 0x26: case 0x2e: |
| 71 | case 0x36: case 0x3e: |
| 72 | case 0x64: case 0x65: |
Roland McGrath | 5f76cb1 | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 73 | case 0xf0: case 0xf2: case 0xf3: |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 74 | continue; |
| 75 | |
Roland McGrath | 7122ec8 | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 76 | #ifdef CONFIG_X86_64 |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 77 | case 0x40 ... 0x4f: |
| 78 | if (regs->cs != __USER_CS) |
| 79 | /* 32-bit mode: register increment */ |
| 80 | return 0; |
| 81 | /* 64-bit mode: REX prefix */ |
| 82 | continue; |
Roland McGrath | 7122ec8 | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 83 | #endif |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 84 | |
| 85 | /* CHECKME: f2, f3 */ |
| 86 | |
| 87 | /* |
| 88 | * pushf: NOTE! We should probably not let |
| 89 | * the user see the TF bit being set. But |
| 90 | * it's more pain than it's worth to avoid |
| 91 | * it, and a debugger could emulate this |
| 92 | * all in user space if it _really_ cares. |
| 93 | */ |
| 94 | case 0x9c: |
| 95 | default: |
| 96 | return 0; |
| 97 | } |
| 98 | } |
| 99 | return 0; |
| 100 | } |
| 101 | |
Roland McGrath | 10faa81 | 2008-01-30 13:30:54 +0100 | [diff] [blame] | 102 | /* |
| 103 | * Enable single-stepping. Return nonzero if user mode is not using TF itself. |
| 104 | */ |
| 105 | static int enable_single_step(struct task_struct *child) |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 106 | { |
| 107 | struct pt_regs *regs = task_pt_regs(child); |
Roland McGrath | 6718d0d | 2008-07-09 01:07:02 -0700 | [diff] [blame^] | 108 | unsigned long oflags; |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 109 | |
| 110 | /* |
| 111 | * Always set TIF_SINGLESTEP - this guarantees that |
| 112 | * we single-step system calls etc.. This will also |
| 113 | * cause us to set TF when returning to user mode. |
| 114 | */ |
| 115 | set_tsk_thread_flag(child, TIF_SINGLESTEP); |
| 116 | |
Roland McGrath | 6718d0d | 2008-07-09 01:07:02 -0700 | [diff] [blame^] | 117 | oflags = regs->flags; |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 118 | |
| 119 | /* Set TF on the kernel stack.. */ |
H. Peter Anvin | 65ea5b0 | 2008-01-30 13:30:56 +0100 | [diff] [blame] | 120 | regs->flags |= X86_EFLAGS_TF; |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 121 | |
| 122 | /* |
| 123 | * ..but if TF is changed by the instruction we will trace, |
| 124 | * don't mark it as being "us" that set it, so that we |
| 125 | * won't clear it by hand later. |
Roland McGrath | 6718d0d | 2008-07-09 01:07:02 -0700 | [diff] [blame^] | 126 | * |
| 127 | * Note that if we don't actually execute the popf because |
| 128 | * of a signal arriving right now or suchlike, we will lose |
| 129 | * track of the fact that it really was "us" that set it. |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 130 | */ |
Roland McGrath | 6718d0d | 2008-07-09 01:07:02 -0700 | [diff] [blame^] | 131 | if (is_setting_trap_flag(child, regs)) { |
| 132 | clear_tsk_thread_flag(child, TIF_FORCED_TF); |
Roland McGrath | 10faa81 | 2008-01-30 13:30:54 +0100 | [diff] [blame] | 133 | return 0; |
Roland McGrath | 6718d0d | 2008-07-09 01:07:02 -0700 | [diff] [blame^] | 134 | } |
| 135 | |
| 136 | /* |
| 137 | * If TF was already set, check whether it was us who set it. |
| 138 | * If not, we should never attempt a block step. |
| 139 | */ |
| 140 | if (oflags & X86_EFLAGS_TF) |
| 141 | return test_tsk_thread_flag(child, TIF_FORCED_TF); |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 142 | |
Roland McGrath | e1f2877 | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 143 | set_tsk_thread_flag(child, TIF_FORCED_TF); |
