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fa826a4bbe
When GDB opens a core file, in 'core_target::build_file_mappings ()', we collection information about the files that are mapped into the core file, specifically, the build-id and the DT_SONAME attribute for the file, which will be set for some shared libraries. We then cache the DT_SONAME to build-id information on the core file bfd object in the function set_cbfd_soname_build_id. Later, when we are loading the shared libraries for the core file, we can use the library's file name to look in the DT_SONAME to build-id map, and, if we find a matching entry, we can use the build-id to validate that we are loading the correct shared library. This works OK, but has some limitations: not every shared library will have a DT_SONAME attribute. Though it is good practice to add such an attribute, it's not required. A library without this attribute will not have its build-id checked, which can lead to GDB loading the wrong shared library. What I want to do in this commit is to improve GDB's ability to use the build-ids extracted in core_target::build_file_mappings to both validate the shared libraries being loaded, and then to use these build-ids to potentially find (via debuginfod) the shared library. To do this I propose making the following changes to GDB: (1) Rather than just recording the DT_SONAME to build-id mapping in set_cbfd_soname_build_id, we should also record, the full filename to build-id mapping, and also the memory ranges to build-id mapping for every memory range covered by every mapped file. (2) Add a new callback solib_ops::find_solib_addr. This callback takes a solib object and returns an (optional) address within the inferior that is part of this library. We can use this address to find a mapped file using the stored memory ranges which will increase the cases in which a match can be found. (3) Move the mapped file record keeping out of solib.c and into corelow.c. Future commits will make use of this information from other parts of GDB. This information was never solib specific, it lived in the solib.c file because that was the only user of the data, but really, the data is all about the core file, and should be stored in core_target, other parts of GDB can then query this data as needed. Now, when we load a shared library for a core file, we do the following lookups: 1. Is the exact filename of the shared library found in the filename to build-id map? If so then use this build-id for validation. 2. Find an address within the shared library using ::find_solib_addr and then look for an entry in the mapped address to build-id map. If an entry is found then use this build-id. 3. Finally, look in the soname to build-id map. If an entry is found then use this build-id. The addition of step #2 here means that GDB is now far more likely to find a suitable build-id for a shared library. Having acquired a build-id the existing code for using debuginfod to lookup a shared library object can trigger more often. On top of this, we also create a build-id to filename map. This is useful as often a shared library is implemented as a symbolic link to the actual shared library file. The mapped file information is stored based on the actual, real file name, while the shared library information holds the original symbolic link file name. If when loading the shared library, we find the symbolic link has disappeared, we can use the build-id to file name map to check if the actual file is still around, if it is (and if the build-id matches) then we can fall back to use that file. This is another way in which we can slightly increase the chances that GDB will find the required files when loading a core file. Adding all of the above required pretty much a full rewrite of the existing set_cbfd_soname_build_id function and the corresponding get_cbfd_soname_build_id function, so I have taken the opportunity to move the information caching out of solib.c and into corelow.c where it is now accessed through the function core_target_find_mapped_file. At this point the benefit of this move is not entirely obvious, though I don't think the new location is significantly worse than where it was originally. The benefit though is that the cached information is no longer tied to the shared library loading code. I already have a second set of patches (not in this series) that make use of this caching from elsewhere in GDB. I've not included those patches in this series as this series is already pretty big, but even if those follow up patches don't arrive, I think the new location is just as good as the original location. Rather that caching the information within the core file BFD via the registry mechanism, the information used for the mapped file lookup is now stored within the core_file target directly.
266 lines
8.7 KiB
C++
266 lines
8.7 KiB
C++
/* Machine independent variables that describe the core file under GDB.
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Copyright (C) 1986-2024 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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/* Interface routines for core, executable, etc. */
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#if !defined (GDBCORE_H)
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#define GDBCORE_H 1
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struct type;
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struct regcache;
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#include "bfd.h"
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#include "exec.h"
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#include "target.h"
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/* Nonzero if there is a core file. */
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extern int have_core_file_p (void);
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/* Report a memory error with error(). */
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extern void memory_error (enum target_xfer_status status, CORE_ADDR memaddr);
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/* The string 'memory_error' would use as exception message. */
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extern std::string memory_error_message (enum target_xfer_status err,
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struct gdbarch *gdbarch,
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CORE_ADDR memaddr);
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/* Like target_read_memory, but report an error if can't read. */
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extern void read_memory (CORE_ADDR memaddr, gdb_byte *myaddr, ssize_t len);
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/* Like target_read_stack, but report an error if can't read. */
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extern void read_stack (CORE_ADDR memaddr, gdb_byte *myaddr, ssize_t len);
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/* Like target_read_code, but report an error if can't read. */
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extern void read_code (CORE_ADDR memaddr, gdb_byte *myaddr, ssize_t len);
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/* Read an integer from debugged memory, given address and number of
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bytes. */
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extern LONGEST read_memory_integer (CORE_ADDR memaddr,
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int len, enum bfd_endian byte_order);
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extern int safe_read_memory_integer (CORE_ADDR memaddr, int len,
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enum bfd_endian byte_order,
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LONGEST *return_value);
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/* Read an unsigned integer from debugged memory, given address and
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number of bytes. */
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extern ULONGEST read_memory_unsigned_integer (CORE_ADDR memaddr,
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int len,
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enum bfd_endian byte_order);
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extern int safe_read_memory_unsigned_integer (CORE_ADDR memaddr, int len,
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enum bfd_endian byte_order,
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ULONGEST *return_value);
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/* Read an integer from debugged code memory, given address,
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number of bytes, and byte order for code. */
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extern LONGEST read_code_integer (CORE_ADDR memaddr, int len,
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enum bfd_endian byte_order);
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/* Read an unsigned integer from debugged code memory, given address,
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number of bytes, and byte order for code. */
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extern ULONGEST read_code_unsigned_integer (CORE_ADDR memaddr,
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int len,
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enum bfd_endian byte_order);
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/* Read the pointer of type TYPE at ADDR, and return the address it
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represents. */
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CORE_ADDR read_memory_typed_address (CORE_ADDR addr, struct type *type);
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/* Same as target_write_memory, but report an error if can't
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write. */
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extern void write_memory (CORE_ADDR memaddr, const gdb_byte *myaddr,
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ssize_t len);
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/* Same as write_memory, but notify 'memory_changed' observers. */
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extern void write_memory_with_notification (CORE_ADDR memaddr,
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const bfd_byte *myaddr,
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ssize_t len);
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/* Store VALUE at ADDR in the inferior as a LEN-byte unsigned integer. */
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extern void write_memory_unsigned_integer (CORE_ADDR addr, int len,
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enum bfd_endian byte_order,
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ULONGEST value);
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/* Store VALUE at ADDR in the inferior as a LEN-byte unsigned integer. */
