[PATCH] add-symbol-file-from-memory command

Roland McGrath
2004-04-08T20:47:45Z

I updated my tree and made a new diff for add-symbol-file-from-memory,
though there were no conflicts to resolve so it's not materially different
from the last version of this patch I posted. It still works with today's
gdb. Several people have looked at this code before. It just needs
authoritative approval to go in. If anyone has any reservations, I haven't
heard them articulated. As I've mentioned before, the new command itself
is not the motivation for the new function. It's the final piece of
necessary infrastructure for vsyscall DSO support for Linux targets.
(After this, the only thing needed is the glue to check for AT_SYSINFO at
the right time.)

Thanks,
Roland

Index: gdb/symfile.c
===================================================================
RCS file: /cvs/src/src/gdb/symfile.c,v
retrieving revision 1.124
diff -p -u -r1.124 symfile.c
--- gdb/symfile.c 28 Feb 2004 18:04:37 -0000 1.124
+++ gdb/symfile.c 8 Apr 2004 20:31:27 -0000
@@ -764,6 +764,10 @@ new_symfile_objfile (struct objfile *obj
NAME is the file name (which will be tilde-expanded and made
absolute herein) (but we don't free or modify NAME itself).

+ If ABFD is not null, it's already open and should be used instead of
+ opening the file by name. This BFD will be closed on error, and
+ is always consumed by this function.
+
FROM_TTY says how verbose to be.

MAINLINE specifies whether this is the main symbol file, or whether
@@ -776,7 +780,7 @@ new_symfile_objfile (struct objfile *obj
Upon success, returns a pointer to the objfile that was added.
Upon failure, jumps back to command level (never returns). */
static struct objfile *
-symbol_file_add_with_addrs_or_offsets (char *name, int from_tty,
+symbol_file_add_with_addrs_or_offsets (char *name, bfd *abfd, int from_tty,
struct section_addr_info *addrs,
struct section_offsets *offsets,
int num_offsets,
@@ -785,14 +789,16 @@ symbol_file_add_with_addrs_or_offsets (c
struct objfile *objfile;
struct partial_symtab *psymtab;
char *debugfile;
- bfd *abfd;
struct section_addr_info *orig_addrs;
struct cleanup *my_cleanups;

/* Open a bfd for the file, and give user a chance to burp if we'd be
interactively wiping out any existing symbols. */

- abfd = symfile_bfd_open (name);
+ if (abfd == NULL)
+ abfd = symfile_bfd_open (name);
+
+ my_cleanups = make_cleanup_bfd_close (abfd);

if ((have_full_symbols () || have_partial_symbols ())
&& mainline
@@ -801,6 +807,7 @@ symbol_file_add_with_addrs_or_offsets (c
error ("Not confirmed.");

objfile = allocate_objfile (abfd, flags);
+ discard_cleanups (my_cleanups);

orig_addrs = alloc_section_addr_info (bfd_count_sections (abfd));
my_cleanups = make_cleanup (xfree, orig_addrs);
@@ -917,7 +924,8 @@ struct objfile *
symbol_file_add (char *name, int from_tty, struct section_addr_info *addrs,
int mainline, int flags)
{
- return symbol_file_add_with_addrs_or_offsets (name, from_tty, addrs, 0, 0,
+ return symbol_file_add_with_addrs_or_offsets (name, NULL, from_tty,
+ addrs, 0, 0,
mainline, flags);
}

