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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 TDX updates from Dave Hansen:
"The majority of this is a rework of the assembly and C wrappers that
are used to talk to the TDX module and VMM. This is a nice cleanup in
general but is also clearing the way for using this code when Linux is
the TDX VMM.
There are also some tidbits to make TDX guests play nicer with Hyper-V
and to take advantage the hardware TSC.
Summary:
- Refactor and clean up TDX hypercall/module call infrastructure
- Handle retrying/resuming page conversion hypercalls
- Make sure to use the (shockingly) reliable TSC in TDX guests"
[ TLA reminder: TDX is "Trust Domain Extensions", Intel's guest VM
confidentiality technology ]
* tag 'x86_tdx_for_6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/tdx: Mark TSC reliable
x86/tdx: Fix __noreturn build warning around __tdx_hypercall_failed()
x86/virt/tdx: Make TDX_MODULE_CALL handle SEAMCALL #UD and #GP
x86/virt/tdx: Wire up basic SEAMCALL functions
x86/tdx: Remove 'struct tdx_hypercall_args'
x86/tdx: Reimplement __tdx_hypercall() using TDX_MODULE_CALL asm
x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE_CALL
x86/tdx: Extend TDX_MODULE_CALL to support more TDCALL/SEAMCALL leafs
x86/tdx: Pass TDCALL/SEAMCALL input/output registers via a structure
x86/tdx: Rename __tdx_module_call() to __tdcall()
x86/tdx: Make macros of TDCALLs consistent with the spec
x86/tdx: Skip saving output regs when SEAMCALL fails with VMFailInvalid
x86/tdx: Zero out the missing RSI in TDX_HYPERCALL macro
x86/tdx: Retry partially-completed page conversion hypercalls
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 mm handling updates from Ingo Molnar:
- Add new NX-stack self-test
- Improve NUMA partial-CFMWS handling
- Fix #VC handler bugs resulting in SEV-SNP boot failures
- Drop the 4MB memory size restriction on minimal NUMA nodes
- Reorganize headers a bit, in preparation to header dependency
reduction efforts
- Misc cleanups & fixes
* tag 'x86-mm-2023-10-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/mm: Drop the 4 MB restriction on minimal NUMA node memory size
selftests/x86/lam: Zero out buffer for readlink()
x86/sev: Drop unneeded #include
x86/sev: Move sev_setup_arch() to mem_encrypt.c
x86/tdx: Replace deprecated strncpy() with strtomem_pad()
selftests/x86/mm: Add new test that userspace stack is in fact NX
x86/sev: Make boot_ghcb_page[] static
x86/boot: Move x86_cache_alignment initialization to correct spot
x86/sev-es: Set x86_virt_bits to the correct value straight away, instead of a two-phase approach
x86/sev-es: Allow copy_from_kernel_nofault() in earlier boot
x86_64: Show CR4.PSE on auxiliaries like on BSP
x86/iommu/docs: Update AMD IOMMU specification document URL
x86/sev/docs: Update document URL in amd-memory-encryption.rst
x86/mm: Move arch_memory_failure() and arch_is_platform_page() definitions from <asm/processor.h> to <asm/pgtable.h>
ACPI/NUMA: Apply SRAT proximity domain to entire CFMWS window
x86/numa: Introduce numa_fill_memblks()
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 boot updates from Ingo Molnar:
- Rework PE header generation, primarily to generate a modern, 4k
aligned kernel image view with narrower W^X permissions.
- Further refine init-lifetime annotations
- Misc cleanups & fixes
* tag 'x86-boot-2023-10-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits)
x86/boot: efistub: Assign global boot_params variable
x86/boot: Rename conflicting 'boot_params' pointer to 'boot_params_ptr'
x86/head/64: Move the __head definition to <asm/init.h>
x86/head/64: Add missing __head annotation to startup_64_load_idt()
x86/head/64: Mark 'startup_gdt[]' and 'startup_gdt_descr' as __initdata
x86/boot: Harmonize the style of array-type parameter for fixup_pointer() calls
x86/boot: Fix incorrect startup_gdt_descr.size
x86/boot: Compile boot code with -std=gnu11 too
x86/boot: Increase section and file alignment to 4k/512
x86/boot: Split off PE/COFF .data section
x86/boot: Drop PE/COFF .reloc section
x86/boot: Construct PE/COFF .text section from assembler
x86/boot: Derive file size from _edata symbol
x86/boot: Define setup size in linker script
x86/boot: Set EFI handover offset directly in header asm
x86/boot: Grab kernel_info offset from zoffset header directly
x86/boot: Drop references to startup_64
x86/boot: Drop redundant code setting the root device
x86/boot: Omit compression buffer from PE/COFF image memory footprint
x86/boot: Remove the 'bugger off' message
...
