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binutils-gdb/gdb/dwarf2/index-write.h

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Add DWARF index cache New in v3: - Remove things related to the dwarf-5 format. - Fix compilation on mingw (scoped_mmap.c). GDB can generate indexes for DWARF debug information, which, when integrated in the original binary, can speed up loading object files. This can be done using the gdb-add-index script or directly by the linker itself. However, not many people know about this. And even among those who do, because it requires additional steps, I don't know a lot of people who actually go through that trouble. To help make using the DWARF index more transparent, this patch introduces a DWARF index cache. When enabled, loading an index-less binary in GDB will automatically save an index file in ~/.cache/gdb. When loading that same object file again, the index file will be looked up and used to load the DWARF index. You therefore get the benefit of the DWARF index without having to do additional manual steps or modifying your build system. When an index section is already present in the file, GDB will prefer that one over looking up the cache. When doing my edit-compile-debug cycle, I often debug multiple times the same build, so the cache helps reducing the load time of the debug sessions after the first one. - The saved index file is exactly the same as the output of the "save gdb-index" command. It is therefore the exact same content that would be found in the .gdb_index or .debug_names section. We just leave it as a standalone file instead of merging it in the binary. - The cache is just a directory with files named after the object file's build-id. It is not possible to save/load the index for an object file without build-id in the cache. - The cache uses the gdb index format. The problem with the dwarf-5 format is that we can generate an addendum to the .debug_str section that you're supposed to integrate to the original binary. This complicates a little bit loading the data from the cached index files, so I would leave this for later. - The size taken up by ~/.cache/gdb is not limited. I was thinking we could add configurable limit (like ccache does), but that would come after. Also, maybe a command to flush the cache. - The cache is disabled by default. I think once it's been out there and tested for a while, it could be turned on by default, so that everybody can enjoy it. - The code was made to follow the XDG specification: if the XDG_CACHE_HOME environment variable, it is used, otherwise it falls back to ~/.cache/gdb. It is possible to change it using "set index-cache directory". On other OSes than GNU/Linux, ~/.cache may not be the best place to put such data. On macOS it should probably default to ~/Library/Caches/... On Windows, %LocalAppData%/... I don't intend to do this part, but further patches are welcome. - I think that we need to be careful that multiple instances of GDB don't interfere with each other (not far fetched at all if you run GDB in some automated script) and the cache is always coherent (either the file is not found, or it is found and entirely valid). Writing the file directly to its final location seems like a recipe for failure. One GDB could read a file in the index while it is being written by another GDB. To mitigate this, I made write_psymtabs_to_index write to temporary files and rename them once it's done. Two GDB instances writing the index for the same file should not step on each other's toes (the last file to be renamed will stay). A GDB looking up a file will only see a complete file or no file. Also, if GDB crashes while generating the index file, it will leave a work-in-progress file, but it won't be picked up by other instances looking up in the cache. gdb/ChangeLog: * common/pathstuff.h (get_standard_cache_dir): New. * common/pathstuff.c (get_standard_cache_dir): New. * build-id.h (build_id_to_string): New. * dwarf-index-common.h (INDEX4_SUFFIX, INDEX5_SUFFIX, DEBUG_STR_SUFFIX): Move to here. * dwarf-index-write.c (INDEX4_SUFFIX, INDEX5_SUFFIX, DEBUG_STR_SUFFIX): Move from there. (write_psymtabs_to_index): Make non-static, add basename parameter. Write to temporary files, rename when done. (save_gdb_index_command): Adjust call to write_psymtabs_to_index. * dwarf2read.h (dwarf2_per_objfile) <index_cache_res>: New field. * dwarf2read.c (dwz_file) <index_cache_res>: New field. (get_gdb_index_contents_from_cache): New. (get_gdb_index_contents_from_cache_dwz): New. (dwarf2_initialize_objfile): Read index from cache. (dwarf2_build_psymtabs): Save to index. * dwarf-index-cache.h: New file. * dwarf-index-cache.c: New file. * dwarf-index-write.h: New file. gdb/testsuite/ChangeLog: * boards/index-cache-gdb.exp: New file. * gdb.dwarf2/index-cache.exp: New file. * gdb.dwarf2/index-cache.c: New file. * gdb.base/maint.exp: Check if we are using the index cache.
