| Message ID | 20221129175616.2089294-3-ardb@kernel.org |
|---|---|
| State | Accepted |
| Commit | 29636a5ce87bebab38c533175d72bb800a7581b8 |
| Headers | show |
| Series | efi: Add generic magic number in header | expand |
On Tue, Nov 29, 2022 at 06:56:16PM +0100, Ard Biesheuvel wrote: > GRUB currently relies on the magic number in the image header of ARM and > arm64 EFI kernel images to decide whether or not the image in question > is a bootable kernel. > > However, the purpose of the magic number is to identify the image as one > that implements the bare metal boot protocol, and so GRUB, which only > does EFI boot, can only boot images that could potentially be booted in > a non-EFI manner as well. > > This is problematic for the new zboot decompressor image format, as it > can only boot in EFI mode, and must therefore not use the bare metal > boot magic number in its header. > > For this reason, the strict magic number was dropped from GRUB, to > permit essentially any kind of EFI executable to be booted via the > 'linux' command, blurring the line between the linux loader and the > chainloader. > > So let's use the same field in the DOS header that RISC-V and arm64 > already use for their 'bare metal' magic numbers to store a 'generic > Linux kernel' magic number, which can be used to identify bootable > kernel images in PE format which don't necessarily implement a bare > metal boot protocol in the same binary. Note that, in the context of > EFI, the MSDOS header is only described in terms of the fields that it s/MSDOS/MS-DOS/ to be consistent with other places in the patch... > shares with the hybrid PE/COFF image format, (i.e., the magic number at > offset #0 and the PE header offset at byte offset #0x3c). Since we aim s/the magic number at offset #0/MS-DOS EXE magic number at offset #0/? "the magic number at offset #0" itself is confusing in the context of number of "magic number" phrases in the patch... :-) > for compatibility with EFI only, and not with MS-DOS or MS-Windows, we > can use the remaining space in the MS-DOS header however we want. > > Let's set the generic magic number for x86 images as well: existing > bootloaders already have their own methods to identify x86 Linux images > that can be booted in a non-EFI manner, and having the magic number in > place there will ease any future transitions in loader implementations > to merge the x86 and non-x86 EFI boot paths. > > Note that 32-bit ARM already uses the same location in the header for a > different purpose, but the ARM support is already widely implemented and > the EFI zboot decompressor is not available on ARM anyway, so we just > disregard it here. > > Cc: Huacai Chen <chenhuacai@kernel.org> > Cc: Atish Patra <atishp@rivosinc.com> > Cc: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> > Cc: Daniel Kiper <daniel.kiper@oracle.com> > Cc: Leif Lindholm <quic_llindhol@quicinc.com> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > --- > arch/loongarch/kernel/head.S | 3 ++- > arch/x86/boot/header.S | 3 ++- > drivers/firmware/efi/libstub/zboot-header.S | 3 ++- > include/linux/pe.h | 7 +++++++ > 4 files changed, 13 insertions(+), 3 deletions(-) > > diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S > index 84970e2666588963..caa74439700eee93 100644 > --- a/arch/loongarch/kernel/head.S > +++ b/arch/loongarch/kernel/head.S > @@ -25,7 +25,8 @@ _head: > .dword kernel_entry /* Kernel entry point */ > .dword _end - _text /* Kernel image effective size */ > .quad 0 /* Kernel image load offset from start of RAM */ > - .org 0x3c /* 0x20 ~ 0x3b reserved */ > + .org 0x38 /* 0x20 ~ 0x38 reserved */ > + .long LINUX_PE_MAGIC > .long pe_header - _head /* Offset to the PE header */ > > pe_header: > diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S > index f912d777013052ea..be8f78a7ee325475 100644 > --- a/arch/x86/boot/header.S > +++ b/arch/x86/boot/header.S > @@ -80,10 +80,11 @@ bs_die: > ljmp $0xf000,$0xfff0 > > #ifdef CONFIG_EFI_STUB > - .org 0x3c > + .org 0x38 > # > # Offset to the PE header. > # > + .long LINUX_PE_MAGIC > .long pe_header > #endif /* CONFIG_EFI_STUB */ > > diff --git a/drivers/firmware/efi/libstub/zboot-header.S b/drivers/firmware/efi/libstub/zboot-header.S > index bc2d7750d7f14174..ec4525d40e0cf6d6 100644 > --- a/drivers/firmware/efi/libstub/zboot-header.S > +++ b/drivers/firmware/efi/libstub/zboot-header.S > @@ -20,7 +20,8 @@ __efistub_efi_zboot_header: > .long __efistub__gzdata_size - 12 // payload size > .long 0, 0 // reserved > .asciz COMP_TYPE // compression type > - .org .Ldoshdr + 0x3c > + .org .Ldoshdr + 0x38 > + .long LINUX_PE_MAGIC > .long .Lpehdr - .Ldoshdr // PE header offset > > .Lpehdr: > diff --git a/include/linux/pe.h b/include/linux/pe.h > index 056a1762de904fc1..1db4c944efd78f51 100644 > --- a/include/linux/pe.h > +++ b/include/linux/pe.h > @@ -31,6 +31,13 @@ > #define LINUX_EFISTUB_MAJOR_VERSION 0x1 > #define LINUX_EFISTUB_MINOR_VERSION 0x1 > > +/* > + * LINUX_PE_MAGIC appears at offset 0x38 into the MSDOS header of EFI bootable s/MSDOS/MS-DOS/ > + * Linux kernel images that target the architecture as specified by the PE/COFF > + * header machine type field. > + */ > +#define LINUX_PE_MAGIC 0x818223cd > + > #define MZ_MAGIC 0x5a4d /* "MZ" */ > > #define PE_MAGIC 0x00004550 /* "PE\0\0" */ If you take into account these minor things mentioned above you can add Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com> to your both patches. Atish, could you respin your GRUB "Unify ARM64 & RISC-V Linux Loader" patch set when both Ard's patches are in at least "efi" Linux kernel branch? Hmmm... I am not sure it will go through "efi" branch. Ard? Daniel
