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, 126 insertions, 0 deletions

diff --git a/include/dt-bindings/clock/am3.h b/include/dt-bindings/clock/am3.h
new file mode 100644
index 000000000..dfbad5c87
--- /dev/null
+++ b/include/dt-bindings/clock/am3.h
@@ -0,0 +1,126 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2017 Texas Instruments, Inc.
+ */
+#ifndef __DT_BINDINGS_CLK_AM3_H
+#define __DT_BINDINGS_CLK_AM3_H
+
+#define AM3_CLKCTRL_OFFSET	0x0
+#define AM3_CLKCTRL_INDEX(offset)	((offset) - AM3_CLKCTRL_OFFSET)
+
+/* l4ls clocks */
+#define AM3_L4LS_CLKCTRL_OFFSET	0x38
+#define AM3_L4LS_CLKCTRL_INDEX(offset)	((offset) - AM3_L4LS_CLKCTRL_OFFSET)
+#define AM3_L4LS_UART6_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x38)
+#define AM3_L4LS_MMC1_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x3c)
+#define AM3_L4LS_ELM_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x40)
+#define AM3_L4LS_I2C3_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x44)
+#define AM3_L4LS_I2C2_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x48)
+#define AM3_L4LS_SPI0_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x4c)
+#define AM3_L4LS_SPI1_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x50)
+#define AM3_L4LS_L4_LS_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x60)
+#define AM3_L4LS_UART2_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x6c)
+#define AM3_L4LS_UART3_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x70)
+#define AM3_L4LS_UART4_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x74)
+#define AM3_L4LS_UART5_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x78)
+#define AM3_L4LS_TIMER7_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x7c)
+#define AM3_L4LS_TIMER2_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x80)
+#define AM3_L4LS_TIMER3_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x84)
+#define AM3_L4LS_TIMER4_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x88)
+#define AM3_L4LS_RNG_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x90)
+#define AM3_L4LS_GPIO2_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xac)
+#define AM3_L4LS_GPIO3_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xb0)
+#define AM3_L4LS_GPIO4_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xb4)
+#define AM3_L4LS_D_CAN0_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xc0)
+#define AM3_L4LS_D_CAN1_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xc4)
+#define AM3_L4LS_EPWMSS1_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xcc)
+#define AM3_L4LS_EPWMSS0_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xd4)
+#define AM3_L4LS_EPWMSS2_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xd8)
+#define AM3_L4LS_TIMER5_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xec)
+#define AM3_L4LS_TIMER6_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xf0)
+#define AM3_L4LS_MMC2_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0xf4)
+#define AM3_L4LS_SPINLOCK_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x10c)
+#define AM3_L4LS_MAILBOX_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x110)
+#define AM3_L4LS_OCPWP_CLKCTRL	AM3_L4LS_CLKCTRL_INDEX(0x130)
+
+/* l3s clocks */
+#define AM3_L3S_CLKCTRL_OFFSET	0x1c
+#define AM3_L3S_CLKCTRL_INDEX(offset)	((offset) - AM3_L3S_CLKCTRL_OFFSET)
