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2022-06-24efi: pstore: Omit efivars caching EFI varstore access layerArd Biesheuvel4-308/+91
Avoid the efivars layer and simply call the newly introduced EFI varstore helpers instead. This simplifies the code substantially, and also allows us to remove some hacks in the shared efivars layer that were added for efi-pstore specifically. In order to be able to delete the EFI variable associated with a record, store the UTF-16 name of the variable in the pstore record's priv field. That way, we don't have to make guesses regarding which variable the record may have been loaded from. Signed-off-by: Ard Biesheuvel <[email protected]>
2022-06-24efi: vars: Add thin wrapper around EFI get/set variable interfaceArd Biesheuvel1-10/+144
The current efivars layer is a jumble of list iterators, shadow data structures and safe variable manipulation helpers that really belong in the efivarfs pseudo file system once the obsolete sysfs access method to EFI variables is removed. So split off a minimal efivar get/set variable API that reuses the existing efivars_lock semaphore to mediate access to the various runtime services, primarily to ensure that performing a SetVariable() on one CPU while another is calling GetNextVariable() in a loop to enumerate the contents of the EFI variable store does not result in surprises. Signed-off-by: Ard Biesheuvel <[email protected]>
2022-06-24efi: vars: Don't drop lock in the middle of efivar_init()Ard Biesheuvel3-20/+14
Even though the efivars_lock lock is documented as protecting the efivars->ops pointer (among other things), efivar_init() happily releases and reacquires the lock for every EFI variable that it enumerates. This used to be needed because the lock was originally a spinlock, which prevented the callback that is invoked for every variable from being able to sleep. However, releasing the lock could potentially invalidate the ops pointer, but more importantly, it might allow a SetVariable() runtime service call to take place concurrently, and the UEFI spec does not define how this affects an enumeration that is running in parallel using the GetNextVariable() runtime service, which is what efivar_init() uses. In the meantime, the lock has been converted into a semaphore, and the only reason we need to drop the lock is because the efivarfs pseudo filesystem driver will otherwise deadlock when it invokes the efivars API from the callback to create the efivar_entry items and insert them into the linked list. (EFI pstore is affected in a similar way) So let's switch to helpers that can be used while the lock is already taken. This way, we can hold on to the lock throughout the enumeration. Signed-off-by: Ard Biesheuvel <[email protected]>
2022-06-21efi: sysfb_efi: remove unnecessary <asm/efi.h> includeJavier Martinez Canillas1-2/+0
Nothing defined in the header is used by drivers/firmware/efi/sysfb_efi.c but also, including it can lead to build errors when built on arches that don't have an asm/efi.h header file. This can happen for example if a driver that is built when COMPILE_TEST is enabled selects the SYSFB symbol, e.g. on powerpc with allyesconfig: drivers/firmware/efi/sysfb_efi.c:29:10: fatal error: asm/efi.h: No such file or directory 29 | #include <asm/efi.h> | ^~~~~~~~~~~ Reported-by: Stephen Rothwell <[email protected]> Signed-off-by: Javier Martinez Canillas <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2022-06-20efi: efibc: avoid efivar API for setting variablesArd Biesheuvel2-47/+30
Avoid abusing the efivar API by passing locally instantiated efivar_entry structs into efivar_set_entry_safe(), rather than using the API as intended. Instead, just call efi.set_variable() directly. Signed-off-by: Ard Biesheuvel <[email protected]>
2022-06-20efi: avoid efivars layer when loading SSDTs from variablesArd Biesheuvel1-62/+41
The efivars intermediate variable access layer provides an abstraction that permits the EFI variable store to be replaced by something else that implements a compatible interface, and caches all variables in the variable store for fast access via the efivarfs pseudo-filesystem. The SSDT override feature does not take advantage of either feature, as it is only used when the generic EFI implementation of efivars is used, and it traverses all variables only once to find the ones it is interested in, and frees all data structures that the efivars layer keeps right after. So in this case, let's just call EFI's code directly, using the function pointers in struct efi. Signed-off-by: Ard Biesheuvel <[email protected]>
2022-06-15efi: Correct comment on efi_memmap_allocLiu Zixian1-2/+1
Returning zero means success now. Signed-off-by: Liu Zixian <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2022-06-15efi: Make code to find mirrored memory ranges genericMa Wupeng2-0/+24
Commit b05b9f5f9dcf ("x86, mirror: x86 enabling - find mirrored memory ranges") introduce the efi_find_mirror() function on x86. In order to reuse the API we make it public. Arm64 can support mirrored memory too, so function efi_find_mirror() is added to efi_init() to this support for arm64. Since efi_init() is shared by ARM, arm64 and riscv, this patch will bring mirror memory support for these architectures, but this support is only tested in arm64. Signed-off-by: Ma Wupeng <[email protected]> Link: https://lore.kernel.org/r/[email protected] [ardb: fix subject to better reflect the payload] Acked-by: Mike Rapoport <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2022-06-03Merge tag 'efi-next-for-v5.19-2' of ↵Linus Torvalds2-30/+26
git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi Pull more EFI updates from Ard Biesheuvel: "Follow-up tweaks for EFI changes - they mostly address issues introduced this merge window, except for Heinrich's patch: - fix new DXE service invocations for mixed mode - use correct Kconfig symbol when setting PE header flag - clean up the drivers/firmware/efi Kconfig dependencies so that features that depend on CONFIG_EFI are hidden from the UI when the symbol is not enabled. Also included is a RISC-V bugfix from Heinrich to avoid read-write mappings of read-only firmware regions in the EFI page tables" * tag 'efi-next-for-v5.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi: efi: clean up Kconfig dependencies on CONFIG_EFI efi/x86: libstub: Make DXE calls mixed mode safe efi: x86: Fix config name for setting the NX-compatibility flag in the PE header riscv: read-only pages should not be writable
2022-06-01efi: clean up Kconfig dependencies on CONFIG_EFIArd Biesheuvel1-28/+24
Geert reports that the new option CONFIG_EFI_DISABLE_RUNTIME is user visible even when EFI support is disabled, which is unnecessary and clutters the Kconfig interface. So let's move this option into the existing Kconfig submenu that already depends on CONFIG_EFI, and while at it, give some other options the same treatment. Also clean up a small wart where the efi/ subdirectory is listed twice. Let's just list it unconditionally so that both EFI and UEFI_CPER based pieces will be built independently (the latter only depends on the former on !X86) Signed-off-by: Ard Biesheuvel <[email protected]>