On Thu, 1 Dec 2022 at 15:30, Daniel Kiper <daniel.kiper@oracle.com> wrote: > > On Tue, Nov 29, 2022 at 06:56:16PM +0100, Ard Biesheuvel wrote: > > GRUB currently relies on the magic number in the image header of ARM and > > arm64 EFI kernel images to decide whether or not the image in question > > is a bootable kernel. > > > > However, the purpose of the magic number is to identify the image as one > > that implements the bare metal boot protocol, and so GRUB, which only > > does EFI boot, can only boot images that could potentially be booted in > > a non-EFI manner as well. > > > > This is problematic for the new zboot decompressor image format, as it > > can only boot in EFI mode, and must therefore not use the bare metal > > boot magic number in its header. > > > > For this reason, the strict magic number was dropped from GRUB, to > > permit essentially any kind of EFI executable to be booted via the > > 'linux' command, blurring the line between the linux loader and the > > chainloader. > > > > So let's use the same field in the DOS header that RISC-V and arm64 > > already use for their 'bare metal' magic numbers to store a 'generic > > Linux kernel' magic number, which can be used to identify bootable > > kernel images in PE format which don't necessarily implement a bare > > metal boot protocol in the same binary. Note that, in the context of > > EFI, the MSDOS header is only described in terms of the fields that it > > s/MSDOS/MS-DOS/ to be consistent with other places in the patch... > > > shares with the hybrid PE/COFF image format, (i.e., the magic number at > > offset #0 and the PE header offset at byte offset #0x3c). Since we aim > > s/the magic number at offset #0/MS-DOS EXE magic number at offset #0/? > > "the magic number at offset #0" itself is confusing in the context of > number of "magic number" phrases in the patch... :-) > > > for compatibility with EFI only, and not with MS-DOS or MS-Windows, we > > can use the remaining space in the MS-DOS header however we want. > > > > Let's set the generic magic number for x86 images as well: existing > > bootloaders already have their own methods to identify x86 Linux images > > that can be booted in a non-EFI manner, and having the magic number in > > place there will ease any future transitions in loader implementations > > to merge the x86 and non-x86 EFI boot paths. > > > > Note that 32-bit ARM already uses the same location in the header for a > > different purpose, but the ARM support is already widely implemented and > > the EFI zboot decompressor is not available on ARM anyway, so we just > > disregard it here. > > > > Cc: Huacai Chen <chenhuacai@kernel.org> > > Cc: Atish Patra <atishp@rivosinc.com> > > Cc: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> > > Cc: Daniel Kiper <daniel.kiper@oracle.com> > > Cc: Leif Lindholm <quic_llindhol@quicinc.com> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > --- > > arch/loongarch/kernel/head.S | 3 ++- > > arch/x86/boot/header.S | 3 ++- > > drivers/firmware/efi/libstub/zboot-header.S | 3 ++- > > include/linux/pe.h | 7 +++++++ > > 4 files changed, 13 insertions(+), 3 deletions(-) > > > > diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S > > index 84970e2666588963..caa74439700eee93 100644 > > --- a/arch/loongarch/kernel/head.S > > +++ b/arch/loongarch/kernel/head.S > > @@ -25,7 +25,8 @@ _head: > > .dword kernel_entry /* Kernel entry point */ > > .dword _end - _text /* Kernel image effective size */ > > .quad 0 /* Kernel image load offset from start of RAM */ > > - .org 0x3c /* 0x20 ~ 0x3b reserved */ > > + .org 0x38 /* 0x20 ~ 0x38 reserved */ > > + .long LINUX_PE_MAGIC > > .long pe_header - _head /* Offset to the PE header */ > > > > pe_header: > > diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S > > index f912d777013052ea..be8f78a7ee325475 100644 > > --- a/arch/x86/boot/header.S > > +++ b/arch/x86/boot/header.S > > @@ -80,10 +80,11 @@ bs_die: > > ljmp $0xf000,$0xfff0 > > > > #ifdef CONFIG_EFI_STUB > > - .org 0x3c > > + .org 0x38 > > # > > # Offset to the PE header. > > # > > + .long LINUX_PE_MAGIC > > .long pe_header > > #endif /* CONFIG_EFI_STUB */ > > > > diff --git a/drivers/firmware/efi/libstub/zboot-header.S b/drivers/firmware/efi/libstub/zboot-header.S > > index bc2d7750d7f14174..ec4525d40e0cf6d6 100644 > > --- a/drivers/firmware/efi/libstub/zboot-header.S > > +++ b/drivers/firmware/efi/libstub/zboot-header.S > > @@ -20,7 +20,8 @@ __efistub_efi_zboot_header: > > .long __efistub__gzdata_size - 12 // payload size > > .long 0, 0 // reserved > > .asciz COMP_TYPE // compression type > > - .org .Ldoshdr + 0x3c > > + .org .Ldoshdr + 0x38 > > + .long LINUX_PE_MAGIC > > .long .Lpehdr - .Ldoshdr // PE header offset > > > > .Lpehdr: > > diff --git a/include/linux/pe.h b/include/linux/pe.h > > index 056a1762de904fc1..1db4c944efd78f51 100644 > > --- a/include/linux/pe.h > > +++ b/include/linux/pe.h > > @@ -31,6 +31,13 @@ > > #define LINUX_EFISTUB_MAJOR_VERSION 0x1 > > #define LINUX_EFISTUB_MINOR_VERSION 0x1 > > > > +/* > > + * LINUX_PE_MAGIC appears at offset 0x38 into the MSDOS header of EFI bootable > > s/MSDOS/MS-DOS/ > > > + * Linux kernel images that target the architecture as specified by the PE/COFF > > + * header machine type field. > > + */ > > +#define LINUX_PE_MAGIC 0x818223cd > > + > > #define MZ_MAGIC 0x5a4d /* "MZ" */ > > > > #define PE_MAGIC 0x00004550 /* "PE\0\0" */ > > If you take into account these minor things mentioned above you can add > Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com> to your both patches. > Thanks > Atish, could you respin your GRUB "Unify ARM64 & RISC-V Linux Loader" > patch set when both Ard's patches are in at least "efi" Linux kernel > branch? Hmmm... I am not sure it will go through "efi" branch. Ard? > Yes, I already pushed a version, but I will update the patch to take your feedback into account. The patch is queued up for v6.2, so it should be in mainline by the end of the year.
