boot/compressed/efi_mixed.S

1 /* SPDX-License-Identifier: GPL-2.0 */
5  * Early support for invoking 32-bit EFI services from a 64-bit kernel.
8  * restore the firmware's 32-bit GDT and IDT before we make EFI service
11  * On the plus side, we don't have to worry about mangling 64-bit
12  * addresses into 32-bits because we're executing with an identity
13  * mapped pagetable and haven't transitioned to 64-bit virtual addresses
20 #include <asm/processor-flags.h>
26  * When booting in 64-bit mode on 32-bit EFI firmware, startup_64_mixed_mode()
29  * enter the kernel, it will either branch to the common 64-bit EFI stub
30  * entrypoint efi_stub_entry() directly, or via the 64-bit EFI PE/COFF
35  *                                                             +--------------+
36  *  +------------------+     +------------+            +------>| efi_pe_entry |
37  *  | efi32_pe_entry   |---->|            |            |       +-----------+--+
38  *  +------------------+     |            |     +------+----------------+  |
39  *                           | startup_32 |---->| startup_64_mixed_mode |  |
40  *  +------------------+     |            |     +------+----------------+  |
41  *  | efi32_stub_entry |---->|            |            |                   |
42  *  +------------------+     +------------+            |                   |
44  *                           +------------+     +----------------+         |
45  *                           | startup_64 |<----| efi_stub_entry |<--------+
46  *                           +------------+     +----------------+
87 	 * Convert x86-64 ABI params to i386 ABI
106 	 * Switch to IDT and GDT with 32-bit segments. These are the firmware
110 	 * Pass the saved DS selector to the 32-bit code, and use far return to
132 	/* Clear out 32-bit selector from FS and GS */
150 	leal	(_bss - 1b)(%ecx), %edi
151 	leal	(_ebss - 1b)(%ecx), %ecx
168  * The stack should represent the 32-bit calling convention.
250 	sgdtl	(efi32_boot_gdt - 1b)(%ebx)
251 	movw	%cs, (efi32_boot_cs - 1b)(%ebx)
252 	movw	%ds, (efi32_boot_ds - 1b)(%ebx)
255 	sidtl	(efi32_boot_idt - 1b)(%ebx)
258 	leal	(efi32_boot_args - 1b)(%ebx), %ebx
279 	pushl	%ebx				// save callee-save registers
293 2:	popl	%edi				// restore callee-save registers