2022-06-01efi/x86: libstub: Make DXE calls mixed mode safeArd Biesheuvel1-2/+2
The newly added DXE calls use 64-bit quantities, which means we need to marshall them explicitly when running in mixed mode. Currently, we get away without it because we just bail when GetMemorySpaceDescriptor() fails, which is guaranteed to happen due to the function argument mixup. Let's fix this properly, though, by defining the macros that describe how to marshall the arguments. While at it, drop an incorrect cast on a status variable. Signed-off-by: Ard Biesheuvel <[email protected]>
2022-05-23Merge tag 'edac_updates_for_v5.19_rc1' of ↵Linus Torvalds1-18/+46
git://git.kernel.org/pub/scm/linux/kernel/git/ras/ras Pull EDAC updates from Borislav Petkov: - Switch ghes_edac to use the CPER error reporting routines and simplify the code considerably this way - Rip out the silly edac_align_ptr() contraption which was computing the size of the private structures of each driver and thus allowing for a one-shot memory allocation. This was clearly unnecessary and confusing so switch to simple and boring kmalloc* calls. - Last but not least, the usual garden variety of fixes, cleanups and improvements all over EDAC land * tag 'edac_updates_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/ras/ras: EDAC/xgene: Fix typo processsors -> processors EDAC/i5100: Remove unused inline function i5100_nrecmema_dm_buf_id() EDAC: Use kcalloc() EDAC/ghes: Change ghes_hw from global to static EDAC/armada_xp: Use devm_platform_ioremap_resource() EDAC/synopsys: Add a SPDX identifier EDAC/synopsys: Add driver support for i.MX platforms EDAC/dmc520: Don't print an error for each unconfigured interrupt line EDAC/mc: Get rid of edac_align_ptr() EDAC/device: Sanitize edac_device_alloc_ctl_info() definition EDAC/device: Get rid of the silly one-shot memory allocation in edac_device_alloc_ctl_info() EDAC/pci: Get rid of the silly one-shot memory allocation in edac_pci_alloc_ctl_info() EDAC/mc: Get rid of silly one-shot struct allocation in edac_mc_alloc() efi/cper: Reformat CPER memory error location to more readable EDAC/ghes: Unify CPER memory error location reporting efi/cper: Add a cper_mem_err_status_str() to decode error description powerpc/85xx: Remove fsl,85... bindings
2022-05-19riscv/efi_stub: Add support for RISCV_EFI_BOOT_PROTOCOLSunil V L2-6/+30
Add support for getting the boot hart ID from the Linux EFI stub using RISCV_EFI_BOOT_PROTOCOL. This method is preferred over the existing DT based approach since it works irrespective of DT or ACPI. The specification of the protocol is hosted at: https://github.com/riscv-non-isa/riscv-uefi Signed-off-by: Sunil V L <[email protected]> Acked-by: Palmer Dabbelt <[email protected]> Reviewed-by: Heinrich Schuchardt <[email protected]> Link: https://lore.kernel.org/r/[email protected] [ardb: minor tweaks for coding style and whitespace] Signed-off-by: Ard Biesheuvel <[email protected]>
2022-05-06efi: stub: prefer mirrored memory for randomized allocationsArd Biesheuvel1-0/+11
If the system exposes memory regions with the EFI_MORE_RELIABLE attribute, it is implied that it is intended to be used for allocations that are relatively important, such as the kernel's static image. Since efi_random_alloc() is mostly (only) used for allocating space for the kernel image, let's update it to take this into account, and disregard all memory without the EFI_MORE_RELIABLE attribute if there is sufficient memory available that does have this attribute. Note that this change only affects booting with randomization enabled. In other cases, the EFI stub runs the kernel image in place unless its placement is unsuitable for some reason (i.e., misaligned, or its BSS overlaps with another allocation), and it is left to the bootloader to ensure that the kernel was loaded into EFI_MORE_RELIABLE memory if this is desired. Signed-off-by: Ard Biesheuvel <[email protected]> Reviewed-by: Kefeng Wang <[email protected]>
2022-05-03efi/arm64: libstub: run image in place if randomized by the loaderArd Biesheuvel1-3/+9
If the loader has already placed the EFI kernel image randomly in physical memory, and indicates having done so by installing the 'fixed placement' protocol onto the image handle, don't bother randomizing the placement again in the EFI stub. Signed-off-by: Ard Biesheuvel <[email protected]>
2022-05-03efi: libstub: pass image handle to handle_kernel_image()Ard Biesheuvel5-5/+9
In a future patch, arm64's implementation of handle_kernel_image() will omit randomizing the placement of the kernel if the load address was chosen randomly by the loader. In order to do this, it needs to locate a protocol on the image handle, so pass it to handle_kernel_image(). Signed-off-by: Ard Biesheuvel <[email protected]>
2022-05-03efi: libstub: ensure allocated memory to be executableBaskov Evgeniy2-4/+118
There are UEFI versions that restrict execution of memory regions, preventing the kernel from booting. Parts that needs to be executable are: * Area used for trampoline placement. * All memory regions that the kernel may be relocated before and during extraction. Use DXE services to ensure aforementioned address ranges to be executable. Only modify attributes that does not have appropriate attributes. Signed-off-by: Baskov Evgeniy <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Ard Biesheuvel <[email protected]>
2022-05-03efi: libstub: declare DXE services tableBaskov Evgeniy2-1/+82
UEFI DXE services are not yet used in kernel code but are required to manipulate page table memory protection flags. Add required declarations to use DXE services functions. Signed-off-by: Baskov Evgeniy <[email protected]> Link: https://lore.kernel.org/r/[email protected] [ardb: ignore absent DXE table but warn if the signature check fails] Signed-off-by: Ard Biesheuvel <[email protected]>
2022-04-13efi: Register efi_secret platform device if EFI secret area is declaredDov Murik1-0/+5
During efi initialization, check if coco_secret is defined in the EFI configuration table; in such case, register platform device "efi_secret". This allows udev to automatically load the efi_secret module (platform driver), which in turn will populate the <securityfs>/secrets/coco directory in guests into which secrets were injected. Note that a declared address of an EFI secret area doesn't mean that secrets where indeed injected to that area; if the secret area is not populated, the driver will not load (but the platform device will still be registered). Signed-off-by: Dov Murik <[email protected]> Reviewed-by: Gerd Hoffmann <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Ard Biesheuvel <[email protected]>