On Thu, Dec 01, 2022 at 03:48:12PM +0100, Ard Biesheuvel wrote: > On Thu, 1 Dec 2022 at 15:30, Daniel Kiper <daniel.kiper@oracle.com> wrote: > > On Tue, Nov 29, 2022 at 06:56:16PM +0100, Ard Biesheuvel wrote: > > > GRUB currently relies on the magic number in the image header of ARM and > > > arm64 EFI kernel images to decide whether or not the image in question > > > is a bootable kernel. > > > > > > However, the purpose of the magic number is to identify the image as one > > > that implements the bare metal boot protocol, and so GRUB, which only > > > does EFI boot, can only boot images that could potentially be booted in > > > a non-EFI manner as well. > > > > > > This is problematic for the new zboot decompressor image format, as it > > > can only boot in EFI mode, and must therefore not use the bare metal > > > boot magic number in its header. > > > > > > For this reason, the strict magic number was dropped from GRUB, to > > > permit essentially any kind of EFI executable to be booted via the > > > 'linux' command, blurring the line between the linux loader and the > > > chainloader. > > > > > > So let's use the same field in the DOS header that RISC-V and arm64 > > > already use for their 'bare metal' magic numbers to store a 'generic > > > Linux kernel' magic number, which can be used to identify bootable > > > kernel images in PE format which don't necessarily implement a bare > > > metal boot protocol in the same binary. Note that, in the context of > > > EFI, the MSDOS header is only described in terms of the fields that it > > > > s/MSDOS/MS-DOS/ to be consistent with other places in the patch... > > > > > shares with the hybrid PE/COFF image format, (i.e., the magic number at > > > offset #0 and the PE header offset at byte offset #0x3c). Since we aim > > > > s/the magic number at offset #0/MS-DOS EXE magic number at offset #0/? > > > > "the magic number at offset #0" itself is confusing in the context of > > number of "magic number" phrases in the patch... :-) > > > > > for compatibility with EFI only, and not with MS-DOS or MS-Windows, we > > > can use the remaining space in the MS-DOS header however we want. > > > > > > Let's set the generic magic number for x86 images as well: existing > > > bootloaders already have their own methods to identify x86 Linux images > > > that can be booted in a non-EFI manner, and having the magic number in > > > place there will ease any future transitions in loader implementations > > > to merge the x86 and non-x86 EFI boot paths. > > > > > > Note that 32-bit ARM already uses the same location in the header for a > > > different purpose, but the ARM support is already widely implemented and > > > the EFI zboot decompressor is not available on ARM anyway, so we just > > > disregard it here. > > > > > > Cc: Huacai Chen <chenhuacai@kernel.org> > > > Cc: Atish Patra <atishp@rivosinc.com> > > > Cc: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> > > > Cc: Daniel Kiper <daniel.kiper@oracle.com> > > > Cc: Leif Lindholm <quic_llindhol@quicinc.com> > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > > --- > > > arch/loongarch/kernel/head.S | 3 ++- > > > arch/x86/boot/header.S | 3 ++- > > > drivers/firmware/efi/libstub/zboot-header.S | 3 ++- > > > include/linux/pe.h | 7 +++++++ > > > 4 files changed, 13 insertions(+), 3 deletions(-) > > > > > > diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S > > > index 84970e2666588963..caa74439700eee93 100644 > > > --- a/arch/loongarch/kernel/head.S > > > +++ b/arch/loongarch/kernel/head.S > > > @@ -25,7 +25,8 @@ _head: > > > .dword kernel_entry /* Kernel entry point */ > > > .dword _end - _text /* Kernel image effective size */ > > > .quad 0 /* Kernel image load offset from start of RAM */ > > > - .org 0x3c /* 0x20 ~ 0x3b reserved */ > > > + .org 0x38 /* 0x20 ~ 0x38 reserved */ > > > + .long LINUX_PE_MAGIC > > > .long pe_header - _head /* Offset to the PE header */ > > > > > > pe_header: > > > diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S > > > index f912d777013052ea..be8f78a7ee325475 100644 > > > --- a/arch/x86/boot/header.S > > > +++ b/arch/x86/boot/header.S > > > @@ -80,10 +80,11 @@ bs_die: > > > ljmp $0xf000,$0xfff0 > > > > > > #ifdef CONFIG_EFI_STUB > > > - .org 0x3c > > > + .org 0x38 > > > # > > > # Offset to the PE header. > > > # > > > + .long LINUX_PE_MAGIC > > > .long pe_header > > > #endif /* CONFIG_EFI_STUB */ > > > > > > diff --git a/drivers/firmware/efi/libstub/zboot-header.S b/drivers/firmware/efi/libstub/zboot-header.S > > > index bc2d7750d7f14174..ec4525d40e0cf6d6 100644 > > > --- a/drivers/firmware/efi/libstub/zboot-header.S > > > +++ b/drivers/firmware/efi/libstub/zboot-header.S > > > @@ -20,7 +20,8 @@ __efistub_efi_zboot_header: > > > .long __efistub__gzdata_size - 12 // payload size > > > .long 0, 0 // reserved > > > .asciz COMP_TYPE // compression type > > > - .org .Ldoshdr + 0x3c > > > + .org .Ldoshdr + 0x38 > > > + .long LINUX_PE_MAGIC > > > .long .Lpehdr - .Ldoshdr // PE header offset > > > > > > .Lpehdr: > > > diff --git a/include/linux/pe.h b/include/linux/pe.h > > > index 056a1762de904fc1..1db4c944efd78f51 100644 > > > --- a/include/linux/pe.h > > > +++ b/include/linux/pe.h > > > @@ -31,6 +31,13 @@ > > > #define LINUX_EFISTUB_MAJOR_VERSION 0x1 > > > #define LINUX_EFISTUB_MINOR_VERSION 0x1 > > > > > > +/* > > > + * LINUX_PE_MAGIC appears at offset 0x38 into the MSDOS header of EFI bootable > > > > s/MSDOS/MS-DOS/ > > > > > + * Linux kernel images that target the architecture as specified by the PE/COFF > > > + * header machine type field. > > > + */ > > > +#define LINUX_PE_MAGIC 0x818223cd > > > + > > > #define MZ_MAGIC 0x5a4d /* "MZ" */ > > > > > > #define PE_MAGIC 0x00004550 /* "PE\0\0" */ > > > > If you take into account these minor things mentioned above you can add > > Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com> to your both patches. > > Thanks You are welcome! > > Atish, could you respin your GRUB "Unify ARM64 & RISC-V Linux Loader" > > patch set when both Ard's patches are in at least "efi" Linux kernel > > branch? Hmmm... I am not sure it will go through "efi" branch. Ard? > > Yes, I already pushed a version, but I will update the patch to take > your feedback into account. Great! > The patch is queued up for v6.2, so it should be in mainline by the > end of the year. Cool! Thanks a lot! Daniel
