1/*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17/*
18 * Backtracing functions for x86.
19 */
20
21#define LOG_TAG "Corkscrew"
22//#define LOG_NDEBUG 0
23
24#include "../backtrace-arch.h"
25#include "../backtrace-helper.h"
26#include <corkscrew/ptrace.h>
27
28#include <stdlib.h>
29#include <signal.h>
30#include <stdbool.h>
31#include <limits.h>
32#include <errno.h>
33#include <sys/ptrace.h>
34#include <cutils/log.h>
35
36#if defined(__BIONIC__)
37
38#if defined(__BIONIC_HAVE_UCONTEXT_T)
39
40// Bionic offers the Linux kernel headers.
41#include <asm/sigcontext.h>
42#include <asm/ucontext.h>
43typedef struct ucontext ucontext_t;
44
45#else /* __BIONIC_HAVE_UCONTEXT_T */
46
47/* Old versions of the Android <signal.h> didn't define ucontext_t. */
48
49typedef struct {
50  uint32_t  gregs[32];
51  void*     fpregs;
52  uint32_t  oldmask;
53  uint32_t  cr2;
54} mcontext_t;
55
56enum {
57  REG_GS = 0, REG_FS, REG_ES, REG_DS,
58  REG_EDI, REG_ESI, REG_EBP, REG_ESP,
59  REG_EBX, REG_EDX, REG_ECX, REG_EAX,
60  REG_TRAPNO, REG_ERR, REG_EIP, REG_CS,
61  REG_EFL, REG_UESP, REG_SS
62};
63
64/* Machine context at the time a signal was raised. */
65typedef struct ucontext {
66    uint32_t uc_flags;
67    struct ucontext* uc_link;
68    stack_t uc_stack;
69    mcontext_t uc_mcontext;
70    uint32_t uc_sigmask;
71} ucontext_t;
72
73#endif /* __BIONIC_HAVE_UCONTEXT_T */
74
75#else /* __BIONIC__ */
76
77// glibc has its own renaming of the Linux kernel's structures.
78#define __USE_GNU // For REG_EBP, REG_ESP, and REG_EIP.
79#include <ucontext.h>
80
81#endif /* __ BIONIC__ */
82
83/* Unwind state. */
84typedef struct {
85    uint32_t ebp;
86    uint32_t eip;
87    uint32_t esp;
88} unwind_state_t;
89
90uintptr_t rewind_pc_arch(const memory_t* memory __attribute__((unused)), uintptr_t pc) {
91    // TODO: Implement for x86.
92    return pc;
93}
94
95static ssize_t unwind_backtrace_common(const memory_t* memory,
96        const map_info_t* map_info_list __attribute__((unused)),
97        unwind_state_t* state, backtrace_frame_t* backtrace,
98        size_t ignore_depth, size_t max_depth) {
99    size_t ignored_frames = 0;
100    size_t returned_frames = 0;
101
102    for (size_t index = 0; state->ebp && returned_frames < max_depth; index++) {
103        backtrace_frame_t* frame = add_backtrace_entry(
104                index ? rewind_pc_arch(memory, state->eip) : state->eip,
105                backtrace, ignore_depth, max_depth,
106                &ignored_frames, &returned_frames);
107        uint32_t next_esp = state->ebp + 8;
108        if (frame) {
109            frame->stack_top = state->esp;
110            if (state->esp < next_esp) {
111                frame->stack_size = next_esp - state->esp;
112            }
113        }
114        state->esp = next_esp;
115        if (!try_get_word(memory, state->ebp + 4, &state->eip)
116                || !try_get_word(memory, state->ebp, &state->ebp)
117                || !state->eip) {
118            break;
119        }
120    }
121
122    return returned_frames;
123}
124
125ssize_t unwind_backtrace_signal_arch(siginfo_t* siginfo __attribute__((unused)), void* sigcontext,
126        const map_info_t* map_info_list,
127        backtrace_frame_t* backtrace, size_t ignore_depth, size_t max_depth) {
128    const ucontext_t* uc = (const ucontext_t*)sigcontext;
129
130    unwind_state_t state;
131    state.ebp = uc->uc_mcontext.gregs[REG_EBP];
132    state.esp = uc->uc_mcontext.gregs[REG_ESP];
133    state.eip = uc->uc_mcontext.gregs[REG_EIP];
134
135    memory_t memory;
136    init_memory(&memory, map_info_list);
137    return unwind_backtrace_common(&memory, map_info_list,
138            &state, backtrace, ignore_depth, max_depth);
139}
140
141ssize_t unwind_backtrace_ptrace_arch(pid_t tid, const ptrace_context_t* context,
142        backtrace_frame_t* backtrace, size_t ignore_depth, size_t max_depth) {
143    pt_regs_x86_t regs;
144    if (ptrace(PTRACE_GETREGS, tid, 0, &regs)) {
145        return -1;
146    }
147
148    unwind_state_t state;
149    state.ebp = regs.ebp;
150    state.eip = regs.eip;
151    state.esp = regs.esp;
152
153    memory_t memory;
154    init_memory_ptrace(&memory, tid);
155    return unwind_backtrace_common(&memory, context->map_info_list,
156            &state, backtrace, ignore_depth, max_depth);
157}
158