Re: [PATCH v2 5/6] multiboot2: Add support for relocatable images

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Jul 20, 2015 at 04:35:53PM +0200, Daniel Kiper wrote:

This parts needs a bit of details I think.

As in why can't the ELF note that is present in the binary
be satisfied. Or under what conditions would the existing code
not work?

> Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
> ---
>  grub-core/loader/i386/multiboot_mbi.c |    6 ++--
>  grub-core/loader/multiboot.c          |   12 +++++--
>  grub-core/loader/multiboot_elfxx.c    |   28 +++++++++++----
>  grub-core/loader/multiboot_mbi2.c     |   63 +++++++++++++++++++++++++++++----
>  include/grub/multiboot.h              |    4 ++-
>  include/multiboot2.h                  |   24 +++++++++++++
>  6 files changed, 118 insertions(+), 19 deletions(-)
> 
> diff --git a/grub-core/loader/i386/multiboot_mbi.c b/grub-core/loader/i386/multiboot_mbi.c
> index 956d0e3..abdb98b 100644
> --- a/grub-core/loader/i386/multiboot_mbi.c
> +++ b/grub-core/loader/i386/multiboot_mbi.c
> @@ -72,7 +72,8 @@ load_kernel (grub_file_t file, const char *filename,
>    grub_err_t err;
>    if (grub_multiboot_quirks & GRUB_MULTIBOOT_QUIRK_BAD_KLUDGE)
>      {
> -      err = grub_multiboot_load_elf (file, filename, buffer);
> +      err = grub_multiboot_load_elf (file, filename, buffer, 0, 0, 0, 0,
> +				     GRUB_RELOCATOR_PREFERENCE_NONE, NULL, 0);
>        if (err == GRUB_ERR_UNKNOWN_OS && (header->flags & MULTIBOOT_AOUT_KLUDGE))
>  	grub_errno = err = GRUB_ERR_NONE;
>      }
> @@ -118,7 +119,8 @@ load_kernel (grub_file_t file, const char *filename,
>        return GRUB_ERR_NONE;
>      }
>  
> -  return grub_multiboot_load_elf (file, filename, buffer);
> +  return grub_multiboot_load_elf (file, filename, buffer, 0, 0, 0, 0,
> +				  GRUB_RELOCATOR_PREFERENCE_NONE, NULL, 0);

Oh boy. That is a bit hard to read. Perhaps another function could be introduced?

grub_multiboot_load_elf_ignore_reloc ? which would just pass the three
parameters and set the rest to the 0 options?


>  }
>  
>  static struct multiboot_header *
> diff --git a/grub-core/loader/multiboot.c b/grub-core/loader/multiboot.c
> index ca7154f..1b1f7a9 100644
> --- a/grub-core/loader/multiboot.c
> +++ b/grub-core/loader/multiboot.c
> @@ -190,12 +190,18 @@ static grub_uint64_t highest_load;
>  /* Load ELF32 or ELF64.  */
>  grub_err_t
>  grub_multiboot_load_elf (grub_file_t file, const char *filename,
> -			 void *buffer)
> +			 void *buffer, int relocatable, grub_uint32_t min_addr,
> +			 grub_uint32_t max_addr, grub_size_t align, grub_uint32_t preference,
> +			 grub_uint32_t *base_addr, int avoid_efi_boot_services)

s/int/bool/ ?

