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

[Konrad Rzeszutek Wilk]

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 <address@hidden>
> ---
>  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
>