Use full protected mode for access to high memory within prefix, to

work around limitations in real-mode virtualisation support on Intel
VT-capable chips.

diff --git a/src/arch/i386/prefix/libprefix.S b/src/arch/i386/prefix/libprefix.S
index 26ec752..d78113c 100644 (file)
--- a/src/arch/i386/prefix/libprefix.S
+++ b/src/arch/i386/prefix/libprefix.S
@@ -47,17 +47,181 @@
        .section ".data16", "aw", @progbits
 
 /****************************************************************************
        .section ".data16", "aw", @progbits
 
 /****************************************************************************

- * install_block (real-mode near call)
+ * pm_call (real-mode near call)
+ *
+ * Call routine in 16-bit protected mode for access to extended memory
+ *
+ * Parameters:
+ *   %ax : address of routine to call in 16-bit protected mode
+ * Returns:
+ *   none
+ * Corrupts:
+ *   %ax
+ *
+ * The specified routine is called in 16-bit protected mode, with:
+ *
+ *   %cs : 16-bit code segment with base matching real-mode %cs
+ *   %ss : 16-bit data segment with base matching real-mode %ss
+ *   %ds,%es,%fs,%gs : 32-bit data segment with zero base and 4GB limit
+ *
+ ****************************************************************************
+ */
+
+#ifndef KEEP_IT_REAL
+
+       /* GDT for protected-mode calls */
+       .section ".data16"
+       .align 16
+gdt:
+gdt_limit:             .word gdt_length - 1
+gdt_base:              .long 0
+                       .word 0 /* padding */
+pm_cs:         /* 16-bit protected-mode code segment */
+       .equ    PM_CS, pm_cs - gdt
+       .word   0xffff, 0
+       .byte   0, 0x9b, 0x00, 0
+pm_ss:         /* 16-bit protected-mode stack segment */
+       .equ    PM_SS, pm_ss - gdt
+       .word   0xffff, 0
+       .byte   0, 0x93, 0x00, 0
+pm_ds:         /* 32-bit protected-mode flat data segment */
+       .equ    PM_DS, pm_ds - gdt
+       .word   0xffff, 0
+       .byte   0, 0x93, 0xcf, 0
+gdt_end:
+       .equ    gdt_length, . - gdt
+       .size   gdt, . - gdt
+
+       .section ".data16"
+       .align 16
+pm_saved_gdt:  
+       .long   0, 0
+       .size   pm_saved_gdt, . - pm_saved_gdt
+
+       .section ".prefix.lib"
+       .code16
+pm_call:
+       /* Preserve registers, flags, GDT, and RM return point */
+       pushfl
+       sgdt    pm_saved_gdt
+       pushw   %gs
+       pushw   %fs
+       pushw   %es
+       pushw   %ds
+       pushw   %ss
+       pushw   %cs
+       pushw   $99f
+
+       /* Set up GDT bases */
+       pushl   %eax
+       pushw   %bx
+       xorl    %eax, %eax
+       movw    %ds, %ax
+       shll    $4, %eax
+       addl    $gdt, %eax
+       movl    %eax, gdt_base
+       movw    %cs, %ax
+       movw    $pm_cs, %bx
+       call    set_seg_base
+       movw    %ss, %ax
+       movw    $pm_ss, %bx
+       call    set_seg_base
+       popw    %bx
+       popl    %eax
+
+       /* Switch CPU to protected mode and load up segment registers */
+       pushl   %eax
+       cli
+       lgdt    gdt
+       movl    %cr0, %eax
+       orb     $CR0_PE, %al
+       movl    %eax, %cr0
+       ljmp    $PM_CS, $1f
+1:     movw    $PM_SS, %ax
+       movw    %ax, %ss
+       movw    $PM_DS, %ax
+       movw    %ax, %ds
+       movw    %ax, %es
+       movw    %ax, %fs
+       movw    %ax, %gs
+       popl    %eax
+
+       /* Call PM routine */
+       call    *%ax
+
+       /* Set real-mode segment limits on %ds, %es, %fs and %gs */
+       movw    %ss, %ax
+       movw    %ax, %ds
+       movw    %ax, %es
+       movw    %ax, %fs
+       movw    %ax, %gs
+
+       /* Return CPU to real mode */
+       movl    %cr0, %eax
+       andb    $0!CR0_PE, %al
+       movl    %eax, %cr0
+
+       /* Restore registers and flags */
+       lret
+99:    popw    %ss
+       popw    %ds
+       popw    %es
+       popw    %fs
+       popw    %gs
+       lgdt    pm_saved_gdt
+       popfl
+
+       ret
+       .size pm_call, . - pm_call
+
+set_seg_base:
+       rolw    $4, %ax
+       movw    %ax, 2(%bx)
+       andw    $0xfff0, 2(%bx)
+       movb    %al, 4(%bx)
+       andb    $0x0f, 4(%bx)
+       ret
+       .size set_seg_base, . - set_seg_base
+
+#endif /* KEEP_IT_REAL */
+
+/****************************************************************************
+ * copy_bytes (real-mode or 16-bit protected-mode near call)
+ *
+ * Copy bytes
+ *
+ * Parameters:
+ *   %ds:esi : source address
+ *   %es:edi : destination address
+ *   %ecx : length
+ * Returns:
+ *   %ds:esi : next source address
+ *   %ds:esi : next destination address
+ * Corrupts:
+ *   None
+ ****************************************************************************
+ */
+       .section ".prefix.lib"
+       .code16
+copy_bytes:
+       pushl %ecx
+       rep addr32 movsb
+       popl %ecx
+       ret
+       .size copy_bytes, . - copy_bytes
+
+/****************************************************************************
+ * install_block (real-mode or 16-bit protected-mode near call)