>  {
>    if (grub_multiboot_is_elf32 (buffer))
> -    return grub_multiboot_load_elf32 (file, filename, buffer);
> +    return grub_multiboot_load_elf32 (file, filename, buffer, relocatable,
> +				      min_addr, max_addr, align, preference,
> +				      base_addr, avoid_efi_boot_services);
>    else if (grub_multiboot_is_elf64 (buffer))
> -    return grub_multiboot_load_elf64 (file, filename, buffer);
> +    return grub_multiboot_load_elf64 (file, filename, buffer, relocatable,
> +				      min_addr, max_addr, align, preference,
> +				      base_addr, avoid_efi_boot_services);
>  
>    return grub_error (GRUB_ERR_UNKNOWN_OS, N_("invalid arch-dependent ELF magic"));
>  }
> diff --git a/grub-core/loader/multiboot_elfxx.c b/grub-core/loader/multiboot_elfxx.c
> index 6a220bd..4fce685 100644
> --- a/grub-core/loader/multiboot_elfxx.c
> +++ b/grub-core/loader/multiboot_elfxx.c
> @@ -51,7 +51,10 @@ CONCAT(grub_multiboot_is_elf, XX) (void *buffer)
>  }
>  
>  static grub_err_t
> -CONCAT(grub_multiboot_load_elf, XX) (grub_file_t file, const char *filename, void *buffer)
> +CONCAT(grub_multiboot_load_elf, XX) (grub_file_t file, const char *filename,
> +				     void *buffer, int relocatable, grub_uint32_t min_addr,
> +				     grub_uint32_t max_addr, grub_size_t align, grub_uint32_t preference,
> +				     grub_uint32_t *base_addr, int avoid_efi_boot_services)
>  {
>    Elf_Ehdr *ehdr = (Elf_Ehdr *) buffer;
>    char *phdr_base;
> @@ -89,19 +92,30 @@ CONCAT(grub_multiboot_load_elf, XX) (grub_file_t file, const char *filename, voi
>  	  if (phdr(i)->p_paddr + phdr(i)->p_memsz > highest_load)
>  	    highest_load = phdr(i)->p_paddr + phdr(i)->p_memsz;
>  
> -	  grub_dprintf ("multiboot_loader", "segment %d: paddr=0x%lx, memsz=0x%lx, vaddr=0x%lx\n",
> -			i, (long) phdr(i)->p_paddr, (long) phdr(i)->p_memsz, (long) phdr(i)->p_vaddr);
> +	  grub_dprintf ("multiboot_loader", "segment %d: paddr=0x%lx, memsz=0x%lx, vaddr=0x%lx,"
> +			"align=0x%lx, relocatable=%d, avoid_efi_boot_services=%d\n", i,

%d to %s 
> +			(long) phdr(i)->p_paddr, (long) phdr(i)->p_memsz, (long) phdr(i)->p_vaddr,
> +			(long) align, relocatable, avoid_efi_boot_services);

and then

avoid_efi_boot_services ? "yes" : "no"