On Thu, Dec 01, 2022 at 03:48:12PM +0100, Ard Biesheuvel wrote: > On Thu, 1 Dec 2022 at 15:30, Daniel Kiper <daniel.kiper@oracle.com> wrote: > > > > On Tue, Nov 29, 2022 at 06:56:16PM +0100, Ard Biesheuvel wrote: > > > GRUB currently relies on the magic number in the image header of ARM and > > > arm64 EFI kernel images to decide whether or not the image in question > > > is a bootable kernel. > > > > > > However, the purpose of the magic number is to identify the image as one > > > that implements the bare metal boot protocol, and so GRUB, which only > > > does EFI boot, can only boot images that could potentially be booted in > > > a non-EFI manner as well. > > > > > > This is problematic for the new zboot decompressor image format, as it > > > can only boot in EFI mode, and must therefore not use the bare metal > > > boot magic number in its header. > > > > > > For this reason, the strict magic number was dropped from GRUB, to > > > permit essentially any kind of EFI executable to be booted via the > > > 'linux' command, blurring the line between the linux loader and the > > > chainloader. > > > > > > So let's use the same field in the DOS header that RISC-V and arm64 > > > already use for their 'bare metal' magic numbers to store a 'generic > > > Linux kernel' magic number, which can be used to identify bootable > > > kernel images in PE format which don't necessarily implement a bare > > > metal boot protocol in the same binary. Note that, in the context of > > > EFI, the MSDOS header is only described in terms of the fields that it > > > > s/MSDOS/MS-DOS/ to be consistent with other places in the patch... > > > > > shares with the hybrid PE/COFF image format, (i.e., the magic number at > > > offset #0 and the PE header offset at byte offset #0x3c). Since we aim > > > > s/the magic number at offset #0/MS-DOS EXE magic number at offset #0/? > > > > "the magic number at offset #0" itself is confusing in the context of > > number of "magic number" phrases in the patch... :-) > > > > > for compatibility with EFI only, and not with MS-DOS or MS-Windows, we > > > can use the remaining space in the MS-DOS header however we want. > > > > > > Let's set the generic magic number for x86 images as well: existing > > > bootloaders already have their own methods to identify x86 Linux images > > > that can be booted in a non-EFI manner, and having the magic number in > > > place there will ease any future transitions in loader implementations > > > to merge the x86 and non-x86 EFI boot paths. > > > > > > Note that 32-bit ARM already uses the same location in the header for a > > > different purpose, but the ARM support is already widely implemented and > > > the EFI zboot decompressor is not available on ARM anyway, so we just > > > disregard it here. > > > > > > Cc: Huacai Chen <chenhuacai@kernel.org> > > > Cc: Atish Patra <atishp@rivosinc.com> > > > Cc: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> > > > Cc: Daniel Kiper <daniel.kiper@oracle.com> > > > Cc: Leif Lindholm <quic_llindhol@quicinc.com> > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > > --- > > > arch/loongarch/kernel/head.S | 3 ++- > > > arch/x86/boot/header.S | 3 ++- > > > drivers/firmware/efi/libstub/zboot-header.S | 3 ++- > > > include/linux/pe.h | 7 +++++++ > > > 4 files changed, 13 insertions(+), 3 deletions(-) > > > > > > diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S > > > index 84970e2666588963..caa74439700eee93 100644 > > > --- a/arch/loongarch/kernel/head.S > > > +++ b/arch/loongarch/kernel/head.S > > > @@ -25,7 +25,8 @@ _head: > > > .dword kernel_entry /* Kernel entry point */ > > > .dword _end - _text /* Kernel image effective size */ > > > .quad 0 /* Kernel image load offset from start of RAM */ > > > - .org 0x3c /* 0x20 ~ 0x3b reserved */ > > > + .org 0x38 /* 0x20 ~ 0x38 reserved */ Sadly one more thing... :-( s/0x20 ~ 0x38 reserved/0x20 ~ 0x37 reserved/ Daniel
On Thu, Dec 1, 2022 at 6:30 AM Daniel Kiper <daniel.kiper@oracle.com> wrote: > > On Tue, Nov 29, 2022 at 06:56:16PM +0100, Ard Biesheuvel wrote: > > GRUB currently relies on the magic number in the image header of ARM and > > arm64 EFI kernel images to decide whether or not the image in question > > is a bootable kernel. > > > > However, the purpose of the magic number is to identify the image as one > > that implements the bare metal boot protocol, and so GRUB, which only > > does EFI boot, can only boot images that could potentially be booted in > > a non-EFI manner as well. > > > > This is problematic for the new zboot decompressor image format, as it > > can only boot in EFI mode, and must therefore not use the bare metal > > boot magic number in its header. > > > > For this reason, the strict magic number was dropped from GRUB, to > > permit essentially any kind of EFI executable to be booted via the > > 'linux' command, blurring the line between the linux loader and the > > chainloader. > > > > So let's use the same field in the DOS header that RISC-V and arm64 > > already use for their 'bare metal' magic numbers to store a 'generic > > Linux kernel' magic number, which can be used to identify bootable > > kernel images in PE format which don't necessarily implement a bare > > metal boot protocol in the same binary. Note that, in the context of > > EFI, the MSDOS header is only described in terms of the fields that it > > s/MSDOS/MS-DOS/ to be consistent with other places in the patch... > > > shares with the hybrid PE/COFF image format, (i.e., the magic number at > > offset #0 and the PE header offset at byte offset #0x3c). Since we aim > > s/the magic number at offset #0/MS-DOS EXE magic number at offset #0/? > > "the magic number at offset #0" itself is confusing in the context of > number of "magic number" phrases in the patch... :-) > > > for compatibility with EFI only, and not with MS-DOS or MS-Windows, we > > can use the remaining space in the MS-DOS header however we want. > > > > Let's set the generic magic number for x86 images as well: existing > > bootloaders already have their own methods to identify x86 Linux images > > that can be booted in a non-EFI manner, and having the magic number in > > place there will ease any future transitions in loader implementations > > to merge the x86 and non-x86 EFI boot paths. > > > > Note that 32-bit ARM already uses the same location in the header for a > > different purpose, but the ARM support is already widely implemented and > > the EFI zboot decompressor is not available on ARM anyway, so we just > > disregard it here. > > > > Cc: Huacai Chen <chenhuacai@kernel.org> > > Cc: Atish Patra <atishp@rivosinc.com> > > Cc: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> > > Cc: Daniel Kiper <daniel.kiper@oracle.com> > > Cc: Leif Lindholm <quic_llindhol@quicinc.com> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > --- > > arch/loongarch/kernel/head.S | 3 ++- > > arch/x86/boot/header.S | 3 ++- > > drivers/firmware/efi/libstub/zboot-header.S | 3 ++- > > include/linux/pe.h | 7 +++++++ > > 4 files changed, 13 insertions(+), 3 deletions(-) > > > > diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S > > index 84970e2666588963..caa74439700eee93 100644 > > --- a/arch/loongarch/kernel/head.S > > +++ b/arch/loongarch/kernel/head.S > > @@ -25,7 +25,8 @@ _head: > > .dword kernel_entry /* Kernel entry point */ > > .dword _end - _text /* Kernel image effective size */ > > .quad 0 /* Kernel image load offset from start of RAM */ > > - .org 0x3c /* 0x20 ~ 0x3b reserved */ > > + .org 0x38 /* 0x20 ~ 0x38 reserved */ > > + .long LINUX_PE_MAGIC > > .long pe_header - _head /* Offset to the PE header */ > > > > pe_header: > > diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S > > index f912d777013052ea..be8f78a7ee325475 100644 > > --- a/arch/x86/boot/header.S > > +++ b/arch/x86/boot/header.S > > @@ -80,10 +80,11 @@ bs_die: > > ljmp $0xf000,$0xfff0 > > > > #ifdef CONFIG_EFI_STUB > > - .org 0x3c > > + .org 0x38 > > # > > # Offset to the PE header. > > # > > + .long LINUX_PE_MAGIC > > .long pe_header > > #endif /* CONFIG_EFI_STUB */ > > > > diff --git a/drivers/firmware/efi/libstub/zboot-header.S b/drivers/firmware/efi/libstub/zboot-header.S > > index bc2d7750d7f14174..ec4525d40e0cf6d6 100644 > > --- a/drivers/firmware/efi/libstub/zboot-header.S > > +++ b/drivers/firmware/efi/libstub/zboot-header.S > > @@ -20,7 +20,8 @@ __efistub_efi_zboot_header: > > .long __efistub__gzdata_size - 12 // payload size > > .long 