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Date:      Thu, 25 Sep 2008 11:02:07 -0700
From:      "Navdeep Parhar" <nparhar@gmail.com>
To:        freebsd-hackers@freebsd.org
Subject:   Re: kgdb's add-kld broken on amd64
Message-ID:  <d04e16b70809251102l750d380axbcfe0ca769ca41db@mail.gmail.com>
In-Reply-To: <200809171628.52406.jhb@freebsd.org>
References:  <d04e16b70809161307p11a44c53i4e0a33edc12257c8@mail.gmail.com> <200809171131.30819.jhb@freebsd.org> <d04e16b70809171251h474df74h89829048582f994a@mail.gmail.com> <200809171628.52406.jhb@freebsd.org>
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> Well, this means gdb can't handle loading .o's, though I guess that is to be
> expected. :(  Even if I fix add-kld there's probably no way I can easily fix
> the sharedlibrary stuff w/o ripping gdb itself up a bunch.
>
> --
> John Baldwin
>

I thought I'd leave this patch here on the list in case anyone
finds it helpful.  This patch works both when "add-kld ..." is
explicitly called, and when kgdb autodetects KLDs and reads in
their symbols automatically.

The changes to kld.c are from what John B. posted in this
thread earlier.  The additional changes to exec.c mimic what
the kernel does in link_elf_obj.c for amd64 modules.

I used "info files" to verify that the segment reloc info was
correct.

Regards,
Navdeep

diff -r 3292f0cda869 contrib/gdb/gdb/exec.c
--- a/contrib/gdb/gdb/exec.c    Wed Sep 24 17:32:58 2008 -0700
+++ b/contrib/gdb/gdb/exec.c    Wed Sep 24 19:54:31 2008 -0700
@@ -348,6 +348,18 @@
   (*table_pp)->bfd = abfd;
   (*table_pp)->the_bfd_section = asect;
   (*table_pp)->addr = bfd_section_vma (abfd, asect);
+  if ((*table_pp)->addr == 0 && asect->index > 0) {
+    /*
+     * KLDs on amd64 go down this code path.  Adjust the addr as is done in
+     * kern/link_elf_obj.c.  We need the previous section's endaddr in order
+     * to do that.
+     */
+    struct section_table *p = (*table_pp) - 1;
+
+    (*table_pp)->addr = align_power(p->endaddr,
+      bfd_section_alignment(abfd, asect));
+  }
+
   (*table_pp)->endaddr = (*table_pp)->addr + bfd_section_size (abfd, asect);
   (*table_pp)++;
 }
diff -r 3292f0cda869 gnu/usr.bin/gdb/kgdb/kld.c
--- a/gnu/usr.bin/gdb/kgdb/kld.c        Wed Sep 24 17:32:58 2008 -0700
+++ b/gnu/usr.bin/gdb/kgdb/kld.c        Wed Sep 24 19:54:31 2008 -0700
@@ -37,6 +37,7 @@
 #include <command.h>
 #include <completer.h>
 #include <environ.h>
+#include <exec.h>
 #include <frame-unwind.h>
 #include <inferior.h>
 #include <objfiles.h>
@@ -196,39 +197,14 @@
        return (0);
 }

-struct add_section_info {
-       struct section_addr_info *section_addrs;
-       int sect_index;
-       CORE_ADDR base_addr;
-};
-
-static void
-add_section (bfd *bfd, asection *sect, void *arg)
-{
-       struct add_section_info *asi = arg;
-       CORE_ADDR address;
-       char *name;
-
-       /* Ignore non-resident sections. */
-       if ((bfd_get_section_flags(bfd, sect) & (SEC_ALLOC | SEC_LOAD)) == 0)
-               return;
-
-       name = xstrdup(bfd_get_section_name(bfd, sect));
-       make_cleanup(xfree, name);
-       address = asi->base_addr + bfd_get_section_vma(bfd, sect);
-       asi->section_addrs->other[asi->sect_index].name = name;
-       asi->section_addrs->other[asi->sect_index].addr = address;
-       asi->section_addrs->other[asi->sect_index].sectindex = sect->index;
-       printf_unfiltered("\t%s_addr = %s\n", name, local_hex_string(address));
-       asi->sect_index++;
-}
-
 static void
 load_kld (char *path, CORE_ADDR base_addr, int from_tty)
 {
-       struct add_section_info asi;
        struct cleanup *cleanup;
+       struct section_addr_info *sap;
+       struct section_table *sections = NULL, *sections_end = NULL, *s;
        bfd *bfd;
+       int i;

        /* Open the kld. */
        bfd = bfd_openr(path, gnutarget);
@@ -244,19 +220,30 @@
        if (bfd_get_section_by_name (bfd, ".text") == NULL)
                error("\"%s\": can't find text section", path);

+       /* Build a section table from the bfd and relocate the sections. */
+       if (build_section_table(bfd, &sections, &sections_end))
+               error("\"%s\": can't find file sections", path);
+       cleanup = make_cleanup(xfree, sections);
+       for (s = sections; s < sections_end; s++) {
+               s->addr += base_addr;
+               s->endaddr += base_addr;
+       }
+
+       /* Build a section addr info to pass to symbol_file_add(). */
+       sap = build_section_addr_info_from_section_table (sections,
+           sections_end);
+       cleanup = make_cleanup((make_cleanup_ftype *)free_section_addr_info,
+           sap);
+
        printf_unfiltered("add symbol table from file \"%s\" at\n", path);
-
-       /* Build a section table for symbol_file_add() from the bfd sections. */
-       asi.section_addrs = alloc_section_addr_info(bfd_count_sections(bfd));
-       cleanup = make_cleanup(xfree, asi.section_addrs);
-       asi.sect_index = 0;
-       asi.base_addr = base_addr;
-       bfd_map_over_sections(bfd, add_section, &asi);
+       for (i = 0; i < sap->num_sections; i++)
+               printf_unfiltered("\t%s_addr = %s\n", sap->other[i].name,
+                   local_hex_string(sap->other[i].addr));

        if (from_tty && (!query("%s", "")))
                error("Not confirmed.");

-       symbol_file_add(path, from_tty, asi.section_addrs, 0, OBJF_USERLOADED);
+       symbol_file_add(path, from_tty, sap, 0, OBJF_USERLOADED);

        do_cleanups(cleanup);
 }

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