>  
>  	  {
>  	    grub_relocator_chunk_t ch;
> -	    err = grub_relocator_alloc_chunk_addr (grub_multiboot_relocator, 
> -						   &ch, phdr(i)->p_paddr,
> -						   phdr(i)->p_memsz);
> +
> +	    if (relocatable)
> +	      err = grub_relocator_alloc_chunk_align (grub_multiboot_relocator, &ch,
> +						      min_addr, max_addr - phdr(i)->p_memsz,
> +						      phdr(i)->p_memsz, align ? align : 1,
> +						      preference, avoid_efi_boot_services);
> +	    else
> +	      err = grub_relocator_alloc_chunk_addr (grub_multiboot_relocator,
> +						     &ch, phdr(i)->p_paddr,
> +						     phdr(i)->p_memsz);
>  	    if (err)
>  	      {
>  		grub_dprintf ("multiboot_loader", "Error loading phdr %d\n", i);
>  		return err;
>  	      }
> +	    if (base_addr)
> +	      *base_addr = get_physical_target_address (ch);
>  	    source = get_virtual_current_address (ch);
>  	  }
>  
> @@ -208,7 +222,7 @@ CONCAT(grub_multiboot_load_elf, XX) (grub_file_t file, const char *filename, voi
>  						    + 1, sh->sh_size,
>  						    sh->sh_addralign,
>  						    GRUB_RELOCATOR_PREFERENCE_NONE,
> -						    0);
> +						    avoid_efi_boot_services);
>  	    if (err)
>  	      {
>  		grub_dprintf ("multiboot_loader", "Error loading shdr %d\n", i);
> diff --git a/grub-core/loader/multiboot_mbi2.c b/grub-core/loader/multiboot_mbi2.c
> index dc9c709..7ac64ec 100644
> --- a/grub-core/loader/multiboot_mbi2.c
> +++ b/grub-core/loader/multiboot_mbi2.c
> @@ -68,6 +68,7 @@ static grub_size_t elf_sec_num, elf_sec_entsize;
>  static unsigned elf_sec_shstrndx;
>  static void *elf_sections;
>  static int keep_bs = 0;
> +static grub_uint32_t base_addr = 0;
>  
>  void
>  grub_multiboot_add_elfsyms (grub_size_t num, grub_size_t entsize,
> @@ -107,11 +108,13 @@ grub_multiboot_load (grub_file_t file, const char *filename)
>    grub_err_t err;
>    struct multiboot_header_tag *tag;
>    struct multiboot_header_tag_address *addr_tag = NULL;
> -  int entry_specified = 0, efi_entry_specified = 0;
> +  int entry_specified = 0, efi_entry_specified = 0, relocatable = 0;
>    grub_addr_t entry = 0, efi_entry = 0;
> -  grub_uint32_t console_required = 0;
> +  grub_uint32_t console_required = 0, min_addr = 0;
> +  grub_uint32_t max_addr = 0, preference = 0;
>    struct multiboot_header_tag_framebuffer *fbtag = NULL;
>    int accepted_consoles = GRUB_MULTIBOOT_CONSOLE_EGA_TEXT;
> +  grub_size_t align = 0;
>  
>    buffer = grub_malloc (MULTIBOOT_SEARCH);
>    if (!buffer)
> @@ -174,6 +177,7 @@ grub_multiboot_load (grub_file_t file, const char *filename)
>  	      case MULTIBOOT_TAG_TYPE_EFI_BS:
>  	      case MULTIBOOT_TAG_TYPE_EFI32_IH:
>  	      case MULTIBOOT_TAG_TYPE_EFI64_IH:
> +	      case MULTIBOOT_TAG_TYPE_BASE_ADDR:
>  		break;
>  
>  	      default:
> @@ -215,6 +219,26 @@ grub_multiboot_load (grub_file_t file, const char *filename)
>  	accepted_consoles |= GRUB_MULTIBOOT_CONSOLE_FRAMEBUFFER;
>  	break;
>  
> +      case MULTIBOOT_HEADER_TAG_RELOCATABLE:
> +	relocatable = 1;

How about:
	struct multiboot_header_tag_relocatable *_tag = (struct multiboot_header_tag_relocatable *)tag;

and then you don't have to use the casting?



