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>

5 files changed, 413 insertions, 0 deletions

diff --git a/arch/microblaze/boot/.gitignore b/arch/microblaze/boot/.gitignore
new file mode 100644
index 000000000..11a9e229f
--- /dev/null
+++ b/arch/microblaze/boot/.gitignore
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+linux.bin*
+simpleImage.*
diff --git a/arch/microblaze/boot/Makefile b/arch/microblaze/boot/Makefile
new file mode 100644
index 000000000..2b42c370d
--- /dev/null
+++ b/arch/microblaze/boot/Makefile
@@ -0,0 +1,35 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# arch/microblaze/boot/Makefile
+#
+
+targets := linux.bin linux.bin.gz linux.bin.ub simpleImage.*
+
+OBJCOPYFLAGS := -R .note -R .comment -R .note.gnu.build-id -O binary
+
+$(obj)/linux.bin: vmlinux FORCE
+	$(call if_changed,objcopy)
+
+$(obj)/linux.bin.ub: $(obj)/linux.bin FORCE
+	$(call if_changed,uimage)
+
+$(obj)/linux.bin.gz: $(obj)/linux.bin FORCE
+	$(call if_changed,gzip)
+
+quiet_cmd_strip = STRIP   $< $@$2
+	cmd_strip = $(STRIP) -K microblaze_start -K _end -K __log_buf \
+				-K _fdt_start $< -o $@$2
+
+UIMAGE_LOADADDR = $(CONFIG_KERNEL_BASE_ADDR)
+
+$(obj)/simpleImage.$(DTB): vmlinux FORCE
+	$(call if_changed,objcopy)
+
+$(obj)/simpleImage.$(DTB).ub: $(obj)/simpleImage.$(DTB) FORCE
+	$(call if_changed,uimage)
+
+$(obj)/simpleImage.$(DTB).unstrip: vmlinux FORCE
+	$(call if_changed,copy)
+
+$(obj)/simpleImage.$(DTB).strip: vmlinux FORCE
+	$(call if_changed,strip)
diff --git a/arch/microblaze/boot/dts/Makefile b/arch/microblaze/boot/dts/Makefile
new file mode 100644
index 000000000..b84e2cbb2
--- /dev/null
+++ b/arch/microblaze/boot/dts/Makefile
@@ -0,0 +1,20 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+
+dtb-y := system.dtb
+
+ifneq ($(DTB),)
+obj-y += linked_dtb.o
+
+# Ensure system.dtb exists
+$(obj)/linked_dtb.o: $(obj)/system.dtb
+
+# Generate system.dtb from $(DTB).dtb
+ifneq ($(DTB),system)
+$(obj)/system.dtb: $(obj)/$(DTB).dtb
+	$(call if_changed,copy)
+endif
+endif
+
+# Rule to build device tree blobs
+DTC_FLAGS := -p 1024
diff --git a/arch/microblaze/boot/dts/linked_dtb.S b/arch/microblaze/boot/dts/linked_dtb.S
new file mode 100644
index 000000000..23345af37
--- /dev/null
+++ b/arch/microblaze/boot/dts/linked_dtb.S
@@ -0,0 +1,2 @@
+.section __fdt_blob,"a"
+.incbin "arch/microblaze/boot/dts/system.dtb"
diff --git a/arch/microblaze/boot/dts/system.dts b/arch/microblaze/boot/dts/system.dts
new file mode 100644
index 000000000..22252451e
--- /dev/null
+++ b/arch/microblaze/boot/dts/system.dts
@@ -0,0 +1,353 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Device Tree Generator version: 1.1
+ *
+ * (C) Copyright 2007-2008 Xilinx, Inc.
+ * (C) Copyright 2007-2009 Michal Simek
+ *
+ * Michal SIMEK <monstr@monstr.eu>
+ *
+ * CAUTION: This file is automatically generated by libgen.
