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This patch originated from this mailing list discussion: https://inbox.sourceware.org/gdb-patches/b9b5bf03c59b58e02ca27b522338c6103d5ae49f.camel@gnu.org The user has some core files which lack an NT_FILE note. They wondered why GDB was still unable to find the shared libraries based on their build-id. The reason right now is that GDB only records the build-id information for mappings based on the entries in the NT_FILE note. With the entries in this note we build several lookup tables; a filename to build-id table, a soname (extracted from the file if it is a shared library) to build-id table, and an address range to build-id table. When a shared library is being loaded we perform a lookup using two pieces of information; the shared library's filename, and an address that we know is within the shared library. If either of these give a build-id, then we can use that build-id to ensure GDB loads the shared library that matches the core file. If the NT_FILE note is missing then none of the lookup tables are created, and so the shared library build-id lookup fails, meaning that all GDB can do is look for the shared library by name on the local file system. This often results in the wrong library version being loaded, or the library not being found at all. However, Linux core files also have the segment table. This table gives address ranges. The segment table doesn't tell us what file was mapped in, or the offset within the file that was mapped in. But if we go back to the three lookup tables, we can use the segment table to build the address to build-id lookup table, and that would be enough to allow GDB to find the build-id for a shared library in most cases. So, here's what this patch does: linux_read_core_file_mappings (in linux-tdep.c) is updated to first parse the NT_FILE note as it currently does. But after this we also walk the segment table (BFD actually converts these into sections with the LOAD flag set), and if a segment has a build-id, and doesn't correspond to an entry found in the NT_FILE note, we create an anonymous mapping. An anonymous mapping is just like a mapping from the NT_FILE note, but without a filename and file offset. This mapping is passed through the callback just like the traditional, non-anonymous, mappings. Then in corelow.c various functions are updated in order to handle anonymous mappings. Back in linux-tdep.c, function linux_core_info_proc_mappings gets a small update to handle anonymous mappings. The corefile-buildid.exp test is updated to remove the NT_FILE notes and rerun the tests. This should make no difference as all this test is checking is that GDB is able to find and load the shared libraries and executable based on their build-ids; this is something we can do fine now without the NT_FILE note. I have also had to update the Python core file API documentation after this commit. Previously we claimed that CorefileMappedFile.filename would never be empty, but this is now possible. Luckily, this API has not yet been in a released version of GDB, so this minor tweak isn't going to break any existing user code. I did consider having CorefileMappedFile.filename be a non-empty string or None, but I couldn't see much value in this, so I just documented that the string could be empty, and what this means. The py-corefile.exp test needed a minor update to filter out anonymous mappings (those without a filename), this matches the behaviour of the builtin 'info proc mappings' command. Reviewed-By: Keith Seitz <keiths@redhat.com>
330 lines
11 KiB
C++
330 lines
11 KiB
C++
/* Machine independent variables that describe the core file under GDB.
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Copyright (C) 1986-2026 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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#ifndef GDB_GDBCORE_H
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#define GDB_GDBCORE_H
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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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[[noreturn]] extern void memory_error (enum target_xfer_status status,
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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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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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/* Type holding information about a single file mapped into the inferior
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at the point when the core file was created. Associates a build-id
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with the list of regions the file is mapped into. It is acceptable to
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have a core_mapped_file with an empty filename, so long as we have a
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build-id for the mapping. */
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struct core_mapped_file
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{
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/* Type for a region of a file that was mapped into the inferior when
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the core file was generated. */
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struct region
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{
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/* Constructor. See member variables for argument descriptions. */
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region (CORE_ADDR start_, CORE_ADDR end_, CORE_ADDR file_ofs_)
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: start (start_),
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end (end_),
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file_ofs (file_ofs_)
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{ /* Nothing. */ }
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/* The inferior address for the start of the mapped region. */
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CORE_ADDR start;
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/* The inferior address immediately after the mapped region. */
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CORE_ADDR end;
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/* The offset within the mapped file for this content. If the
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filename of the mapping is empty then this field will be 0, but has
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no meaning. */
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CORE_ADDR file_ofs;
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};
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/* The filename as recorded in the core file. This can be empty meaning
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that GDB was unable to find a filename for this mapping. If the
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filename is empty then the build_id field MUST be non-NULL. If this
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is empty then the region::file_ofs fields will all be 0, and have no
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meaning. */
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std::string filename;
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/* If not nullptr, then this is the build-id associated with this
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mapping. If the filename field is empty, then this MUST be
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non-NULL. */
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const bfd_build_id *build_id = nullptr;
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/* All the mapped regions of this file. */
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std::vector<region> regions;
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/* True if this is the main executable. */
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bool is_main_exec = false;
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/* Convert the REGIONS to a vector of mem_range objects. */
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std::vector<mem_range>
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mem_ranges () const
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{
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std::vector<mem_range> ranges;
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for (const core_mapped_file::region ®ion : this->regions)
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ranges.emplace_back (region.start, region.end - region.start);
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normalize_mem_ranges (&ranges);
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return ranges;
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}
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};
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extern std::vector<core_mapped_file> gdb_read_core_file_mappings
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(struct gdbarch *gdbarch, struct bfd *cbfd);
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/* Return the core file bfd for inferior INF, if that inferior has a core
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file loaded. Otherwise, return NULL. */
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extern bfd *get_inferior_core_bfd (inferior *inf);
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#endif /* GDB_GDBCORE_H */
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