Committed.
On Thu, Aug 07, 2008 at 01:27:53AM +0200, Robert Millan wrote:
>
> Hi,
>
> It seems when adding the relocators for ELF, I failed to notice both ELF and
> a.out loaders share the same grub_multiboot_real_boot function, and hence my
> code was trashing %eax.
>
> Since this functionality is useful for the a.out loader anyway, I decided to
> implement it as well. In the process I did some cleanup, mostly to reduce
> code duplication among both users of the relocators.
>
> So here's the patch. Please comment!
>
> --
> 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."
> Index: kern/i386/loader.S
> ===================================================================
> --- kern/i386/loader.S (revision 1787)
> +++ kern/i386/loader.S (working copy)
> @@ -132,6 +132,36 @@
> VARIABLE(grub_multiboot_payload_entry_offset)
> .long 0
>
> +/*
> + * The relocators below understand the following parameters:
> + * ecx: Size of the block to be copied.
> + * esi: Where to copy from (always lowest address, even if we're
> relocating
> + * backwards).
> + * edi: Where to copy to (likewise).
> + * edx: Offset of the entry point (relative to the beginning of the
> block).
> + */
> +VARIABLE(grub_multiboot_forward_relocator)
> + cld
> + addl %edi, %edx
> + rep
> + movsb
> + jmp *%edx
> +VARIABLE(grub_multiboot_forward_relocator_end)
> +
> +VARIABLE(grub_multiboot_backward_relocator)
> + std
> + addl %ecx, %esi
> + addl %ecx, %edi
> + /* backward movsb is implicitly off-by-one. compensate that. */
> + incl %ecx
> + rep
> + movsb
> + /* same problem again. */
> + incl %edi
> + addl %edi, %edx
> + jmp *%edx
> +VARIABLE(grub_multiboot_backward_relocator_end)
> +
> FUNCTION(grub_multiboot_real_boot)
> /* Push the entry address on the stack. */
> pushl %eax
> @@ -149,11 +179,14 @@
> movl EXT_C(grub_multiboot_payload_size), %ecx
> movl EXT_C(grub_multiboot_payload_orig), %esi
> movl EXT_C(grub_multiboot_payload_dest), %edi
> - movl EXT_C(grub_multiboot_payload_entry_offset), %eax
> -
> + movl EXT_C(grub_multiboot_payload_entry_offset), %edx
> +
> + /* Move the magic value into eax. */
> + movl $MULTIBOOT_MAGIC2, %eax
> +
> /* Jump to the relocator. */
> - popl %edx
> - jmp *%edx
> + popl %ebp
> + jmp *%ebp
>
> /*
> * This starts the multiboot 2 kernel.
> Index: include/grub/i386/loader.h
> ===================================================================
> --- include/grub/i386/loader.h (revision 1787)
> +++ include/grub/i386/loader.h (working copy)
> @@ -53,4 +53,11 @@
> void grub_rescue_cmd_linux (int argc, char *argv[]);
> void grub_rescue_cmd_initrd (int argc, char *argv[]);
>
> +extern grub_uint8_t EXPORT_VAR(grub_multiboot_forward_relocator);
> +extern grub_uint8_t EXPORT_VAR(grub_multiboot_forward_relocator_end);
> +extern grub_uint8_t EXPORT_VAR(grub_multiboot_backward_relocator);
> +extern grub_uint8_t EXPORT_VAR(grub_multiboot_backward_relocator_end);
> +
> +#define RELOCATOR_SIZEOF(x) (&grub_multiboot_##x##_relocator_end -
> &grub_multiboot_##x##_relocator)
> +
> #endif /* ! GRUB_LOADER_CPU_HEADER */
> Index: loader/i386/pc/multiboot.c
> ===================================================================
> --- loader/i386/pc/multiboot.c (revision 1787)
> +++ loader/i386/pc/multiboot.c (working copy)
> @@ -52,31 +52,6 @@
>
> static char *playground = NULL;
>
> -static grub_uint8_t forward_relocator[] =
> -{
> - 0xfc, /* cld */
> - 0x89, 0xf2, /* movl %esi, %edx */
> - 0xf3, 0xa4, /* rep movsb */
> - 0x01, 0xc2, /* addl %eax, %edx */
> - 0xb8, 0x02, 0xb0, 0xad, 0x2b, /* movl $MULTIBOOT_MAGIC2, %eax */
> - 0xff, 0xe2, /* jmp *%edx */
> -};
> -
> -static grub_uint8_t backward_relocator[] =
> -{
> - 0xfd, /* std */
> - 0x01, 0xce, /* addl %ecx, %esi */
> - 0x01, 0xcf, /* addl %ecx, %edi */
> - /* backward movsb is implicitly off-by-one.