2018-08-08 06:14:20 +08:00
/* DWARF index writing support for GDB.
Automatic Copyright Year update after running gdb/copyright.py This commit brings all the changes made by running gdb/copyright.py as per GDB's Start of New Year Procedure. For the avoidance of doubt, all changes in this commits were performed by the script.
2022-01-01 22:56:03 +08:00
Copyright (C) 2018-2022 Free Software Foundation, Inc.
Add DWARF index cache New in v3: - Remove things related to the dwarf-5 format. - Fix compilation on mingw (scoped_mmap.c). GDB can generate indexes for DWARF debug information, which, when integrated in the original binary, can speed up loading object files. This can be done using the gdb-add-index script or directly by the linker itself. However, not many people know about this. And even among those who do, because it requires additional steps, I don't know a lot of people who actually go through that trouble. To help make using the DWARF index more transparent, this patch introduces a DWARF index cache. When enabled, loading an index-less binary in GDB will automatically save an index file in ~/.cache/gdb. When loading that same object file again, the index file will be looked up and used to load the DWARF index. You therefore get the benefit of the DWARF index without having to do additional manual steps or modifying your build system. When an index section is already present in the file, GDB will prefer that one over looking up the cache. When doing my edit-compile-debug cycle, I often debug multiple times the same build, so the cache helps reducing the load time of the debug sessions after the first one. - The saved index file is exactly the same as the output of the "save gdb-index" command. It is therefore the exact same content that would be found in the .gdb_index or .debug_names section. We just leave it as a standalone file instead of merging it in the binary. - The cache is just a directory with files named after the object file's build-id. It is not possible to save/load the index for an object file without build-id in the cache. - The cache uses the gdb index format. The problem with the dwarf-5 format is that we can generate an addendum to the .debug_str section that you're supposed to integrate to the original binary. This complicates a little bit loading the data from the cached index files, so I would leave this for later. - The size taken up by ~/.cache/gdb is not limited. I was thinking we could add configurable limit (like ccache does), but that would come after. Also, maybe a command to flush the cache. - The cache is disabled by default. I think once it's been out there and tested for a while, it could be turned on by default, so that everybody can enjoy it. - The code was made to follow the XDG specification: if the XDG_CACHE_HOME environment variable, it is used, otherwise it falls back to ~/.cache/gdb. It is possible to change it using "set index-cache directory". On other OSes than GNU/Linux, ~/.cache may not be the best place to put such data. On macOS it should probably default to ~/Library/Caches/... On Windows, %LocalAppData%/... I don't intend to do this part, but further patches are welcome. - I think that we need to be careful that multiple instances of GDB don't interfere with each other (not far fetched at all if you run GDB in some automated script) and the cache is always coherent (either the file is not found, or it is found and entirely valid). Writing the file directly to its final location seems like a recipe for failure. One GDB could read a file in the index while it is being written by another GDB. To mitigate this, I made write_psymtabs_to_index write to temporary files and rename them once it's done. Two GDB instances writing the index for the same file should not step on each other's toes (the last file to be renamed will stay). A GDB looking up a file will only see a complete file or no file. Also, if GDB crashes while generating the index file, it will leave a work-in-progress file, but it won't be picked up by other instances looking up in the cache. gdb/ChangeLog: * common/pathstuff.h (get_standard_cache_dir): New. * common/pathstuff.c (get_standard_cache_dir): New. * build-id.h (build_id_to_string): New. * dwarf-index-common.h (INDEX4_SUFFIX, INDEX5_SUFFIX, DEBUG_STR_SUFFIX): Move to here. * dwarf-index-write.c (INDEX4_SUFFIX, INDEX5_SUFFIX, DEBUG_STR_SUFFIX): Move from there. (write_psymtabs_to_index): Make non-static, add basename parameter. Write to temporary files, rename when done. (save_gdb_index_command): Adjust call to write_psymtabs_to_index. * dwarf2read.h (dwarf2_per_objfile) <index_cache_res>: New field. * dwarf2read.c (dwz_file) <index_cache_res>: New field. (get_gdb_index_contents_from_cache): New. (get_gdb_index_contents_from_cache_dwz): New. (dwarf2_initialize_objfile): Read index from cache. (dwarf2_build_psymtabs): Save to index. * dwarf-index-cache.h: New file. * dwarf-index-cache.c: New file. * dwarf-index-write.h: New file. gdb/testsuite/ChangeLog: * boards/index-cache-gdb.exp: New file. * gdb.dwarf2/index-cache.exp: New file. * gdb.dwarf2/index-cache.c: New file. * gdb.base/maint.exp: Check if we are using the index cache.