> +	min_addr = ((struct multiboot_header_tag_relocatable *) tag)->min_addr;
> +	max_addr = ((struct multiboot_header_tag_relocatable *) tag)->max_addr;
> +	align = ((struct multiboot_header_tag_relocatable *) tag)->align;
> +	switch (((struct multiboot_header_tag_relocatable *) tag)->preference)
> +	  {
> +	  case MULTIBOOT_LOAD_PREFERENCE_LOW:
> +	    preference = GRUB_RELOCATOR_PREFERENCE_LOW;
> +	    break;
> +
> +	  case MULTIBOOT_LOAD_PREFERENCE_HIGH:
> +	    preference = GRUB_RELOCATOR_PREFERENCE_HIGH;
> +	    break;
> +
> +	  default:
> +	    preference = GRUB_RELOCATOR_PREFERENCE_NONE;
> +	  }
> +	break;
> +
>  	/* GRUB always page-aligns modules.  */
>        case MULTIBOOT_HEADER_TAG_MODULE_ALIGN:
>  	break;
> @@ -260,15 +284,22 @@ grub_multiboot_load (grub_file_t file, const char *filename)
>        else
>  	code_size = load_size;
>  
> -      err = grub_relocator_alloc_chunk_addr (grub_multiboot_relocator, 
> -					     &ch, load_addr,
> -					     code_size);
> +      if (relocatable)
> +	err = grub_relocator_alloc_chunk_align (grub_multiboot_relocator, &ch,
> +						min_addr, max_addr - code_size,
> +						code_size, align ? align : 1,
> +						preference, keep_bs);
> +      else
> +	err = grub_relocator_alloc_chunk_addr (grub_multiboot_relocator,
> +					       &ch, load_addr,
> +					       code_size);
>        if (err)
>  	{
>  	  grub_dprintf ("multiboot_loader", "Error loading aout kludge\n");
>  	  grub_free (buffer);
>  	  return err;
>  	}
> +      base_addr = get_physical_target_address (ch);
>        source = get_virtual_current_address (ch);
>  
>        if ((grub_file_seek (file, offset)) == (grub_off_t) -1)
> @@ -290,7 +321,9 @@ grub_multiboot_load (grub_file_t file, const char *filename)
>      }
>    else
>      {
> -      err = grub_multiboot_load_elf (file, filename, buffer);
> +      err = grub_multiboot_load_elf (file, filename, buffer,
> +				     relocatable, min_addr, max_addr,
> +				     align, preference, &base_addr, keep_bs);
>        if (err)
>  	{
>  	  grub_free (buffer);
> @@ -303,6 +336,14 @@ grub_multiboot_load (grub_file_t file, const char *filename)
>    else if (entry_specified)
>      grub_multiboot_payload_eip = entry;
>  
> +  if (relocatable)
> +    {
> +      if (base_addr > min_addr)
> +	grub_multiboot_payload_eip += base_addr - min_addr;
> +      else
> +	grub_multiboot_payload_eip -= min_addr - base_addr;
> +    }
> +
>    if (fbtag)
>      err = grub_multiboot_set_console (GRUB_MULTIBOOT_CONSOLE_FRAMEBUFFER,
>  				      accepted_consoles,
> @@ -409,6 +450,7 @@ grub_multiboot_get_mbi_size (void)
>  		 + grub_get_multiboot_mmap_count ()
>  		 * sizeof (struct multiboot_mmap_entry)), MULTIBOOT_TAG_ALIGN)
>      + ALIGN_UP (sizeof (struct multiboot_tag_framebuffer), MULTIBOOT_TAG_ALIGN)
> +    + ALIGN_UP (sizeof (struct multiboot_tag_base_addr), MULTIBOOT_TAG_ALIGN)
>  #ifdef GRUB_MACHINE_EFI
>      + ALIGN_UP (sizeof (struct multiboot_tag_efi32), MULTIBOOT_TAG_ALIGN)
>      + ALIGN_UP (sizeof (struct multiboot_tag_efi64), MULTIBOOT_TAG_ALIGN)
> @@ -693,6 +735,15 @@ grub_multiboot_make_mbi (grub_uint32_t *target)
>    ptrorig += (2 * sizeof (grub_uint32_t)) / sizeof (grub_properly_aligned_t);
>  
>    {
> +    struct multiboot_tag_base_addr *tag = (struct multiboot_tag_base_addr *) ptrorig;
> +    tag->type = MULTIBOOT_TAG_TYPE_BASE_ADDR;
> +    tag->size = sizeof (struct multiboot_tag_base_addr); 

You have an extra space at the end.

