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, 173 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-hisi-sec b/Documentation/ABI/testing/debugfs-hisi-sec
new file mode 100644
index 000000000..676e2dc2d
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-hisi-sec
@@ -0,0 +1,173 @@
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/clear_enable
+Date:		Oct 2019
+Contact:	linux-crypto@vger.kernel.org
+Description:	Enabling/disabling of clear action after reading
+		the SEC debug registers.
+		0: disable, 1: enable.
+		Only available for PF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/current_qm
+Date:		Oct 2019
+Contact:	linux-crypto@vger.kernel.org
+Description:	One SEC controller has one PF and multiple VFs, each function
+		has a QM. This file can be used to select the QM which below
+		qm refers to.
+		Only available for PF.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/alg_qos
+Date:		Jun 2021
+Contact:	linux-crypto@vger.kernel.org
+Description:	The <bdf> is related the function for PF and VF.
+		SEC driver supports to configure each function's QoS, the driver
+		supports to write <bdf> value to alg_qos in the host. Such as
+		"echo <bdf> value > alg_qos". The qos value is 1~1000, means
+		1/1000~1000/1000 of total QoS. The driver reading alg_qos to
+		get related QoS in the host and VM, Such as "cat alg_qos".
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/dev_usage
+Date:		Mar 2026
+Contact:	linux-crypto@vger.kernel.org
+Description:	Query the real-time bandwidth usage of device.
+		Returns the bandwidth usage of each channel on the device.
+		The returned number is in percentage.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/qm_regs
+Date:		Oct 2019
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump of QM related debug registers.
+		Available for PF and VF in host. VF in guest currently only
+		has one debug register.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/current_q
+Date:		Oct 2019
+Contact:	linux-crypto@vger.kernel.org
+Description:	One QM of SEC may contain multiple queues. Select specific
+		queue to show its debug registers in above 'regs'.
+		Only available for PF.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/clear_enable
+Date:		Oct 2019
+Contact:	linux-crypto@vger.kernel.org
+Description:	Enabling/disabling of clear action after reading
+		the SEC's QM debug registers.
+		0: disable, 1: enable.
+		Only available for PF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/err_irq
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the number of invalid interrupts for
+		QM task completion.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/aeq_irq
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the number of QM async event queue interrupts.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/abnormal_irq
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the number of interrupts for QM abnormal event.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/create_qp_err
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the number of queue allocation errors.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/mb_err
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the number of failed QM mailbox commands.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/status
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the status of the QM.
+		Two states: work, stop.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/diff_regs
+Date:		Mar 2022
+Contact:	linux-crypto@vger.kernel.org
+Description:	QM debug registers(regs) read hardware register value. This
+		node is used to show the change of the qm register values. This
+		node can be help users to check the change of register values.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/qm_state
+Date:		Jan 2024
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the state of the device.
+		0: busy, 1: idle.
+		Only available for PF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/dev_timeout
+Date:		Feb 2024
+Contact:	linux-crypto@vger.kernel.org
+Description:	Set the wait time when stop queue fails. Available for both PF
+		and VF, and take no other effect on SEC.
+		0: not wait(default), others value: wait dev_timeout * 20 microsecond.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/qm/dev_state
+Date:		Feb 2024
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the stop queue status of the QM. The default value is 0,
+		if dev_timeout is set, when stop queue fails, the dev_state
+		will return non-zero value. Available for both PF and VF,
+		and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/sec_dfx/diff_regs
+Date:		Mar 2022
+Contact:	linux-crypto@vger.kernel.org
+Description:	SEC debug registers(regs) read hardware register value. This
+		node is used to show the change of the register values. This
+		node can be help users to check the change of register values.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/sec_dfx/send_cnt
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the total number of sent requests.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/sec_dfx/recv_cnt
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the total number of received requests.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/sec_dfx/send_busy_cnt
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the total number of requests sent with returning busy.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/sec_dfx/err_bd_cnt
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the total number of BD type error requests
+		to be received.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/sec_dfx/invalid_req_cnt
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the total number of invalid requests being received.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:		/sys/kernel/debug/hisi_sec2/<bdf>/sec_dfx/done_flag_cnt
+Date:		Apr 2020
+Contact:	linux-crypto@vger.kernel.org
+Description:	Dump the total number of completed but marked error requests
+		to be received.
+		Available for both PF and VF, and take no other effect on SEC.
+
+What:           /sys/kernel/debug/hisi_sec2/<bdf>/cap_regs
+Date:           Oct 2024
+Contact:        linux-crypto@vger.kernel.org
+Description:    Dump the values of the qm and sec capability bit registers and
+                support the query of device specifications to facilitate fault locating.
+                Available for both PF and VF, and take no other effect on SEC.