| Debugging with GDB: Auto-loading safe path |
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As the files of inferior can come from untrusted source (such as submitted by an application user) GDB does not always load any files automatically. GDB provides the ‘set auto-load safe-path’ setting to list directories trusted for loading files not explicitly requested by user. Each directory can also be a shell wildcard pattern.
If the path is not set properly you will see a warning and the file will not get loaded:
$ ./gdb -q ./gdb
Reading symbols from /home/user/gdb/gdb...done.
warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
declined by your `auto-load safe-path' set
to "$debugdir:$datadir/auto-load".
warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
declined by your `auto-load safe-path' set
to "$debugdir:$datadir/auto-load".
To instruct GDB to go ahead and use the init files anyway, invoke GDB like this:
$ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
The list of trusted directories is controlled by the following commands:
set auto-load safe-path [
directories
]
Set the list of directories (and their subdirectories) trusted for automatic
loading and execution of scripts. You can also enter a specific trusted file.
Each directory can also be a shell wildcard pattern; wildcards do not match
directory separator - see FNM_PATHNAME for system function fnmatch
(see fnmatch in GNU C Library Reference Manual).
If you omit directories, ‘auto-load safe-path’ will be reset to
its default value as specified during GDB compilation.
The list of directories uses path separator (‘:’ on GNU and Unix
systems, ‘;’ on MS-Windows and MS-DOS) to separate directories, similarly
to the PATH environment variable.
show auto-load safe-path
Show the list of directories trusted for automatic loading and execution of scripts.
add-auto-load-safe-path
Add an entry (or list of entries) to the list of directories trusted for automatic loading and execution of scripts. Multiple entries may be delimited by the host platform path separator in use.
This variable defaults to what --with-auto-load-dir has been configured
to (see with-auto-load-dir). $debugdir and $datadir
substitution applies the same as for set auto-load scripts-directory.
The default set auto-load safe-path value can be also overriden by
GDB configuration option --with-auto-load-safe-path.
Setting this variable to / disables this security protection, corresponding GDB configuration option is --without-auto-load-safe-path. This variable is supposed to be set to the system directories writable by the system superuser only. Users can add their source directories in init files in their home directories (see Home Directory Init File). See also deprecated init file in the current directory (see Init File in the Current Directory during Startup).
To force GDB to load the files it declined to load in the previous example, you could use one of the following ways:
Specify this trusted directory (or a file) as additional component of the list. You have to specify also any existing directories displayed by by ‘show auto-load safe-path’ (such as ‘/usr:/bin’ in this example).
Specify this directory as in the previous case but just for a single GDB session.
Disable auto-loading safety for a single GDB session. This assumes all the files you debug during this GDB session will come from trusted sources.
During compilation of GDB you may disable any auto-loading safety. This assumes all the files you will ever debug with this GDB come from trusted sources.
On the other hand you can also explicitly forbid automatic files loading which also suppresses any such warning messages:
You can use GDB command-line option for a single GDB session.
Disable auto-loading globally for the user (see Home Directory Init File). While it is improbable, you could also use system init file instead (see System-wide configuration).
This setting applies to the file names as entered by user. If no entry matches GDB tries as a last resort to also resolve all the file names into their canonical form (typically resolving symbolic links) and compare the entries again. GDB already canonicalizes most of the filenames on its own before starting the comparison so a canonical form of directories is recommended to be entered.
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