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2008-08-02 Robert Millan <rmh@aybabtu.com>

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* loader/i386/pc/multiboot.c (playground, forward_relocator)
        (backward_relocator): New variables.  Used to allocate and relocate
        the payload, respectively.
        (grub_multiboot_load_elf32): Load into heap instead of requested
        address, install the appropiate relocator code in each bound of
        the payload, and set the entry point such that
        grub_multiboot_real_boot() will jump to one of them.

        * kern/i386/loader.S (grub_multiboot_payload_size)
        (grub_multiboot_payload_orig, grub_multiboot_payload_dest)
        (grub_multiboot_payload_entry_offset): New variables.
        (grub_multiboot_real_boot): Set cpu context to what the relocator
        expects, and jump to the relocator instead of the payload.

        * include/grub/i386/loader.h (grub_multiboot_payload_size)
        (grub_multiboot_payload_orig, grub_multiboot_payload_dest)
        (grub_multiboot_payload_entry_offset): Export.
This commit is contained in:
robertmh 2008-08-02 12:12:14 +00:00
parent b15d8a0cc6
commit a927cc7383
4 changed files with 104 additions and 26 deletions
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20
ChangeLog
View file

@ -1,3 +1,23 @@
2008-08-02 Robert Millan <rmh@aybabtu.com>
* loader/i386/pc/multiboot.c (playground, forward_relocator)
(backward_relocator): New variables. Used to allocate and relocate
the payload, respectively.
(grub_multiboot_load_elf32): Load into heap instead of requested
address, install the appropiate relocator code in each bound of
the payload, and set the entry point such that
grub_multiboot_real_boot() will jump to one of them.
* kern/i386/loader.S (grub_multiboot_payload_size)
(grub_multiboot_payload_orig, grub_multiboot_payload_dest)
(grub_multiboot_payload_entry_offset): New variables.
(grub_multiboot_real_boot): Set cpu context to what the relocator
expects, and jump to the relocator instead of the payload.
* include/grub/i386/loader.h (grub_multiboot_payload_size)
(grub_multiboot_payload_orig, grub_multiboot_payload_dest)
(grub_multiboot_payload_entry_offset): Export.
2008-08-01 Bean <bean123ch@gmail.com>
* normal/menu_entry.c (editor_getline): Don't return the original

4
include/grub/i386/loader.h
View file

@ -43,6 +43,10 @@ void EXPORT_FUNC(grub_multiboot2_real_boot) (grub_addr_t entry,
void EXPORT_FUNC(grub_unix_real_boot) (grub_addr_t entry, ...)
__attribute__ ((cdecl,noreturn));
extern grub_addr_t EXPORT_VAR(grub_multiboot_payload_orig);
extern grub_addr_t EXPORT_VAR(grub_multiboot_payload_dest);
extern grub_size_t EXPORT_VAR(grub_multiboot_payload_size);
extern grub_uint32_t EXPORT_VAR(grub_multiboot_payload_entry_offset);
/* It is necessary to export these functions, because normal mode commands
reuse rescue mode commands. */

22
kern/i386/loader.S
View file

@ -123,6 +123,15 @@ linux_setup_seg:
* This starts the multiboot kernel.
*/
VARIABLE(grub_multiboot_payload_size)
.long 0
VARIABLE(grub_multiboot_payload_orig)
.long 0
VARIABLE(grub_multiboot_payload_dest)
.long 0
VARIABLE(grub_multiboot_payload_entry_offset)
.long 0
FUNCTION(grub_multiboot_real_boot)
/* Push the entry address on the stack. */
pushl %eax
@ -136,10 +145,15 @@ FUNCTION(grub_multiboot_real_boot)
/* Interrupts should be disabled. */
cli
/* Move the magic value into eax and jump to the kernel. */
movl $MULTIBOOT_MAGIC2,%eax
popl %ecx
jmp *%ecx
/* Where do we copy what from. */
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
/* Jump to the relocator. */
popl %edx
jmp *%edx
/*
* This starts the multiboot 2 kernel.

