kernel.git/drivers/firmware/efi/libstub, branch linux-6.15.y

efi/libstub: Describe missing 'out' parameter in efi_load_initrd

2025-06-19T13:39:51Z

[ Upstream commit c8e1927e7f7d63721e32ec41d27ccb0eb1a1b0fc ] The function efi_load_initrd() had a documentation warning due to the missing description for the 'out' parameter. Add the parameter description to the kernel-doc comment to resolve the warning and improve API documentation. Fixes the following compiler warning: drivers/firmware/efi/libstub/efi-stub-helper.c:611: warning: Function parameter or struct member 'out' not described in 'efi_load_initrd' Fixes: f4dc7fffa987 ("efi: libstub: unify initrd loading between architectures") Signed-off-by: Hans Zhang <18255117159@163.com> Signed-off-by: Ard Biesheuvel Signed-off-by: Sasha Levin

Merge tag 'efi-next-for-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi

2025-03-29T18:36:19Z

Pull EFI updates from Ard Biesheuvel: - Decouple mixed mode startup code from the traditional x86 decompressor - Revert zero-length file hack in efivarfs - Prevent EFI zboot from using the CopyMem/SetMem boot services after ExitBootServices() - Update EFI zboot to use the ZLIB/ZSTD library interfaces directly * tag 'efi-next-for-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi: efi/libstub: Avoid legacy decompressor zlib/zstd wrappers efi/libstub: Avoid CopyMem/SetMem EFI services after ExitBootServices efi: efibc: change kmalloc(size * count, ...) to kmalloc_array() efivarfs: Revert "allow creation of zero length files" x86/efi/mixed: Move mixed mode startup code into libstub x86/efi/mixed: Simplify and document thunking logic x86/efi/mixed: Remove dependency on legacy startup_32 code x86/efi/mixed: Set up 1:1 mapping of lower 4GiB in the stub x86/efi/mixed: Factor out and clean up long mode entry x86/efi/mixed: Check CPU compatibility without relying on verify_cpu() x86/efistub: Merge PE and handover entrypoints

efi/libstub: Avoid legacy decompressor zlib/zstd wrappers

2025-03-14T11:36:11Z

Remove EFI zboot's dependency on the decompression wrappers used by the legacy decompressor boot code, which can only process the input in one go, and this will not work for upcoming support for embedded ELF images. They also do some odd things like providing a barebones malloc() implementation, which is not needed in a hosted environment such as the EFI boot services. So instead, implement GZIP deflate and ZSTD decompression in terms of the underlying libraries. Support for other compression algoritms has already been dropped. Signed-off-by: Ard Biesheuvel

efi/libstub: Avoid physical address 0x0 when doing random allocation

2025-03-14T11:21:29Z

Ben reports spurious EFI zboot failures on a system where physical RAM starts at 0x0. When doing random memory allocation from the EFI stub on such a platform, a random seed of 0x0 (which means no entropy source is available) will result in the allocation to be placed at address 0x0 if sufficient space is available. When this allocation is subsequently passed on to the decompression code, the 0x0 address is mistaken for NULL and the code complains and gives up. So avoid address 0x0 when doing random allocation, and set the minimum address to the minimum alignment. Cc: Reported-by: Ben Schneider Tested-by: Ben Schneider Reviewed-by: Ilias Apalodimas Signed-off-by: Ard Biesheuvel

efi/libstub: Avoid CopyMem/SetMem EFI services after ExitBootServices

2025-03-13T10:52:05Z

Given that memset/memcpy are intrinsics, the compiler might insert calls to these routines unexpectedly, including in code that executes after ExitBootServices(). In this case, the respective boot services are no longer accessible, and calling them will cause a crash. So fall back to a bytewise copy/store if this happens to occur, even though no such occurrences are known to exist in the kernel currently. Signed-off-by: Ard Biesheuvel

