f0c5872637
Keep track of whether memory maps are readable. Use the information in try_get_word to try to avoid accidentally dereferencing an invalid pointer within the current process. (Note that I haven't ever seen that happen during normal unwinding, but it pays to be a little more careful.) Refactored try_get_word a little to make it easier to pass it the needed state for validation checks by way of a little memory_t struct. Improved how the memory map for the current process is cached. This is important because we need up to date information about readable maps. Use a 5 second cache expiration. Improved the PC -> LR fallback logic in the unwinder so we can eke out an extra frame sometimes. Fixed a bug reading ELF program headers. The phnum & phentsize fields are half-words. We were incorrectly interpreting phnum as a whole word. Used android_atomic_* operations carefully in the unwinder to prevent possible memory races between the dumper and the dumpee. This was highly unlikely (or even impossible due to the presence of other barriers along the way) but the code is clearer now about its invariants. Fixed a bug in debuggerd where the pid was being passed to have its stack dump taken instead of the tid, resulting in short stacks because ptrace couldn't read the data if pid != tid. Did a full sweep to ensure that we use pid / tid correctly everywhere. Ported old code from debuggerd to rewind the program counter back one instruction so that it points to the branch instruction itself instead of the return address. Change-Id: Icc4eb08320052975a4ae7f0f5f0ac9308a2d33d7
120 lines
3.3 KiB
C
120 lines
3.3 KiB
C
/*
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* Copyright (C) 2011 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/* Useful ptrace() utility functions. */
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#ifndef _CORKSCREW_PTRACE_H
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#define _CORKSCREW_PTRACE_H
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#include <corkscrew/map_info.h>
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#include <corkscrew/symbol_table.h>
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#include <sys/types.h>
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#include <stdbool.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Stores information about a process that is used for several different
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* ptrace() based operations. */
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typedef struct {
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map_info_t* map_info_list;
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} ptrace_context_t;
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/* Describes how to access memory from a process. */
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typedef struct {
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pid_t tid;
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const map_info_t* map_info_list;
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} memory_t;
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#if __i386__
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/* ptrace() register context. */
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typedef struct pt_regs_x86 {
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uint32_t ebx;
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uint32_t ecx;
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uint32_t edx;
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uint32_t esi;
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uint32_t edi;
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uint32_t ebp;
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uint32_t eax;
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uint32_t xds;
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uint32_t xes;
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uint32_t xfs;
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uint32_t xgs;
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uint32_t orig_eax;
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uint32_t eip;
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uint32_t xcs;
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uint32_t eflags;
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uint32_t esp;
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uint32_t xss;
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} pt_regs_x86_t;
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#endif
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/*
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* Initializes a memory structure for accessing memory from this process.
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*/
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void init_memory(memory_t* memory, const map_info_t* map_info_list);
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/*
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* Initializes a memory structure for accessing memory from another process
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* using ptrace().
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*/
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void init_memory_ptrace(memory_t* memory, pid_t tid);
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/*
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* Reads a word of memory safely.
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* If the memory is local, ensures that the address is readable before dereferencing it.
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* Returns false and a value of 0xffffffff if the word could not be read.
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*/
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bool try_get_word(const memory_t* memory, uintptr_t ptr, uint32_t* out_value);
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/*
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* Reads a word of memory safely using ptrace().
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* Returns false and a value of 0xffffffff if the word could not be read.
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*/
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bool try_get_word_ptrace(pid_t tid, uintptr_t ptr, uint32_t* out_value);
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/*
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* Loads information needed for examining a remote process using ptrace().
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* The caller must already have successfully attached to the process
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* using ptrace().
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*
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* The context can be used for any threads belonging to that process
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* assuming ptrace() is attached to them before performing the actual
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* unwinding. The context can continue to be used to decode backtraces
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* even after ptrace() has been detached from the process.
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*/
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ptrace_context_t* load_ptrace_context(pid_t pid);
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/*
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* Frees a ptrace context.
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*/
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void free_ptrace_context(ptrace_context_t* context);
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/*
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* Finds a symbol using ptrace.
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* Returns the containing map and information about the symbol, or
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* NULL if one or the other is not available.
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*/
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void find_symbol_ptrace(const ptrace_context_t* context,
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uintptr_t addr, const map_info_t** out_map_info, const symbol_t** out_symbol);
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#ifdef __cplusplus
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}
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#endif
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#endif // _CORKSCREW_PTRACE_H
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