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This is a reland of 95e97a32eba4d505ab9591e683d2147c441eea48 Original change's description: > Use a relative address in .note.crashpad.info > > The desc value in the note is now the offset of CRASHPAD_INFO_SYMBOL > from desc. > > Making this note writable can trigger a linker error resulting in > the binary embedding .note.crashpad.info to be rejected by the > kernel during program loading. > > The error was observed with: > GNU ld (GNU Binutils for Debian) 2.30 > clang version 4.0.1-10 (tags/RELEASE_401/final) > Debian 4.17.17-1rodete2 > > When the note is made writable, crashpad_snapshot_test contains two > PT_LOAD segments which map to the same page. > > LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000 > 0x0000000000000258 0x0000000000000258 R 0x200000 > LOAD 0x0000000000000258 0x0000000000000258 0x0000000000000258 > 0x00000000002b84d8 0x00000000002b8950 RWE 0x200000 > > Executing this binary with the execv system call triggers a segfault > during program loading (an error can't be returned because the original > process vm has already been discarded). > > I suspect (I haven't set up a debuggable kernel) the failure occurs > while attempting to map the second load segment because its virtual > address, 0x258, is in the same page as the first load segment. > https://elixir.bootlin.com/linux/v4.17.17/source/fs/binfmt_elf.c#L380 > > The linker normally produces consecutive load segments where the second > segment is loaded 0x200000 bytes after the first, which I think is the > maximum expected page size. Modifying the test executable to load the > second segment at 0x1258 (4096 byte page size) allows program loading > to succeed (but of course crashes after control is given to it). > > Bug: crashpad:260 > Change-Id: I2b9f1e66e98919138baef3da991a9710bd970dc4 > Reviewed-on: https://chromium-review.googlesource.com/c/1292232 > Reviewed-by: Scott Graham <scottmg@chromium.org> > Reviewed-by: Mark Mentovai <mark@chromium.org> > Commit-Queue: Joshua Peraza <jperaza@chromium.org> Bug: crashpad:260 Change-Id: I66713de84cc26c9119e0454d19c9c189263fe054 Reviewed-on: https://chromium-review.googlesource.com/c/1318066 Commit-Queue: Joshua Peraza <jperaza@chromium.org> Reviewed-by: Mark Mentovai <mark@chromium.org> Reviewed-by: Scott Graham <scottmg@chromium.org>
52 lines
1.9 KiB
ArmAsm
52 lines
1.9 KiB
ArmAsm
// Copyright 2018 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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// This note section is used on ELF platforms to give ElfImageReader a method
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// of finding the instance of CrashpadInfo g_crashpad_info without requiring
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// that symbol to be in the dynamic symbol table.
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#include "util/misc/elf_note_types.h"
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// namespace crashpad {
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// CrashpadInfo g_test_crashpad_info;
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// } // namespace crashpad
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#define TEST_CRASHPAD_INFO_SYMBOL _ZN8crashpad20g_test_crashpad_infoE
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#define NOTE_ALIGN 4
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// This section must be "a"llocated so that it appears in the final binary at
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// runtime. The reference to TEST_CRASHPAD_INFO_SYMBOL uses an offset relative
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// to this note to avoid making this note writable, which triggers a bug in
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// GNU ld, or adding text relocations which require the target system to allow
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// making text segments writable. https://crbug.com/crashpad/260.
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.section .note.crashpad.info,"a",%note
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.balign NOTE_ALIGN
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.type info_size_test_note, %object
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info_size_test_note:
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.long name_end - name // namesz
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.long desc_end - desc // descsz
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.long CRASHPAD_ELF_NOTE_TYPE_CRASHPAD_INFO // type
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name:
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.asciz CRASHPAD_ELF_NOTE_NAME
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name_end:
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.balign NOTE_ALIGN
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desc:
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#if defined(__LP64__)
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.quad TEST_CRASHPAD_INFO_SYMBOL - desc
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#else
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.long TEST_CRASHPAD_INFO_SYMBOL - desc
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#endif // __LP64__
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desc_end:
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.size info_size_test_note, .-info_size_test_note
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