2022-04-13efi: Save location of EFI confidential computing areaDov Murik2-0/+22
Confidential computing (coco) hardware such as AMD SEV (Secure Encrypted Virtualization) allows a guest owner to inject secrets into the VMs memory without the host/hypervisor being able to read them. Firmware support for secret injection is available in OVMF, which reserves a memory area for secret injection and includes a pointer to it the in EFI config table entry LINUX_EFI_COCO_SECRET_TABLE_GUID. If EFI exposes such a table entry, uefi_init() will keep a pointer to the EFI config table entry in efi.coco_secret, so it can be used later by the kernel (specifically drivers/virt/coco/efi_secret). It will also appear in the kernel log as "CocoSecret=ADDRESS"; for example: [ 0.000000] efi: EFI v2.70 by EDK II [ 0.000000] efi: CocoSecret=0x7f22e680 SMBIOS=0x7f541000 ACPI=0x7f77e000 ACPI 2.0=0x7f77e014 MEMATTR=0x7ea0c018 The new functionality can be enabled with CONFIG_EFI_COCO_SECRET=y. Signed-off-by: Dov Murik <[email protected]> Reviewed-by: Gerd Hoffmann <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Ard Biesheuvel <[email protected]>
2022-04-13efi: Allow to enable EFI runtime services by default on RTJavier Martinez Canillas2-1/+16
Commit d9f283ae71af ("efi: Disable runtime services on RT") disabled EFI runtime services by default when the CONFIG_PREEMPT_RT option is enabled. The rationale for that commit is that some EFI calls could take too much time, leading to large latencies which is an issue for Real-Time kernels. But a side effect of that change was that now is not possible anymore to enable the EFI runtime services by default when CONFIG_PREEMPT_RT is set, without passing an efi=runtime command line parameter to the kernel. Instead, let's add a new EFI_DISABLE_RUNTIME boolean Kconfig option, that would be set to n by default but to y if CONFIG_PREEMPT_RT is enabled. That way, the current behaviour is preserved but gives users a mechanism to enable the EFI runtimes services in their kernels if that is required. For example, if the firmware could guarantee bounded time for EFI calls. Also, having a separate boolean config could allow users to disable the EFI runtime services by default even when CONFIG_PREEMPT_RT is not set. Reported-by: Alexander Larsson <[email protected]> Fixes: d9f283ae71af ("efi: Disable runtime services on RT") Signed-off-by: Javier Martinez Canillas <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Ard Biesheuvel <[email protected]>
2022-04-08efi/cper: Reformat CPER memory error location to more readableShuai Xue1-15/+15
Remove the space after the colon in cper_mem_err_location() so that it is easier to parse its output this way, both by humans and tools. No functional changes. Signed-off-by: Shuai Xue <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Acked-by: Ard Biesheuvel <[email protected]> Link: https://lore.kernel.org/r/[email protected]
2022-04-08EDAC/ghes: Unify CPER memory error location reportingShuai Xue1-2/+2
Switch the GHES EDAC memory error reporting functions to use the common CPER ones and get rid of code duplication. [ bp: - rewrite commit message, remove useless text - rip out useless reformatting - align function params on the opening brace - rename function to a more descriptive name - drop useless function exports - handle buffer lengths properly when printing other detail - remove useless casting ] Signed-off-by: Shuai Xue <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Link: https://lore.kernel.org/r/[email protected]
2022-04-08efi/cper: Add a cper_mem_err_status_str() to decode error descriptionShuai Xue1-1/+29
Introduce a new helper function cper_mem_err_status_str() to decode the error status value into a human readable string. [ bp: Massage. ] Signed-off-by: Shuai Xue <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Acked-by: Ard Biesheuvel <[email protected]> Link: https://lore.kernel.org/r/[email protected]
2022-03-21Merge tag 'pstore-v5.18-rc1' of ↵Linus Torvalds1-1/+1
git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux Pull pstore updates from Kees Cook: - Don't use semaphores in always-atomic-context code (Jann Horn) - Add "ECC:" prefix to ECC messages (Vincent Whitchurch) * tag 'pstore-v5.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: pstore: Don't use semaphores in always-atomic-context code pstore: Add prefix to ECC messages
2022-03-21Merge tag 'tpmdd-next-v5.18-v2' of ↵Linus Torvalds1-1/+1
git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd Pull tpm updates from Jarkko Sakkinen: "In order to split the work a bit we've aligned with David Howells more or less that I take more hardware/firmware aligned keyring patches, and he takes care more of the framework aligned patches. For TPM the patches worth of highlighting are the fixes for refcounting provided by Lino Sanfilippo and James Bottomley. Eric B. has done a bunch obvious (but important) fixes but there's one a bit controversial: removal of asym_tpm. It was added in 2018 when TPM1 was already declared as insecure and world had moved on to TPM2. I don't know how this has passed all the filters but I did not have a chance to see the patches when they were out. I simply cannot commit to maintaining this because it was from all angles just wrong to take it in the first place to the mainline kernel. Nobody should use this module really for anything. Finally, there is a new keyring '.machine' to hold MOK keys ('Machine Owner Keys'). In the mok side MokListTrustedRT UEFI variable can be set, from which kernel knows that MOK keys are kernel trusted keys and they are populated to the machine keyring. This keyring linked to the secondary trusted keyring, which means that can be used like any kernel trusted keys. This keyring of course can be used to hold other MOK'ish keys in other platforms in future" * tag 'tpmdd-next-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd: (24 commits) tpm: use try_get_ops() in tpm-space.c KEYS: asymmetric: properly validate hash_algo and encoding KEYS: asymmetric: enforce that sig algo matches key algo KEYS: remove support for asym_tpm keys tpm: fix reference counting for struct tpm_chip integrity: Only use machine keyring when uefi_check_trust_mok_keys is true integrity: Trust MOK keys if MokListTrustedRT found efi/mokvar: move up init order KEYS: Introduce link restriction for machine keys KEYS: store reference to machine keyring integrity: add new keyring handler for mok keys integrity: Introduce a Linux keyring called machine integrity: Fix warning about missing prototypes KEYS: trusted: Avoid calling null function trusted_key_exit KEYS: trusted: Fix trusted key backends when building as module tpm: xen-tpmfront: Use struct_size() helper KEYS: x509: remove dead code that set ->unsupported_sig KEYS: x509: remove never-set ->unsupported_key flag KEYS: x509: remove unused fields KEYS: x509: clearly distinguish between key and signature algorithms ...
