[romprefix] Align PMM temporary decompression area to a page boundary

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/arch/x86/prefix/romprefix.S b/src/arch/x86/prefix/romprefix.S
index 57eb31af434cf74a000d711d708805ea692347f1..287a986c41b91c5af7496c2e0a4e7892005eb153 100644 (file)
--- a/src/arch/x86/prefix/romprefix.S
+++ b/src/arch/x86/prefix/romprefix.S
@@ -402,19 +402,22 @@ pmm_scan:
        /* Shrink ROM */
        movb    shrunk_rom_size, %al
        movb    %al, romheader_size
-1:     /* Allocate decompression PMM block.  Round up the size to the
-        * nearest 128kB and use the size within the PMM handle; this
-        * allows the same decompression area to be shared between
-        * multiple iPXE ROMs even with differing build IDs
+1:     /* Allocate decompression PMM block.  Allow 4kB for page
+        * alignment and round up the size to the nearest 128kB, then
+        * use the size within the PMM handle; this allows the same
+        * decompression area to be shared between multiple iPXE ROMs
+        * even with differing build IDs
         */
        movl    $_textdata_memsz_pgh, %ecx
-       addl    $0x00001fff, %ecx
-       andl    $0xffffe000, %ecx
+       addl    $( 0x00000100 /* 4kB */ + 0x00001fff /* 128kB - 1 */ ), %ecx
+       andl    $( 0xffffe000 /* ~( 128kB - 1 ) */ ), %ecx
        movl    %ecx, %ebx
        shrw    $12, %bx
        orl     $PMM_HANDLE_BASE_DECOMPRESS_TO, %ebx
        movw    $get_pmm_decompress_to, %bp
        call    get_pmm
+       addl    $( 0x00000fff /* 4kB - 1 */ ), %esi
+       andl    $( 0xfffff000 /* ~( 4kB - 1 ) */ ), %esi
        movl    %esi, decompress_to
        /* Restore registers */
        popal