@@ -1767,6 +1775,88 @@ add_shared_symbol_files_command (char *a
#endif
}
\f
+/* Read inferior memory at ADDR to find the header of a loaded object file
+ and read its in-core symbols out of inferior memory. TEMPL is a bfd
+ representing the target's format. */
+struct objfile *
+symbol_file_add_from_memory (bfd *templ, CORE_ADDR addr, int from_tty)
+{
+ struct objfile *objf;
+ bfd *nbfd;
+ asection *sec;
+ bfd_vma loadbase;
+ struct section_addr_info *sai;
+ unsigned int i;
+
+ if (bfd_get_flavour (templ) != bfd_target_elf_flavour)
+ error ("add-symbol-file-from-memory not supported for this target");
+
+ nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, &loadbase,
+ target_read_memory);
+ if (nbfd == NULL)
+ {
+ error ("Failed to read a valid object file image from memory.");
+ return NULL;
+ }
+
+ nbfd->filename = xstrdup ("shared object read from target memory");
+
+ if (!bfd_check_format (nbfd, bfd_object))
+ {
+ /* FIXME: should be checking for errors from bfd_close (for one thing,
+ on error it does not free all the storage associated with the
+ bfd). */
+ bfd_close (nbfd);
+ error ("Got object file from memory but can't read symbols: %s.",
+ bfd_errmsg (bfd_get_error ()));
+ return NULL;
+ }
+
+ sai = alloc_section_addr_info (bfd_count_sections (nbfd));
+ make_cleanup (xfree, sai);
+ i = 0;
+ for (sec = nbfd->sections; sec != NULL; sec = sec->next)
+ if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
+ {
+ sai->other[i].addr = bfd_get_section_vma (nbfd, sec) + loadbase;
+ sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec);
+ sai->other[i].sectindex = sec->index;
+ ++i;
+ }
+
+ objf = symbol_file_add_with_addrs_or_offsets ((char *) nbfd->filename, nbfd,
+ from_tty, sai, NULL, 0, 0,
+ OBJF_SHARED);
+
+ /* This might change our ideas about frames already looked at. */
+ reinit_frame_cache ();
+
+ return objf;
+}
+
+static void
+add_symbol_file_from_memory_command (char *args, int from_tty)
+{
+ CORE_ADDR addr;
+ bfd *templ;
+
+ if (args == NULL)
+ error ("add-symbol-file-from-memory requires an expression argument");
+
+ addr = parse_and_eval_address (args);
+
+ /* We need some representative bfd to know the target we are looking at. */
+ if (symfile_objfile != NULL)
+ templ = symfile_objfile->obfd;
+ else
+ templ = exec_bfd;
+ if (templ == NULL)
+ error ("\
+Must use symbol-file or exec-file before add-symbol-file-from-memory.");
+
+ (void) symbol_file_add_from_memory (templ, addr, from_tty);
+}
+\f
/* Re-read symbols if a symbol-file has changed. */
void
reread_symbols (void)
@@ -2023,7 +2113,7 @@ reread_separate_symbols (struct objfile
Preserve the flags from objfile that make sense. */
objfile->separate_debug_objfile
= (symbol_file_add_with_addrs_or_offsets
- (debug_file,
+ (debug_file, NULL,
info_verbose, /* from_tty: Don't override the default. */
0, /* No addr table. */
objfile->section_offsets, objfile->num_sections,
@@ -3526,6 +3616,13 @@ with the text. SECT is a section name t
&cmdlist);
set_cmd_completer (c, filename_completer);

+ c = add_cmd ("add-symbol-file-from-memory", class_files,
+ add_symbol_file_from_memory_command,
+ "\
+Load the symbols out of memory from a dynamically loaded object file.\n\
+Give an expression for the address of the file's shared object file header.",
+ &cmdlist);
+
c = add_cmd ("add-shared-symbol-files", class_files,
add_shared_symbol_files_command,
"Load the symbols from shared objects in the dynamic linker's link map.",
Index: gdb/symfile.h
===================================================================
RCS file: /cvs/src/src/gdb/symfile.h,v
retrieving revision 1.28
diff -p -u -r1.28 symfile.h
--- gdb/symfile.h 2 Apr 2004 19:23:05 -0000 1.28
+++ gdb/symfile.h 8 Apr 2004 20:31:27 -0000
@@ -302,6 +302,12 @@ extern CORE_ADDR symbol_overlayed_addres
/* Load symbols from a file. */
extern void symbol_file_add_main (char *args, int from_tty);

+/* Read inferior memory at ADDR to find the header of a loaded object file
+ and read its in-core symbols out of inferior memory. TEMPL is a bfd
+ representing the target's format. */
+extern struct objfile *symbol_file_add_from_memory (bfd *templ, CORE_ADDR addr,
+ int from_tty);
+
/* Clear GDB symbol tables. */
extern void symbol_file_clear (int from_tty);