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The x86 decompressor is built and linked as a separate executable, but
it shares components with the kernel proper, which are either #include'd
as C files, or linked into the decompresor as a static library (e.g, the
EFI stub)
Both the kernel itself and the decompressor define a global symbol
'boot_params' to refer to the boot_params struct, but in the former
case, it refers to the struct directly, whereas in the decompressor, it
refers to a global pointer variable referring to the struct boot_params
passed by the bootloader or constructed from scratch.
This ambiguity is unfortunate, and makes it impossible to assign this
decompressor variable from the x86 EFI stub, given that declaring it as
extern results in a clash. So rename the decompressor version (whose
scope is limited) to boot_params_ptr.
[ mingo: Renamed 'boot_params_p' to 'boot_params_ptr' for clarity ]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
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Check the memory operand of INS/OUTS before emulating the instruction.
The #VC exception can get raised from user-space, but the memory operand
can be manipulated to access kernel memory before the emulation actually
begins and after the exception handler has run.
[ bp: Massage commit message. ]
Fixes: 597cfe48212a ("x86/boot/compressed/64: Setup a GHCB-based VC Exception handler")
Reported-by: Tom Dohrmann <erbse.13@gmx.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
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Check the IO permission bitmap (if present) before emulating IOIO #VC
exceptions for user-space. These permissions are checked by hardware
already before the #VC is raised, but due to the VC-handler decoding
race it needs to be checked again in software.
Fixes: 25189d08e516 ("x86/sev-es: Add support for handling IOIO exceptions")
Reported-by: Tom Dohrmann <erbse.13@gmx.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Tom Dohrmann <erbse.13@gmx.de>
Cc: <stable@kernel.org>
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boot_ghcb_page is not used by any other file, so make it static.
This also resolves sparse warning:
arch/x86/boot/compressed/sev.c:28:13: warning: symbol 'boot_ghcb_page' was not declared. Should it be static?
Signed-off-by: GUO Zihua <guozihua@huawei.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
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Align x86 with other EFI architectures, and increase the section
alignment to the EFI page size (4k), so that firmware is able to honour
the section permission attributes and map code read-only and data
non-executable.
There are a number of requirements that have to be taken into account:
- the sign tools get cranky when there are gaps between sections in the
file view of the image
- the virtual offset of each section must be aligned to the image's
section alignment
- the file offset *and size* of each section must be aligned to the
image's file alignment
- the image size must be aligned to the section alignment
- each section's virtual offset must be greater than or equal to the
size of the headers.
In order to meet all these requirements, while avoiding the need for
lots of padding to accommodate the .compat section, the latter is placed
at an arbitrary offset towards the end of the image, but aligned to the
minimum file alignment (512 bytes). The space before the .text section
is therefore distributed between the PE header, the .setup section and
the .compat section, leaving no gaps in the file coverage, making the
signing tools happy.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-18-ardb@google.com
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Describe the code and data of the decompressor binary using separate
.text and .data PE/COFF sections, so that we will be able to map them
using restricted permissions once we increase the section and file
alignment sufficiently. This avoids the need for memory mappings that
are writable and executable at the same time, which is something that
is best avoided for security reasons.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-17-ardb@google.com
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Ancient buggy EFI loaders may have required a .reloc section to be
present at some point in time, but this has not been true for a long
time so the .reloc section can just be dropped.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-16-ardb@google.com
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Now that the size of the setup block is visible to the assembler, it is
possible to populate the PE/COFF header fields from the asm code
directly, instead of poking the values into the binary using the build
tool. This will make it easier to reorganize the section layout without
having to tweak the build tool in lockstep.
This change has no impact on the resulting bzImage binary.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-15-ardb@google.com
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Tweak the linker script so that the value of _edata represents the
decompressor binary's file size rounded up to the appropriate alignment.
This removes the need to calculate it in the build tool, and will make
it easier to refer to the file size from the header directly in
subsequent changes to the PE header layout.
