kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 305 insertions, 0 deletions

diff --git a/security/Kconfig b/security/Kconfig
new file mode 100644
index 000000000..f7bf6cdc6
--- /dev/null
+++ b/security/Kconfig
@@ -0,0 +1,305 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Security configuration
+#
+
+menu "Security options"
+
+source "security/keys/Kconfig"
+
+config SECURITY_DMESG_RESTRICT
+	bool "Restrict unprivileged access to the kernel syslog"
+	default n
+	help
+	  This enforces restrictions on unprivileged users reading the kernel
+	  syslog via dmesg(8).
+
+	  If this option is not selected, no restrictions will be enforced
+	  unless the dmesg_restrict sysctl is explicitly set to (1).
+
+	  If you are unsure how to answer this question, answer N.
+
+choice
+	prompt "Allow /proc/pid/mem access override"
+	default PROC_MEM_FORCE_PTRACE
+	help
+	  Traditionally /proc/pid/mem allows users to override memory
+	  permissions for users like ptrace, assuming they have ptrace
+	  capability.
+
+	  This allows people to limit that - either never override, or
+	  require actual active ptrace attachment (default).
+
+config PROC_MEM_ALWAYS_FORCE
+	bool "Traditional /proc/pid/mem behavior"
+	help
+	  This allows /proc/pid/mem accesses to override memory mapping
+	  permissions if you have ptrace access rights.
+
+config PROC_MEM_FORCE_PTRACE
+	bool "Require active ptrace() use for access override"
+	help
+	  This allows /proc/pid/mem accesses to override memory mapping
+	  permissions for active ptracers like gdb.
+
+config PROC_MEM_NO_FORCE
+	bool "Never"
+	help
+	  Never override memory mapping permissions
+
+endchoice
+
+config MSEAL_SYSTEM_MAPPINGS
+	bool "mseal system mappings"
+	depends on 64BIT
+	depends on ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS
+	depends on !CHECKPOINT_RESTORE
+	help
+	  Apply mseal on system mappings.
+	  The system mappings includes vdso, vvar, vvar_vclock,
+	  vectors (arm compat-mode), sigpage (arm compat-mode), uprobes.
+
+	  A 64-bit kernel is required for the memory sealing feature.
+	  No specific hardware features from the CPU are needed.
+
+	  WARNING: This feature breaks programs which rely on relocating
+	  or unmapping system mappings. Known broken software at the time
+	  of writing includes CHECKPOINT_RESTORE, UML, gVisor, rr. Therefore
+	  this config can't be enabled universally.
+
+	  For complete descriptions of memory sealing, please see
+	  Documentation/userspace-api/mseal.rst
+
+config SECURITY
+	bool "Enable different security models"
+	depends on SYSFS
+	depends on MULTIUSER
+	help
+	  This allows you to choose different security modules to be
+	  configured into your kernel.
+
+	  If this option is not selected, the default Linux security
+	  model will be used.
+
+	  If you are unsure how to answer this question, answer N.
+
+config HAS_SECURITY_AUDIT
+	def_bool y
+	depends on AUDIT
+	depends on SECURITY
+
+config SECURITYFS
+	bool "Enable the securityfs filesystem"
+	help
+	  This will build the securityfs filesystem.  It is currently used by
+	  various security modules (AppArmor, IMA, SafeSetID, TOMOYO, TPM).
+
+	  If you are unsure how to answer this question, answer N.
+
+config SECURITY_NETWORK
+	bool "Socket and Networking Security Hooks"
+	depends on SECURITY
+	help
+	  This enables the socket and networking security hooks.
+	  If enabled, a security module can use these hooks to
+	  implement socket and networking access controls.
+	  If you are unsure how to answer this question, answer N.
+
+config SECURITY_INFINIBAND
+	bool "Infiniband Security Hooks"
+	depends on SECURITY && INFINIBAND
+	help
+	  This enables the Infiniband security hooks.
+	  If enabled, a security module can use these hooks to
+	  implement Infiniband access controls.
+	  If you are unsure how to answer this question, answer N.