+ * Version: Xilinx EDK 10.1.03 EDK_K_SP3.6
+ *
+ * XPS project directory: Xilinx-ML505-ll_temac-sgdma-MMU-FDT-edk101
+ */
+
+/dts-v1/;
+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+	compatible = "xlnx,microblaze";
+	model = "testing";
+	DDR2_SDRAM: memory@90000000 {
+		device_type = "memory";
+		reg = < 0x90000000 0x10000000 >;
+	} ;
+	aliases {
+		ethernet0 = &Hard_Ethernet_MAC;
+		serial0 = &RS232_Uart_1;
+	} ;
+	chosen {
+		bootargs = "console=ttyUL0,115200 highres=on";
+		stdout-path = "/plb@0/serial@84000000";
+	} ;
+	cpus {
+		#address-cells = <1>;
+		#cpus = <0x1>;
+		#size-cells = <0>;
+		microblaze_0: cpu@0 {
+			clock-frequency = <125000000>;
+			compatible = "xlnx,microblaze-7.10.d";
+			d-cache-baseaddr = <0x90000000>;
+			d-cache-highaddr = <0x9fffffff>;
+			d-cache-line-size = <0x10>;
+			d-cache-size = <0x2000>;
+			device_type = "cpu";
+			i-cache-baseaddr = <0x90000000>;
+			i-cache-highaddr = <0x9fffffff>;
+			i-cache-line-size = <0x10>;
+			i-cache-size = <0x2000>;
+			model = "microblaze,7.10.d";
+			reg = <0>;
+			timebase-frequency = <125000000>;
+			xlnx,addr-tag-bits = <0xf>;
+			xlnx,allow-dcache-wr = <0x1>;
+			xlnx,allow-icache-wr = <0x1>;
+			xlnx,area-optimized = <0x0>;
+			xlnx,cache-byte-size = <0x2000>;
+			xlnx,d-lmb = <0x1>;
+			xlnx,d-opb = <0x0>;
+			xlnx,d-plb = <0x1>;
+			xlnx,data-size = <0x20>;
+			xlnx,dcache-addr-tag = <0xf>;
+			xlnx,dcache-always-used = <0x1>;
+			xlnx,dcache-byte-size = <0x2000>;
+			xlnx,dcache-line-len = <0x4>;
+			xlnx,dcache-use-fsl = <0x1>;
+			xlnx,debug-enabled = <0x1>;
+			xlnx,div-zero-exception = <0x1>;
+			xlnx,dopb-bus-exception = <0x0>;
+			xlnx,dynamic-bus-sizing = <0x1>;
+			xlnx,edge-is-positive = <0x1>;
+			xlnx,family = "virtex5";
+			xlnx,endianness = <0x1>;
+			xlnx,fpu-exception = <0x1>;
+			xlnx,fsl-data-size = <0x20>;
+			xlnx,fsl-exception = <0x0>;
+			xlnx,fsl-links = <0x0>;
+			xlnx,i-lmb = <0x1>;
+			xlnx,i-opb = <0x0>;
+			xlnx,i-plb = <0x1>;
+			xlnx,icache-always-used = <0x1>;
+			xlnx,icache-line-len = <0x4>;
+			xlnx,icache-use-fsl = <0x1>;
+			xlnx,ill-opcode-exception = <0x1>;
+			xlnx,instance = "microblaze_0";
+			xlnx,interconnect = <0x1>;
+			xlnx,interrupt-is-edge = <0x0>;
+			xlnx,iopb-bus-exception = <0x0>;
+			xlnx,mmu-dtlb-size = <0x4>;
+			xlnx,mmu-itlb-size = <0x2>;
+			xlnx,mmu-tlb-access = <0x3>;
+			xlnx,mmu-zones = <0x10>;
+			xlnx,number-of-pc-brk = <0x1>;
+			xlnx,number-of-rd-addr-brk = <0x0>;
+			xlnx,number-of-wr-addr-brk = <0x0>;
+			xlnx,opcode-0x0-illegal = <0x1>;