While adding _edata to the sed regex that parses the compressed
vmlinux's symbol list, tweak the regex a bit for conciseness.
This change has no impact on the resulting bzImage binary when
configured with CONFIG_EFI_STUB=y.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-14-ardb@google.com
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The setup block contains the real mode startup code that is used when
booting from a legacy BIOS, along with the boot_params/setup_data that
is used by legacy x86 bootloaders to pass the command line and initial
ramdisk parameters, among other things.
The setup block also contains the PE/COFF header of the entire combined
image, which includes the compressed kernel image, the decompressor and
the EFI stub.
This PE header describes the layout of the executable image in memory,
and currently, the fact that the setup block precedes it makes it rather
fiddly to get the right values into the right place in the final image.
Let's make things a bit easier by defining the setup_size in the linker
script so it can be referenced from the asm code directly, rather than
having to rely on the build tool to calculate it. For the time being,
add 64 bytes of fixed padding for the .reloc and .compat sections - this
will be removed in a subsequent patch after the PE/COFF header has been
reorganized.
This change has no impact on the resulting bzImage binary when
configured with CONFIG_EFI_MIXED=y.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-13-ardb@google.com
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The offsets of the EFI handover entrypoints are available to the
assembler when constructing the header, so there is no need to set them
from the build tool afterwards.
This change has no impact on the resulting bzImage binary.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-12-ardb@google.com
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Instead of parsing zoffset.h and poking the kernel_info offset value
into the header from the build tool, just grab the value directly in the
asm file that describes this header.
This change has no impact on the resulting bzImage binary.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-11-ardb@google.com
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The decompressor has a hard limit on the number of page tables it can
allocate. This limit is defined at compile-time and will cause boot
failure if it is reached.
The kernel is very strict and calculates the limit precisely for the
worst-case scenario based on the current configuration. However, it is
easy to forget to adjust the limit when a new use-case arises. The
worst-case scenario is rarely encountered during sanity checks.
In the case of enabling 5-level paging, a use-case was overlooked. The
limit needs to be increased by one to accommodate the additional level.
This oversight went unnoticed until Aaron attempted to run the kernel
via kexec with 5-level paging and unaccepted memory enabled.
Update wost-case calculations to include 5-level paging.
To address this issue, let's allocate some extra space for page tables.
128K should be sufficient for any use-case. The logic can be simplified
by using a single value for all kernel configurations.
[ Also add a warning, should this memory run low - by Dave Hansen. ]
Fixes: 34bbb0009f3b ("x86/boot/compressed: Enable 5-level paging during decompression stage")
Reported-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915070221.10266-1-kirill.shutemov@linux.intel.com
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The x86 boot image generation tool assign a default value to startup_64
and subsequently parses the actual value from zoffset.h but it never
actually uses the value anywhere. So remove this code.
This change has no impact on the resulting bzImage binary.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230912090051.4014114-25-ardb@google.com
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The root device defaults to 0,0 and is no longer configurable at build
time [0], so there is no need for the build tool to ever write to this
field.
[0] 079f85e624189292 ("x86, build: Do not set the root_dev field in bzImage")
This change has no impact on the resulting bzImage binary.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230912090051.4014114-23-ardb@google.com
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Now that the EFI stub decompresses the kernel and hands over to the
decompressed image directly, there is no longer a need to provide a
decompression buffer as part of the .BSS allocation of the PE/COFF
image. It also means the PE/COFF image can be loaded anywhere in memory,
and setting the preferred image base is unnecessary. So drop the
handling of this from the header and from the build tool.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230912090051.4014114-22-ardb@google.com
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Ancient (pre-2003) x86 kernels could boot from a floppy disk straight from
the BIOS, using a small real mode boot stub at the start of the image
where the BIOS would expect the boot record (or boot block) to appear.
Due to its limitations (kernel size < 1 MiB, no support for IDE, USB or
El Torito floppy emulation), this support was dropped, and a Linux aware
bootloader is now always required to boot the kernel from a legacy BIOS.
To smoothen this transition, the boot stub was not removed entirely, but
replaced with one that just prints an error message telling the user to
install a bootloader.
As it is unlikely that anyone doing direct floppy boot with such an
ancient kernel is going to upgrade to v6.5+ and expect that this boot
method still works, printing this message is kind of pointless, and so
it should be possible to remove the logic that emits it.
