When KCSAN and CONSTRUCTORS are enabled, one can trigger the

"Unpatched return thunk in use. This should not happen!"

catch-all warning.

Usually, when objtool runs on the .o objects, it does generate a section
.return_sites which contains all offsets in the objects to the return
thunks of the functions present there. Those return thunks then get
patched at runtime by the alternatives.

KCSAN and CONSTRUCTORS add this to the object file's .text.startup
section:

-------------------
Disassembly of section .text.startup:

...

0000000000000010 <_sub_I_00099_0>:
10: f3 0f 1e fa endbr64
14: e8 00 00 00 00 call 19 <_sub_I_00099_0+0x9>
15: R_X86_64_PLT32 __tsan_init-0x4
19: e9 00 00 00 00 jmp 1e <__UNIQUE_ID___addressable_cryptd_alloc_aead349+0x6>
1a: R_X86_64_PLT32 __x86_return_thunk-0x4
-------------------

which, if it is built as a module goes through the intermediary stage of
creating a <module>.mod.c file which, when translated, receives a second
constructor:

-------------------
Disassembly of section .text.startup:

0000000000000010 <_sub_I_00099_0>:
10: f3 0f 1e fa endbr64
14: e8 00 00 00 00 call 19 <_sub_I_00099_0+0x9>
15: R_X86_64_PLT32 __tsan_init-0x4
19: e9 00 00 00 00 jmp 1e <_sub_I_00099_0+0xe>
1a: R_X86_64_PLT32 __x86_return_thunk-0x4

...

0000000000000030 <_sub_I_00099_0>:
30: f3 0f 1e fa endbr64
34: e8 00 00 00 00 call 39 <_sub_I_00099_0+0x9>
35: R_X86_64_PLT32 __tsan_init-0x4
39: e9 00 00 00 00 jmp 3e <__ksymtab_cryptd_alloc_ahash+0x2>
3a: R_X86_64_PLT32 __x86_return_thunk-0x4
-------------------

in the .ko file.

Objtool has run already so that second constructor's return thunk cannot
be added to the .return_sites section and thus the return thunk remains
unpatched and the warning rightfully fires.

Drop KCSAN flags from the mod.c generation stage as those constructors
do not contain data races one would be interested about.

Debugged together with David Kaplan <David.Kaplan@amd.com> and Nikolay
Borisov <nik.borisov@suse.com>.

Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Closes: https://lore.kernel.org/r/0851a207-7143-417e-be31-8bf2b3afb57d@molgen.mpg.de
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Paul Menzel <pmenzel@molgen.mpg.de> # Dell XPS 13
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

The -Woverride-init warn about code that may be intentional or not,
but the inintentional ones tend to be real bugs, so there is a bit of
disagreement on whether this warning option should be enabled by default
and we have multiple settings in scripts/Makefile.extrawarn as well as
individual subsystems.

Older versions of clang only supported -Wno-initializer-overrides with
the same meaning as gcc's -Woverride-init, though all supported versions
now work with both. Because of this difference, an earlier cleanup of
mine accidentally turned the clang warning off for W=1 builds and only
left it on for W=2, while it's still enabled for gcc with W=1.

There is also one driver that only turns the warning off for newer
versions of gcc but not other compilers, and some but not all the
Makefiles still use a cc-disable-warning conditional that is no
longer needed with supported compilers here.

Address all of the above by removing the special cases for clang
and always turning the warning off unconditionally where it got
in the way, using the syntax that is supported by both compilers.

Fixes: 2cd3271b7a31 ("kbuild: avoid duplicate warning options")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Andrew Jeffery <andrew@codeconstruct.com.au>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

As mentioned in commit 397586506c3d ("modpost: Add '.ltext' and
'.ltext.*' to TEXT_SECTIONS"), modpost can result in a segmentation
fault due to a NULL pointer dereference in default_mismatch_handler().

find_tosym() can return the original symbol pointer instead of NULL
if a better one is not found.

This fixes the reported segmentation fault.

Fixes: a23e7584ecf3 ("modpost: unify 'sym' and 'to' in default_mismatch_handler()")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Commit 3a6dd5f614a1 ("riscv: remove unneeded #include
<asm-generic/export.h>") removed the last use of
include/asm-generic/export.h.