2018-08-08 06:14:20 +08:00
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef DWARF_INDEX_WRITE_H
#define DWARF_INDEX_WRITE_H
Move DWARF code to dwarf2/ subdirectory This moves all the remaining DWARF code to the new dwarf2 subdirectory. This is just a simple renaming, with updates to includes as needed. gdb/ChangeLog 2020-02-08 Tom Tromey <tom@tromey.com> * dwarf2/expr.c: Rename from dwarf2expr.c. * dwarf2/expr.h: Rename from dwarf2expr.h. * dwarf2/frame-tailcall.c: Rename from dwarf2-frame-tailcall.c. * dwarf2/frame-tailcall.h: Rename from dwarf2-frame-tailcall.h. * dwarf2/frame.c: Rename from dwarf2-frame.c. * dwarf2/frame.h: Rename from dwarf2-frame.h. * dwarf2/index-cache.c: Rename from dwarf-index-cache.c. * dwarf2/index-cache.h: Rename from dwarf-index-cache.h. * dwarf2/index-common.c: Rename from dwarf-index-common.c. * dwarf2/index-common.h: Rename from dwarf-index-common.h. * dwarf2/index-write.c: Rename from dwarf-index-write.c. * dwarf2/index-write.h: Rename from dwarf-index-write.h. * dwarf2/loc.c: Rename from dwarf2loc.c. * dwarf2/loc.h: Rename from dwarf2loc.h. * dwarf2/read.c: Rename from dwarf2read.c. * dwarf2/read.h: Rename from dwarf2read.h. * dwarf2/abbrev.c, aarch64-tdep.c, alpha-tdep.c, amd64-darwin-tdep.c, arc-tdep.c, arm-tdep.c, bfin-tdep.c, compile/compile-c-symbols.c, compile/compile-cplus-symbols.c, compile/compile-loc2c.c, cris-tdep.c, csky-tdep.c, findvar.c, gdbtypes.c, guile/scm-type.c, h8300-tdep.c, hppa-bsd-tdep.c, hppa-linux-tdep.c, i386-darwin-tdep.c, i386-linux-tdep.c, i386-tdep.c, iq2000-tdep.c, m32c-tdep.c, m68hc11-tdep.c, m68k-tdep.c, microblaze-tdep.c, mips-tdep.c, mn10300-tdep.c, msp430-tdep.c, nds32-tdep.c, nios2-tdep.c, or1k-tdep.c, riscv-tdep.c, rl78-tdep.c, rs6000-tdep.c, rx-tdep.c, s12z-tdep.c, s390-tdep.c, score-tdep.c, sh-tdep.c, sparc-linux-tdep.c, sparc-tdep.c, sparc64-linux-tdep.c, sparc64-tdep.c, tic6x-tdep.c, tilegx-tdep.c, v850-tdep.c, xstormy16-tdep.c, xtensa-tdep.c: Update. * Makefile.in (COMMON_SFILES): Update. (HFILES_NO_SRCDIR): Update. Change-Id: Ied9ce1436cd27ac4a4cffef10ec92e396f181928
2020-02-09 04:40:54 +08:00
#include "dwarf2/read.h"
Introduce dwarf2/public.h This moves some more DWARF code out of symfile.h and into a new header, dwarf2/public.h. This header is intended to describe the public API of the DWARF reader. gdb/ChangeLog 2021-03-20 Tom Tromey <tom@tromey.com> * coffread.c: Include dwarf2/public.h. * dwarf2/frame.c: Include dwarf2/public.h. * dwarf2/index-write.h: Include dwarf2/public.h, not symfile.h. * dwarf2/public.h: New file. * dwarf2/read.c: Include dwarf2/public.h. * elfread.c: Include dwarf2/public.h. * machoread.c: Include dwarf2/public.h. * symfile.h (dwarf2_has_info, enum dw_index_kind) (dwarf2_initialize_objfile, dwarf2_build_psymtabs) (dwarf2_build_frame_info): Move to dwarf2/public.h. * xcoffread.c: Include dwarf2/public.h.
2021-03-21 07:23:40 +08:00
#include "dwarf2/public.h"
Add DWARF index cache New in v3: - Remove things related to the dwarf-5 format. - Fix compilation on mingw (scoped_mmap.c). GDB can generate indexes for DWARF debug information, which, when integrated in the original binary, can speed up loading object files. This can be done using the gdb-add-index script or directly by the linker itself. However, not many people know about this. And even among those who do, because it requires additional steps, I don't know a lot of people who actually go through that trouble. To help make using the DWARF index more transparent, this patch introduces a DWARF index cache. When enabled, loading an index-less binary in GDB will automatically save an index file in ~/.cache/gdb. When loading that same object file again, the index file will be looked up and used to load the DWARF index. You therefore get the benefit of the DWARF index without having to do additional