On Tue, Aug 12, 2008 at 04:48:29PM +0000, Jonathan A. Kollasch wrote:
> hi,
>
> Robert noted that I should mention this:
>
> The ELF section header table MBI seems to not be implemented in grub2.
> NetBSD/i386 uses this to find symbol names in it's kernel debugger.
For the record (Jonathan already knows), I made this patch, which is supposed
to implement it using code from GRUB Legacy.
It needs some cleanup, but since I have no readily available testcase (NetBSD's
kernel seems to have some trouble involving MBI corruption), I can't finish it
yet.
I'm sending it here for reference.
--
Robert Millan
The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
how) you may access your data; but nobody's threatening your freedom: we
still allow you to remove your data and not access it at all."
diff -ur grub2.old/include/grub/multiboot.h grub2/include/grub/multiboot.h
--- grub2.old/include/grub/multiboot.h 2008-09-07 19:02:04.000000000 +0200
+++ grub2/include/grub/multiboot.h 2008-09-08 15:35:44.000000000 +0200
@@ -1,7 +1,7 @@
/* multiboot.h - multiboot header file with grub definitions. */
/*
* GRUB -- GRand Unified Bootloader
- * Copyright (C) 2003,2007,2008 Free Software Foundation, Inc.
+ * Copyright (C) 2000,2003,2007,2008 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -73,8 +73,27 @@
grub_uint32_t mods_count;
grub_uint32_t mods_addr;
- grub_uint32_t syms[4];
-
+ union
+ {
+ struct
+ {
+ /* a.out payload symbol table info */
+ grub_uint32_t tabsize;
+ grub_uint32_t strsize;
+ grub_uint32_t addr;
+ grub_uint32_t pad;
+ } aout;
+
+ struct
+ {
+ /* ELF payload section header table */
+ grub_uint32_t num;
+ grub_uint32_t size;
+ grub_uint32_t addr;
+ grub_uint32_t shndx;
+ } elf;
+ } syms;
+
/* Memory Mapping buffer */
grub_uint32_t mmap_length;
grub_uint32_t mmap_addr;
diff -ur grub2.old/loader/i386/pc/multiboot.c grub2/loader/i386/pc/multiboot.c
--- grub2.old/loader/i386/pc/multiboot.c 2008-09-07 19:03:20.000000000 +0200
+++ grub2/loader/i386/pc/multiboot.c 2008-09-08 15:35:44.000000000 +0200
@@ -21,7 +21,7 @@
* FIXME: The following features from the Multiboot specification still
* need to be implemented:
* - VBE support
- * - symbol table
+ * - a.out symbol table
* - drives table
* - ROM configuration table
* - APM table
@@ -204,6 +204,60 @@
#undef phdr
+ mbi->syms.elf.num = ehdr->e_shnum;
+ mbi->syms.elf.size = ehdr->e_shentsize;
+ mbi->syms.elf.shndx = ehdr->e_shstrndx;
+
+ grub_file_seek (file, ehdr->e_shoff);
+
+ /* FIXME: move to the relocatable block */
+ mbi->syms.elf.addr = (grub_uint32_t) grub_malloc (sizeof (Elf32_Shdr) * ehdr->e_shnum);
+
+ /* FIXME: get rid of cur_addr; use proper types? */
+ grub_uint32_t cur_addr = mbi->syms.elf.addr;
+
+ grub_file_read (file, (void *) cur_addr, ehdr->e_shentsize * ehdr->e_shnum);
+ cur_addr += ehdr->e_shentsize * ehdr->e_shnum;
+
+ /* FIXME: does this belong here? */
+ grub_printf (", shtab=0x%x\n", cur_addr);
+
+ Elf32_Shdr *shdr = (Elf32_Shdr *) mbi->syms.elf.addr;
+
+ for (i = 0; i < ehdr->e_shnum; i++)
+ {
+ /* This section is a loaded section, so we don't care. */
+ if (shdr[i].sh_addr != 0)
+ continue;
+
+ /* This section is empty, so we don't care. */
+ if (shdr[i].sh_size == 0)
+ continue;
+
+ /* Align the section to a sh_addralign bits boundary. */
+ cur_addr = ((cur_addr + shdr[i].sh_addralign) &
+ - (int) shdr[i].sh_addralign);
+
+ grub_file_seek (file, shdr[i].sh_offset);
+
+ /* FIXME: is this useful? */
+#if 0
+ if (! (memcheck (cur_addr, shdr[i].sh_size)
+ && (grub_read ((char *) RAW_ADDR (cur_addr),
+ shdr[i].sh_size)
+ == shdr[i].sh_size)))
+ {
+ symtab_err = 1;
+ break;
+ }
+#endif
+
+ shdr[i].sh_addr = cur_addr;
+ cur_addr += shdr[i].sh_size;
+ }
+
+ mbi->flags |= MULTIBOOT_INFO_ELF_SHDR;
+
return grub_errno;
}
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