This deprecated header can go away.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

The boolean 'choice' is used to list exclusively selected config
options.

You must not add a dependency between choice members, because such a
dependency would create an invisible entry.

In the following test case, it is impossible to choose 'C'.

[Test Case 1]

choice
prompt "Choose one, but how to choose C?"

config A
bool "A"

config B
bool "B"

config C
bool "C"
depends on A

endchoice

Hence, Kconfig shows the following error message:

Kconfig:1:error: recursive dependency detected!
Kconfig:1: choice <choice> contains symbol C
Kconfig:10: symbol C is part of choice A
Kconfig:4: symbol A is part of choice <choice>
For a resolution refer to Documentation/kbuild/kconfig-language.rst
subsection "Kconfig recursive dependency limitations"

However, Kconfig does not report anything for the following similar code:

[Test Case 2]

choice
prompt "Choose one, but how to choose B?"

config A
bool "A"

config B
bool "B"
depends on A

config C
bool "C"

endchoice

This is because menu_finalize() reparents the menu tree when an entry
depends on the preceding one.

With reparenting, the menu tree:

choice
|- A
|- B
\- C

... will be transformed into the following structure:

choice
|- A
| \- B
\- C

Consequently, Kconfig considers only 'A' and 'C' as choice members.
This behavior is awkward. The second test case should be an error too.

This commit stops reparenting inside a choice.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

The reason is described in 5033ad566016 ("MIPS: move unselectable
entries out of the "CPU type" choice").

At the same time, commit 101bd58fde10 ("MIPS: Add support for Mobileye
EyeQ5") introduced another unselectable choice member.

(In fact, 5033ad566016 and 101bd58fde10 have the same commit time.)

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Commit 5d7107c72796 ("perf: CXL Performance Monitoring Unit driver")
added the config entries for CXL_PMU in drivers/cxl/Kconfig and
drivers/perf/Kconfig, so it can be toggled from multiple locations:

[1] Device Drivers
-> PCI support
-> CXL (Compute Expres Link) Devices
-> CXL Performance Monitoring Unit

[2] Device Drivers
-> Performance monitor support
-> CXL Performance Monitoring Unit

This complicates things, and nobody else does this.

I kept the one in drivers/perf/Kconfig because CONFIG_CXL_PMU controls
the compilation of drivers/perf/cxl_pmu.c.

Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Pull EFI fixes from Ard Biesheuvel:

- Fix logic that is supposed to prevent placement of the kernel image
below LOAD_PHYSICAL_ADDR

- Use the firmware stack in the EFI stub when running in mixed mode

- Clear BSS only once when using mixed mode

- Check efi.get_variable() function pointer for NULL before trying to
call it

* tag 'efi-fixes-for-v6.9-2' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi:
efi: fix panic in kdump kernel
x86/efistub: Don't clear BSS twice in mixed mode
x86/efistub: Call mixed mode boot services on the firmware's stack
efi/libstub: fix efi_random_alloc() to allocate memory at alloc_min or higher address

Pull x86 fixes from Thomas Gleixner:

- Ensure that the encryption mask at boot is properly propagated on
5-level page tables, otherwise the PGD entry is incorrectly set to
non-encrypted, which causes system crashes during boot.

- Undo the deferred 5-level page table setup as it cannot work with
memory encryption enabled.

- Prevent inconsistent XFD state on CPU hotplug, where the MSR is reset
to the default value but the cached variable is not, so subsequent
comparisons might yield the wrong result and as a consequence the
result prevents updating the MSR.

- Register the local APIC address only once in the MPPARSE enumeration
to prevent triggering the related WARN_ONs() in the APIC and topology
code.

- Handle the case where no APIC is found gracefully by registering a
fake APIC in the topology code. That makes all related topology
functions work correctly and does not affect the actual APIC driver
code at all.

- Don't evaluate logical IDs during early boot as the local APIC IDs
are not yet enumerated and the invoked function returns an error
code. Nothing requires the logical IDs before the final CPUID
enumeration takes place, which happens after the enumeration.

- Cure the fallout of the per CPU rework on UP which misplaced the
copying of boot_cpu_data to per CPU data so that the final update to
boot_cpu_data got lost which caused inconsistent state and boot
crashes.