manual steps or modifying your build system. When an index section is already present in the file, GDB will prefer that one over looking up the cache. When doing my edit-compile-debug cycle, I often debug multiple times the same build, so the cache helps reducing the load time of the debug sessions after the first one. - The saved index file is exactly the same as the output of the "save gdb-index" command. It is therefore the exact same content that would be found in the .gdb_index or .debug_names section. We just leave it as a standalone file instead of merging it in the binary. - The cache is just a directory with files named after the object file's build-id. It is not possible to save/load the index for an object file without build-id in the cache. - The cache uses the gdb index format. The problem with the dwarf-5 format is that we can generate an addendum to the .debug_str section that you're supposed to integrate to the original binary. This complicates a little bit loading the data from the cached index files, so I would leave this for later. - The size taken up by ~/.cache/gdb is not limited. I was thinking we could add configurable limit (like ccache does), but that would come after. Also, maybe a command to flush the cache. - The cache is disabled by default. I think once it's been out there and tested for a while, it could be turned on by default, so that everybody can enjoy it. - The code was made to follow the XDG specification: if the XDG_CACHE_HOME environment variable, it is used, otherwise it falls back to ~/.cache/gdb. It is possible to change it using "set index-cache directory". On other OSes than GNU/Linux, ~/.cache may not be the best place to put such data. On macOS it should probably default to ~/Library/Caches/... On Windows, %LocalAppData%/... I don't intend to do this part, but further patches are welcome. - I think that we need to be careful that multiple instances of GDB don't interfere with each other (not far fetched at all if you run GDB in some automated script) and the cache is always coherent (either the file is not found, or it is found and entirely valid). Writing the file directly to its final location seems like a recipe for failure. One GDB could read a file in the index while it is being written by another GDB. To mitigate this, I made write_psymtabs_to_index write to temporary files and rename them once it's done. Two GDB instances writing the index for the same file should not step on each other's toes (the last file to be renamed will stay). A GDB looking up a file will only see a complete file or no file. Also, if GDB crashes while generating the index file, it will leave a work-in-progress file, but it won't be picked up by other instances looking up in the cache. gdb/ChangeLog: * common/pathstuff.h (get_standard_cache_dir): New. * common/pathstuff.c (get_standard_cache_dir): New. * build-id.h (build_id_to_string): New. * dwarf-index-common.h (INDEX4_SUFFIX, INDEX5_SUFFIX, DEBUG_STR_SUFFIX): Move to here. * dwarf-index-write.c (INDEX4_SUFFIX, INDEX5_SUFFIX, DEBUG_STR_SUFFIX): Move from there. (write_psymtabs_to_index): Make non-static, add basename parameter. Write to temporary files, rename when done. (save_gdb_index_command): Adjust call to write_psymtabs_to_index. * dwarf2read.h (dwarf2_per_objfile) <index_cache_res>: New field. * dwarf2read.c (dwz_file) <index_cache_res>: New field. (get_gdb_index_contents_from_cache): New. (get_gdb_index_contents_from_cache_dwz): New. (dwarf2_initialize_objfile): Read index from cache. (dwarf2_build_psymtabs): Save to index. * dwarf-index-cache.h: New file. * dwarf-index-cache.c: New file. * dwarf-index-write.h: New file. gdb/testsuite/ChangeLog: * boards/index-cache-gdb.exp: New file. * gdb.dwarf2/index-cache.exp: New file. * gdb.dwarf2/index-cache.c: New file. * gdb.base/maint.exp: Check if we are using the index cache.