  *
  * Install block to specified address
  *
  * Parameters:
  *
  * Install block to specified address
  *
  * Parameters:

- *   %esi : start offset within loaded image (must be a multiple of 16)
+ *   %ds:esi : source address (must be a multiple of 16)

  *   %es:edi : destination address
  *   %ecx : length of (decompressed) data
  *   %edx : total length of block (including any uninitialised data portion)
  * Returns:
  *   %es:edi : destination address
  *   %ecx : length of (decompressed) data
  *   %edx : total length of block (including any uninitialised data portion)
  * Returns:

- *   %esi : end offset within image (rounded up to next multiple of 16)
+ *   %ds:esi : next source address (will be a multiple of 16)

  * Corrupts:
  *   %edi, %ecx, %edx
  ****************************************************************************
  * Corrupts:
  *   %edi, %ecx, %edx
  ****************************************************************************


@@ -65,46 +229,26 @@
        .section ".prefix.lib"
        .code16
 install_block:
        .section ".prefix.lib"
        .code16
 install_block:

-       /* Preserve registers */
-       pushw   %ds
-       pushl   %eax
-       pushl   %ebx
-       movl    %esi, %ebx
-       
-       /* Starting segment => %ds */
-       movw    %cs, %ax
-       shrl    $4, %esi
-       addw    %si, %ax
-       movw    %ax, %ds
-       xorl    %esi, %esi
-
-       /* Calculate start and length of uninitialised data portion */
-       addr32 leal     (%edi,%ecx), %eax
-       subl    %ecx, %edx
-       
-       /* Do the copy */
-       cld

 #if COMPRESS
 #if COMPRESS

+       /* Decompress source to destination */

        call    decompress16
 #else
        call    decompress16
 #else

-       rep addr32 movsb
+       /* Copy source to destination */
+       call    copy_bytes

 #endif
 
 #endif
 

-       /* Zero remaining space */
-       movl    %eax, %edi
-       movl    %edx, %ecx
-       xorb    %al, %al
+       /* Zero .bss portion */
+       negl    %ecx
+       addl    %edx, %ecx
+       pushw   %ax
+       xorw    %ax, %ax

        rep addr32 stosb
        rep addr32 stosb

+       popw    %ax

 
 

