The 32-bit EFI handover entry point requires segments to be setup in the
same way as for the regular 32-bit boot.
Signed-off-by: Arvind Sankar <nivedita@xxxxxxxxxxxx>
---
Documentation/x86/boot.rst | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/Documentation/x86/boot.rst b/Documentation/x86/boot.rst
index c9c201596c3e..3e13b7d57271 100644
--- a/Documentation/x86/boot.rst
+++ b/Documentation/x86/boot.rst
@@ -1412,6 +1412,12 @@ from the boot media and jump to the EFI handover protocol entry point
which is hdr->handover_offset bytes from the beginning of
startup_{32,64}.
+For the 32-bit handover entry point, the GDT and segments must be setup as for
+the 32-bit boot protocol, i.e. a GDT must be loaded with the descriptors for
+selectors __BOOT_CS(0x10) and __BOOT_DS(0x18); both descriptors must be 4G flat
+segment; __BOOT_CS must have execute/read permission, and __BOOT_DS must have
+read/write permission; CS must be __BOOT_CS and DS, ES, SS must be __BOOT_DS.
+
The function prototype for the handover entry point looks like this::
efi_main(void *handle, efi_system_table_t *table, struct boot_params *bp)
--
2.24.1