2018-08-08 06:14:20 +08:00
Write index for dwz -m file PR 24445 ("dwz multifile index not written to index cache") exposed the fact that we are not doing things right when we generate an index for an object file that has is linked to a dwz file. The same happens whether the index is generated with the intent of populating the index cache or using the save gdb-index command. The problem can be observed when running these tests with the cc-with-dwz-m board: FAIL: gdb.base/index-cache.exp: test_cache_enabled_hit: check index-cache stats FAIL: gdb.dwarf2/gdb-index.exp: index used FAIL: gdb.dwarf2/gdb-index.exp: index used after symbol reloading When generating the index for such file and inspecting the CU list of the resulting index (with readelf --debug-dump=gdb_index), we can see something like: CU table: [ 0] 0x0 - 0xb9 [ 1] 0x0 - 0x44 This is supposed to be a sorted list of the ranges of all CUs in the file this index represents, so already having some overlap is a red flag. It turns out that we save the ranges of CUs coming from both the main file and the dwz file in the same index. After digging a little bit, it became quite obvious that the index in the main file should only list the CUs present in the main file, and a separate index should be generated for the dwz file, listing the CUs present in that file. First, that's what happens if you run dwz on a file that already has a GDB index embedded. Second, dwarf2read.c has code to read an index from a dwz file. The index in the dwz file is actually required to be present, if the main file has an index. So this patch changes write_psymtabs_to_index to generate an index for the dwz file, if present. That index only contains a CU list, just like what the dwz tool does when processing a file that already contains an index. Some notes about the implementation: - The file management (creating a temp file, make sure it's close/removed on error - in the right order) is a bit heavy in write_psymtabs_to_index, and I needed to add a third file. I factored this pattern in a separate class, index_wip_file. - It became a bit tedious to keep the call to assert_file_size in write_psymtabs_to_index, write_gdbindex would have had to return two sizes. Instead, I moved the calls to assert_file_size where the file is written. The downside is that we lose the filename at this point, but it was only used for the very improbable case of ftell failing, so I think it's not a problem. - The actual writing of the index file is factored out to write_gdbindex_1, so it can be re-used for both index files. - While the "save gdb-index" command will now write two .gdb-index files, this patch does not update the gdb-add-index.sh script, this will come in a later patch. gdb/ChangeLog: YYYY-MM-DD Simon Marchi <simon.marchi@efficios.com> PR gdb/24445 * dwarf-index-write.h (write_psymtabs_to_index): Add dwz_basename parameter. * dwarf-index-write.c (write_gdbindex): Move file writing to write_gdbindex_1. Change return type void. (assert_file_size): Move up, remove filename parameter. (write_gdbindex_1): New function. (write_debug_names): Change return type to void, call assert_file_size. (struct index_wip_file): New struct. (write_psymtabs_to_index): Add dwz_basename parameter. Move file logic to index_wip_file. Write index for dwz file if needed. (save_gdb_index_command): Pass basename of dwz file, if present. * dwarf-index-cache.c (index_cache::store): Obtain and pass build-id of dwz file, if present. * dwarf2read.c (struct dwz_file): Move to dwarf2read.h. (dwarf2_get_dwz_file): Likewise. * dwarf2read.h (struct dwz_file): Move from dwarf2read.c. (dwarf2_get_dwz_file): Likewise. gdb/testsuite/ChangeLog: YYYY-MM-DD Tom de Vries <tdevries@suse.de> PR gdb/24445 * gdb.dwarf2/gdb-index.exp (add_gdb_index): Update dwz file with generated index.