2022-03-15pstore: Don't use semaphores in always-atomic-context codeJann Horn1-1/+1
pstore_dump() is *always* invoked in atomic context (nowadays in an RCU read-side critical section, before that under a spinlock). It doesn't make sense to try to use semaphores here. This is mostly a revert of commit ea84b580b955 ("pstore: Convert buf_lock to semaphore"), except that two parts aren't restored back exactly as they were: - keep the lock initialization in pstore_register - in efi_pstore_write(), always set the "block" flag to false - omit "is_locked", that was unnecessary since commit 959217c84c27 ("pstore: Actually give up during locking failure") - fix the bailout message The actual problem that the buggy commit was trying to address may have been that the use of preemptible() in efi_pstore_write() was wrong - it only looks at preempt_count() and the state of IRQs, but __rcu_read_lock() doesn't touch either of those under CONFIG_PREEMPT_RCU. (Sidenote: CONFIG_PREEMPT_RCU means that the scheduler can preempt tasks in RCU read-side critical sections, but you're not allowed to actively block/reschedule.) Lockdep probably never caught the problem because it's very rare that you actually hit the contended case, so lockdep always just sees the down_trylock(), not the down_interruptible(), and so it can't tell that there's a problem. Fixes: ea84b580b955 ("pstore: Convert buf_lock to semaphore") Cc: [email protected] Acked-by: Sebastian Andrzej Siewior <[email protected]> Signed-off-by: Jann Horn <[email protected]> Signed-off-by: Kees Cook <[email protected]> Link: https://lore.kernel.org/r/[email protected]
2022-03-08efi/mokvar: move up init orderEric Snowberg1-1/+1
Move up the init order so it can be used by the new machine keyring. Signed-off-by: Eric Snowberg <[email protected]> Reviewed-by: Jarkko Sakkinen <[email protected]> Signed-off-by: Jarkko Sakkinen <[email protected]>
2022-03-01efi: fix return value of __setup handlersRandy Dunlap2-2/+2
When "dump_apple_properties" is used on the kernel boot command line, it causes an Unknown parameter message and the string is added to init's argument strings: Unknown kernel command line parameters "dump_apple_properties BOOT_IMAGE=/boot/bzImage-517rc6 efivar_ssdt=newcpu_ssdt", will be passed to user space. Run /sbin/init as init process with arguments: /sbin/init dump_apple_properties with environment: HOME=/ TERM=linux BOOT_IMAGE=/boot/bzImage-517rc6 efivar_ssdt=newcpu_ssdt Similarly when "efivar_ssdt=somestring" is used, it is added to the Unknown parameter message and to init's environment strings, polluting them (see examples above). Change the return value of the __setup functions to 1 to indicate that the __setup options have been handled. Fixes: 58c5475aba67 ("x86/efi: Retrieve and assign Apple device properties") Fixes: 475fb4e8b2f4 ("efi / ACPI: load SSTDs from EFI variables") Signed-off-by: Randy Dunlap <[email protected]> Reported-by: Igor Zhbanov <[email protected]> Link: lore.kernel.org/r/[email protected] Cc: Ard Biesheuvel <[email protected]> Cc: [email protected] Cc: Lukas Wunner <[email protected]> Cc: Octavian Purdila <[email protected]> Cc: "Rafael J. Wysocki" <[email protected]> Cc: Matt Fleming <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Ard Biesheuvel <[email protected]>
2022-02-28efivars: Respect "block" flag in efivar_entry_set_safe()Jann Horn1-1/+4
When the "block" flag is false, the old code would sometimes still call check_var_size(), which wrongly tells ->query_variable_store() that it can block. As far as I can tell, this can't really materialize as a bug at the moment, because ->query_variable_store only does something on X86 with generic EFI, and in that configuration we always take the efivar_entry_set_nonblocking() path. Fixes: ca0e30dcaa53 ("efi: Add nonblocking option to efi_query_variable_store()") Signed-off-by: Jann Horn <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]> Link: https://lore.kernel.org/r/[email protected]
2022-02-28riscv/efi_stub: Fix get_boot_hartid_from_fdt() return valueSunil V L1-7/+10
The get_boot_hartid_from_fdt() function currently returns U32_MAX for failure case which is not correct because U32_MAX is a valid hartid value. This patch fixes the issue by returning error code. Cc: <[email protected]> Fixes: d7071743db31 ("RISC-V: Add EFI stub support.") Signed-off-by: Sunil V L <[email protected]> Reviewed-by: Heinrich Schuchardt <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2022-01-23efi: runtime: avoid EFIv2 runtime services on Apple x86 machinesArd Biesheuvel1-0/+7