+			xlnx,pvr = <0x2>;
+			xlnx,pvr-user1 = <0x0>;
+			xlnx,pvr-user2 = <0x0>;
+			xlnx,reset-msr = <0x0>;
+			xlnx,sco = <0x0>;
+			xlnx,unaligned-exceptions = <0x1>;
+			xlnx,use-barrel = <0x1>;
+			xlnx,use-dcache = <0x1>;
+			xlnx,use-div = <0x1>;
+			xlnx,use-ext-brk = <0x1>;
+			xlnx,use-ext-nm-brk = <0x1>;
+			xlnx,use-extended-fsl-instr = <0x0>;
+			xlnx,use-fpu = <0x2>;
+			xlnx,use-hw-mul = <0x2>;
+			xlnx,use-icache = <0x1>;
+			xlnx,use-interrupt = <0x1>;
+			xlnx,use-mmu = <0x3>;
+			xlnx,use-msr-instr = <0x1>;
+			xlnx,use-pcmp-instr = <0x1>;
+		} ;
+	} ;
+	mb_plb: plb@0 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "xlnx,plb-v46-1.03.a", "xlnx,plb-v46-1.00.a", "simple-bus";
+		ranges ;
+		FLASH: flash@a0000000 {
+			bank-width = <2>;
+			compatible = "xlnx,xps-mch-emc-2.00.a", "cfi-flash";
+			reg = < 0xa0000000 0x2000000 >;
+			xlnx,family = "virtex5";
+			xlnx,include-datawidth-matching-0 = <0x1>;
+			xlnx,include-datawidth-matching-1 = <0x0>;
+			xlnx,include-datawidth-matching-2 = <0x0>;
+			xlnx,include-datawidth-matching-3 = <0x0>;
+			xlnx,include-negedge-ioregs = <0x0>;
+			xlnx,include-plb-ipif = <0x1>;
+			xlnx,include-wrbuf = <0x1>;
+			xlnx,max-mem-width = <0x10>;
+			xlnx,mch-native-dwidth = <0x20>;
+			xlnx,mch-plb-clk-period-ps = <0x1f40>;
+			xlnx,mch-splb-awidth = <0x20>;
+			xlnx,mch0-accessbuf-depth = <0x10>;
+			xlnx,mch0-protocol = <0x0>;
+			xlnx,mch0-rddatabuf-depth = <0x10>;
+			xlnx,mch1-accessbuf-depth = <0x10>;
+			xlnx,mch1-protocol = <0x0>;
+			xlnx,mch1-rddatabuf-depth = <0x10>;
+			xlnx,mch2-accessbuf-depth = <0x10>;
+			xlnx,mch2-protocol = <0x0>;
+			xlnx,mch2-rddatabuf-depth = <0x10>;
+			xlnx,mch3-accessbuf-depth = <0x10>;
+			xlnx,mch3-protocol = <0x0>;
+			xlnx,mch3-rddatabuf-depth = <0x10>;
+			xlnx,mem0-width = <0x10>;
+			xlnx,mem1-width = <0x20>;
+			xlnx,mem2-width = <0x20>;
+			xlnx,mem3-width = <0x20>;
+			xlnx,num-banks-mem = <0x1>;
+			xlnx,num-channels = <0x0>;
+			xlnx,priority-mode = <0x0>;
+			xlnx,synch-mem-0 = <0x0>;
+			xlnx,synch-mem-1 = <0x0>;
+			xlnx,synch-mem-2 = <0x0>;
+			xlnx,synch-mem-3 = <0x0>;
+			xlnx,synch-pipedelay-0 = <0x2>;
+			xlnx,synch-pipedelay-1 = <0x2>;
+			xlnx,synch-pipedelay-2 = <0x2>;
+			xlnx,synch-pipedelay-3 = <0x2>;
+			xlnx,tavdv-ps-mem-0 = <0x1adb0>;
+			xlnx,tavdv-ps-mem-1 = <0x3a98>;
+			xlnx,tavdv-ps-mem-2 = <0x3a98>;
+			xlnx,tavdv-ps-mem-3 = <0x3a98>;
+			xlnx,tcedv-ps-mem-0 = <0x1adb0>;
+			xlnx,tcedv-ps-mem-1 = <0x3a98>;
+			xlnx,tcedv-ps-mem-2 = <0x3a98>;