2019-06-16 22:13:56 +08:00
/* Create index files for OBJFILE in the directory DIR.
An index file is created for OBJFILE itself, and is created for its
associated dwz file, if it has one.
BASENAME is the desired filename base for OBJFILE's index. An extension
derived from INDEX_KIND is added to this base name. DWZ_BASENAME is the
same, but for the dwz file's index. */
Add DWARF index cache New in v3: - Remove things related to the dwarf-5 format. - Fix compilation on mingw (scoped_mmap.c). GDB can generate indexes for DWARF debug information, which, when integrated in the original binary, can speed up loading object files. This can be done using the gdb-add-index script or directly by the linker itself. However, not many people know about this. And even among those who do, because it requires additional steps, I don't know a lot of people who actually go through that trouble. To help make using the DWARF index more transparent, this patch introduces a DWARF index cache. When enabled, loading an index-less binary in GDB will automatically save an index file in ~/.cache/gdb. When loading that same object file again, the index file will be looked up and used to load the DWARF index. You therefore get the benefit of the DWARF index without having to do additional manual steps or modifying your build system. When an index section is already present in the file, GDB will prefer that one over looking up the cache. When doing my edit-compile-debug cycle, I often debug multiple times the same build, so the cache helps reducing the load time of the debug sessions after the first one. - The saved index file is exactly the same as the output of the "save gdb-index" command. It is therefore the exact same content that would be found in the .gdb_index or .debug_names section. We just leave it as a standalone file instead of merging it in the binary. - The cache is just a directory with files named after the object file's build-id. It is not possible to save/load the index for an object file without build-id in the cache. - The cache uses the gdb index format. The problem with the dwarf-5 format is that we can generate an addendum to the .debug_str section that you're supposed to integrate to the original binary. This complicates a little bit loading the data from the cached index files, so I would leave this for later. - The size taken up by ~/.cache/gdb is not limited. I was thinking we could add configurable limit (like ccache does), but that would come after. Also, maybe a command to flush the cache. - The cache is disabled by default. I think once it's been out there and tested for a while, it could be turned on by default, so that everybody can enjoy it. - The code was made to follow the XDG specification: if the XDG_CACHE_HOME environment variable, it is used, otherwise it falls back to ~/.cache/gdb. It is possible to change it using "set index-cache directory". On other OSes than GNU/Linux, ~/.cache may not be the best place to put such data. On macOS it should probably default to ~/Library/Caches/... On Windows, %LocalAppData%/... I don't intend to do this part, but further patches are welcome. - I think that we need to be careful that multiple instances of GDB don't interfere with each other (not far fetched at all if you run GDB in some automated script) and the cache is always coherent (either the file is not found, or it is found and entirely valid). Writing the file directly to its final location seems like a recipe for failure. One GDB could read a file in the index while it is being written by another GDB. To mitigate this, I made write_psymtabs_to_index write to temporary files and rename them once it's done. Two GDB instances writing the index for the same file should not step on each other's toes (the last file to be