Aditya reports [0] that his recent MacbookPro crashes in the firmware when using the variable services at runtime. The culprit appears to be a call to QueryVariableInfo(), which we did not use to call on Apple x86 machines in the past as they only upgraded from EFI v1.10 to EFI v2.40 firmware fairly recently, and QueryVariableInfo() (along with UpdateCapsule() et al) was added in EFI v2.00. The only runtime service introduced in EFI v2.00 that we actually use in Linux is QueryVariableInfo(), as the capsule based ones are optional, generally not used at runtime (all the LVFS/fwupd firmware update infrastructure uses helper EFI programs that invoke capsule update at boot time, not runtime), and not implemented by Apple machines in the first place. QueryVariableInfo() is used to 'safely' set variables, i.e., only when there is enough space. This prevents machines with buggy firmwares from corrupting their NVRAMs when they run out of space. Given that Apple machines have been using EFI v1.10 services only for the longest time (the EFI v2.0 spec was released in 2006, and Linux support for the newly introduced runtime services was added in 2011, but the MacbookPro12,1 released in 2015 still claims to be EFI v1.10 only), let's avoid the EFI v2.0 ones on all Apple x86 machines. [0] https://lore.kernel.org/all/[email protected]/ Cc: <[email protected]> Cc: Jeremy Kerr <[email protected]> Cc: Matthew Garrett <[email protected]> Reported-by: Aditya Garg <[email protected]> Tested-by: Orlando Chamberlain <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]> Tested-by: Aditya Garg <[email protected]> Link: https://bugzilla.kernel.org/show_bug.cgi?id=215277
2022-01-23efi/libstub: arm64: Fix image check alignment at entryMihai Carabas1-3/+3
The kernel is aligned at SEGMENT_SIZE and this is the size populated in the PE headers: arch/arm64/kernel/efi-header.S: .long SEGMENT_ALIGN // SectionAlignment EFI_KIMG_ALIGN is defined as: (SEGMENT_ALIGN > THREAD_ALIGN ? SEGMENT_ALIGN : THREAD_ALIGN) So it depends on THREAD_ALIGN. On newer builds this message started to appear even though the loader is taking into account the PE header (which is stating SEGMENT_ALIGN). Fixes: c32ac11da3f8 ("efi/libstub: arm64: Double check image alignment at entry") Signed-off-by: Mihai Carabas <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2022-01-19RISC-V: Introduce sv48 support without relocatable kernelPalmer Dabbelt1-0/+2
This patchset allows to have a single kernel for sv39 and sv48 without being relocatable. The idea comes from Arnd Bergmann who suggested to do the same as x86, that is mapping the kernel to the end of the address space, which allows the kernel to be linked at the same address for both sv39 and sv48 and then does not require to be relocated at runtime. This implements sv48 support at runtime. The kernel will try to boot with 4-level page table and will fallback to 3-level if the HW does not support it. Folding the 4th level into a 3-level page table has almost no cost at runtime. Note that kasan region had to be moved to the end of the address space since its location must be known at compile-time and then be valid for both sv39 and sv48 (and sv57 that is coming). * riscv-sv48-v3: riscv: Explicit comment about user virtual address space size riscv: Use pgtable_l4_enabled to output mmu_type in cpuinfo riscv: Implement sv48 support asm-generic: Prepare for riscv use of pud_alloc_one and pud_free riscv: Allow to dynamically define VA_BITS riscv: Introduce functions to switch pt_ops riscv: Split early kasan mapping to prepare sv48 introduction riscv: Move KASAN mapping next to the kernel mapping riscv: Get rid of MAXPHYSMEM configs Signed-off-by: Palmer Dabbelt <[email protected]>
2022-01-19riscv: Implement sv48 supportAlexandre Ghiti1-0/+2
By adding a new 4th level of page table, give the possibility to 64bit kernel to address 2^48 bytes of virtual address: in practice, that offers 128TB of virtual address space to userspace and allows up to 64TB of physical memory. If the underlying hardware does not support sv48, we will automatically fallback to a standard 3-level page table by folding the new PUD level into PGDIR level. In order to detect HW capabilities at runtime, we use SATP feature that ignores writes with an unsupported mode. Signed-off-by: Alexandre Ghiti <[email protected]> Signed-off-by: Palmer Dabbelt <[email protected]>
2022-01-12Merge tag 'devicetree-for-5.17' of ↵Linus Torvalds1-0/+5
git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux Pull devicetree updates from Rob Herring: "Bindings: - DT schema conversions for Samsung clocks, RNG bindings, Qcom Command DB and rmtfs, gpio-restart, i2c-mux-gpio, i2c-mux-pinctl, Tegra I2C and BPMP, pwm-vibrator, Arm DSU, and Cadence macb - DT schema conversions for Broadcom platforms: interrupt controllers, STB GPIO, STB waketimer, STB reset, iProc MDIO mux, iProc PCIe, Cygnus PCIe PHY, PWM, USB BDC, BCM6328 LEDs, TMON, SYSTEMPORT, AMAC, Northstar 2 PCIe PHY, GENET, moca PHY, GISB arbiter, and SATA - Add binding schemas for Tegra210 EMC table, TI DC-DC converters, - Clean-ups of MDIO bus schemas to fix 'unevaluatedProperties' issues - More fixes due to 'unevaluatedProperties' enabling - Data type fixes and clean-ups of binding examples found in preparation to move to validating DTB files directly (instead of intermediate YAML