-       /* Adjust %esi */
-       addl    %ebx, %esi
+       /* Round up %esi to start of next source block */

        addl    $0xf, %esi
        andl    $~0xf, %esi
 
        addl    $0xf, %esi
        andl    $~0xf, %esi
 

-       /* Restore registers */
-       popl    %ebx
-       popl    %eax
-       popw    %ds

        ret
        .size install_block, . - install_block
        
        ret
        .size install_block, . - install_block
        


@@ -159,9 +303,9 @@ alloc_basemem:
  * Parameters: 
  *   %ax : .text16 segment address
  *   %bx : .data16 segment address
  * Parameters: 
  *   %ax : .text16 segment address
  *   %bx : .data16 segment address

- *   %esi : start offset within loaded image (must be a multiple of 16)
+ *   %esi : source physical address (must be a multiple of 16)

  * Returns:
  * Returns:

- *   %esi : end offset within image (rounded up to next multiple of 16)
+ *   %esi : next source physical address (will be a multiple of 16)

  * Corrupts:
  *   none
  ****************************************************************************
  * Corrupts:
  *   none
  ****************************************************************************


@@ -170,43 +314,57 @@ alloc_basemem:
        .code16
 install_basemem:
        /* Preserve registers */
        .code16
 install_basemem:
        /* Preserve registers */

+       pushw   %ds

        pushw   %es
        pushl   %edi
        pushl   %ecx
        pushl   %edx
 
        /* Install .text16 */
        pushw   %es
        pushl   %edi
        pushl   %ecx
        pushl   %edx
 
        /* Install .text16 */

+       pushl   %esi
+       shrl    $4, %esi
+       movw    %si, %ds
+       xorw    %si, %si

        movw    %ax, %es
        xorl    %edi, %edi
        movl    $_text16_size, %ecx
        movl    %ecx, %edx
        call    install_block
        movw    %ax, %es
        xorl    %edi, %edi
        movl    $_text16_size, %ecx
        movl    %ecx, %edx
        call    install_block

+       popl    %ecx
+       addl    %ecx, %esi

 
        /* Install .data16 */
 
        /* Install .data16 */

+       pushl   %esi
+       shrl    $4, %esi
+       movw    %si, %ds
+       xorw    %si, %si

        movw    %bx, %es
        movw    %bx, %es

-       xorl    %edi, %edi      
+       xorl    %edi, %edi

        movl    $_data16_progbits_size, %ecx
        movl    $_data16_size, %edx
        call    install_block
        movl    $_data16_progbits_size, %ecx
        movl    $_data16_size, %edx
        call    install_block

+       popl    %ecx
+       addl    %ecx, %esi

 
        /* Restore registers */
        popl    %edx
        popl    %ecx
        popl    %edi
        popw    %es
 
        /* Restore registers */
        popl    %edx
        popl    %ecx
        popl    %edi
        popw    %es

+       popw    %ds

        ret
        .size install_basemem, . - install_basemem
 
 /****************************************************************************
        ret
        .size install_basemem, . - install_basemem
 
 /****************************************************************************

- * install_highmem (flat real-mode near call)
+ * install_highmem (real-mode near call)

  *
  * Install .text and .data into high memory
  *
  * Parameters:
  *
  * Install .text and .data into high memory
  *
  * Parameters:

- *   %esi : start offset within loaded image (must be a multiple of 16)
- *   %es:edi : address in high memory
+ *   %esi : source physical address (must be a multiple of 16)
+ *   %edi : destination physical address

  * Returns:
  * Returns:

- *   %esi : end offset within image (rounded up to next multiple of 16)
+ *   %esi : next source physical address (will be a multiple of 16)

  * Corrupts:
  *   none
  ****************************************************************************
  * Corrupts:
  *   none
  ****************************************************************************


@@ -218,115 +376,27 @@ install_basemem:
        .code16
 install_highmem:
        /* Preserve registers */
        .code16
 install_highmem:
        /* Preserve registers */