> +    tag->base_addr = base_addr;
> +    ptrorig += ALIGN_UP (tag->size, MULTIBOOT_TAG_ALIGN)
> +       / sizeof (grub_properly_aligned_t);
> +  }
> +
> +  {
>      struct multiboot_tag_string *tag = (struct multiboot_tag_string *) ptrorig;
>      tag->type = MULTIBOOT_TAG_TYPE_CMDLINE;
>      tag->size = sizeof (struct multiboot_tag_string) + cmdline_size; 
> diff --git a/include/grub/multiboot.h b/include/grub/multiboot.h
> index e13c084..ec322b0 100644
> --- a/include/grub/multiboot.h
> +++ b/include/grub/multiboot.h
> @@ -94,7 +94,9 @@ grub_multiboot_load (grub_file_t file, const char *filename);
>  /* Load ELF32 or ELF64.  */
>  grub_err_t
>  grub_multiboot_load_elf (grub_file_t file, const char *filename,
> -			 void *buffer);
> +			 void *buffer, int relocatable, grub_uint32_t min_addr,
> +			 grub_uint32_t max_addr, grub_size_t align, grub_uint32_t preference,
> +			 grub_uint32_t *base_addr, int avoid_efi_boot_services);
>  extern grub_size_t grub_multiboot_pure_size;
>  extern grub_size_t grub_multiboot_alloc_mbi;
>  extern grub_uint32_t grub_multiboot_payload_eip;
> diff --git a/include/multiboot2.h b/include/multiboot2.h
> index 9f97ddc..941a95d 100644
> --- a/include/multiboot2.h
> +++ b/include/multiboot2.h
> @@ -62,6 +62,7 @@
>  #define MULTIBOOT_TAG_TYPE_EFI_BS            18
>  #define MULTIBOOT_TAG_TYPE_EFI32_IH          19
>  #define MULTIBOOT_TAG_TYPE_EFI64_IH          20
> +#define MULTIBOOT_TAG_TYPE_BASE_ADDR         21
>  
>  #define MULTIBOOT_HEADER_TAG_END  0
>  #define MULTIBOOT_HEADER_TAG_INFORMATION_REQUEST  1
> @@ -72,11 +73,16 @@
>  #define MULTIBOOT_HEADER_TAG_MODULE_ALIGN  6
>  #define MULTIBOOT_HEADER_TAG_EFI_BS  7
>  #define MULTIBOOT_HEADER_TAG_ENTRY_ADDRESS_EFI64  9
> +#define MULTIBOOT_HEADER_TAG_RELOCATABLE  10
>  
>  #define MULTIBOOT_ARCHITECTURE_I386  0
>  #define MULTIBOOT_ARCHITECTURE_MIPS32  4
>  #define MULTIBOOT_HEADER_TAG_OPTIONAL 1
>  
> +#define MULTIBOOT_LOAD_PREFERENCE_NONE 0
> +#define MULTIBOOT_LOAD_PREFERENCE_LOW 1
> +#define MULTIBOOT_LOAD_PREFERENCE_HIGH 2
> +
>  #define MULTIBOOT_CONSOLE_FLAGS_CONSOLE_REQUIRED 1
>  #define MULTIBOOT_CONSOLE_FLAGS_EGA_TEXT_SUPPORTED 2
>  
> @@ -169,6 +175,17 @@ struct multiboot_header_tag_module_align
>    multiboot_uint32_t size;
>  };
>  
> +struct multiboot_header_tag_relocatable
> +{
> +  multiboot_uint16_t type;
> +  multiboot_uint16_t flags;
> +  multiboot_uint32_t size;
> +  multiboot_uint32_t min_addr;
> +  multiboot_uint32_t max_addr;
> +  multiboot_uint32_t align;
> +  multiboot_uint32_t preference;
> +};
> +
>  struct multiboot_color
>  {
>    multiboot_uint8_t red;
> @@ -395,6 +412,13 @@ struct multiboot_tag_efi64_ih
>    multiboot_uint64_t pointer;
>  };
>  
> +struct multiboot_tag_base_addr
> +{
> +  multiboot_uint32_t type;
> +  multiboot_uint32_t size;
> +  multiboot_uint32_t base_addr;
> +};
> +
>  #endif /* ! ASM_FILE */
>  
>  #endif /* ! MULTIBOOT_HEADER */
> -- 
> 1.7.10.4
>