Let's free up this space so it can be used to expand the PE header in a
subsequent patch.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Link: https://lore.kernel.org/r/20230912090051.4014114-21-ardb@google.com
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The section header flags for alignment are documented in the PE/COFF
spec as being applicable to PE object files only, not to PE executables
such as the Linux bzImage, so let's drop them from the PE header.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230912090051.4014114-20-ardb@google.com
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Now that the EFI stub always zero inits its BSS section upon entry,
there is no longer a need to place the BSS symbols carried by the stub
into the .data section.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230912090051.4014114-18-ardb@google.com
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Now 'struct tdx_hypercall_args' is basically 'struct tdx_module_args'
minus RCX. Although from __tdx_hypercall()'s perspective RCX isn't
used as shared register thus not part of input/output registers, it's
not worth to have a separate structure just due to one register.
Remove the 'struct tdx_hypercall_args' and use 'struct tdx_module_args'
instead in __tdx_hypercall() related code. This also saves the memory
copy between the two structures within __tdx_hypercall().
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/798dad5ce24e9d745cf0e16825b75ccc433ad065.1692096753.git.kai.huang%40intel.com
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Now the 'struct tdx_hypercall_args' and 'struct tdx_module_args' are
almost the same, and the TDX_HYPERCALL and TDX_MODULE_CALL asm macro
share similar code pattern too. The __tdx_hypercall() and __tdcall()
should be unified to use the same assembly code.
As a preparation to unify them, simplify the TDX_HYPERCALL to make it
more like the TDX_MODULE_CALL.
The TDX_HYPERCALL takes the pointer of 'struct tdx_hypercall_args' as
function call argument, and does below extra things comparing to the
TDX_MODULE_CALL:
1) It sets RAX to 0 (TDG.VP.VMCALL leaf) internally;
2) It sets RCX to the (fixed) bitmap of shared registers internally;
3) It calls __tdx_hypercall_failed() internally (and panics) when the
TDCALL instruction itself fails;
4) After TDCALL, it moves R10 to RAX to return the return code of the
VMCALL leaf, regardless the '\ret' asm macro argument;
Firstly, change the TDX_HYPERCALL to take the same function call
arguments as the TDX_MODULE_CALL does: TDCALL leaf ID, and the pointer
to 'struct tdx_module_args'. Then 1) and 2) can be moved to the
caller:
- TDG.VP.VMCALL leaf ID can be passed via the function call argument;
- 'struct tdx_module_args' is 'struct tdx_hypercall_args' + RCX, thus
the bitmap of shared registers can be passed via RCX in the
structure.
Secondly, to move 3) and 4) out of assembly, make the TDX_HYPERCALL
always save output registers to the structure. The caller then can:
- Call __tdx_hypercall_failed() when TDX_HYPERCALL returns error;
- Return R10 in the structure as the return code of the VMCALL leaf;
With above changes, change the asm function from __tdx_hypercall() to
__tdcall_hypercall(), and reimplement __tdx_hypercall() as the C wrapper
of it. This avoids having to add another wrapper of __tdx_hypercall()
(_tdx_hypercall() is already taken).
The __tdcall_hypercall() will be replaced with a __tdcall() variant
using TDX_MODULE_CALL in a later commit as the final goal is to have one
assembly to handle both TDCALL and TDVMCALL.
Currently, the __tdx_hypercall() asm is in '.noinstr.text'. To keep
this unchanged, annotate __tdx_hypercall(), which is a C function now,
as 'noinstr'.
Remove the __tdx_hypercall_ret() as __tdx_hypercall() already does so.
Implement __tdx_hypercall() in tdx-shared.c so it can be shared with the
compressed code.
Opportunistically fix a checkpatch error complaining using space around
parenthesis '(' and ')' while moving the bitmap of shared registers to
<asm/shared/tdx.h>.
[ dhansen: quash new calls of __tdx_hypercall_ret() that showed up ]
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/0cbf25e7aee3256288045023a31f65f0cef90af4.1692096753.git.kai.huang%40intel.com
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull misc x86 cleanups from Ingo Molnar:
"The following commit deserves special mention:
22dc02f81cddd Revert "sched/fair: Move unused stub functions to header"
This is in x86/cleanups, because the revert is a re-application of a
number of cleanups that got removed inadvertedly"
[ This also effectively undoes the amd_check_microcode() microcode
declaration change I had done in my microcode loader merge in commit
42a7f6e3ffe0 ("Merge tag 'x86_microcode_for_v6.6_rc1' [...]").
