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The load bias is documented to be the difference between the preferred and actual load address for a module, but is declared as an unsigned number, and math using it relies on it being a pointer-precisioned two's complement number that might cause over- or under-flow. ElfImageReader and DebugRendezvous both provide ways to get the load bias for a module and are corroborated in tests. However, the load bias computed by DebugRendezvous does not have access to the preferred address, so there is not enough information to determine the signedness to use with a VMOffset. This patch compares the load biases modulo the numeric range for a pointer to ignore the signedness of the value. Also update the test module to trigger a negative load bias. Bug: chromium:1147922 Change-Id: I55bc49195cfb2def06777e26388380fb9bc0f710 Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/2569886 Commit-Queue: Joshua Peraza <jperaza@chromium.org> Reviewed-by: Mark Mentovai <mark@chromium.org>
89 lines
2.9 KiB
C++
89 lines
2.9 KiB
C++
// Copyright 2017 The Crashpad Authors. All rights reserved.
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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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#ifndef CRASHPAD_SNAPSHOT_LINUX_DEBUG_RENDEZVOUS_H_
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#define CRASHPAD_SNAPSHOT_LINUX_DEBUG_RENDEZVOUS_H_
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#include <string>
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#include <vector>
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#include "base/macros.h"
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#include "util/linux/address_types.h"
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#include "util/misc/initialization_state_dcheck.h"
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#include "util/process/process_memory_range.h"
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namespace crashpad {
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//! \brief Reads an `r_debug` struct defined in `<link.h>` via
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//! ProcessMemoryRange.
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class DebugRendezvous {
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public:
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//! \brief An entry in the dynamic linker's list of loaded objects.
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//!
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//! All of these values should be checked before use. Whether and how they are
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//! populated may vary by dynamic linker.
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struct LinkEntry {
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LinkEntry();
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//! \brief A filename identifying the object.
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std::string name;
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//! \brief The difference between the preferred load address in the ELF file
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//! and the actual loaded address in memory.
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VMAddress load_bias;
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//! \brief The address of the dynamic array for this object.
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LinuxVMAddress dynamic_array;
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};
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DebugRendezvous();
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~DebugRendezvous();
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//! \brief Initializes this object by reading an `r_debug` struct from a
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//! target process.
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//!
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//! This method must be called successfully prior to calling any other method
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//! in this class.
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//!
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//! \param[in] memory A memory reader for the remote process.
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//! \param[in] address The address of an `r_debug` struct in the remote
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//! process.
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//! \return `true` on success. `false` on failure with a message logged.
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bool Initialize(const ProcessMemoryRange& memory, LinuxVMAddress address);
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//! \brief Returns the LinkEntry for the main executable.
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const LinkEntry* Executable() const;
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//! \brief Returns a vector of modules found in the link map.
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//!
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//! This list excludes the entry for the executable and may include entries
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//! for the VDSO and loader.
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const std::vector<LinkEntry>& Modules() const;
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private:
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template <typename Traits>
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bool InitializeSpecific(const ProcessMemoryRange& memory,
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LinuxVMAddress address);
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std::vector<LinkEntry> modules_;
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LinkEntry executable_;
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InitializationStateDcheck initialized_;
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DISALLOW_COPY_AND_ASSIGN(DebugRendezvous);
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};
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} // namespace crashpad
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#endif // CRASHPAD_SNAPSHOT_LINUX_DEBUG_RENDEZVOUS_H_
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