representation. - Vendor prefixes for T-Head Semiconductor, OnePlus, and Sunplus - Add various new compatible strings DT core: - Silence a warning for overlapping reserved memory regions - Reimplement unittest overlay tracking - Fix stack frame size warning in unittest - Clean-ups of early FDT scanning functions - Fix handling of "linux,usable-memory-range" on EFI booted systems - Add support for 'fail' status on CPU nodes - Improve error message in of_phandle_iterator_next() - kbuild: Disable duplicate unit-address warnings for disabled nodes" * tag 'devicetree-for-5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux: (114 commits) dt-bindings: net: mdio: Drop resets/reset-names child properties dt-bindings: clock: samsung: convert S5Pv210 to dtschema dt-bindings: clock: samsung: convert Exynos5410 to dtschema dt-bindings: clock: samsung: convert Exynos5260 to dtschema dt-bindings: clock: samsung: extend Exynos7 bindings with UFS dt-bindings: clock: samsung: convert Exynos7 to dtschema dt-bindings: clock: samsung: convert Exynos5433 to dtschema dt-bindings: i2c: maxim,max96712: Add bindings for Maxim Integrated MAX96712 dt-bindings: iio: adi,ltc2983: Fix 64-bit property sizes dt-bindings: power: maxim,max17040: Fix incorrect type for 'maxim,rcomp' dt-bindings: interrupt-controller: arm,gic-v3: Fix 'interrupts' cell size in example dt-bindings: iio/magnetometer: yamaha,yas530: Fix invalid 'interrupts' in example dt-bindings: clock: imx5: Drop clock consumer node from example dt-bindings: Drop required 'interrupt-parent' dt-bindings: net: ti,dp83869: Drop value on boolean 'ti,max-output-impedance' dt-bindings: net: wireless: mt76: Fix 8-bit property sizes dt-bindings: PCI: snps,dw-pcie-ep: Drop conflicting 'max-functions' schema dt-bindings: i2c: st,stm32-i2c: Make each example a separate entry dt-bindings: net: stm32-dwmac: Make each example a separate entry dt-bindings: net: Cleanup MDIO node schemas ...
2022-01-06efi: use default_groups in kobj_typeGreg Kroah-Hartman3-3/+7
There are currently 2 ways to create a set of sysfs files for a kobj_type, through the default_attrs field, and the default_groups field. Move the firmware efi sysfs code to use default_groups field which has been the preferred way since aa30f47cf666 ("kobject: Add support for default attribute groups to kobj_type") so that we can soon get rid of the obsolete default_attrs field. Cc: Ard Biesheuvel <[email protected]> Cc: [email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2022-01-06efi/libstub: measure loaded initrd info into the TPMIlias Apalodimas1-14/+58
In an effort to ensure the initrd observed and used by the OS is the same one that was meant to be loaded, which is difficult to guarantee otherwise, let's measure the initrd if the EFI stub and specifically the newly introduced LOAD_FILE2 protocol was used. Modify the initrd loading sequence so that the contents of the initrd are measured into PCR9. Note that the patch is currently using EV_EVENT_TAG to create the eventlog entry instead of EV_IPL. According to the TCP PC Client specification this is used for PCRs defined for OS and application usage. Co-developed-by: Ard Biesheuvel <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]> Signed-off-by: Ilias Apalodimas <[email protected]> Link: https://lore.kernel.org/r/[email protected] [ardb: add braces to initializer of tagged_event_data] Link: https://github.com/ClangBuiltLinux/linux/issues/1547 Signed-off-by: Ard Biesheuvel <[email protected]>
2021-12-22efi: apply memblock cap after memblock_add()Pingfan Liu1-0/+5
On arm64, during kdump kernel saves vmcore, it runs into the following bug: ... [ 15.148919] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmem_cache_node' (offset 0, size 4096)! [ 15.159707] ------------[ cut here ]------------ [ 15.164311] kernel BUG at mm/usercopy.c:99! [ 15.168482] Internal error: Oops - BUG: 0 [#1] SMP [ 15.173261] Modules linked in: xfs libcrc32c crct10dif_ce ghash_ce sha2_ce sha256_arm64 sha1_ce sbsa_gwdt ast i2c_algo_bit drm_vram_helper drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cec drm_ttm_helper ttm drm nvme nvme_core xgene_hwmon i2c_designware_platform i2c_designware_core dm_mirror dm_region_hash dm_log dm_mod overlay squashfs zstd_decompress loop [ 15.206186] CPU: 0 PID: 542 Comm: cp Not tainted 5.16.0-rc4 #1 [ 15.212006] Hardware name: GIGABYTE R272-P30-JG/MP32-AR0-JG, BIOS F12 (SCP: 1.5.20210426) 05/13/2021 [ 15.221125] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 15.228073] pc : usercopy_abort+0x9c/0xa0 [ 15.232074] lr : usercopy_abort+0x9c/0xa0 [ 15.236070] sp : ffff8000121abba0 [ 15.239371] x29: ffff8000121abbb0 x28: 0000000000003000 x27: 0000000000000000 [ 15.246494] x26: 0000000080000400 x25: 0000ffff885c7000 x24: 0000000000000000 [ 15.253617] x23: 000007ff80400000 x22: ffff07ff80401000 x21: 0000000000000001 [ 15.260739] x20: 0000000000001000 x19: ffff07ff80400000 x18: ffffffffffffffff [ 15.267861] x17: 656a626f2042554c x16: 