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extern void write_memory_signed_integer (CORE_ADDR addr, int len,
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enum bfd_endian byte_order,
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LONGEST value);
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/* Hook for "file_command", which is more useful than above
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(because it is invoked AFTER symbols are read, not before). */
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extern void (*deprecated_file_changed_hook) (const char *filename);
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/* Whether to open exec and core files read-only or read-write. */
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extern bool write_files;
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/* Open and set up the core file bfd. */
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extern void core_target_open (const char *arg, int from_tty);
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extern void core_file_command (const char *filename, int from_tty);
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extern void exec_file_attach (const char *filename, int from_tty);
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/* If the filename of the main executable is unknown, attempt to
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determine it. If a filename is determined, proceed as though
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it was just specified with the "file" command. Do nothing if
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the filename of the main executable is already known.
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DEFER_BP_RESET uses SYMFILE_DEFER_BP_RESET for the main symbol file. */
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extern void exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty);
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extern void validate_files (void);
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/* Give the user a message if the current exec file does not match the exec
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file determined from the target. In case of mismatch, ask the user
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if the exec file determined from target must be loaded. */
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extern void validate_exec_file (int from_tty);
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/* The current default bfd target. */
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extern const char *gnutarget;
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extern void set_gnutarget (const char *);
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/* Build either a single-thread or multi-threaded section name for
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PTID.
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If ptid's lwp member is zero, we want to do the single-threaded
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thing: look for a section named NAME (as passed to the
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constructor). If ptid's lwp member is non-zero, we'll want do the
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multi-threaded thing: look for a section named "NAME/LWP", where
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LWP is the shortest ASCII decimal representation of ptid's lwp
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member. */
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class thread_section_name
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{
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public:
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/* NAME is the single-threaded section name. If PTID represents an
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LWP, then the build section name is "NAME/LWP", otherwise it's
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just "NAME" unmodified. */
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thread_section_name (const char *name, ptid_t ptid)
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{
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if (ptid.lwp_p ())
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{
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m_storage = string_printf ("%s/%ld", name, ptid.lwp ());
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m_section_name = m_storage.c_str ();
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}
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else
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m_section_name = name;
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}
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/* Return the computed section name. The result is valid as long as
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this thread_section_name object is live. */
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const char *c_str () const
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{ return m_section_name; }
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DISABLE_COPY_AND_ASSIGN (thread_section_name);
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private:
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/* Either a pointer into M_STORAGE, or a pointer to the name passed
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as parameter to the constructor. */
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const char *m_section_name;
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/* If we need to build a new section name, this is where we store
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it. */
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std::string m_storage;
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};
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/* Type returned from core_target_find_mapped_file. Holds information
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about a mapped file that was processed when a core file was initially
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loaded. */
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struct core_target_mapped_file_info
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{
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/* Constructor. BUILD_ID is not nullptr, and is the build-id for the
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mapped file. FILENAME is the location of the file that GDB loaded to
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provide the mapped file. This might be different from the name of the
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mapped file mentioned in the core file, e.g. if GDB downloads a file
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from debuginfod then FILENAME would point into the debuginfod client
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cache. The FILENAME can be the empty string if GDB was unable to find
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a file to provide the mapped file. */
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core_target_mapped_file_info (const bfd_build_id *build_id,
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const std::string filename)
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: m_build_id (build_id),
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m_filename (filename)
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{
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gdb_assert (m_build_id != nullptr);
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}
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/* The build-id for this mapped file. */
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const bfd_build_id *
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build_id () const
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{
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return m_build_id;
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}
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/* The file GDB used to provide this mapped file. */
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const std::string &
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filename () const
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{
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return m_filename;
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}
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private:
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const bfd_build_id *m_build_id = nullptr;
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const std::string m_filename;
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};
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/* If the current inferior has a core_target for its process target, then
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lookup information about a mapped file that was discovered when the
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core file was loaded.
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The FILENAME is the file we're looking for. The ADDR, if provided, is a
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mapped address within the inferior which is known to be part of the file
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we are looking for.
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As an example, when loading shared libraries this function can be
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called, in that case FILENAME will be the name of the shared library
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that GDB is trying to load and ADDR will be an inferior address which is
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part of the shared library we are looking for.
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This function looks for a mapped file which matches FILENAME and/or
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which covers ADDR and returns information about that file.
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The returned information includes the name of the mapped file if known
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and the build-id for the mapped file if known.
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*/
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std::optional<core_target_mapped_file_info>
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core_target_find_mapped_file (const char *filename,
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std::optional<CORE_ADDR> addr);
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#endif /* !defined (GDBCORE_H) */
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