+
+config SECURITY_NETWORK_XFRM
+	bool "XFRM (IPSec) Networking Security Hooks"
+	depends on XFRM && SECURITY_NETWORK
+	help
+	  This enables the XFRM (IPSec) networking security hooks.
+	  If enabled, a security module can use these hooks to
+	  implement per-packet access controls based on labels
+	  derived from IPSec policy.  Non-IPSec communications are
+	  designated as unlabelled, and only sockets authorized
+	  to communicate unlabelled data can send without using
+	  IPSec.
+	  If you are unsure how to answer this question, answer N.
+
+config SECURITY_PATH
+	bool "Security hooks for pathname based access control"
+	depends on SECURITY
+	help
+	  This enables the security hooks for pathname based access control.
+	  If enabled, a security module can use these hooks to
+	  implement pathname based access controls.
+	  If you are unsure how to answer this question, answer N.
+
+config INTEL_TXT
+	bool "Enable Intel(R) Trusted Execution Technology (Intel(R) TXT)"
+	depends on HAVE_INTEL_TXT
+	help
+	  This option enables support for booting the kernel with the
+	  Trusted Boot (tboot) module. This will utilize
+	  Intel(R) Trusted Execution Technology to perform a measured launch
+	  of the kernel. If the system does not support Intel(R) TXT, this
+	  will have no effect.
+
+	  Intel TXT will provide higher assurance of system configuration and
+	  initial state as well as data reset protection.  This is used to
+	  create a robust initial kernel measurement and verification, which
+	  helps to ensure that kernel security mechanisms are functioning
+	  correctly. This level of protection requires a root of trust outside
+	  of the kernel itself.
+
+	  Intel TXT also helps solve real end user concerns about having
+	  confidence that their hardware is running the VMM or kernel that
+	  it was configured with, especially since they may be responsible for
+	  providing such assurances to VMs and services running on it.
+
+	  See <https://www.intel.com/technology/security/> for more information
+	  about Intel(R) TXT.
+	  See <http://tboot.sourceforge.net> for more information about tboot.
+	  See Documentation/arch/x86/intel_txt.rst for a description of how to enable
+	  Intel TXT support in a kernel boot.
+
+	  If you are unsure as to whether this is required, answer N.
+
+config LSM_MMAP_MIN_ADDR
+	int "Low address space for LSM to protect from user allocation"
+	depends on SECURITY && SECURITY_SELINUX
+	default 32768 if ARM || (ARM64 && COMPAT)
+	default 65536
+	help
+	  This is the portion of low virtual memory which should be protected
+	  from userspace allocation.  Keeping a user from writing to low pages
+	  can help reduce the impact of kernel NULL pointer bugs.
+
+	  For most ia64, ppc64 and x86 users with lots of address space
+	  a value of 65536 is reasonable and should cause no problems.
+	  On arm and other archs it should not be higher than 32768.
+	  Programs which use vm86 functionality or have some need to map
+	  this low address space will need the permission specific to the
+	  systems running LSM.
+
+config STATIC_USERMODEHELPER
+	bool "Force all usermode helper calls through a single binary"
+	help
+	  By default, the kernel can call many different userspace
+	  binary programs through the "usermode helper" kernel
+	  interface.  Some of these binaries are statically defined
+	  either in the kernel code itself, or as a kernel configuration
+	  option.  However, some of these are dynamically created at
+	  runtime, or can be modified after the kernel has started up.
+	  To provide an additional layer of security, route all of these
+	  calls through a single executable that can not have its name
+	  changed.
+
+	  Note, it is up to this single binary to then call the relevant
+	  "real" usermode helper binary, based on the first argument
+	  passed to it.  If desired, this program can filter and pick
+	  and choose what real programs are called.
+
+	  If you wish for all usermode helper programs are to be
+	  disabled, choose this option and then set
+	  STATIC_USERMODEHELPER_PATH to an empty string.
+
+config STATIC_USERMODEHELPER_PATH
+	string "Path to the static usermode helper binary"
+	depends on STATIC_USERMODEHELPER
+	default "/sbin/usermode-helper"
+	help
+	  The binary called by the kernel when any usermode helper
+	  program is wish to be run.  The "real" application's name will
+	  be in the first argument passed to this program on the command
+	  line.