Roland McGrath | 10faa81 | 2008-01-30 13:30:54 +0100 | [diff] [blame] | 144 | |
| 145 | return 1; |
| 146 | } |
| 147 | |
| 148 | /* |
| 149 | * Install this value in MSR_IA32_DEBUGCTLMSR whenever child is running. |
| 150 | */ |
| 151 | static void write_debugctlmsr(struct task_struct *child, unsigned long val) |
| 152 | { |
Roland McGrath | 4ba51fd | 2008-04-03 14:18:55 -0700 | [diff] [blame] | 153 | if (child->thread.debugctlmsr == val) |
| 154 | return; |
| 155 | |
Roland McGrath | 10faa81 | 2008-01-30 13:30:54 +0100 | [diff] [blame] | 156 | child->thread.debugctlmsr = val; |
| 157 | |
| 158 | if (child != current) |
| 159 | return; |
| 160 | |
Jan Beulich | 5b0e508 | 2008-03-10 13:11:17 +0000 | [diff] [blame] | 161 | update_debugctlmsr(val); |
Roland McGrath | 10faa81 | 2008-01-30 13:30:54 +0100 | [diff] [blame] | 162 | } |
| 163 | |
| 164 | /* |
| 165 | * Enable single or block step. |
| 166 | */ |
| 167 | static void enable_step(struct task_struct *child, bool block) |
| 168 | { |
| 169 | /* |
| 170 | * Make sure block stepping (BTF) is not enabled unless it should be. |
| 171 | * Note that we don't try to worry about any is_setting_trap_flag() |
| 172 | * instructions after the first when using block stepping. |
| 173 | * So noone should try to use debugger block stepping in a program |
| 174 | * that uses user-mode single stepping itself. |
| 175 | */ |
| 176 | if (enable_single_step(child) && block) { |
| 177 | set_tsk_thread_flag(child, TIF_DEBUGCTLMSR); |
Markus Metzger | eee3af4 | 2008-01-30 13:31:09 +0100 | [diff] [blame] | 178 | write_debugctlmsr(child, |
| 179 | child->thread.debugctlmsr | DEBUGCTLMSR_BTF); |
| 180 | } else { |
Roland McGrath | 4ba51fd | 2008-04-03 14:18:55 -0700 | [diff] [blame] | 181 | write_debugctlmsr(child, |
| 182 | child->thread.debugctlmsr & ~DEBUGCTLMSR_BTF); |
Markus Metzger | eee3af4 | 2008-01-30 13:31:09 +0100 | [diff] [blame] | 183 | |
Roland McGrath | 4ba51fd | 2008-04-03 14:18:55 -0700 | [diff] [blame] | 184 | if (!child->thread.debugctlmsr) |
| 185 | clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR); |
Roland McGrath | 10faa81 | 2008-01-30 13:30:54 +0100 | [diff] [blame] | 186 | } |
| 187 | } |
| 188 | |
| 189 | void user_enable_single_step(struct task_struct *child) |
| 190 | { |
| 191 | enable_step(child, 0); |
| 192 | } |
| 193 | |
| 194 | void user_enable_block_step(struct task_struct *child) |
| 195 | { |
| 196 | enable_step(child, 1); |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 197 | } |
| 198 | |
| 199 | void user_disable_single_step(struct task_struct *child) |
| 200 | { |
Roland McGrath | 10faa81 | 2008-01-30 13:30:54 +0100 | [diff] [blame] | 201 | /* |
| 202 | * Make sure block stepping (BTF) is disabled. |
| 203 | */ |
Markus Metzger | eee3af4 | 2008-01-30 13:31:09 +0100 | [diff] [blame] | 204 | write_debugctlmsr(child, |
Jan Beulich | d032b31 | 2008-03-05 08:36:48 +0000 | [diff] [blame] | 205 | child->thread.debugctlmsr & ~DEBUGCTLMSR_BTF); |
Markus Metzger | eee3af4 | 2008-01-30 13:31:09 +0100 | [diff] [blame] | 206 | |
| 207 | if (!child->thread.debugctlmsr) |
| 208 | clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR); |
Roland McGrath | 10faa81 | 2008-01-30 13:30:54 +0100 | [diff] [blame] | 209 | |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 210 | /* Always clear TIF_SINGLESTEP... */ |
| 211 | clear_tsk_thread_flag(child, TIF_SINGLESTEP); |
| 212 | |
| 213 | /* But touch TF only if it was set by us.. */ |
Roland McGrath | e1f2877 | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 214 | if (test_and_clear_tsk_thread_flag(child, TIF_FORCED_TF)) |
H. Peter Anvin | 65ea5b0 | 2008-01-30 13:30:56 +0100 | [diff] [blame] | 215 | task_pt_regs(child)->flags &= ~X86_EFLAGS_TF; |
Roland McGrath | fa1e03e | 2008-01-30 13:30:50 +0100 | [diff] [blame] | 216 | } |