- Use copy_from_kernel_nofault() in the kprobes setup as there is no
guarantee that the address can be safely accessed.

- Reorder struct members in struct saved_context to work around another
kmemleak false positive

- Remove the buggy code which tries to update the E820 kexec table for
setup_data as that is never passed to the kexec kernel.

- Update the resource control documentation to use the proper units.

- Fix a Kconfig warning observed with tinyconfig

* tag 'x86-urgent-2024-03-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/boot/64: Move 5-level paging global variable assignments back
x86/boot/64: Apply encryption mask to 5-level pagetable update
x86/cpu: Add model number for another Intel Arrow Lake mobile processor
x86/fpu: Keep xfd_state in sync with MSR_IA32_XFD
Documentation/x86: Document that resctrl bandwidth control units are MiB
x86/mpparse: Register APIC address only once
x86/topology: Handle the !APIC case gracefully
x86/topology: Don't evaluate logical IDs during early boot
x86/cpu: Ensure that CPU info updates are propagated on UP
kprobes/x86: Use copy_from_kernel_nofault() to read from unsafe address
x86/pm: Work around false positive kmemleak report in msr_build_context()
x86/kexec: Do not update E820 kexec table for setup_data
x86/config: Fix warning for 'make ARCH=x86_64 tinyconfig'

Check if get_next_variable() is actually valid pointer before
calling it. In kdump kernel this method is set to NULL that causes
panic during the kexec-ed kernel boot.

Tested with QEMU and OVMF firmware.

Fixes: bad267f9e18f ("efi: verify that variable services are supported")
Signed-off-by: Oleksandr Tymoshenko <ovt@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Pull scheduler doc clarification from Thomas Gleixner:
"A single update for the documentation of the base_slice_ns tunable to
clarify that any value which is less than the tick slice has no effect
because the scheduler tick is not guaranteed to happen within the set
time slice"

* tag 'sched-urgent-2024-03-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/doc: Update documentation for base_slice_ns and CONFIG_HZ relation

Commit 63bed9660420 ("x86/startup_64: Defer assignment of 5-level paging
global variables") moved assignment of 5-level global variables to later
in the boot in order to avoid having to use RIP relative addressing in
order to set them. However, when running with 5-level paging and SME
active (mem_encrypt=on), the variables are needed as part of the page
table setup needed to encrypt the kernel (using pgd_none(), p4d_offset(),
etc.). Since the variables haven't been set, the page table manipulation
is done as if 4-level paging is active, causing the system to crash on
boot.

While only a subset of the assignments that were moved need to be set
early, move all of the assignments back into check_la57_support() so that
these assignments aren't spread between two locations. Instead of just
reverting the fix, this uses the new RIP_REL_REF() macro when assigning
the variables.

Fixes: 63bed9660420 ("x86/startup_64: Defer assignment of 5-level paging global variables")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/2ca419f4d0de719926fd82353f6751f717590a86.1711122067.git.thomas.lendacky@amd.com

Clearing BSS should only be done once, at the very beginning.
efi_pe_entry() is the entrypoint from the firmware, which may not clear
BSS and so it is done explicitly. However, efi_pe_entry() is also used
as an entrypoint by the mixed mode startup code, in which case BSS will
already have been cleared, and doing it again at this point will corrupt
global variables holding the firmware's GDT/IDT and segment selectors.

So make the memset() conditional on whether the EFI stub is running in
native mode.

Fixes: b3810c5a2cc4a666 ("x86/efistub: Clear decompressor BSS in native EFI entrypoint")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Pull dma-mapping fixes from Christoph Hellwig:
"This has a set of swiotlb alignment fixes for sometimes very long
standing bugs from Will. We've been discussion them for a while and
they should be solid now"

* tag 'dma-mapping-6.9-2024-03-24' of git://git.infradead.org/users/hch/dma-mapping:
swiotlb: Reinstate page-alignment for mappings >= PAGE_SIZE
iommu/dma: Force swiotlb_max_mapping_size on an untrusted device
swiotlb: Fix alignment checks when both allocation and DMA masks are present
swiotlb: Honour dma_alloc_coherent() alignment in swiotlb_alloc()
swiotlb: Enforce page alignment in swiotlb_alloc()
swiotlb: Fix double-allocation of slots due to broken alignment handling