+
+	  If you wish for all usermode helper programs to be disabled,
+	  specify an empty string here (i.e. "").
+
+source "security/selinux/Kconfig"
+source "security/smack/Kconfig"
+source "security/tomoyo/Kconfig"
+source "security/apparmor/Kconfig"
+source "security/loadpin/Kconfig"
+source "security/yama/Kconfig"
+source "security/safesetid/Kconfig"
+source "security/lockdown/Kconfig"
+source "security/landlock/Kconfig"
+source "security/ipe/Kconfig"
+
+source "security/integrity/Kconfig"
+
+choice
+	prompt "First legacy 'major LSM' to be initialized"
+	default DEFAULT_SECURITY_SELINUX if SECURITY_SELINUX
+	default DEFAULT_SECURITY_SMACK if SECURITY_SMACK
+	default DEFAULT_SECURITY_TOMOYO if SECURITY_TOMOYO
+	default DEFAULT_SECURITY_APPARMOR if SECURITY_APPARMOR
+	default DEFAULT_SECURITY_DAC
+
+	help
+	  This choice is there only for converting CONFIG_DEFAULT_SECURITY
+	  in old kernel configs to CONFIG_LSM in new kernel configs. Don't
+	  change this choice unless you are creating a fresh kernel config,
+	  for this choice will be ignored after CONFIG_LSM has been set.
+
+	  Selects the legacy "major security module" that will be
+	  initialized first. Overridden by non-default CONFIG_LSM.
+
+	config DEFAULT_SECURITY_SELINUX
+		bool "SELinux" if SECURITY_SELINUX=y
+
+	config DEFAULT_SECURITY_SMACK
+		bool "Simplified Mandatory Access Control" if SECURITY_SMACK=y
+
+	config DEFAULT_SECURITY_TOMOYO
+		bool "TOMOYO" if SECURITY_TOMOYO=y
+
+	config DEFAULT_SECURITY_APPARMOR
+		bool "AppArmor" if SECURITY_APPARMOR=y
+
+	config DEFAULT_SECURITY_DAC
+		bool "Unix Discretionary Access Controls"
+
+endchoice
+
+config LSM
+	string "Ordered list of enabled LSMs"
+	depends on SECURITY
+	default "landlock,lockdown,yama,loadpin,safesetid,smack,selinux,tomoyo,apparmor,ipe,bpf" if DEFAULT_SECURITY_SMACK
+	default "landlock,lockdown,yama,loadpin,safesetid,apparmor,selinux,smack,tomoyo,ipe,bpf" if DEFAULT_SECURITY_APPARMOR
+	default "landlock,lockdown,yama,loadpin,safesetid,tomoyo,ipe,bpf" if DEFAULT_SECURITY_TOMOYO
+	default "landlock,lockdown,yama,loadpin,safesetid,ipe,bpf" if DEFAULT_SECURITY_DAC
+	default "landlock,lockdown,yama,loadpin,safesetid,selinux,smack,tomoyo,apparmor,ipe,bpf"
+	help
+	  A comma-separated list of LSMs, in initialization order.
+	  Any LSMs left off this list, except for those with order
+	  LSM_ORDER_FIRST and LSM_ORDER_LAST, which are always enabled
+	  if selected in the kernel configuration, will be ignored.
+	  This can be controlled at boot with the "lsm=" parameter.
+
+	  If unsure, leave this as the default.
+
+config SECURITY_COMMONCAP_KUNIT_TEST
+	bool "Build KUnit tests for commoncap" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y && USER_NS
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the commoncap KUnit tests.
+
+	  KUnit tests run during boot and output the results to the debug log
+	  in TAP format (https://testanything.org/). Only useful for kernel devs
+	  running KUnit test harness and are not for inclusion into a
+	  production build.
+
+	  For more information on KUnit and unit tests in general please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
+
+source "security/Kconfig.hardening"
+
+endmenu
+