+       pushw   %ax

        pushl   %edi
        pushl   %ecx
        pushl   %edx
        pushl   %edi
        pushl   %ecx
        pushl   %edx

-               
+

        /* Install .text and .data to specified address */
        movl    $_textdata_progbits_size, %ecx
        movl    $_textdata_size, %edx
        /* Install .text and .data to specified address */
        movl    $_textdata_progbits_size, %ecx
        movl    $_textdata_size, %edx

-       call    install_block
+       movw    $install_block, %ax
+       call    pm_call

 
 

-       /* Restore registers and interrupt status */
+       /* Restore registers */

        popl    %edx
        popl    %ecx
        popl    %edi
        popl    %edx
        popl    %ecx
        popl    %edi

+       popw    %ax

        ret
        .size install_highmem, . - install_highmem
        
 #endif /* KEEP_IT_REAL */
        
        ret
        .size install_highmem, . - install_highmem
        
 #endif /* KEEP_IT_REAL */
        

-/****************************************************************************
- * GDT for flat real mode
- *
- * We only ever use this GDT to set segment limits; the bases are
- * unused.  Also, we only change data segments, so we don't need to
- * worry about the code or stack segments.  This makes everything much
- * simpler.
- ****************************************************************************
- */
-       
-#ifndef KEEP_IT_REAL
-       
-       .section ".prefix.lib"
-       .align 16
-gdt:
-gdt_limit:             .word gdt_length - 1
-gdt_base:              .long 0
-                       .word 0 /* padding */
-
-flat_ds:       /* Flat real mode data segment */
-       .equ    FLAT_DS, flat_ds - gdt
-       .word   0xffff, 0
-       .byte   0, 0x93, 0xcf, 0
-
-real_ds:       /* Normal real mode data segment */
-       .equ    REAL_DS, real_ds - gdt
-       .word   0xffff, 0
-       .byte   0, 0x93, 0x00, 0
-
-gdt_end:
-       .equ    gdt_length, gdt_end - gdt
-       .size gdt, . - gdt
-       
-#endif /* KEEP_IT_REAL */
-
-/****************************************************************************
- * set_real_mode_limits (real-mode near call)
- *
- * Sets limits on the data segments %ds and %es.
- *
- * Parameters:
- *   %dx : segment type (FLAT_DS for 4GB or REAL_DS for 64kB)
- ****************************************************************************
- */
-
-#ifndef KEEP_IT_REAL
-       
-       .section ".prefix.lib"
-       .code16
-set_real_mode_limits:
-       /* Preserve real-mode segment values and temporary registers */
-       pushw   %es
-       pushw   %ds
-       pushw   %bp
-       pushl   %eax
-
-       /* Set GDT base and load GDT */
-       xorl    %eax, %eax
-       movw    %cs, %ax
-       shll    $4, %eax
-       addl    $gdt, %eax
-       pushl   %eax
-       pushw   %cs:gdt_limit
-       movw    %sp, %bp
-       lgdt    (%bp)
-       addw    $6, %sp
-
-       /* Switch to protected mode */
-       movl    %cr0, %eax
-       orb     $CR0_PE, %al
-       movl    %eax, %cr0
-
-       /* Set flat segment limits */
-       movw    %dx, %ds
-       movw    %dx, %es
-
-       /* Switch back to real mode */
-       movl    %cr0, %eax
-       andb    $0!CR0_PE, %al
-       movl    %eax, %cr0
-
-       /* Restore real-mode segment values and temporary registers */
-       popl    %eax
-       popw    %bp
-       popw    %ds
-       popw    %es
-       ret
-       .size set_real_mode_limits, . - set_real_mode_limits
-       
-#endif /* KEEP_IT_REAL */
-       

 /****************************************************************************
  * install (real-mode near call)
  * install_prealloc (real-mode near call)
 /****************************************************************************
  * install (real-mode near call)
  * install_prealloc (real-mode near call)


@@ -354,72 +424,70 @@ install:
        .globl install_prealloc
 install_prealloc:
        /* Save registers */
        .globl install_prealloc
 install_prealloc:
        /* Save registers */