0, 0 // reserved > > .asciz COMP_TYPE // compression type > > - .org .Ldoshdr + 0x3c > > + .org .Ldoshdr + 0x38 > > + .long LINUX_PE_MAGIC > > .long .Lpehdr - .Ldoshdr // PE header offset > > > > .Lpehdr: > > diff --git a/include/linux/pe.h b/include/linux/pe.h > > index 056a1762de904fc1..1db4c944efd78f51 100644 > > --- a/include/linux/pe.h > > +++ b/include/linux/pe.h > > @@ -31,6 +31,13 @@ > > #define LINUX_EFISTUB_MAJOR_VERSION 0x1 > > #define LINUX_EFISTUB_MINOR_VERSION 0x1 > > > > +/* > > + * LINUX_PE_MAGIC appears at offset 0x38 into the MSDOS header of EFI bootable > > s/MSDOS/MS-DOS/ > > > + * Linux kernel images that target the architecture as specified by the PE/COFF > > + * header machine type field. > > + */ > > +#define LINUX_PE_MAGIC 0x818223cd > > + > > #define MZ_MAGIC 0x5a4d /* "MZ" */ > > > > #define PE_MAGIC 0x00004550 /* "PE\0\0" */ > > If you take into account these minor things mentioned above you can add > Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com> to your both patches. > > Atish, could you respin your GRUB "Unify ARM64 & RISC-V Linux Loader" > patch set when both Ard's patches are in at least "efi" Linux kernel > branch? Hmmm... I am not sure it will go through "efi" branch. Ard? > Sure. We need to remove the arch specific header files in the next version as well. I am planning to revise the series before/during the holidays. Hope that's fine w.r.t Grub release. Otherwise, please let me know. > Daniel
On Wed, 7 Dec 2022 at 08:51, Xiaotian Wu <wuxiaotian@loongson.cn> wrote: > > 在 2022-11-29星期二的 18:56 +0100，Ard Biesheuvel写道： > > GRUB currently relies on the magic number in the image header of ARM > > and > > arm64 EFI kernel images to decide whether or not the image in > > question > > is a bootable kernel. > > > > However, the purpose of the magic number is to identify the image as > > one > > that implements the bare metal boot protocol, and so GRUB, which only > > does EFI boot, can only boot images that could potentially be booted > > in > > a non-EFI manner as well. > > > > This is problematic for the new zboot decompressor image format, as > > it > > can only boot in EFI mode, and must therefore not use the bare metal > > boot magic number in its header. > > > > For this reason, the strict magic number was dropped from GRUB, to > > permit essentially any kind of EFI executable to be booted via the > > 'linux' command, blurring the line between the linux loader and the > > chainloader. > > > > So let's use the same field in the DOS header that RISC-V and arm64 > > already use for their 'bare metal' magic numbers to store a 'generic > > Linux kernel' magic number, which can be used to identify bootable > > kernel images in PE format which don't necessarily implement a bare > > metal boot protocol in the same binary. Note that, in the context of > > EFI, the MSDOS header is only described in terms of the fields that > > it > > shares with the hybrid PE/COFF image format, (i.e., the magic number > > at > > offset #0 and the PE header offset at byte offset #0x3c). Since we > > aim > > for compatibility with EFI only, and not with MS-DOS or MS-Windows, > > we > > can use the remaining space in the MS-DOS header however we want. > > > > Let's set the generic magic number for x86 images as well: existing > > bootloaders already have their own methods to identify x86 Linux > > images > > that can be booted in a non-EFI manner, and having the magic number > > in > > place there will ease any future transitions in loader > > implementations > > to merge the x86 and non-x86 EFI boot paths. > > > > Note that 32-bit ARM already uses the same location in the header for > > a > > different purpose, but the ARM support is already widely implemented > > and > > the EFI zboot decompressor is not available on ARM anyway, so we just > > disregard it here. > > > > Cc: Huacai Chen <chenhuacai@kernel.org> > > Cc: Atish Patra <atishp@rivosinc.com> > > Cc: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> > > Cc: Daniel Kiper <daniel.kiper@oracle.com> > > Cc: Leif Lindholm <quic_llindhol@quicinc.com> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > --- > > arch/loongarch/kernel/head.S | 3 ++- > > arch/x86/boot/header.S | 3 ++- > > drivers/firmware/efi/libstub/zboot-header.S | 3 ++- > > include/linux/pe.h | 7 +++++++ > > 4 files changed, 13 insertions(+), 3 deletions(-) > > > > diff --git a/arch/loongarch/kernel/head.S > > b/arch/loongarch/kernel/head.S > > index 84970e2666588963..caa74439700eee93 100644 > > --- a/arch/loongarch/kernel/head.S > > +++ b/arch/loongarch/kernel/head.S > > @@ -25,7 +25,8 @@ _head: > > .dword kernel_entry /* Kernel entry point */ > > .dword _end - _text /* Kernel image effective > > size */ > > .quad 0 /* Kernel image load offset > > from start of RAM */ > > - .org 0x3c /* 0x20 ~ 0x3b reserved */ > > + .org 0x38 /* 0x20 ~ 0x38 reserved */ > > + .long LINUX_PE_MAGIC > > .long pe_header - _head /* Offset to the PE header */ > > > > pe_header: > > diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S > > index f912d777013052ea..be8f78a7ee325475 100644 > > --- a/arch/x86/boot/header.S > > +++ b/arch/x86/boot/header.S > > @@ -80,10 +80,11 @@ bs_die: > > ljmp $0xf000,$0xfff0 > > > > #ifdef CONFIG_EFI_STUB > > - .org 0x3c > > + .org 0x38 > > # > > # Offset to the PE header. > > # > > + .long LINUX_PE_MAGIC > > .long pe_header > > #endif /* CONFIG_EFI_STUB */ > > > > diff --git a/drivers/firmware/efi/libstub/zboot-header.S > > b/drivers/firmware/efi/libstub/zboot-header.S > > index bc2d7750d7f14174..ec4525d40e0cf6d6 100644 > > --- a/drivers/firmware/efi/libstub/zboot-header.S > > +++ b/drivers/firmware/efi/libstub/zboot-header.S > > @@ -20,7 +20,8 @@ __efistub_efi_zboot_header: > > .long __efistub__gzdata_size - 12 // > > payload size > > .long 0, 0 // > > reserved > > .asciz COMP_TYPE // > > compression type > > - .org .Ldoshdr + 0x3c > > + .org .Ldoshdr + 0x38 > > + .long LINUX_PE_MAGIC > > .long .Lpehdr - .Ldoshdr // PE > > header offset > > > > .Lpehdr: > > diff --git a/include/linux/pe.h b/include/linux/pe.h > > index 056a1762de904fc1..1db4c944efd78f51 100644 > > --- a/include/linux/pe.h > > +++ b/include/linux/pe.h > > @@ -31,6 +31,13 @@ > > #define LINUX_EFISTUB_MAJOR_VERSION 0x1 > > #define LINUX_EFISTUB_MINOR_VERSION 0x1 > > > > +/* > > + * LINUX_PE_MAGIC appears at offset 0x38 into the MSDOS header of > > EFI bootable > > + * Linux kernel images that target the architecture as specified by > > the PE/COFF > > + * header machine type field. > > + */ > > +#define LINUX_PE_MAGIC 0x818223cd > > + > > #define MZ_MAGIC 0x5a4d /* "MZ" */ > > > > #define PE_MAGIC 0x00004550 /* "PE\0\0" */ > > > As far as I know, Archlinux automatically generates initramfs according > to the version number in the kernel file. The latest generic compressed > EFI designs do not seem to provide kernel version number information. No, but nor do the gzip'ed images arm64 uses today, and the script seems take care of that. The EFI zboot image has metadata in the header, so the script can decompress it and grep for the version number it it needs to. > This may change the usage habits of Archlinux users. Is it possible to > add the kernel version number to vmlinuz.efi? > > https://gitlab.archlinux.org/archlinux/mkinitcpio/mkinitcpio/-/blob/master/functions#L209 > The current header doesn't have that so I don't think EFI zboot should be adding it either.
