Re: [PATCH 4/7] New commands for loading and unloading a reader.

[Abhijit Halder <abhijit dot k dot halder at gmail dot com>]

On Sat, Aug 27, 2011 at 6:42 PM, Sanjoy Das
<sanjoy@playingwithpointers.com> wrote:
> Introduces two new GDB commands - `load-jit-reader' and
> `unload-jit-reader'.
>
> gdb/ChangeLog:
> ? ? ? ?* gdb/jit.c: Include gdb-dlfcn.h.
> ? ? ? ?(loaded_jit_reader, reader_init_fn_sym): New static variables.
> ? ? ? ?(jit_reader_load, jit_reader_load_command)
> ? ? ? ?(jit_reader_unload_command): New functions.
> ? ? ? ?(_initialize_jit): Add commands "jit-reader-load" and
> ? ? ? ?"jit-reader-unload".
> ---
> ?gdb/ChangeLog | ? ?9 +++++
> ?gdb/jit.c ? ? | ?103 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> ?2 files changed, 112 insertions(+), 0 deletions(-)
>
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 3536807..78076ef 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,5 +1,14 @@
> ?2011-08-27 ?Sanjoy Das ?<sdas@igalia.com>
>
> + ? ? ? * gdb/jit.c: Include gdb-dlfcn.h.
> + ? ? ? (loaded_jit_reader, reader_init_fn_sym): New static variables.
> + ? ? ? (jit_reader_load, jit_reader_load_command)
> + ? ? ? (jit_reader_unload_command): New functions.
> + ? ? ? (_initialize_jit): Add commands "jit-reader-load" and
> + ? ? ? "jit-reader-unload".
> +
> +2011-08-27 ?Sanjoy Das ?<sdas@igalia.com>
> +
> ? ? ? ?* gdb/Makefile.in: Add gdb-dlfcn.c and gdb-dlfcn.h to build
> ? ? ? ?system.
> ? ? ? ?* gdb/config.in: Add new #define HAVE_LIBDL.
> diff --git a/gdb/jit.c b/gdb/jit.c
> index cab27a9..4fc5819 100644
> --- a/gdb/jit.c
> +++ b/gdb/jit.c
> @@ -31,6 +31,7 @@
> ?#include "symfile.h"
> ?#include "symtab.h"
> ?#include "target.h"
> +#include "gdb-dlfcn.h"
> ?#include "gdb_stat.h"
>
> ?static const char *jit_reader_dir = NULL;
> @@ -115,6 +116,97 @@ mem_bfd_iovec_stat (struct bfd *abfd, void *stream, struct stat *sb)
> ? return 0;
> ?}
>
> +/* One reader that has been loaded successfully, and can potentially be used to
> + ? parse debug info. */
> +
> +static struct jit_reader
> +{
> + ?struct gdb_reader_funcs *functions;
> +} *loaded_jit_reader = NULL;
> +
> +typedef struct gdb_reader_funcs * (reader_init_fn_type) (void);
> +static const char *reader_init_fn_sym = "gdb_init_reader";
> +
> +/* Try to load FILE_NAME as a JIT debug info reader. */
> +
> +static struct jit_reader *
> +jit_reader_load (const char *file_name)
> +{
> + ?void *so;
> + ?reader_init_fn_type *init_fn;
> + ?struct jit_reader *new_reader = NULL;
> + ?struct gdb_reader_funcs *funcs = NULL;
> + ?struct cleanup *old_cleanups;
> +
> + ?if (jit_debug)
> + ? ?fprintf_unfiltered (gdb_stdlog, _("Opening shared object %s.\n"),
> + ? ? ? ? ? ? ? ? ? ? ? ?file_name);
> + ?so = gdb_dlopen (file_name);
> + ?old_cleanups = make_cleanup_dlclose (so);
> +
> + ?init_fn = gdb_dlsym (so, reader_init_fn_sym);
> + ?if (!init_fn)
> + ? ?error(_("Could not locate initialization function: %s."),
> + ? ? ? ? ?reader_init_fn_sym);
> +
> + ?if (gdb_dlsym (so, "plugin_is_GPL_compatible") == NULL)
> + ? ?error(_("Reader not GPL compatible."));
> +
> + ?funcs = init_fn ();
> + ?if (funcs->reader_version != GDB_READER_INTERFACE_VERSION)
> + ? ?error(_("Reader version does not match GDB version."));
> +
> + ?new_reader = XZALLOC (struct jit_reader);
> + ?new_reader->functions = funcs;
> +
> + ?discard_cleanups (old_cleanups);
> + ?return new_reader;
> +}
> +
> +/* Provides the jit-reader-load command. */
> +
> +static void
> +jit_reader_load_command (char *args, int from_tty)
> +{
> + ?char so_name[PATH_MAX];
> + ?int len;
> +
> + ?if (args == NULL)
> + ? ?{
> + ? ? ?error (_("No reader name provided."));
> + ? ? ?return;
This return statement is of no use.

> + ? ?}
> +
> + ?if (loaded_jit_reader != NULL)
> + ? ?{
> + ? ? ?error (_("JIT reader already loaded. ?Run jit-reader-unload first."));
> + ? ? ?return;
Same here.

> + ? ?}
> +
> + ?len = strlen (jit_reader_dir);
> + ?strcpy(so_name, jit_reader_dir);
> + ?so_name[len] = '/';
> + ?so_name[len + 1] = 0;
> +
> + ?strncat (so_name, args, PATH_MAX - (len + 1));
Why can't you use snprintf instead of all the above functions as below?
snprintf (so_name, sizeof (so_name), "%s/%s", jit_reader_dir, args);

> + ?loaded_jit_reader = jit_reader_load (so_name);
> +}
> +
> +/* Provides the jit-reader-unload command. */
> +
> +static void
> +jit_reader_unload_command (char *args, int from_tty)
> +{
> + ?if (!loaded_jit_reader)
> + ? ?{
> + ? ? ?error(_("No JIT reader loaded."));
> + ? ? ?return;
return statement of no use.

> + ? ?}
> + ?loaded_jit_reader->functions->destroy (loaded_jit_reader->functions);
> + ?free (loaded_jit_reader);
Should be xfree instead of free.

> + ?loaded_jit_reader = NULL;
> +}
> +
> ?/* Open a BFD from the target's memory. ?*/
>
> ?static struct bfd *
> @@ -566,4 +658,15 @@ _initialize_jit (void)
> ? jit_objfile_data = register_objfile_data ();
> ? jit_inferior_data =
> ? ? register_inferior_data_with_cleanup (jit_inferior_data_cleanup);
> + ?add_com ("jit-reader-load", no_class, jit_reader_load_command, _("\
> +Load FILE as debug info reader and unwinder for JIT compiled code.\n\
> +Try to load file FILE as a debug info reader (and unwinder) for\n\
> +JIT compiled code. The file is loaded from\n\
> +" JIT_READER_DIR ", relocated \n\
> +relative to the GDB executable if required.\n\
> +Usage is `jit-reader-load FILE`."));
> + ?add_com ("jit-reader-unload", no_class, jit_reader_unload_command, _("\
> +Unload the currently loaded JIT debug info reader.\n\
> +See jit-reader-load for how to load JIT debug readers.\n\
> +"));
> ?}
> --
> 1.7.5.4
>
>