+       pushw   %ds

        pushl   %esi
        pushl   %esi

-       pushw   %dx
+
+       /* Sanity: clear the direction flag asap */
+       cld
+
+       /* Calculate physical address of payload (i.e. first source) */
+       xorl    %esi, %esi
+       movw    %cs, %si
+       shll    $4, %esi
+       addl    $_payload_offset, %esi
+

        /* Install .text16 and .data16 */
        /* Install .text16 and .data16 */

-       movl    $_payload_offset, %esi

        call    install_basemem
 
        call    install_basemem
 

-#ifdef KEEP_IT_REAL
-       /* Preserve %ds, call init_libkir, restore registers */
-       pushw   %ds
+       /* Set up %ds for access to .data16 */

        movw    %bx, %ds
        movw    %bx, %ds

+
+#ifdef KEEP_IT_REAL
+       /* Initialise libkir */

        movw    %ax, (init_libkir_vector+2)
        lcall   *init_libkir_vector
        movw    %ax, (init_libkir_vector+2)
        lcall   *init_libkir_vector

-       popw    %ds

 #else
 #else

-       /* Preserve registers and interrupt status, and disable interrupts */
-       pushfw
-       pushw   %ds
-       pushw   %es
+       /* Save registers */
+       pushl   %edi

        pushl   %ecx
        pushl   %ecx

-       cli

 
 

-       /* Load up %ds and %es, and set up vectors for far calls to .text16 */
-       movw    %bx, %ds
-       xorw    %cx, %cx
-       movw    %cx, %es
-       movw    %ax, (init_librm_vector+2)
-       movw    %ax, (prot_call_vector+2)
-       

        /* Install .text and .data to temporary area in high memory,
         * prior to reading the E820 memory map and relocating
         * properly.
         */
        /* Install .text and .data to temporary area in high memory,
         * prior to reading the E820 memory map and relocating
         * properly.
         */

-       movw    $FLAT_DS, %dx
-       call    set_real_mode_limits

        movl    $HIGHMEM_LOADPOINT, %edi
        call    install_highmem
 
        movl    $HIGHMEM_LOADPOINT, %edi
        call    install_highmem
 

-       /* Set up initial protected-mode GDT, call relocate().
+       /* Initialise librm at current location */
+       movw    %ax, (init_librm_vector+2)
+       lcall   *init_librm_vector
+
+       /* Call relocate() to determine target address for relocation.

         * relocate() will return with %esi, %edi and %ecx set up
         * ready for the copy to the new location.
         */
         * relocate() will return with %esi, %edi and %ecx set up
         * ready for the copy to the new location.
         */

-       lcall   *init_librm_vector
+       movw    %ax, (prot_call_vector+2)

        pushl   $relocate
        lcall   *prot_call_vector
        addw    $4, %sp
 
        pushl   $relocate
        lcall   *prot_call_vector
        addw    $4, %sp
 

-       /* Move code to new location, set up new protected-mode GDT */
-       movw    $FLAT_DS, %dx
-       call    set_real_mode_limits
+       /* Copy code to new location */

        pushl   %edi
        pushl   %edi

-       es rep addr32 movsb
+       pushw   %ax
+       movw    $copy_bytes, %ax
+       call    pm_call
+       popw    %ax

        popl    %edi
        popl    %edi

-       lcall   *init_librm_vector

 
 

-       /* Restore real-mode segment limits */
-       movw    $REAL_DS, %dx
-       call    set_real_mode_limits
+       /* Initialise librm at new location */
+       lcall   *init_librm_vector

 
 

-       /* Restore registers and interrupt status */
+       /* Restore registers */

        popl    %ecx
        popl    %ecx

-       popw    %es
-       popw    %ds
-       popfw
+       popl    %edi

 #endif
 #endif

-       popw    %dx

        popl    %esi
        popl    %esi

+       popw    %ds

        ret
        .size install_prealloc, . - install_prealloc
 
        ret
        .size install_prealloc, . - install_prealloc