renamed will stay). A GDB looking up a file will only see a complete file or no file. Also, if GDB crashes while generating the index file, it will leave a work-in-progress file, but it won't be picked up by other instances looking up in the cache. gdb/ChangeLog: * common/pathstuff.h (get_standard_cache_dir): New. * common/pathstuff.c (get_standard_cache_dir): New. * build-id.h (build_id_to_string): New. * dwarf-index-common.h (INDEX4_SUFFIX, INDEX5_SUFFIX, DEBUG_STR_SUFFIX): Move to here. * dwarf-index-write.c (INDEX4_SUFFIX, INDEX5_SUFFIX, DEBUG_STR_SUFFIX): Move from there. (write_psymtabs_to_index): Make non-static, add basename parameter. Write to temporary files, rename when done. (save_gdb_index_command): Adjust call to write_psymtabs_to_index. * dwarf2read.h (dwarf2_per_objfile) <index_cache_res>: New field. * dwarf2read.c (dwz_file) <index_cache_res>: New field. (get_gdb_index_contents_from_cache): New. (get_gdb_index_contents_from_cache_dwz): New. (dwarf2_initialize_objfile): Read index from cache. (dwarf2_build_psymtabs): Save to index. * dwarf-index-cache.h: New file. * dwarf-index-cache.c: New file. * dwarf-index-write.h: New file. gdb/testsuite/ChangeLog: * boards/index-cache-gdb.exp: New file. * gdb.dwarf2/index-cache.exp: New file. * gdb.dwarf2/index-cache.c: New file. * gdb.base/maint.exp: Check if we are using the index cache.
2018-08-08 06:14:20 +08:00
extern void write_psymtabs_to_index
gdb: rename dwarf2_per_objfile variables/fields to per_objfile While doing the psymtab-sharing patchset, I avoided renaming variables unnecessarily to avoid adding noise to patches, but I'd like to do it now. Basically, we have these dwarf2 per-something structures: - dwarf2_per_objfile - dwarf2_per_bfd - dwarf2_per_cu_data I named the instances of dwarf2_per_bfd `per_bfd` and most of instances of dwarf2_per_cu_data are called `per_cu`. Most pre-existing instances of dwarf2_per_objfile are named `dwarf2_per_objfile`. For consistency with the other type, I'd like to rename them to just `per_objfile`. The `dwarf2_` prefix is superfluous, since it's already clear we are in dwarf2 code. It also helps reducing the line wrapping by saving 7 precious columns. gdb/ChangeLog: * dwarf2/comp-unit.c, dwarf2/comp-unit.h, dwarf2/index-cache.c, dwarf2/index-cache.h, dwarf2/index-write.c, dwarf2/index-write.h, dwarf2/line-header.c, dwarf2/line-header.h, dwarf2/macro.c, dwarf2/macro.h, dwarf2/read.c, dwarf2/read.h: Rename struct dwarf2_per_objfile variables and fields from `dwarf2_per_objfile` to just `per_objfile` throughout. Change-Id: I3c45cdcc561265e90df82cbd36b4b4ef2fa73aef
2020-05-30 03:15:10 +08:00
(dwarf2_per_objfile *per_objfile, const char *dir, const char *basename,
const char *dwz_basename, dw_index_kind index_kind);
Add DWARF index cache New in v3: - Remove things related to the dwarf-5 format. - Fix compilation on mingw (scoped_mmap.c). GDB can generate indexes for DWARF debug information, which, when integrated in the original binary, can speed up loading object files. This can be done using the gdb-add-index script or directly by the linker itself. However, not many people know about this. And even among those who do, because it requires additional steps, I don't know a lot of people who actually go through that trouble. To help make using the DWARF index more transparent, this patch introduces a DWARF index cache. When enabled, loading an index-less binary in GDB will automatically save an index file in ~/.cache/gdb. When loading that same object file again, the index file will be looked up and used to load the DWARF index. You therefore get the benefit of the DWARF index without having to do additional manual steps or modifying your build system. When an index section is already present in the file, GDB will prefer that one over looking up the cache. When doing