> compensate that. */
> - 0x41, /* incl %ecx */
> - 0xf3, 0xa4, /* rep movsb */
> - /* same problem again. */
> - 0x47, /* incl %edi */
> - 0x01, 0xc7, /* addl %eax, %edi */
> - 0xb8, 0x02, 0xb0, 0xad, 0x2b, /* movl $MULTIBOOT_MAGIC2, %eax */
> - 0xff, 0xe7, /* jmp *%edi */
> -};
> -
> static grub_err_t
> grub_multiboot_boot (void)
> {
> @@ -155,17 +130,12 @@
> grub_multiboot_payload_size = (phdr(highest_segment)->p_paddr +
> phdr(highest_segment)->p_memsz) - phdr(lowest_segment)->p_paddr;
> grub_multiboot_payload_dest = phdr(lowest_segment)->p_paddr;
>
> - if (playground)
> - grub_free (playground);
> - playground = grub_malloc (sizeof (forward_relocator) +
> grub_multiboot_payload_size + sizeof (backward_relocator));
> + playground = grub_malloc (RELOCATOR_SIZEOF(forward) +
> grub_multiboot_payload_size + RELOCATOR_SIZEOF(backward));
> if (! playground)
> return grub_errno;
>
> - grub_multiboot_payload_orig = (long) playground + sizeof
> (forward_relocator);
> + grub_multiboot_payload_orig = (long) playground +
> RELOCATOR_SIZEOF(forward);
>
> - grub_memmove (playground, forward_relocator, sizeof (forward_relocator));
> - grub_memmove ((char *) (grub_multiboot_payload_orig +
> grub_multiboot_payload_size), backward_relocator, sizeof
> (backward_relocator));
> -
> /* Load every loadable segment in memory. */
> for (i = 0; i < ehdr->e_phnum; i++)
> {
> @@ -196,16 +166,6 @@
>
> #undef phdr
>
> - if (grub_multiboot_payload_dest >= grub_multiboot_payload_orig)
> - entry = (grub_addr_t) playground;
> - else
> - entry = (grub_addr_t) grub_multiboot_payload_orig +
> grub_multiboot_payload_size;
> -
> - grub_dprintf ("multiboot_loader", "dest=%p, size=0x%x,
> entry_offset=0x%x\n",
> - (void *) grub_multiboot_payload_dest,
> - grub_multiboot_payload_size,
> - grub_multiboot_payload_entry_offset);
> -
> return grub_errno;
> }
>
> @@ -413,24 +373,66 @@
> goto fail;
> }
>
> + if (playground)
> + {
> + grub_free (playground);
> + playground = NULL;
> + }
> +
> if (header->flags & MULTIBOOT_AOUT_KLUDGE)
> {
> - int ofs;
> + int offset = ((char *) header - buffer -
> + (header->header_addr - header->load_addr));
> + int load_size = ((header->load_end_addr == 0) ? file->size - offset :
> + header->load_end_addr - header->load_addr);
>
> - ofs = (char *) header - buffer -
> - (header->header_addr - header->load_addr);
> - if ((grub_aout_load (file, ofs, header->load_addr,
> - ((header->load_end_addr == 0) ? 0 :
> - header->load_end_addr - header->load_addr),
> - header->bss_end_addr))
> - !=GRUB_ERR_NONE)
> - goto fail;
> + if (header->bss_end_addr)
> + grub_multiboot_payload_size = (header->bss_end_addr -
> header->load_addr);
> + else
> + grub_multiboot_payload_size = load_size;
> + grub_multiboot_payload_dest = header->load_addr;
>
> - entry = header->entry_addr;
> + playground = grub_malloc (RELOCATOR_SIZEOF(forward) +
> grub_multiboot_payload_size + RELOCATOR_SIZEOF(backward));
> + if (! playground)
> + goto fail;
> +
> + grub_multiboot_payload_orig = (long) playground +
> RELOCATOR_SIZEOF(forward);
> +
> + if ((grub_file_seek (file, offset)) == (grub_off_t) - 1)
> + goto fail;
> +
> + grub_file_read (file, grub_multiboot_payload_orig, load_size);
> + if (grub_errno)
> + goto fail;
> +
> + if (header->bss_end_addr)
> + grub_memset (grub_multiboot_payload_orig + load_size, 0,
> + header->bss_end_addr - header->load_addr - load_size);
> +
> + grub_multiboot_payload_entry_offset = header->entry_addr -
> header->load_addr;
> +
> }
> else if (grub_multiboot_load_elf (file, buffer) != GRUB_ERR_NONE)
> goto fail;
>
> +
> + if (grub_multiboot_payload_dest >= grub_multiboot_payload_orig)
> + {
> + grub_memmove (playground, &grub_multiboot_forward_relocator,
> RELOCATOR_SIZEOF(forward));
> + entry = (grub_addr_t) playground;
> + }
> + else
> + {
> + grub_memmove ((char *) (grub_multiboot_payload_orig +
> grub_multiboot_payload_size),
> + &grub_multiboot_backward_relocator,
> RELOCATOR_SIZEOF(backward));
> + entry = (grub_addr_t) grub_multiboot_payload_orig +
> grub_multiboot_payload_size;
> + }
> +
> + grub_dprintf ("multiboot_loader", "dest=%p, size=0x%x,
> entry_offset=0x%x\n",
> + (void *) grub_multiboot_payload_dest,
> + grub_multiboot_payload_size,
> + grub_multiboot_payload_entry_offset);
> +
> mbi = grub_malloc (sizeof (struct grub_multiboot_info));
> if (! mbi)
> goto fail;
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> http://lists.gnu.org/mailman/listinfo/grub-devel
--
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."
_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
http://lists.gnu.org/mailman/listinfo/grub-devel
