[1760] 2008-08-02 Robert Millan <address@hidden>

[Robert Millan]

Revision: 1760
          http://svn.sv.gnu.org/viewvc/?view=rev&root=grub&revision=1760
Author:   robertmh
Date:     2008-08-02 12:12:14 +0000 (Sat, 02 Aug 2008)

Log Message:
-----------
2008-08-02  Robert Millan  <address@hidden>

        * 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.

Modified Paths:
--------------
    trunk/grub2/ChangeLog
    trunk/grub2/include/grub/i386/loader.h
    trunk/grub2/kern/i386/loader.S
    trunk/grub2/loader/i386/pc/multiboot.c

Modified: trunk/grub2/ChangeLog
===================================================================
--- trunk/grub2/ChangeLog       2008-08-01 18:18:32 UTC (rev 1759)
+++ trunk/grub2/ChangeLog       2008-08-02 12:12:14 UTC (rev 1760)
@@ -1,3 +1,23 @@
+2008-08-02  Robert Millan  <address@hidden>
+
+       * 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  <address@hidden>
 
        * normal/menu_entry.c (editor_getline): Don't return the original

Modified: trunk/grub2/include/grub/i386/loader.h
===================================================================
--- trunk/grub2/include/grub/i386/loader.h      2008-08-01 18:18:32 UTC (rev 
1759)
+++ trunk/grub2/include/grub/i386/loader.h      2008-08-02 12:12:14 UTC (rev 
1760)
@@ -43,6 +43,10 @@
 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.  */

Modified: trunk/grub2/kern/i386/loader.S
===================================================================
--- trunk/grub2/kern/i386/loader.S      2008-08-01 18:18:32 UTC (rev 1759)
+++ trunk/grub2/kern/i386/loader.S      2008-08-02 12:12:14 UTC (rev 1760)
@@ -123,6 +123,15 @@
  * 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
@@ -136,11 +145,16 @@
        /* 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.
  */

Modified: trunk/grub2/loader/i386/pc/multiboot.c
===================================================================
--- trunk/grub2/loader/i386/pc/multiboot.c      2008-08-01 18:18:32 UTC (rev 
1759)
+++ trunk/grub2/loader/i386/pc/multiboot.c      2008-08-02 12:12:14 UTC (rev 
1760)
@@ -50,6 +50,33 @@
 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 @@
   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 @@
   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;
 }