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

Roland McGrath
2003-05-20T07:01:53Z

This patch relies on the BFD patch I posted earlier adding the function
bfd_elf_bfd_from_remote_memory. This adds a user command
add-symbol-file-from-memory, which is like add-symbol-file but takes just
the address of an ELF header in inferior memory (and no other args) instead
of a file name.

This command may not really be worth having, but it serves to exercise the
underlying function symbol_file_add_from_memory. That function does the
work of reading symbols and unwind info from the Linux vsyscall DSO.
So please examine that new code.

This makes symfile.c call bfd_elf_bfd_from_remote_memory, which is
implemented in bfd/elf.c and so won't exist if there is no ELF target
backend configured into libbfd. I couldn't see any obvious place in gdb
that is conditionalized at compile-time on ELF; unless I'm missing
something elfread.c is always built in regardless of the presence of ELF
targets. Should I not be using this function in this file?

Thanks,
Roland

2003-05-19 Roland McGrath <roland@redhat.com>

* symfile.c (symbol_file_add_with_addrs_or_offsets): Take ABFD as
a new argument. Call symfile_bfd_open only if passed a null pointer.
(symbol_file_add, reread_separate_symbols): Update callers.
(build_addr_info): New function, helper for ...
(symbol_file_add_from_memory): New function.
(add_symbol_file_from_memory_command): New function using that.
(_initialize_symfile): Register it for add-symbol-file-from-memory.
* symfile.h (symbol_file_add_from_memory): Declare it.

Index: symfile.c
===================================================================
RCS file: /cvs/src/src/gdb/symfile.c,v
retrieving revision 1.93.6.1
diff -B -p -u -r1.93.6.1 symfile.c
--- symfile.c 18 May 2003 09:44:22 -0000 1.93.6.1
+++ symfile.c 20 May 2003 00:13:39 -0000
@@ -834,6 +834,10 @@ 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
@@ -846,7 +850,7 @@ 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,
@@ -855,16 +859,19 @@ 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 *old_chain;
+
if (addrs)
orig_addrs = *addrs;

/* 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);
+
+ old_chain = make_cleanup_bfd_close (abfd);

if ((have_full_symbols () || have_partial_symbols ())
&& mainline
@@ -873,6 +880,7 @@ symbol_file_add_with_addrs_or_offsets (c
error ("Not confirmed.");

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

/* If the objfile uses a mapped symbol file, and we have a psymtab for
it, then skip reading any symbols at this time. */
@@ -998,7 +1006,8 @@ 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);
}

@@ -1848,6 +1857,102 @@ add_shared_symbol_files_command (char *a
#endif
}
\f
+/* Helper function passed to bfd_map_over_sections. */
+static void
+build_addr_info (bfd *abfd, asection *sectp, void *info)
+{
+ struct section_addr_info *const sai = info;
+ unsigned int i = 0;
+
+ if ((bfd_get_section_flags (abfd, sectp) & (SEC_ALLOC|SEC_LOAD)) == 0)
+ return;
+
+ while (sai->other[i++].name != NULL)
+ if (i == MAX_SECTIONS)
+ return;
+
+ sai->other[i].addr = bfd_get_section_vma (abfd, sectp);
+ sai->other[i].name = (char *) bfd_get_section_name (abfd, sectp);
+ sai->other[i].sectindex = sectp->index;
+}
+
+/* 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;
+ bfd_vma loadbase;
+ struct section_addr_info sai;
+ unsigned int i;
+
+ if (from_tty)
+ {
+ if (bfd_get_flavour (templ) != bfd_target_elf_flavour)
+ error ("add-symbol-file-from-memory not supported for this target");
+ }
+ else
+ gdb_assert (bfd_get_flavour (templ) == bfd_target_elf_flavour);
+
+ nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, &loadbase,
+ target_read_memory);
+ if (nbfd == NULL)
+ {
+ if (from_tty)
+ error ("Failed to read a valid object file image from memory.");
+ return NULL;
+ }
+
+ 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);
+ if (from_tty)
+ error ("Got object file from memory but can't read symbols: %s.",
+ bfd_errmsg (bfd_get_error ()));
+ return NULL;
+ }
+
+ memset (&sai, 0, sizeof sai);
+ bfd_map_over_sections (nbfd, build_addr_info, &sai);
+ for (i = 0; i < MAX_SECTIONS && sai.other[i].name != NULL; ++i)
+ sai.other[i].addr += loadbase;
+
+ objf = symbol_file_add_with_addrs_or_offsets ("<in-memory>", nbfd, from_tty,
+ &sai, NULL, 0, 0, 0);
+
+ 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)
Index: symfile.h
===================================================================
RCS file: /cvs/src/src/gdb/symfile.h,v
retrieving revision 1.20.2.1
diff -B -p -u -r1.20.2.1 symfile.h
--- symfile.h 18 May 2003 09:44:23 -0000 1.20.2.1
+++ symfile.h 20 May 2003 00:13:39 -0000
@@ -297,6 +297,12 @@ 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);