I picked the declaration change by Arnd from this branch instead,
which put it in <asm/processor.h> instead of <asm/microcode.h> like I
had done in my merge resolution - Linus ]
* tag 'x86-cleanups-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/platform/uv: Refactor code using deprecated strncpy() interface to use strscpy()
x86/hpet: Refactor code using deprecated strncpy() interface to use strscpy()
x86/platform/uv: Refactor code using deprecated strcpy()/strncpy() interfaces to use strscpy()
x86/qspinlock-paravirt: Fix missing-prototype warning
x86/paravirt: Silence unused native_pv_lock_init() function warning
x86/alternative: Add a __alt_reloc_selftest() prototype
x86/purgatory: Include header for warn() declaration
x86/asm: Avoid unneeded __div64_32 function definition
Revert "sched/fair: Move unused stub functions to header"
x86/apic: Hide unused safe_smp_processor_id() on 32-bit UP
x86/cpu: Fix amd_check_microcode() declaration
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 SEV updates from Borislav Petkov:
- Handle the case where the beginning virtual address of the address
range whose SEV encryption status needs to change, is not page
aligned so that callers which round up the number of pages to be
decrypted, would mark a trailing page as decrypted and thus cause
corruption during live migration.
- Return an error from the #VC handler on AMD SEV-* guests when the
debug registers swapping is enabled as a DR7 access should not happen
then - that register is guest/host switched.
* tag 'x86_sev_for_v6.6_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/sev: Make enc_dec_hypercall() accept a size instead of npages
x86/sev: Do not handle #VC for DR7 read/write
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With MSR_AMD64_SEV_DEBUG_SWAP enabled, the guest is not expected to
receive a #VC for reads or writes of DR7.
Update the SNP_FEATURES_PRESENT mask with MSR_AMD64_SNP_DEBUG_SWAP so
an SNP guest doesn't gracefully terminate during SNP feature negotiation
if MSR_AMD64_SEV_DEBUG_SWAP is enabled.
Since a guest is not expected to receive a #VC on DR7 accesses when
MSR_AMD64_SEV_DEBUG_SWAP is enabled, return an error from the #VC
handler in this situation.
Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Carlos Bilbao <carlos.bilbao@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Link: https://lore.kernel.org/r/20230816022122.981998-1-aik@amd.com
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The bare metal decompressor code was never really intended to run in a
hosted environment such as the EFI boot services, and does a few things
that are becoming problematic in the context of EFI boot now that the
logo requirements are getting tighter: EFI executables will no longer be
allowed to consist of a single executable section that is mapped with
read, write and execute permissions if they are intended for use in a
context where Secure Boot is enabled (and where Microsoft's set of
certificates is used, i.e., every x86 PC built to run Windows).
To avoid stepping on reserved memory before having inspected the E820
tables, and to ensure the correct placement when running a kernel build
that is non-relocatable, the bare metal decompressor moves its own
executable image to the end of the allocation that was reserved for it,
in order to perform the decompression in place. This means the region in
question requires both write and execute permissions, which either need
to be given upfront (which EFI will no longer permit), or need to be
applied on demand using the existing page fault handling framework.
However, the physical placement of the kernel is usually randomized
anyway, and even if it isn't, a dedicated decompression output buffer
can be allocated anywhere in memory using EFI APIs when still running in
the boot services, given that EFI support already implies a relocatable
kernel. This means that decompression in place is never necessary, nor
is moving the compressed image from one end to the other.
Since EFI already maps all of memory 1:1, it is also unnecessary to
create new page tables or handle page faults when decompressing the
kernel. That means there is also no need to replace the special
exception handlers for SEV. Generally, there is little need to do
any of the things that the decompressor does beyond
- initialize SEV encryption, if needed,
- perform the 4/5 level paging switch, if needed,
- decompress the kernel
- relocate the kernel
So do all of this from the EFI stub code, and avoid the bare metal
decompressor altogether.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-24-ardb@kernel.org
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Before refactoring the EFI stub boot flow to avoid the legacy bare metal
decompressor, duplicate the SNP feature check in the EFI stub before
handing over to the kernel proper.