82
loader/i386/pc/multiboot.c
View file

@ -50,6 +50,33 @@ extern grub_dl_t my_mod;
static struct grub_multiboot_info *mbi;
static grub_addr_t entry;
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)
{
@ -99,6 +126,7 @@ grub_multiboot_load_elf32 (grub_file_t file, void *buffer)
Elf32_Ehdr *ehdr = (Elf32_Ehdr *) buffer;
char *phdr_base;
grub_addr_t physical_entry_addr = 0;
int lowest_segment = 0, highest_segment = 0;
int i;
if (ehdr->e_ident[EI_CLASS] != ELFCLASS32)
@ -114,50 +142,62 @@ grub_multiboot_load_elf32 (grub_file_t file, void *buffer)
if (ehdr->e_phoff + ehdr->e_phnum * ehdr->e_phentsize > MULTIBOOT_SEARCH)
return grub_error (GRUB_ERR_BAD_OS, "program header at a too high offset");
entry = ehdr->e_entry;
phdr_base = (char *) buffer + ehdr->e_phoff;
#define phdr(i) ((Elf32_Phdr *) (phdr_base + (i) * ehdr->e_phentsize))
for (i = 0; i < ehdr->e_phnum; i++)
if (phdr(i)->p_type == PT_LOAD)
{
if (phdr(i)->p_paddr < phdr(lowest_segment)->p_paddr)
lowest_segment = i;
if (phdr(i)->p_paddr > phdr(highest_segment)->p_paddr)
highest_segment = i;
}
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));
if (! playground)
return grub_errno;
grub_multiboot_payload_orig = playground + sizeof (forward_relocator);
grub_memmove (playground, forward_relocator, sizeof (forward_relocator));
grub_memmove (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++)
{
if (phdr(i)->p_type == PT_LOAD)
{
/* The segment should fit in the area reserved for the OS. */
if (phdr(i)->p_paddr < grub_os_area_addr)
return grub_error (GRUB_ERR_BAD_OS,
"segment doesn't fit in memory reserved for the OS (0x%lx < 0x%lx)",
phdr(i)->p_paddr, grub_os_area_addr);
if (phdr(i)->p_paddr + phdr(i)->p_memsz > grub_os_area_addr + grub_os_area_size)
return grub_error (GRUB_ERR_BAD_OS,
"segment doesn't fit in memory reserved for the OS (0x%lx > 0x%lx)",
phdr(i)->p_paddr + phdr(i)->p_memsz,
grub_os_area_addr + grub_os_area_size);
char *load_this_module_at = grub_multiboot_payload_orig + (phdr(i)->p_paddr - phdr(0)->p_paddr);
if (grub_file_seek (file, (grub_off_t) phdr(i)->p_offset)
if (grub_file_seek (file, (grub_off_t) phdr(i)->p_offset)
== (grub_off_t) -1)
return grub_error (GRUB_ERR_BAD_OS,
"invalid offset in program header");
if (grub_file_read (file, (void *) phdr(i)->p_paddr, phdr(i)->p_filesz)
if (grub_file_read (file, load_this_module_at, phdr(i)->p_filesz)
!= (grub_ssize_t) phdr(i)->p_filesz)
return grub_error (GRUB_ERR_BAD_OS,
"couldn't read segment from file");
if (phdr(i)->p_filesz < phdr(i)->p_memsz)
grub_memset ((char *) phdr(i)->p_paddr + phdr(i)->p_filesz, 0,
grub_memset (load_this_module_at + phdr(i)->p_filesz, 0,
phdr(i)->p_memsz - phdr(i)->p_filesz);
if ((entry >= phdr(i)->p_vaddr) &&
(entry < phdr(i)->p_vaddr + phdr(i)->p_memsz))
physical_entry_addr = entry + phdr(i)->p_paddr - phdr(i)->p_vaddr;
}
}
grub_multiboot_payload_entry_offset = ehdr->e_entry - phdr(lowest_segment)->p_vaddr;
#undef phdr
if (physical_entry_addr)
entry = physical_entry_addr;
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;
return grub_errno;
}