Merge branch 'x86-mixed-mode' into efi/next

2025-03-07T11:30:53Z

x86/efi/mixed: Move mixed mode startup code into libstub

2025-02-21T15:54:39Z

The EFI mixed mode code has been decoupled from the legacy decompressor, in order to be able to reuse it with generic EFI zboot images for x86. Move the source file into the libstub source directory to facilitate this. Acked-by: Ingo Molnar Signed-off-by: Ard Biesheuvel

x86/efistub: Merge PE and handover entrypoints

2025-02-21T15:54:05Z

The difference between the PE and handover entrypoints in the EFI stub is that the former allocates a struct boot_params whereas the latter expects one from the caller. Currently, these are two completely separate entrypoints, duplicating some logic and both relying of efi_exit() to return straight back to the firmware on an error. Simplify this by making the PE entrypoint call the handover entrypoint with NULL as the argument for the struct boot_params parameter. This makes the code easier to follow, and removes the need to support two different calling conventions in the mixed mode asm code. While at it, move the assignment of boot_params_ptr into the function that actually calls into the legacy decompressor, which is where its value is required. Acked-by: Ingo Molnar Signed-off-by: Ard Biesheuvel

efi: Avoid cold plugged memory for placing the kernel

2025-02-04T13:08:22Z

UEFI 2.11 introduced EFI_MEMORY_HOT_PLUGGABLE to annotate system memory regions that are 'cold plugged' at boot, i.e., hot pluggable memory that is available from early boot, and described as system RAM by the firmware. Existing loaders and EFI applications running in the boot context will happily use this memory for allocating data structures that cannot be freed or moved at runtime, and this prevents the memory from being unplugged. Going forward, the new EFI_MEMORY_HOT_PLUGGABLE attribute should be tested, and memory annotated as such should be avoided for such allocations. In the EFI stub, there are a couple of occurrences where, instead of the high-level AllocatePages() UEFI boot service, a low-level code sequence is used that traverses the EFI memory map and carves out the requested number of pages from a free region. This is needed, e.g., for allocating as low as possible, or for allocating pages at random. While AllocatePages() should presumably avoid special purpose memory and cold plugged regions, this manual approach needs to incorporate this logic itself, in order to prevent the kernel itself from ending up in a hot unpluggable region, preventing it from being unplugged. So add the EFI_MEMORY_HOTPLUGGABLE macro definition, and check for it where appropriate. Cc: stable@vger.kernel.org Signed-off-by: Ard Biesheuvel

efi: libstub: Use '-std=gnu11' to fix build with GCC 15

2025-01-22T11:57:45Z

GCC 15 changed the default C standard version to C23, which should not have impacted the kernel because it requests the gnu11 standard via '-std=' in the main Makefile. However, the EFI libstub Makefile uses its own set of KBUILD_CFLAGS for x86 without a '-std=' value (i.e., using the default), resulting in errors from the kernel's definitions of bool, true, and false in stddef.h, which are reserved keywords under C23. ./include/linux/stddef.h:11:9: error: expected identifier before ‘false’ 11 | false = 0, ./include/linux/types.h:35:33: error: two or more data types in declaration specifiers 35 | typedef _Bool bool; Set '-std=gnu11' in the x86 cflags to resolve the error and consistently use the same C standard version for the entire kernel. All other architectures reuse KBUILD_CFLAGS from the rest of the kernel, so this issue is not visible for them. Cc: stable@vger.kernel.org Reported-by: Kostadin Shishmanov Closes: https://lore.kernel.org/4OAhbllK7x4QJGpZjkYjtBYNLd_2whHx9oFiuZcGwtVR4hIzvduultkgfAIRZI3vQpZylu7Gl929HaYFRGeMEalWCpeMzCIIhLxxRhq4U-Y=@protonmail.com/ Reported-by: Jakub Jelinek Closes: https://lore.kernel.org/Z4467umXR2PZ0M1H@tucnak/ Signed-off-by: Nathan Chancellor Signed-off-by: Ard Biesheuvel