The SNP feature check can be performed while running under the EFI boot
services, which means it can force the boot to fail gracefully and
return an error to the bootloader if the loaded kernel does not
implement support for all the features that the hypervisor enabled.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-23-ardb@kernel.org
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Factor out the decompressor sequence that invokes the decompressor,
parses the ELF and applies the relocations so that it can be called
directly from the EFI stub.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-21-ardb@kernel.org
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It is no longer necessary to be cautious when referring to global
variables in the position independent decompressor code, now that it is
built using PIE codegen and makes an assertion in the linker script that
no GOT entries exist (which would require adjustment for the actual
runtime load address of the decompressor binary).
This means global variables can be referenced directly from C code,
instead of having to pass their runtime addresses into C routines from
asm code, which needs to happen at each call site. Do so for the code
that will be called directly from the EFI stub after a subsequent patch,
and avoid the need to duplicate this logic a third time.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-20-ardb@kernel.org
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Now that the trampoline setup code and the actual invocation of it are
all done from the C routine, the trampoline cleanup can be merged into
it as well, instead of returning to asm just to call another C function.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/20230807162720.545787-16-ardb@kernel.org
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The only remaining use of the trampoline address by the trampoline
itself is deriving the page table address from it, and this involves
adding an offset of 0x0. So simplify this, and pass the new CR3 value
directly.
This makes the fact that the page table happens to be at the start of
the trampoline allocation an implementation detail of the caller.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-15-ardb@kernel.org
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Since the current and desired number of paging levels are known when the
trampoline is being prepared, avoid calling the trampoline at all if it
is clear that calling it is not going to result in a change to the
number of paging levels.
Given that the CPU is already running in long mode, the PAE and LA57
settings are necessarily consistent with the currently active page
tables, and other fields in CR4 will be initialized by the startup code
in the kernel proper. So limit the manipulation of CR4 to toggling the
LA57 bit, which is the only thing that really needs doing at this point
in the boot. This also means that there is no need to pass the value of
l5_required to toggle_la57(), as it will not be called unless CR4.LA57
needs to toggle.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/20230807162720.545787-14-ardb@kernel.org
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Instead of returning to the asm calling code to invoke the trampoline,
call it straight from the C code that sets it up. That way, the struct
return type is no longer needed for returning two values, and the call
can be made conditional more cleanly in a subsequent patch.
This means that all callee save 64-bit registers need to be preserved
and restored, as their contents may not survive the legacy mode switch.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/20230807162720.545787-13-ardb@kernel.org
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The 32-bit trampoline no longer uses the stack for anything except
performing a far return back to long mode, and preserving the caller's
stack pointer value. Currently, the trampoline stack is placed in the
same page that carries the trampoline code, which means this page must
be mapped writable and executable, and the stack is therefore executable
as well.
Replace the far return with a far jump, so that the return address can
be pre-calculated and patched into the code before it is called. This
removes the need for a 32-bit addressable stack entirely, and in a later
patch, this will be taken advantage of by removing writable permissions
from (and adding executable permissions to) the trampoline code page
when booting via the EFI stub.
Note that the value of RSP still needs to be preserved explicitly across
the switch into 32-bit mode, as the register may get truncated to 32
bits.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/20230807162720.545787-12-ardb@kernel.org
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Update the trampoline code so its arguments are passed via RDI and RSI,
which matches the ordinary SysV calling convention for x86_64. This will
allow this code to be called directly from C.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/20230807162720.545787-11-ardb@kernel.org
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Move the long return to switch to 32-bit mode into the trampoline code
so it can be called as an ordinary function. This will allow it to be
called directly from C code in a subsequent patch.
While at it, reorganize the code somewhat to keep the prologue and
epilogue of the function together, making the code a bit easier to
follow. Also, given that the trampoline is now entered in 64-bit mode, a
simple RIP-relative reference can be used to take the address of the
exit point.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/20230807162720.545787-10-ardb@kernel.org
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There is no need to defer the assignment of the paging related global
variables 'pgdir_shift' and 'ptrs_per_p4d' until after the trampoline is
cleaned up, so assign them as soon as it is clear that 5-level paging
will be enabled.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-9-ardb@kernel.org
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Instead of pushing and popping %RSI several times to preserve the struct
boot_params pointer across the execution of the startup code, move it
into a callee save register before the first call into C, and copy it
back when needed.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-8-ardb@kernel.org
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The so-called EFI handover protocol is value-add from the distros that
permits a loader to simply copy a PE kernel image into memory and call
an alternative entrypoint that is described by an embedded boot_params
structure.