my edit-compile-debug cycle, I often debug multiple times the same build, so the cache helps reducing the load time of the debug sessions after the first one. - The saved index file is exactly the same as the output of the "save gdb-index" command. It is therefore the exact same content that would be found in the .gdb_index or .debug_names section. We just leave it as a standalone file instead of merging it in the binary. - The cache is just a directory with files named after the object file's build-id. It is not possible to save/load the index for an object file without build-id in the cache. - The cache uses the gdb index format. The problem with the dwarf-5 format is that we can generate an addendum to the .debug_str section that you're supposed to integrate to the original binary. This complicates a little bit loading the data from the cached index files, so I would leave this for later. - The size taken up by ~/.cache/gdb is not limited. I was thinking we could add configurable limit (like ccache does), but that would come after. Also, maybe a command to flush the cache. - The cache is disabled by default. I think once it's been out there and tested for a while, it could be turned on by default, so that everybody can enjoy it. - The code was made to follow the XDG specification: if the XDG_CACHE_HOME environment variable, it is used, otherwise it falls back to ~/.cache/gdb. It is possible to change it using "set index-cache directory". On other OSes than GNU/Linux, ~/.cache may not be the best place to put such data. On macOS it should probably default to ~/Library/Caches/... On Windows, %LocalAppData%/... I don't intend to do this part, but further patches are welcome. - I think that we need to be careful that multiple instances of GDB don't interfere with each other (not far fetched at all if you run GDB in some automated script) and the cache is always coherent (either the file is not found, or it is found and entirely valid). Writing the file directly to its final location seems like a recipe for failure. One GDB could read a file in the index while it is being written by another GDB. To mitigate this, I made write_psymtabs_to_index write to temporary files and rename them once it's done. Two GDB instances writing the index for the same file should not step on each other's toes (the last file to be renamed will stay). A GDB looking up a file will only see a complete file or no file. Also, if GDB crashes while generating the index file, it will leave a work-in-progress file, but it won't be picked up by other instances looking up in the cache. gdb/ChangeLog: * common/pathstuff.h (get_standard_cache_dir): New. * common/pathstuff.c (get_standard_cache_dir): New. * build-id.h (build_id_to_string): New. * dwarf-index-common.h (INDEX4_SUFFIX, INDEX5_SUFFIX, DEBUG_STR_SUFFIX): Move to here. * dwarf-index-write.c (INDEX4_SUFFIX, INDEX5_SUFFIX, DEBUG_STR_SUFFIX): Move from there. (write_psymtabs_to_index): Make non-static, add basename parameter. Write to temporary files, rename when done. (save_gdb_index_command): Adjust call to write_psymtabs_to_index. * dwarf2read.h (dwarf2_per_objfile) <index_cache_res>: New field. * dwarf2read.c (dwz_file) <index_cache_res>: New field. (get_gdb_index_contents_from_cache): New. (get_gdb_index_contents_from_cache_dwz): New. (dwarf2_initialize_objfile): Read index from cache. (dwarf2_build_psymtabs): Save to index. * dwarf-index-cache.h: New file. * dwarf-index-cache.c: New file. * dwarf-index-write.h: New file. gdb/testsuite/ChangeLog: * boards/index-cache-gdb.exp: New file. * gdb.dwarf2/index-cache.exp: New file. * gdb.dwarf2/index-cache.c: New file. * gdb.base/maint.exp: Check if we are using the index cache.
2018-08-08 06:14:20 +08:00
#endif /* DWARF_INDEX_WRITE_H */
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