[prefix] Use area at top of INT 15,88 memory map for temporary decompression

[gpxe.git] / src / arch / i386 / prefix / libprefix.S

diff --git a/src/arch/i386/prefix/libprefix.S b/src/arch/i386/prefix/libprefix.S
index bcf4685..f5f6691 100644 (file)
--- a/src/arch/i386/prefix/libprefix.S
+++ b/src/arch/i386/prefix/libprefix.S
@@ -21,16 +21,6 @@ FILE_LICENCE ( GPL2_OR_LATER )
 
        .arch i386
 
 
        .arch i386
 

-/**
- * High memory temporary load address
- *
- * Temporary buffer into which to copy (or decompress) our runtime
- * image, prior to calling get_memmap() and relocate().  We don't
- * actually leave anything here once install() has returned.
- */
-       .globl  HIGHMEM_LOADPOINT
-       .equ    HIGHMEM_LOADPOINT, ( 1 << 20 )
-

 /* Image compression enabled */
 #define COMPRESS 1
 
 /* Image compression enabled */
 #define COMPRESS 1
 


@@ -451,8 +441,8 @@ install:
        call    alloc_basemem
        /* Image source = %cs:0000 */
        xorl    %esi, %esi
        call    alloc_basemem
        /* Image source = %cs:0000 */
        xorl    %esi, %esi

-       /* Image destination = HIGHMEM_LOADPOINT */
-       movl    $HIGHMEM_LOADPOINT, %edi
+       /* Image destination = default */
+       xorl    %edi, %edi

        /* Install text and data segments */
        call    install_prealloc
        /* Restore registers and return */
        /* Install text and data segments */
        call    install_prealloc
        /* Restore registers and return */


@@ -470,7 +460,7 @@ install:
  *   %ax  : .text16 segment address
  *   %bx  : .data16 segment address
  *   %esi : Image source physical address (or zero for %cs:0000)
  *   %ax  : .text16 segment address
  *   %bx  : .data16 segment address
  *   %esi : Image source physical address (or zero for %cs:0000)

- *   %edi : Decompression temporary area physical address
+ *   %edi : Decompression temporary area physical address (or zero for default)

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


@@ -550,6 +540,22 @@ a20_death_message:
        movw    %ax, (init_libkir_vector+2)
        lcall   *init_libkir_vector
 #else
        movw    %ax, (init_libkir_vector+2)
        lcall   *init_libkir_vector
 #else

+       /* Find a suitable decompression temporary area, if none specified */
+       testl   %ebp, %ebp
+       jnz     1f
+       /* Use INT 15,88 to find the highest available address via INT
+        * 15,88.  This limits us to around 64MB, which should avoid
+        * all of the POST-time memory map failure modes.
+        */
+       pushl   %eax
+       movb    $0x88, %ah
+       int     $0x15
+       movw    %ax, %bp
+       addl    $0x400, %ebp
+       subl    $_textdata_memsz_kb, %ebp
+       shll    $10, %ebp
+       popl    %eax
+1:

        /* 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.