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-rw-r--r--Documentation/efi-stub.txt12
1 files changed, 9 insertions, 3 deletions
diff --git a/Documentation/efi-stub.txt b/Documentation/efi-stub.txt
index 26be7b02a164..7747024d3bb7 100644
--- a/Documentation/efi-stub.txt
+++ b/Documentation/efi-stub.txt
@@ -12,6 +12,11 @@ arch/arm/boot/compressed/efi-header.S and
12arch/arm/boot/compressed/efi-stub.c. EFI stub code that is shared 12arch/arm/boot/compressed/efi-stub.c. EFI stub code that is shared
13between architectures is in drivers/firmware/efi/efi-stub-helper.c. 13between architectures is in drivers/firmware/efi/efi-stub-helper.c.
14 14
15For arm64, there is no compressed kernel support, so the Image itself
16masquerades as a PE/COFF image and the EFI stub is linked into the
17kernel. The arm64 EFI stub lives in arch/arm64/kernel/efi-entry.S
18and arch/arm64/kernel/efi-stub.c.
19
15By using the EFI boot stub it's possible to boot a Linux kernel 20By using the EFI boot stub it's possible to boot a Linux kernel
16without the use of a conventional EFI boot loader, such as grub or 21without the use of a conventional EFI boot loader, such as grub or
17elilo. Since the EFI boot stub performs the jobs of a boot loader, in 22elilo. Since the EFI boot stub performs the jobs of a boot loader, in
@@ -28,7 +33,8 @@ the extension the EFI firmware loader will refuse to execute it. It's
28not possible to execute bzImage.efi from the usual Linux file systems 33not possible to execute bzImage.efi from the usual Linux file systems
29because EFI firmware doesn't have support for them. For ARM the 34because EFI firmware doesn't have support for them. For ARM the
30arch/arm/boot/zImage should be copied to the system partition, and it 35arch/arm/boot/zImage should be copied to the system partition, and it
31may not need to be renamed. 36may not need to be renamed. Similarly for arm64, arch/arm64/boot/Image
37should be copied but not necessarily renamed.
32 38
33 39
34**** Passing kernel parameters from the EFI shell 40**** Passing kernel parameters from the EFI shell
@@ -72,7 +78,7 @@ is passed to bzImage.efi.
72 78
73**** The "dtb=" option 79**** The "dtb=" option
74 80
75For the ARM architecture, we also need to be able to provide a device 81For the ARM and arm64 architectures, we also need to be able to provide a
76tree to the kernel. This is done with the "dtb=" command line option, 82device tree to the kernel. This is done with the "dtb=" command line option,
77and is processed in the same manner as the "initrd=" option that is 83and is processed in the same manner as the "initrd=" option that is
78described above. 84described above.