53206d6f72662064 x15: 6574636574656420 [ 15.274983] x14: 74706d6574746120 x13: 2129363930342065 x12: 7a6973202c302074 [ 15.282105] x11: ffffc8b041d1b148 x10: 00000000ffff8000 x9 : ffffc8b04012812c [ 15.289228] x8 : 00000000ffff7fff x7 : ffffc8b041d1b148 x6 : 0000000000000000 [ 15.296349] x5 : 0000000000000000 x4 : 0000000000007fff x3 : 0000000000000000 [ 15.303471] x2 : 0000000000000000 x1 : ffff07ff8c064800 x0 : 000000000000006b [ 15.310593] Call trace: [ 15.313027] usercopy_abort+0x9c/0xa0 [ 15.316677] __check_heap_object+0xd4/0xf0 [ 15.320762] __check_object_size.part.0+0x160/0x1e0 [ 15.325628] __check_object_size+0x2c/0x40 [ 15.329711] copy_oldmem_page+0x7c/0x140 [ 15.333623] read_from_oldmem.part.0+0xfc/0x1c0 [ 15.338142] __read_vmcore.constprop.0+0x23c/0x350 [ 15.342920] read_vmcore+0x28/0x34 [ 15.346309] proc_reg_read+0xb4/0xf0 [ 15.349871] vfs_read+0xb8/0x1f0 [ 15.353088] ksys_read+0x74/0x100 [ 15.356390] __arm64_sys_read+0x28/0x34 ... This bug introduced by commit b261dba2fdb2 ("arm64: kdump: Remove custom linux,usable-memory-range handling"), which moves memblock_cap_memory_range() to fdt, but it breaches the rules that memblock_cap_memory_range() should come after memblock_add() etc as said in commit e888fa7bb882 ("memblock: Check memory add/cap ordering"). As a consequence, the virtual address set up by copy_oldmem_page() does not bail out from the test of virt_addr_valid() in check_heap_object(), and finally hits the BUG_ON(). Since memblock allocator has no idea about when the memblock is fully populated, while efi_init() is aware, so tackling this issue by calling the interface early_init_dt_check_for_usable_mem_range() exposed by of/fdt. Fixes: b261dba2fdb2 ("arm64: kdump: Remove custom linux,usable-memory-range handling") Signed-off-by: Pingfan Liu <[email protected]> Cc: Rob Herring <[email protected]> Cc: Zhen Lei <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: Will Deacon <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Mike Rapoport <[email protected]> Cc: Geert Uytterhoeven <[email protected]> Cc: Frank Rowand <[email protected]> Cc: Ard Biesheuvel <[email protected]> Cc: Nick Terrell <[email protected]> Cc: [email protected] To: [email protected] To: [email protected] Acked-by: Ard Biesheuvel <[email protected]> Signed-off-by: Rob Herring <[email protected]> Link: https://lore.kernel.org/r/[email protected]
2021-11-21efi/libstub: consolidate initrd handling across architecturesArd Biesheuvel4-29/+21
Before adding TPM measurement of the initrd contents, refactor the initrd handling slightly to be more self-contained and consistent. Signed-off-by: Ard Biesheuvel <[email protected]> Signed-off-by: Ilias Apalodimas <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Ard Biesheuvel <[email protected]>
2021-11-21efi/libstub: add prototype of efi_tcg2_protocol::hash_log_extend_event()Ard Biesheuvel1-1/+28
Define the right prototype for efi_tcg2_protocol::hash_log_extend_event() and add the required structs so we can start using it to measure the initrd into the TPM if it was loaded by the EFI stub itself. Signed-off-by: Ard Biesheuvel <[email protected]> Signed-off-by: Ilias Apalodimas <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Ard Biesheuvel <[email protected]>
2021-11-06Merge branch 'akpm' (patches from Andrew)Linus Torvalds1-1/+1
Merge misc updates from Andrew Morton: "257 patches. Subsystems affected by this patch series: scripts, ocfs2, vfs, and mm (slab-generic, slab, slub, kconfig, dax, kasan, debug, pagecache, gup, swap, memcg, pagemap, mprotect, mremap, iomap, tracing, vmalloc, pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, tools, memblock, oom-kill, hugetlbfs, migration, thp, readahead, nommu, ksm, vmstat, madvise, memory-hotplug, rmap, zsmalloc, highmem, zram, cleanups, kfence, and damon)" * emailed patches from Andrew Morton <[email protected]>: (257 commits) mm/damon: remove return value from before_terminate callback mm/damon: fix a few spelling mistakes in comments and a pr_debug message mm/damon: simplify stop mechanism Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions Docs/admin-guide/mm/damon/start: simplify the content Docs/admin-guide/mm/damon/start: fix a wrong link Docs/admin-guide/mm/damon/start: fix wrong example commands mm/damon/dbgfs: add adaptive_targets list check before enable monitor_on mm/damon: remove unnecessary variable initialization Documentation/admin-guide/mm/damon: add a document for DAMON_RECLAIM mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM) selftests/damon: support watermarks mm/damon/dbgfs: support watermarks mm/damon/schemes: activate schemes based on a watermarks mechanism tools/selftests/damon: update for regions prioritization of schemes mm/damon/dbgfs: support prioritization weights mm/damon/vaddr,paddr: support pageout prioritization mm/damon/schemes: prioritize regions within the quotas mm/damon/selftests: support schemes quotas mm/damon/dbgfs: support quotas of schemes ...