Most implementations of this protocol do not bother to check the PE
header for minimum alignment, section placement, etc, and therefore also
don't clear the image's BSS, or even allocate enough memory for it.
Allocating more memory on the fly is rather difficult, but at least
clear the BSS region explicitly when entering in this manner, so that
the EFI stub code does not get confused by global variables that were
not zero-initialized correctly.
When booting in mixed mode, this BSS clearing must occur before any
global state is created, so clear it in the 32-bit asm entry point.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-7-ardb@kernel.org
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The native 32-bit or 64-bit EFI handover protocol entrypoint offset
relative to the respective startup_32/64 address is described in
boot_params as handover_offset, so that the special Linux/x86 aware EFI
loader can find it there.
When mixed mode is enabled, this single field has to describe this
offset for both the 32-bit and 64-bit entrypoints, so their respective
relative offsets have to be identical. Given that startup_32 and
startup_64 are 0x200 bytes apart, and the EFI handover entrypoint
resides at a fixed offset, the 32-bit and 64-bit versions of those
entrypoints must be exactly 0x200 bytes apart as well.
Currently, hard-coded fixed offsets are used to ensure this, but it is
sufficient to emit the 64-bit entrypoint 0x200 bytes after the 32-bit
one, wherever it happens to reside. This allows this code (which is now
EFI mixed mode specific) to be moved into efi_mixed.S and out of the
startup code in head_64.S.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-6-ardb@kernel.org
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Now that the EFI entry code in assembler is only used by the optional
and deprecated EFI handover protocol, and given that the EFI stub C code
no longer returns to it, most of it can simply be dropped.
While at it, clarify the symbol naming, by merging efi_main() and
efi_stub_entry(), making the latter the shared entry point for all
different boot modes that enter via the EFI stub.
The efi32_stub_entry() and efi64_stub_entry() names are referenced
explicitly by the tooling that populates the setup header, so these must
be retained, but can be emitted as aliases of efi_stub_entry() where
appropriate.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-5-ardb@kernel.org
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The 4-to-5 level mode switch trampoline disables long mode and paging in
order to be able to flick the LA57 bit. According to section 3.4.1.1 of
the x86 architecture manual [0], 64-bit GPRs might not retain the upper
32 bits of their contents across such a mode switch.
Given that RBP, RBX and RSI are live at this point, preserve them on the
stack, along with the return address that might be above 4G as well.
[0] Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1: Basic Architecture
"Because the upper 32 bits of 64-bit general-purpose registers are
undefined in 32-bit modes, the upper 32 bits of any general-purpose
register are not preserved when switching from 64-bit mode to a 32-bit
mode (to protected mode or compatibility mode). Software must not
depend on these bits to maintain a value after a 64-bit to 32-bit
mode switch."
Fixes: 194a9749c73d650c ("x86/boot/compressed/64: Handle 5-level paging boot if kernel is above 4G")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-2-ardb@kernel.org
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Tao Liu reported a boot hang on an Intel Atom machine due to an unmapped
EFI config table. The reason being that the CC blob which contains the
CPUID page for AMD SNP guests is parsed for before even checking
whether the machine runs on AMD hardware.
Usually that's not a problem on !AMD hw - it simply won't find the CC
blob's GUID and return. However, if any parts of the config table
pointers array is not mapped, the kernel will #PF very early in the
decompressor stage without any opportunity to recover.
Therefore, do a superficial CPUID check before poking for the CC blob.
This will fix the current issue on real hardware. It would also work as
a guest on a non-lying hypervisor.
For the lying hypervisor, the check is done again, *after* parsing the
CC blob as the real CPUID page will be present then.
Clear the #VC handler in case SEV-{ES,SNP} hasn't been detected, as
a precaution.
Fixes: c01fce9cef84 ("x86/compressed: Add SEV-SNP feature detection/setup")
Reported-by: Tao Liu <ltao@redhat.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Tested-by: Tao Liu <ltao@redhat.com>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/20230601072043.24439-1-ltao@redhat.com
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The purgatory code uses parts of the decompressor and provides its own
warn() function, but has to include the corresponding header file to
avoid a -Wmissing-prototypes warning.