在 2022-12-07星期三的 09:06 +0100，Ard Biesheuvel写道： > On Wed, 7 Dec 2022 at 08:51, Xiaotian Wu <wuxiaotian@loongson.cn> > wrote: > > > > 在 2022-11-29星期二的 18:56 +0100，Ard Biesheuvel写道： > > > GRUB currently relies on the magic number in the image header of > > > ARM > > > and > > > arm64 EFI kernel images to decide whether or not the image in > > > question > > > is a bootable kernel. > > > > > > However, the purpose of the magic number is to identify the image > > > as > > > one > > > that implements the bare metal boot protocol, and so GRUB, which > > > only > > > does EFI boot, can only boot images that could potentially be > > > booted > > > in > > > a non-EFI manner as well. > > > > > > This is problematic for the new zboot decompressor image format, > > > as > > > it > > > can only boot in EFI mode, and must therefore not use the bare > > > metal > > > boot magic number in its header. > > > > > > For this reason, the strict magic number was dropped from GRUB, > > > to > > > permit essentially any kind of EFI executable to be booted via > > > the > > > 'linux' command, blurring the line between the linux loader and > > > the > > > chainloader. > > > > > > So let's use the same field in the DOS header that RISC-V and > > > arm64 > > > already use for their 'bare metal' magic numbers to store a > > > 'generic > > > Linux kernel' magic number, which can be used to identify > > > bootable > > > kernel images in PE format which don't necessarily implement a > > > bare > > > metal boot protocol in the same binary. Note that, in the context > > > of > > > EFI, the MSDOS header is only described in terms of the fields > > > that > > > it > > > shares with the hybrid PE/COFF image format, (i.e., the magic > > > number > > > at > > > offset #0 and the PE header offset at byte offset #0x3c). Since > > > we > > > aim > > > for compatibility with EFI only, and not with MS-DOS or MS- > > > Windows, > > > we > > > can use the remaining space in the MS-DOS header however we want. > > > > > > Let's set the generic magic number for x86 images as well: > > > existing > > > bootloaders already have their own methods to identify x86 Linux > > > images > > > that can be booted in a non-EFI manner, and having the magic > > > number > > > in > > > place there will ease any future transitions in loader > > > implementations > > > to merge the x86 and non-x86 EFI boot paths. > > > > > > Note that 32-bit ARM already uses the same location in the header > > > for > > > a > > > different purpose, but the ARM support is already widely > > > implemented > > > and > > > the EFI zboot decompressor is not available on ARM anyway, so we > > > just > > > disregard it here. > > > > > > Cc: Huacai Chen <chenhuacai@kernel.org> > > > Cc: Atish Patra <atishp@rivosinc.com> > > > Cc: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> > > > Cc: Daniel Kiper <daniel.kiper@oracle.com> > > > Cc: Leif Lindholm <quic_llindhol@quicinc.com> > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > > --- > > > arch/loongarch/kernel/head.S | 3 ++- > > > arch/x86/boot/header.S | 3 ++- > > > drivers/firmware/efi/libstub/zboot-header.S | 3 ++- > > > include/linux/pe.h | 7 +++++++ > > > 4 files changed, 13 insertions(+), 3 deletions(-) > > > > > > diff --git a/arch/loongarch/kernel/head.S > > > b/arch/loongarch/kernel/head.S > > > index 84970e2666588963..caa74439700eee93 100644 > > > --- a/arch/loongarch/kernel/head.S > > > +++ b/arch/loongarch/kernel/head.S > > > @@ -25,7 +25,8 @@ _head: > > > .dword kernel_entry /* Kernel entry point */ > > > .dword _end - _text /* Kernel image effective > > > size */ > > > .quad 0 /* Kernel image load > > > offset > > > from start of RAM */ > > > - .org 0x3c /* 0x20 ~ 0x3b reserved > > > */ > > > + .org 0x38 /* 0x20 ~ 0x38 reserved > > > */ > > > + .long LINUX_PE_MAGIC > > > .long pe_header - _head /* Offset to the PE > > > header */ > > > > > > pe_header: > > > diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S > > > index f912d777013052ea..be8f78a7ee325475 100644 > > > --- a/arch/x86/boot/header.S > > > +++ b/arch/x86/boot/header.S > > > @@ -80,10 +80,11 @@ bs_die: > > > ljmp $0xf000,$0xfff0 > > > > > > #ifdef CONFIG_EFI_STUB > > > - .org 0x3c > > > + .org 0x38 > > > # > > > # Offset to the PE header. > > > # > > > + .long LINUX_PE_MAGIC > > > .long pe_header > > > #endif /* CONFIG_EFI_STUB */ > > > > > > diff --git a/drivers/firmware/efi/libstub/zboot-header.S > > > b/drivers/firmware/efi/libstub/zboot-header.S > > > index bc2d7750d7f14174..ec4525d40e0cf6d6 100644 > > > --- a/drivers/firmware/efi/libstub/zboot-header.S > > > +++ b/drivers/firmware/efi/libstub/zboot-header.S > > > @@ -20,7 +20,8 @@ __efistub_efi_zboot_header: > > > .long __efistub__gzdata_size - 12 > > > // > > > payload size > > > .long 0, 0 > > > // > > > reserved > > > .asciz COMP_TYPE > > > // > > > compression type > > > - .org .Ldoshdr + 0x3c > > > + .org .Ldoshdr + 0x38 > > > + .long LINUX_PE_MAGIC > > > .long .Lpehdr - .Ldoshdr > > > // PE > > > header offset > > > > > > .Lpehdr: > > > diff --git a/include/linux/pe.h b/include/linux/pe.h > > > index 056a1762de904fc1..1db4c944efd78f51 100644 > > > --- a/include/linux/pe.h > > > +++ b/include/linux/pe.h > > > @@ -31,6 +31,13 @@ > > > #define LINUX_EFISTUB_MAJOR_VERSION 0x1 > > > #define LINUX_EFISTUB_MINOR_VERSION 0x1 > > > > > > +/* > > > + * LINUX_PE_MAGIC appears at offset 0x38 into the MSDOS header > > > of > > > EFI bootable > > > + * Linux kernel images that target the architecture as specified > > > by > > > the PE/COFF > > > + * header machine type field. > > > + */ > > > +#define LINUX_PE_MAGIC 0x818223cd > > > + > > > #define MZ_MAGIC 0x5a4d /* "MZ" */ > > > > > > #define PE_MAGIC 0x00004550 /* "PE\0\0" */ > > > > > > As far as I know, Archlinux automatically generates initramfs > > according > > to the version number in the kernel file. The latest generic > > compressed > > EFI designs do not seem to provide kernel version number > > information. > > No, but nor do the gzip'ed images arm64 uses today, and the script > seems take care of that. > > The EFI zboot image has metadata in the header, so the script can > decompress it and grep for the version number it it needs to. I tested it, and the decompression can be completed, thank you. > > > This may change the usage habits of Archlinux users. Is it possible > > to > > add the kernel version number to vmlinuz.efi? > > > > https://gitlab.archlinux.org/archlinux/mkinitcpio/mkinitcpio/-/blob/master/functions#L209 > > > > The current header doesn't have that so I don't think EFI zboot > should > be adding it either. > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > https://lists.gnu.org/mailman/listinfo/grub-devel