+			xlnx,tcedv-ps-mem-3 = <0x3a98>;
+			xlnx,thzce-ps-mem-0 = <0x88b8>;
+			xlnx,thzce-ps-mem-1 = <0x1b58>;
+			xlnx,thzce-ps-mem-2 = <0x1b58>;
+			xlnx,thzce-ps-mem-3 = <0x1b58>;
+			xlnx,thzoe-ps-mem-0 = <0x1b58>;
+			xlnx,thzoe-ps-mem-1 = <0x1b58>;
+			xlnx,thzoe-ps-mem-2 = <0x1b58>;
+			xlnx,thzoe-ps-mem-3 = <0x1b58>;
+			xlnx,tlzwe-ps-mem-0 = <0x88b8>;
+			xlnx,tlzwe-ps-mem-1 = <0x0>;
+			xlnx,tlzwe-ps-mem-2 = <0x0>;
+			xlnx,tlzwe-ps-mem-3 = <0x0>;
+			xlnx,twc-ps-mem-0 = <0x2af8>;
+			xlnx,twc-ps-mem-1 = <0x3a98>;
+			xlnx,twc-ps-mem-2 = <0x3a98>;
+			xlnx,twc-ps-mem-3 = <0x3a98>;
+			xlnx,twp-ps-mem-0 = <0x11170>;
+			xlnx,twp-ps-mem-1 = <0x2ee0>;
+			xlnx,twp-ps-mem-2 = <0x2ee0>;
+			xlnx,twp-ps-mem-3 = <0x2ee0>;
+			xlnx,xcl0-linesize = <0x4>;
+			xlnx,xcl0-writexfer = <0x1>;
+			xlnx,xcl1-linesize = <0x4>;
+			xlnx,xcl1-writexfer = <0x1>;
+			xlnx,xcl2-linesize = <0x4>;
+			xlnx,xcl2-writexfer = <0x1>;
+			xlnx,xcl3-linesize = <0x4>;
+			xlnx,xcl3-writexfer = <0x1>;
+		} ;
+		Hard_Ethernet_MAC: xps-ll-temac@81c00000 {
+			#address-cells = <1>;
+			#size-cells = <1>;
+			compatible = "xlnx,compound";
+			ranges ;
+			ethernet@81c00000 {
+				compatible = "xlnx,xps-ll-temac-1.01.b", "xlnx,xps-ll-temac-1.00.a";
+				interrupt-parent = <&xps_intc_0>;
+				interrupts = < 5 2 >;
+				llink-connected = <&PIM3>;
+				local-mac-address = [ 00 0a 35 00 00 00 ];
+				reg = < 0x81c00000 0x40 >;
+				xlnx,bus2core-clk-ratio = <0x1>;
+				xlnx,phy-type = <0x1>;
+				xlnx,phyaddr = <0x1>;
+				xlnx,rxcsum = <0x0>;
+				xlnx,rxfifo = <0x1000>;
+				xlnx,temac-type = <0x0>;
+				xlnx,txcsum = <0x0>;
+				xlnx,txfifo = <0x1000>;
+			} ;
+		} ;
+		IIC_EEPROM: i2c@81600000 {
+			compatible = "xlnx,xps-iic-2.00.a";
+			interrupt-parent = <&xps_intc_0>;
+			interrupts = < 6 2 >;
+			reg = < 0x81600000 0x10000 >;
+			xlnx,clk-freq = <0x7735940>;
+			xlnx,family = "virtex5";
+			xlnx,gpo-width = <0x1>;
+			xlnx,iic-freq = <0x186a0>;
+			xlnx,scl-inertial-delay = <0x0>;
+			xlnx,sda-inertial-delay = <0x0>;
+			xlnx,ten-bit-adr = <0x0>;
+		} ;
+		LEDs_8Bit: gpio@81400000 {
+			compatible = "xlnx,xps-gpio-1.00.a";
+			interrupt-parent = <&xps_intc_0>;
+			interrupts = < 7 2 >;
+			reg = < 0x81400000 0x10000 >;
+			xlnx,all-inputs = <0x0>;
+			xlnx,all-inputs-2 = <0x0>;
+			xlnx,dout-default = <0x0>;
+			xlnx,dout-default-2 = <0x0>;
+			xlnx,family = "virtex5";
+			xlnx,gpio-width = <0x8>;
+			xlnx,interrupt-present = <0x1>;
+			xlnx,is-bidir = <0x1>;
+			xlnx,is-bidir-2 = <0x1>;