It turns out that this function prototype actually differs from the
declaration, so change it to get a constant pointer in the declaration
and the other definition as well.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230803082619.1369127-5-arnd@kernel.org
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 tdx updates from Dave Hansen:
- Fix a race window where load_unaligned_zeropad() could cause a fatal
shutdown during TDX private<=>shared conversion
The race has never been observed in practice but might allow
load_unaligned_zeropad() to catch a TDX page in the middle of its
conversion process which would lead to a fatal and unrecoverable
guest shutdown.
- Annotate sites where VM "exit reasons" are reused as hypercall
numbers.
* tag 'x86_tdx_for_6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/mm: Fix enc_status_change_finish_noop()
x86/tdx: Fix race between set_memory_encrypted() and load_unaligned_zeropad()
x86/mm: Allow guest.enc_status_change_prepare() to fail
x86/tdx: Wrap exit reason with hcall_func()
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 cpu updates from Borislav Petkov:
- Compute the purposeful misalignment of zen_untrain_ret automatically
and assert __x86_return_thunk's alignment so that future changes to
the symbol macros do not accidentally break them.
- Remove CONFIG_X86_FEATURE_NAMES Kconfig option as its existence is
pointless
* tag 'x86_cpu_for_v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/retbleed: Add __x86_return_thunk alignment checks
x86/cpu: Remove X86_FEATURE_NAMES
x86/Kconfig: Make X86_FEATURE_NAMES non-configurable in prompt
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 confidential computing update from Borislav Petkov:
- Add support for unaccepted memory as specified in the UEFI spec v2.9.
The gist of it all is that Intel TDX and AMD SEV-SNP confidential
computing guests define the notion of accepting memory before using
it and thus preventing a whole set of attacks against such guests
like memory replay and the like.
There are a couple of strategies of how memory should be accepted -
the current implementation does an on-demand way of accepting.
* tag 'x86_cc_for_v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
virt: sevguest: Add CONFIG_CRYPTO dependency
x86/efi: Safely enable unaccepted memory in UEFI
x86/sev: Add SNP-specific unaccepted memory support
x86/sev: Use large PSC requests if applicable
x86/sev: Allow for use of the early boot GHCB for PSC requests
x86/sev: Put PSC struct on the stack in prep for unaccepted memory support
x86/sev: Fix calculation of end address based on number of pages
x86/tdx: Add unaccepted memory support
x86/tdx: Refactor try_accept_one()
x86/tdx: Make _tdx_hypercall() and __tdx_module_call() available in boot stub
efi/unaccepted: Avoid load_unaligned_zeropad() stepping into unaccepted memory
efi: Add unaccepted memory support
x86/boot/compressed: Handle unaccepted memory
efi/libstub: Implement support for unaccepted memory
efi/x86: Get full memory map in allocate_e820()
mm: Add support for unaccepted memory
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The Linux build process on x86 roughly consists of compiling all input
files, statically linking them into a vmlinux ELF file, and then taking
and turning this file into an actual bzImage bootable file.
vmlinux has in this process two main purposes:
1) It is an intermediate build target on the way to produce the final
bootable image.
2) It is a file that is expected to be used by debuggers and standard
ELF tooling to work with the built kernel.
For the second purpose, a vmlinux file is typically collected by various
package build recipes, such as distribution spec files, including the
kernel's own tar-pkg target.
When building a kernel supporting KASLR with CONFIG_X86_NEED_RELOCS,
vmlinux contains also relocation information produced by using the
--emit-relocs linker option. This is utilized by subsequent build steps
to create vmlinux.relocs and produce a relocatable image. However, the
information is not needed by debuggers and other standard ELF tooling.
The issue is then that the collected vmlinux file and hence distribution
packages end up unnecessarily large because of this extra data. The
following is a size comparison of vmlinux v6.0 with and without the
relocation information:
| Configuration | With relocs | Stripped relocs |
| x86_64_defconfig | 70 MB | 43 MB |
| +CONFIG_DEBUG_INFO | 818 MB | 367 MB |
Optimize a resulting vmlinux by adding a postlink step that splits the
relocation information into vmlinux.relocs and then strips it from the
vmlinux binary.
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20220927084632.14531-1-petr.pavlu@suse.com
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Linus Torvalds
Ard Biesheuvel
Joerg Roedel
GUO Zihua
Kirill A. Shutemov
Kai Huang
Alexey Kardashevskiy
Borislav Petkov (AMD)
Arnd Bergmann
Petr Pavlu