+#define AM3_L3S_USB_OTG_HS_CLKCTRL	AM3_L3S_CLKCTRL_INDEX(0x1c)
+#define AM3_L3S_GPMC_CLKCTRL	AM3_L3S_CLKCTRL_INDEX(0x30)
+#define AM3_L3S_MCASP0_CLKCTRL	AM3_L3S_CLKCTRL_INDEX(0x34)
+#define AM3_L3S_MCASP1_CLKCTRL	AM3_L3S_CLKCTRL_INDEX(0x68)
+#define AM3_L3S_MMC3_CLKCTRL	AM3_L3S_CLKCTRL_INDEX(0xf8)
+
+/* l3 clocks */
+#define AM3_L3_CLKCTRL_OFFSET	0x24
+#define AM3_L3_CLKCTRL_INDEX(offset)	((offset) - AM3_L3_CLKCTRL_OFFSET)
+#define AM3_L3_TPTC0_CLKCTRL	AM3_L3_CLKCTRL_INDEX(0x24)
+#define AM3_L3_EMIF_CLKCTRL	AM3_L3_CLKCTRL_INDEX(0x28)
+#define AM3_L3_OCMCRAM_CLKCTRL	AM3_L3_CLKCTRL_INDEX(0x2c)
+#define AM3_L3_AES_CLKCTRL	AM3_L3_CLKCTRL_INDEX(0x94)
+#define AM3_L3_SHAM_CLKCTRL	AM3_L3_CLKCTRL_INDEX(0xa0)
+#define AM3_L3_TPCC_CLKCTRL	AM3_L3_CLKCTRL_INDEX(0xbc)
+#define AM3_L3_L3_INSTR_CLKCTRL	AM3_L3_CLKCTRL_INDEX(0xdc)
+#define AM3_L3_L3_MAIN_CLKCTRL	AM3_L3_CLKCTRL_INDEX(0xe0)
+#define AM3_L3_TPTC1_CLKCTRL	AM3_L3_CLKCTRL_INDEX(0xfc)
+#define AM3_L3_TPTC2_CLKCTRL	AM3_L3_CLKCTRL_INDEX(0x100)
+
+/* l4hs clocks */
+#define AM3_L4HS_CLKCTRL_OFFSET	0x120
+#define AM3_L4HS_CLKCTRL_INDEX(offset)	((offset) - AM3_L4HS_CLKCTRL_OFFSET)
+#define AM3_L4HS_L4_HS_CLKCTRL	AM3_L4HS_CLKCTRL_INDEX(0x120)
+
+/* pruss_ocp clocks */
+#define AM3_PRUSS_OCP_CLKCTRL_OFFSET	0xe8
+#define AM3_PRUSS_OCP_CLKCTRL_INDEX(offset)	((offset) - AM3_PRUSS_OCP_CLKCTRL_OFFSET)
+#define AM3_PRUSS_OCP_PRUSS_CLKCTRL	AM3_PRUSS_OCP_CLKCTRL_INDEX(0xe8)
+
+/* cpsw_125mhz clocks */
+#define AM3_CPSW_125MHZ_CPGMAC0_CLKCTRL	AM3_CLKCTRL_INDEX(0x14)
+
+/* lcdc clocks */
+#define AM3_LCDC_CLKCTRL_OFFSET	0x18
+#define AM3_LCDC_CLKCTRL_INDEX(offset)	((offset) - AM3_LCDC_CLKCTRL_OFFSET)
+#define AM3_LCDC_LCDC_CLKCTRL	AM3_LCDC_CLKCTRL_INDEX(0x18)
+
+/* clk_24mhz clocks */
+#define AM3_CLK_24MHZ_CLKCTRL_OFFSET	0x14c
+#define AM3_CLK_24MHZ_CLKCTRL_INDEX(offset)	((offset) - AM3_CLK_24MHZ_CLKCTRL_OFFSET)
+#define AM3_CLK_24MHZ_CLKDIV32K_CLKCTRL	AM3_CLK_24MHZ_CLKCTRL_INDEX(0x14c)
+
+/* l4_wkup clocks */
+#define AM3_L4_WKUP_CONTROL_CLKCTRL	AM3_CLKCTRL_INDEX(0x4)
+#define AM3_L4_WKUP_GPIO1_CLKCTRL	AM3_CLKCTRL_INDEX(0x8)
+#define AM3_L4_WKUP_L4_WKUP_CLKCTRL	AM3_CLKCTRL_INDEX(0xc)
+#define AM3_L4_WKUP_UART1_CLKCTRL	AM3_CLKCTRL_INDEX(0xb4)
+#define AM3_L4_WKUP_I2C1_CLKCTRL	AM3_CLKCTRL_INDEX(0xb8)
+#define AM3_L4_WKUP_ADC_TSC_CLKCTRL	AM3_CLKCTRL_INDEX(0xbc)
+#define AM3_L4_WKUP_SMARTREFLEX0_CLKCTRL	AM3_CLKCTRL_INDEX(0xc0)
+#define AM3_L4_WKUP_TIMER1_CLKCTRL	AM3_CLKCTRL_INDEX(0xc4)
+#define AM3_L4_WKUP_SMARTREFLEX1_CLKCTRL	AM3_CLKCTRL_INDEX(0xc8)
+#define AM3_L4_WKUP_WD_TIMER2_CLKCTRL	AM3_CLKCTRL_INDEX(0xd4)
+
+/* l3_aon clocks */
+#define AM3_L3_AON_CLKCTRL_OFFSET	0x14
+#define AM3_L3_AON_CLKCTRL_INDEX(offset)	((offset) - AM3_L3_AON_CLKCTRL_OFFSET)
+#define AM3_L3_AON_DEBUGSS_CLKCTRL	AM3_L3_AON_CLKCTRL_INDEX(0x14)
+
+/* l4_wkup_aon clocks */
+#define AM3_L4_WKUP_AON_CLKCTRL_OFFSET	0xb0
+#define AM3_L4_WKUP_AON_CLKCTRL_INDEX(offset)	((offset) - AM3_L4_WKUP_AON_CLKCTRL_OFFSET)
+#define AM3_L4_WKUP_AON_WKUP_M3_CLKCTRL	AM3_L4_WKUP_AON_CLKCTRL_INDEX(0xb0)
+
+/* mpu clocks */
+#define AM3_MPU_MPU_CLKCTRL	AM3_CLKCTRL_INDEX(0x4)
+
+/* l4_rtc clocks */
+#define AM3_L4_RTC_RTC_CLKCTRL	AM3_CLKCTRL_INDEX(0x0)
+
+/* gfx_l3 clocks */
+#define AM3_GFX_L3_GFX_CLKCTRL	AM3_CLKCTRL_INDEX(0x4)
+
+/* l4_cefuse clocks */
+#define AM3_L4_CEFUSE_CEFUSE_CLKCTRL	AM3_CLKCTRL_INDEX(0x20)
+
+#endif