2021-11-06memblock: rename memblock_free to memblock_phys_freeMike Rapoport1-1/+1
Since memblock_free() operates on a physical range, make its name reflect it and rename it to memblock_phys_free(), so it will be a logical counterpart to memblock_phys_alloc(). The callers are updated with the below semantic patch: @@ expression addr; expression size; @@ - memblock_free(addr, size); + memblock_phys_free(addr, size); Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Mike Rapoport <[email protected]> Cc: Christophe Leroy <[email protected]> Cc: Juergen Gross <[email protected]> Cc: Shahab Vahedi <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
2021-11-01Merge tag 'efi-next-for-v5.16' of ↵Linus Torvalds1-1/+4
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull EFI updates from Borislav Petkov: "The last EFI pull request which is forwarded through the tip tree, for v5.16. From now on, Ard will be sending stuff directly. Disable EFI runtime services by default on PREEMPT_RT, while adding the ability to re-enable them on demand by passing efi=runtime on the command line" * tag 'efi-next-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: efi: Allow efi=runtime efi: Disable runtime services on RT
2021-10-05efi: Change down_interruptible() in virt_efi_reset_system() to down_trylock()Zhang Jianhua1-1/+1
While reboot the system by sysrq, the following bug will be occur. BUG: sleeping function called from invalid context at kernel/locking/semaphore.c:90 in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 10052, name: rc.shutdown CPU: 3 PID: 10052 Comm: rc.shutdown Tainted: G W O 5.10.0 #1 Call trace: dump_backtrace+0x0/0x1c8 show_stack+0x18/0x28 dump_stack+0xd0/0x110 ___might_sleep+0x14c/0x160 __might_sleep+0x74/0x88 down_interruptible+0x40/0x118 virt_efi_reset_system+0x3c/0xd0 efi_reboot+0xd4/0x11c machine_restart+0x60/0x9c emergency_restart+0x1c/0x2c sysrq_handle_reboot+0x1c/0x2c __handle_sysrq+0xd0/0x194 write_sysrq_trigger+0xbc/0xe4 proc_reg_write+0xd4/0xf0 vfs_write+0xa8/0x148 ksys_write+0x6c/0xd8 __arm64_sys_write+0x18/0x28 el0_svc_common.constprop.3+0xe4/0x16c do_el0_svc+0x1c/0x2c el0_svc+0x20/0x30 el0_sync_handler+0x80/0x17c el0_sync+0x158/0x180 The reason for this problem is that irq has been disabled in machine_restart() and then it calls down_interruptible() in virt_efi_reset_system(), which would occur sleep in irq context, it is dangerous! Commit 99409b935c9a("locking/semaphore: Add might_sleep() to down_*() family") add might_sleep() in down_interruptible(), so the bug info is here. down_trylock() can solve this problem, cause there is no might_sleep. -------- Cc: <[email protected]> Signed-off-by: Zhang Jianhua <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2021-10-05efi/cper: use stack buffer for error record decodingArd Biesheuvel1-2/+2
Joe reports that using a statically allocated buffer for converting CPER error records into human readable text is probably a bad idea. Even though we are not aware of any actual issues, a stack buffer is clearly a better choice here anyway, so let's move the buffer into the stack frames of the two functions that refer to it. Cc: <[email protected]> Reported-by: Joe Perches <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2021-10-05efi/libstub: Simplify "Exiting bootservices" messageHeinrich Schuchardt1-1/+1
The message "Exiting boot services and installing virtual address map...\n" is even shown if we have efi=novamap on the command line or the firmware does not provide EFI_RT_SUPPORTED_SET_VIRTUAL_ADDRESS_MAP. To avoid confusion just print "Exiting boot services...\n" Signed-off-by: Heinrich Schuchardt <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2021-09-28efi: Allow efi=runtimeSebastian Andrzej Siewior1-0/+3
In case the command line option "efi=noruntime" is default at built-time, the user could overwrite its state by `efi=runtime' and allow it again. This is useful on PREEMPT_RT where "efi=noruntime" is default and the user might need to alter the boot order for instance. Acked-by: Thomas Gleixner <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2021-09-28efi: Disable runtime services on RTSebastian Andrzej Siewior1-1/+1
Based on measurements the EFI functions get_variable / get_next_variable take up to 2us which looks okay. The functions get_time, set_time take around 10ms. These 10ms are too much. Even one ms would be too much. Ard mentioned that SetVariable might even trigger larger latencies if the firmware will erase flash blocks on NOR. The time-functions are used by efi-rtc and can be triggered during run-time (either via explicit read/write or ntp sync). The variable write could be used by pstore. These functions can be disabled without much of a loss. The poweroff / reboot hooks may be provided by PSCI. Disable EFI's runtime wrappers on PREEMPT_RT. This was observed on "EFI v2.60 by SoftIron Overdrive 1000". Acked-by: Thomas Gleixner <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]>
2021-09-03Merge tag 'kbuild-v5.15' of ↵Linus Torvalds2-2/+2
git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild Pull Kbuild updates from Masahiro Yamada: - Add -s option (strict mode) to merge_config.sh to make it fail when any symbol is redefined. - Show a warning if a different compiler is used for building external modules. - Infer --target from ARCH for CC=clang to let you cross-compile the kernel without CROSS_COMPILE. - Make the integrated assembler default (LLVM_IAS=1) for CC=clang. - Add <linux/stdarg.h> to the kernel source instead of borrowing <stdarg.h> from the compiler. - Add Nick Desaulniers as a Kbuild reviewer. - Drop stale cc-option tests. - Fix the combination of CONFIG_TRIM_UNUSED_KSYMS and CONFIG_LTO_CLANG to handle symbols in inline assembly. - Show a warning if 'FORCE' is missing for if_changed rules. - Various cleanups * tag 'kbuild-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (39 commits) kbuild: redo fake deps at include/ksym/*.h kbuild: clean up objtool_args slightly modpost: get the *.mod file path more simply checkkconfigsymbols.py: Fix the '--ignore' option kbuild: merge vmlinux_link() between ARCH=um and other architectures kbuild: do not remove 'linux' link in scripts/link-vmlinux.sh kbuild: merge vmlinux_link() between the ordinary link and Clang LTO kbuild: remove stale *.symversions kbuild: remove unused quiet_cmd_update_lto_symversions gen_compile_commands: extract compiler command from a series of commands x86: remove cc-option-yn test for -mtune= arc: replace cc-option-yn uses with cc-option s390: replace cc-option-yn uses with cc-option ia64: move core-y in arch/ia64/Makefile to arch/ia64/Kbuild sparc: move the install rule to arch/sparc/Makefile security: remove unneeded subdir-$(CONFIG_...) kbuild: sh: remove unused install script kbuild: Fix 'no symbols' warning when CONFIG_TRIM_UNUSD_KSYMS=y kbuild: Switch to 'f' variants of integrated assembler flag kbuild: Shuffle blank line to improve comment meaning ...