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, 129 insertions, 0 deletions

diff --git a/drivers/net/phy/bcm-phy-lib.h b/drivers/net/phy/bcm-phy-lib.h
new file mode 100644
index 000000000..bba94ce96
--- /dev/null
+++ b/drivers/net/phy/bcm-phy-lib.h
@@ -0,0 +1,129 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2015 Broadcom Corporation
+ */
+
+#ifndef _LINUX_BCM_PHY_LIB_H
+#define _LINUX_BCM_PHY_LIB_H
+
+#include <linux/brcmphy.h>
+#include <linux/phy.h>
+#include <linux/interrupt.h>
+
+struct ethtool_wolinfo;
+
+/* 28nm only register definitions */
+#define MISC_ADDR(base, channel)	base, channel
+
+#define DSP_TAP10			MISC_ADDR(0x0a, 0)
+#define PLL_PLLCTRL_1			MISC_ADDR(0x32, 1)
+#define PLL_PLLCTRL_2			MISC_ADDR(0x32, 2)
+#define PLL_PLLCTRL_4			MISC_ADDR(0x33, 0)
+
+#define AFE_RXCONFIG_0			MISC_ADDR(0x38, 0)
+#define AFE_RXCONFIG_1			MISC_ADDR(0x38, 1)
+#define AFE_RXCONFIG_2			MISC_ADDR(0x38, 2)
+#define AFE_RX_LP_COUNTER		MISC_ADDR(0x38, 3)
+#define AFE_TX_CONFIG			MISC_ADDR(0x39, 0)
+#define AFE_VDCA_ICTRL_0		MISC_ADDR(0x39, 1)
+#define AFE_VDAC_OTHERS_0		MISC_ADDR(0x39, 3)
+#define AFE_HPF_TRIM_OTHERS		MISC_ADDR(0x3a, 0)
+
+
+int __bcm_phy_write_exp(struct phy_device *phydev, u16 reg, u16 val);
+int __bcm_phy_read_exp(struct phy_device *phydev, u16 reg);
+int __bcm_phy_modify_exp(struct phy_device *phydev, u16 reg, u16 mask, u16 set);
+int bcm_phy_write_exp(struct phy_device *phydev, u16 reg, u16 val);
+int bcm_phy_read_exp(struct phy_device *phydev, u16 reg);
+int bcm_phy_modify_exp(struct phy_device *phydev, u16 reg, u16 mask, u16 set);
+
+static inline int bcm_phy_write_exp_sel(struct phy_device *phydev,
+					u16 reg, u16 val)
+{
+	return bcm_phy_write_exp(phydev, reg | MII_BCM54XX_EXP_SEL_ER, val);
+}
+
+static inline int bcm_phy_read_exp_sel(struct phy_device *phydev, u16 reg)
+{
+	return bcm_phy_read_exp(phydev, reg | MII_BCM54XX_EXP_SEL_ER);
+}
+
+int bcm54xx_auxctl_write(struct phy_device *phydev, u16 regnum, u16 val);
+int bcm54xx_auxctl_read(struct phy_device *phydev, u16 regnum);
+
+int bcm_phy_write_misc(struct phy_device *phydev,
+		       u16 reg, u16 chl, u16 value);
+int bcm_phy_read_misc(struct phy_device *phydev,
+		      u16 reg, u16 chl);
+
+int bcm_phy_write_shadow(struct phy_device *phydev, u16 shadow,
+			 u16 val);
+int bcm_phy_read_shadow(struct phy_device *phydev, u16 shadow);
+
+int __bcm_phy_write_rdb(struct phy_device *phydev, u16 rdb, u16 val);
+int bcm_phy_write_rdb(struct phy_device *phydev, u16 rdb, u16 val);
+int __bcm_phy_read_rdb(struct phy_device *phydev, u16 rdb);
+int bcm_phy_read_rdb(struct phy_device *phydev, u16 rdb);
+int __bcm_phy_modify_rdb(struct phy_device *phydev, u16 rdb, u16 mask,
+			 u16 set);
+int bcm_phy_modify_rdb(struct phy_device *phydev, u16 rdb, u16 mask,
+		       u16 set);
+
+int bcm_phy_ack_intr(struct phy_device *phydev);
+int bcm_phy_config_intr(struct phy_device *phydev);
+irqreturn_t bcm_phy_handle_interrupt(struct phy_device *phydev);
+
+int bcm_phy_enable_apd(struct phy_device *phydev, bool dll_pwr_down);
+
+int bcm_phy_set_eee(struct phy_device *phydev, bool enable);
+
+int bcm_phy_downshift_get(struct phy_device *phydev, u8 *count);
+
+int bcm_phy_downshift_set(struct phy_device *phydev, u8 count);
+
+int bcm_phy_get_sset_count(struct phy_device *phydev);
+void bcm_phy_get_strings(struct phy_device *phydev, u8 *data);
+void bcm_phy_get_stats(struct phy_device *phydev, u64 *shadow,
+		       struct ethtool_stats *stats, u64 *data);
+void bcm_phy_update_stats_shadow(struct phy_device *phydev, u64 *shadow);
+void bcm_phy_r_rc_cal_reset(struct phy_device *phydev);
+int bcm_phy_28nm_a0b0_afe_config_init(struct phy_device *phydev);
+int bcm_phy_enable_jumbo(struct phy_device *phydev);
+
+int bcm_phy_cable_test_get_status_rdb(struct phy_device *phydev,
+				      bool *finished);
+int bcm_phy_cable_test_start_rdb(struct phy_device *phydev);
+int bcm_phy_cable_test_start(struct phy_device *phydev);
+int bcm_phy_cable_test_get_status(struct phy_device *phydev, bool *finished);
+
+#if IS_ENABLED(CONFIG_BCM_NET_PHYPTP)
+struct bcm_ptp_private *bcm_ptp_probe(struct phy_device *phydev);
+void bcm_ptp_config_init(struct phy_device *phydev);
+void bcm_ptp_stop(struct bcm_ptp_private *priv);
+#else
+static inline struct bcm_ptp_private *bcm_ptp_probe(struct phy_device *phydev)
+{
+	return NULL;
+}
+
+static inline void bcm_ptp_config_init(struct phy_device *phydev)
+{
+}
+
+static inline void bcm_ptp_stop(struct bcm_ptp_private *priv)
+{
+}
+#endif
+
+int bcm_phy_set_wol(struct phy_device *phydev, struct ethtool_wolinfo *wol);
+void bcm_phy_get_wol(struct phy_device *phydev, struct ethtool_wolinfo *wol);
+irqreturn_t bcm_phy_wol_isr(int irq, void *dev_id);
+
+int bcm_phy_led_brightness_set(struct phy_device *phydev,
+			       u8 index, enum led_brightness value);
+
+int bcm_setup_lre_master_slave(struct phy_device *phydev);
+int bcm_config_lre_aneg(struct phy_device *phydev, bool changed);
+int bcm_config_lre_advert(struct phy_device *phydev);
+
+#endif /* _LINUX_BCM_PHY_LIB_H */