+			xlnx,is-dual = <0x0>;
+			xlnx,tri-default = <0xffffffff>;
+			xlnx,tri-default-2 = <0xffffffff>;
+			#gpio-cells = <2>;
+			gpio-controller;
+		} ;
+
+		gpio-leds {
+			compatible = "gpio-leds";
+
+			heartbeat {
+				label = "Heartbeat";
+				gpios = <&LEDs_8Bit 4 1>;
+				linux,default-trigger = "heartbeat";
+			};
+
+			yellow {
+				label = "Yellow";
+				gpios = <&LEDs_8Bit 5 1>;
+			};
+
+			red {
+				label = "Red";
+				gpios = <&LEDs_8Bit 6 1>;
+			};
+
+			green {
+				label = "Green";
+				gpios = <&LEDs_8Bit 7 1>;
+			};
+		} ;
+
+		gpio-restart {
+			compatible = "gpio-restart";
+			/*
+			 * FIXME: is this active low or active high?
+			 * the current flag (1) indicates active low.
+			 * delay measures are templates, should be adjusted
+			 * to datasheet or trial-and-error with real hardware.
+			 */
+			gpios = <&LEDs_8Bit 2 1>;
+			active-delay = <100>;
+			inactive-delay = <10>;
+			wait-delay = <100>;
+		};
+
+		RS232_Uart_1: serial@84000000 {
+			clock-frequency = <125000000>;
+			compatible = "xlnx,xps-uartlite-1.00.a";
+			current-speed = <115200>;
+			device_type = "serial";
+			interrupt-parent = <&xps_intc_0>;
+			interrupts = < 8 0 >;
+			port-number = <0>;
+			reg = < 0x84000000 0x10000 >;
+			xlnx,baudrate = <0x1c200>;
+			xlnx,data-bits = <0x8>;
+			xlnx,family = "virtex5";
+			xlnx,odd-parity = <0x0>;
+			xlnx,use-parity = <0x0>;
+		} ;
+		debug_module: debug@84400000 {
+			compatible = "xlnx,mdm-1.00.d";
+			reg = < 0x84400000 0x10000 >;
+			xlnx,family = "virtex5";
+			xlnx,interconnect = <0x1>;
+			xlnx,jtag-chain = <0x2>;
+			xlnx,mb-dbg-ports = <0x1>;
+			xlnx,uart-width = <0x8>;
+			xlnx,use-uart = <0x1>;
+			xlnx,write-fsl-ports = <0x0>;
+		} ;
+		mpmc@90000000 {
+			#address-cells = <1>;
+			#size-cells = <1>;
+			compatible = "xlnx,mpmc-4.02.a";
+			ranges ;
+			PIM3: sdma@84600180 {
+				compatible = "xlnx,ll-dma-1.00.a";
+				interrupt-parent = <&xps_intc_0>;
+				interrupts = < 2 2 1 2 >;
+				reg = < 0x84600180 0x80 >;
+			} ;
+		} ;
+		xps_intc_0: interrupt-controller@81800000 {
+			#interrupt-cells = <0x2>;
+			compatible = "xlnx,xps-intc-1.00.a";
+			interrupt-controller ;
+			reg = < 0x81800000 0x10000 >;
+			xlnx,kind-of-intr = <0x100>;
+			xlnx,num-intr-inputs = <0x9>;
+		} ;
+		xps_timer_1: timer@83c00000 {
+			compatible = "xlnx,xps-timer-1.00.a";
+			interrupt-parent = <&xps_intc_0>;
+			interrupts = < 3 2 >;
+			reg = < 0x83c00000 0x10000 >;
+			xlnx,count-width = <0x20>;
+			xlnx,one-timer-only = <0x0>;
+		} ;
+	} ;
+}  ;