On Wed, 7 Dec 2022 at 11:36, Xiaotian Wu <wuxiaotian@loongson.cn> wrote: > > 在 2022-12-07星期三的 09:06 +0100，Ard Biesheuvel写道： > > On Wed, 7 Dec 2022 at 08:51, Xiaotian Wu <wuxiaotian@loongson.cn> > > wrote: > > > > > > 在 2022-11-29星期二的 18:56 +0100，Ard Biesheuvel写道： > > > > GRUB currently relies on the magic number in the image header of > > > > ARM > > > > and > > > > arm64 EFI kernel images to decide whether or not the image in > > > > question > > > > is a bootable kernel. > > > > > > > > However, the purpose of the magic number is to identify the image > > > > as > > > > one > > > > that implements the bare metal boot protocol, and so GRUB, which > > > > only > > > > does EFI boot, can only boot images that could potentially be > > > > booted > > > > in > > > > a non-EFI manner as well. > > > > > > > > This is problematic for the new zboot decompressor image format, > > > > as > > > > it > > > > can only boot in EFI mode, and must therefore not use the bare > > > > metal > > > > boot magic number in its header. > > > > > > > > For this reason, the strict magic number was dropped from GRUB, > > > > to > > > > permit essentially any kind of EFI executable to be booted via > > > > the > > > > 'linux' command, blurring the line between the linux loader and > > > > the > > > > chainloader. > > > > > > > > So let's use the same field in the DOS header that RISC-V and > > > > arm64 > > > > already use for their 'bare metal' magic numbers to store a > > > > 'generic > > > > Linux kernel' magic number, which can be used to identify > > > > bootable > > > > kernel images in PE format which don't necessarily implement a > > > > bare > > > > metal boot protocol in the same binary. Note that, in the context > > > > of > > > > EFI, the MSDOS header is only described in terms of the fields > > > > that > > > > it > > > > shares with the hybrid PE/COFF image format, (i.e., the magic > > > > number > > > > at > > > > offset #0 and the PE header offset at byte offset #0x3c). Since > > > > we > > > > aim > > > > for compatibility with EFI only, and not with MS-DOS or MS- > > > > Windows, > > > > we > > > > can use the remaining space in the MS-DOS header however we want. > > > > > > > > Let's set the generic magic number for x86 images as well: > > > > existing > > > > bootloaders already have their own methods to identify x86 Linux > > > > images > > > > that can be booted in a non-EFI manner, and having the magic > > > > number > > > > in > > > > place there will ease any future transitions in loader > > > > implementations > > > > to merge the x86 and non-x86 EFI boot paths. > > > > > > > > Note that 32-bit ARM already uses the same location in the header > > > > for > > > > a > > > > different purpose, but the ARM support is already widely > > > > implemented > > > > and > > > > the EFI zboot decompressor is not available on ARM anyway, so we > > > > just > > > > disregard it here. > > > > > > > > Cc: Huacai Chen <chenhuacai@kernel.org> > > > > Cc: Atish Patra <atishp@rivosinc.com> > > > > Cc: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> > > > > Cc: Daniel Kiper <daniel.kiper@oracle.com> > > > > Cc: Leif Lindholm <quic_llindhol@quicinc.com> > > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > > > --- > > > > arch/loongarch/kernel/head.S | 3 ++- > > > > arch/x86/boot/header.S | 3 ++- > > > > drivers/firmware/efi/libstub/zboot-header.S | 3 ++- > > > > include/linux/pe.h | 7 +++++++ > > > > 4 files changed, 13 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/arch/loongarch/kernel/head.S > > > > b/arch/loongarch/kernel/head.S > > > > index 84970e2666588963..caa74439700eee93 100644 > > > > --- a/arch/loongarch/kernel/head.S > > > > +++ b/arch/loongarch/kernel/head.S > > > > @@ -25,7 +25,8 @@ _head: > > > > .dword kernel_entry /* Kernel entry point */ > > > > .dword _end - _text /* Kernel image effective > > > > size */ > > > > .quad 0 /* Kernel image load > > > > offset > > > > from start of RAM */ > > > > - .org 0x3c /* 0x20 ~ 0x3b reserved > > > > */ > > > > + .org 0x38 /* 0x20 ~ 0x38 reserved > > > > */ > > > > + .long LINUX_PE_MAGIC > > > > .long pe_header - _head /* Offset to the PE > > > > header */ > > > > > > > > pe_header: > > > > diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S > > > > index f912d777013052ea..be8f78a7ee325475 100644 > > > > --- a/arch/x86/boot/header.S > > > > +++ b/arch/x86/boot/header.S > > > > @@ -80,10 +80,11 @@ bs_die: > > > > ljmp $0xf000,$0xfff0 > > > > > > > > #ifdef CONFIG_EFI_STUB > > > > - .org 0x3c > > > > + .org 0x38 > > > > # > > > > # Offset to the PE header. > > > > # > > > > + .long LINUX_PE_MAGIC > > > > .long pe_header > > > > #endif /* CONFIG_EFI_STUB */ > > > > > > > > diff --git a/drivers/firmware/efi/libstub/zboot-header.S > > > > b/drivers/firmware/efi/libstub/zboot-header.S > > > > index bc2d7750d7f14174..ec4525d40e0cf6d6 100644 > > > > --- a/drivers/firmware/efi/libstub/zboot-header.S > > > > +++ b/drivers/firmware/efi/libstub/zboot-header.S > > > > @@ -20,7 +20,8 @@ __efistub_efi_zboot_header: > > > > .long __efistub__gzdata_size - 12 > > > > // > > > > payload size > > > > .long 0, 0 > > > > // > > > > reserved > > > > .asciz COMP_TYPE > > > > // > > > > compression type > > > > - .org .Ldoshdr + 0x3c > > > > + .org .Ldoshdr + 0x38 > > > > + .long LINUX_PE_MAGIC > > > > .long .Lpehdr - .Ldoshdr > > > > // PE > > > > header offset > > > > > > > > .Lpehdr: > > > > diff --git a/include/linux/pe.h b/include/linux/pe.h > > > > index 056a1762de904fc1..1db4c944efd78f51 100644 > > > > --- a/include/linux/pe.h > > > > +++ b/include/linux/pe.h > > > > @@ -31,6 +31,13 @@ > > > > #define LINUX_EFISTUB_MAJOR_VERSION 0x1 > > > > #define LINUX_EFISTUB_MINOR_VERSION 0x1 > > > > > > > > +/* > > > > + * LINUX_PE_MAGIC appears at offset 0x38 into the MSDOS header > > > > of > > > > EFI bootable > > > > + * Linux kernel images that target the architecture as specified > > > > by > > > > the PE/COFF > > > > + * header machine type field. > > > > + */ > > > > +#define LINUX_PE_MAGIC 0x818223cd > > > > + > > > > #define MZ_MAGIC 0x5a4d /* "MZ" */ > > > > > > > > #define PE_MAGIC 0x00004550 /* "PE\0\0" */ > > > > > > > > > As far as I know, Archlinux automatically generates initramfs > > > according > > > to the version number in the kernel file. The latest generic > > > compressed > > > EFI designs do not seem to provide kernel version number > > > information. > > > > No, but nor do the gzip'ed images arm64 uses today, and the script > > seems take care of that. > > > > The EFI zboot image has metadata in the header, so the script can > > decompress it and grep for the version number it it needs to. > > I tested it, and the decompression can be completed, thank you. Excellent! Thanks for confirming.
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S index 84970e2666588963..caa74439700eee93 100644 --- a/arch/loongarch/kernel/head.S +++ b/arch/loongarch/kernel/head.S @@ -25,7 +25,8 @@ _head: .dword kernel_entry /* Kernel entry point */ .dword _end - _text /* Kernel image effective size */ .quad 0 /* Kernel image load offset from start of RAM */ - .org 0x3c /* 0x20 ~ 0x3b reserved */ + .org 0x38 /* 0x20 ~ 0x38 reserved */ + .long LINUX_PE_MAGIC .long pe_header - _head /* Offset to the PE header */ pe_header: diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S index f912d777013052ea..be8f78a7ee325475 100644 --- a/arch/x86/boot/header.S +++ b/arch/x86/boot/header.S @@ -80,10 +80,11 @@ bs_die: ljmp $0xf000,$0xfff0 #ifdef CONFIG_EFI_STUB - .org 0x3c + .org 0x38 # # Offset to the PE header. # + .long LINUX_PE_MAGIC .long pe_header #endif /* CONFIG_EFI_STUB */ diff --git a/drivers/firmware/efi/libstub/zboot-header.S b/drivers/firmware/efi/libstub/zboot-header.S index bc2d7750d7f14174..ec4525d40e0cf6d6 100644 --- a/drivers/firmware/efi/libstub/zboot-header.S +++ b/drivers/firmware/efi/libstub/zboot-header.S @@ -20,7 +20,8 @@ __efistub_efi_zboot_header: .long __efistub__gzdata_size - 12 // payload size .long 0, 0 // reserved .asciz COMP_TYPE // compression type - .org .Ldoshdr + 0x3c + .org .Ldoshdr + 0x38 + .long LINUX_PE_MAGIC .long .Lpehdr - .Ldoshdr // PE header offset .Lpehdr: diff --git a/include/linux/pe.h b/include/linux/pe.h index 056a1762de904fc1..1db4c944efd78f51 100644 --- a/include/linux/pe.h +++ b/include/linux/pe.h @@ -31,6 +31,13 @@ #define LINUX_EFISTUB_MAJOR_VERSION 0x1 #define LINUX_EFISTUB_MINOR_VERSION 0x1 +/* + * LINUX_PE_MAGIC appears at offset 0x38 into the MSDOS header of EFI bootable + * Linux kernel images that target the architecture as specified by the PE/COFF + * header machine type field. + */ +#define LINUX_PE_MAGIC 0x818223cd + #define MZ_MAGIC 0x5a4d /* "MZ" */ #define PE_MAGIC 0x00004550 /* "PE\0\0" */
GRUB currently relies on the magic number in the image header of ARM and arm64 EFI kernel images to decide whether or not the image in question is a bootable kernel. However, the purpose of the magic number is to identify the image as one that implements the bare metal boot protocol, and so GRUB, which only does EFI boot, can only boot images that could potentially be booted in a non-EFI manner as well. This is problematic for the new zboot decompressor image format, as it can only boot in EFI mode, and must therefore not use the bare metal boot magic number in its header. For this reason, the strict magic number was dropped from GRUB, to permit essentially any kind of EFI executable to be booted via the 'linux' command, blurring the line between the linux loader and the chainloader. So let's use the same field in the DOS header that RISC-V and arm64 already use for their 'bare metal' magic numbers to store a 'generic Linux kernel' magic number, which can be used to identify bootable kernel images in PE format which don't necessarily implement a bare metal boot protocol in the same binary. Note that, in the context of EFI, the MSDOS header is only described in terms of the fields that it shares with the hybrid PE/COFF image format, (i.e., the magic number at offset #0 and the PE header offset at byte offset #0x3c). Since we aim for compatibility with EFI only, and not with MS-DOS or MS-Windows, we can use the remaining space in the MS-DOS header however we want. Let's set the generic magic number for x86 images as well: existing bootloaders already have their own methods to identify x86 Linux images that can be booted in a non-EFI manner, and having the magic number in place there will ease any future transitions in loader implementations to merge the x86 and non-x86 EFI boot paths. Note that 32-bit ARM already uses the same location in the header for a different purpose, but the ARM support is already widely implemented and the EFI zboot decompressor is not available on ARM anyway, so we just disregard it here. Cc: Huacai Chen <chenhuacai@kernel.org> Cc: Atish Patra <atishp@rivosinc.com> Cc: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> Cc: Daniel Kiper <daniel.kiper@oracle.com> Cc: Leif Lindholm <quic_llindhol@quicinc.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- arch/loongarch/kernel/head.S | 3 ++- arch/x86/boot/header.S | 3 ++- drivers/firmware/efi/libstub/zboot-header.S | 3 ++- include/linux/pe.h | 7 +++++++ 4 files changed, 13 insertions(+), 3 deletions(-)