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-rw-r--r--Documentation/i386/zero-page.txt11
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/i386/zero-page.txt b/Documentation/i386/zero-page.txt
index c04a421f4a7c..6c0817c45683 100644
--- a/Documentation/i386/zero-page.txt
+++ b/Documentation/i386/zero-page.txt
@@ -1,3 +1,13 @@
+---------------------------------------------------------------------------
+!!!!!!!!!!!!!!!WARNING!!!!!!!!
+The zero page is a kernel internal data structure, not a stable ABI. It might change
+without warning and the kernel has no way to detect old version of it.
+If you're writing some external code like a boot loader you should only use
+the stable versioned real mode boot protocol described in boot.txt. Otherwise the kernel
+might break you at any time.
+!!!!!!!!!!!!!WARNING!!!!!!!!!!!
+----------------------------------------------------------------------------
+
Summary of boot_params layout (kernel point of view)
( collected by Hans Lermen and Martin Mares )
@@ -37,6 +47,7 @@ Offset Type Description
0x1d0 unsigned long EFI memory descriptor map pointer
0x1d4 unsigned long EFI memory descriptor map size
0x1e0 unsigned long ALT_MEM_K, alternative mem check, in Kb
+0x1e4 unsigned long Scratch field for the kernel setup code
0x1e8 char number of entries in E820MAP (below)
0x1e9 unsigned char number of entries in EDDBUF (below)
0x1ea unsigned char number of entries in EDD_MBR_SIG_BUFFER (below)