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, 327 insertions, 0 deletions

diff --git a/arch/mips/bcm63xx/dev-enet.c b/arch/mips/bcm63xx/dev-enet.c
new file mode 100644
index 000000000..8e73d65f3
--- /dev/null
+++ b/arch/mips/bcm63xx/dev-enet.c
@@ -0,0 +1,327 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2008 Maxime Bizon <mbizon@freebox.fr>
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/export.h>
+#include <bcm63xx_dev_enet.h>
+#include <bcm63xx_io.h>
+#include <bcm63xx_regs.h>
+
+static const unsigned long bcm6348_regs_enetdmac[] = {
+	[ENETDMAC_CHANCFG]	= ENETDMAC_CHANCFG_REG,
+	[ENETDMAC_IR]		= ENETDMAC_IR_REG,
+	[ENETDMAC_IRMASK]	= ENETDMAC_IRMASK_REG,
+	[ENETDMAC_MAXBURST]	= ENETDMAC_MAXBURST_REG,
+};
+
+static const unsigned long bcm6345_regs_enetdmac[] = {
+	[ENETDMAC_CHANCFG]	= ENETDMA_6345_CHANCFG_REG,
+	[ENETDMAC_IR]		= ENETDMA_6345_IR_REG,
+	[ENETDMAC_IRMASK]	= ENETDMA_6345_IRMASK_REG,
+	[ENETDMAC_MAXBURST]	= ENETDMA_6345_MAXBURST_REG,
+	[ENETDMAC_BUFALLOC]	= ENETDMA_6345_BUFALLOC_REG,
+	[ENETDMAC_RSTART]	= ENETDMA_6345_RSTART_REG,
+	[ENETDMAC_FC]		= ENETDMA_6345_FC_REG,
+	[ENETDMAC_LEN]		= ENETDMA_6345_LEN_REG,
+};
+
+const unsigned long *bcm63xx_regs_enetdmac;
+EXPORT_SYMBOL(bcm63xx_regs_enetdmac);
+
+static __init void bcm63xx_enetdmac_regs_init(void)
+{
+	if (BCMCPU_IS_6345())
+		bcm63xx_regs_enetdmac = bcm6345_regs_enetdmac;
+	else
+		bcm63xx_regs_enetdmac = bcm6348_regs_enetdmac;
+}
+
+static struct resource shared_res[] = {
+	{
+		.start		= -1, /* filled at runtime */
+		.end		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		.start		= -1, /* filled at runtime */
+		.end		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		.start		= -1, /* filled at runtime */
+		.end		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+};
+
+static struct platform_device bcm63xx_enet_shared_device = {
+	.name		= "bcm63xx_enet_shared",
+	.id		= 0,
+	.num_resources	= ARRAY_SIZE(shared_res),
+	.resource	= shared_res,
+};
+
+static int shared_device_registered;
+
+static u64 enet_dmamask = DMA_BIT_MASK(32);
+
+static struct resource enet0_res[] = {
+	{
+		.start		= -1, /* filled at runtime */
+		.end		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		.start		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+	{
+		.start		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+	{
+		.start		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct bcm63xx_enet_platform_data enet0_pd;
+
+static struct platform_device bcm63xx_enet0_device = {
+	.name		= "bcm63xx_enet",
+	.id		= 0,
+	.num_resources	= ARRAY_SIZE(enet0_res),
+	.resource	= enet0_res,
+	.dev		= {
+		.platform_data = &enet0_pd,
+		.dma_mask = &enet_dmamask,
+		.coherent_dma_mask = DMA_BIT_MASK(32),
+	},
+};
+
+static struct resource enet1_res[] = {
+	{
+		.start		= -1, /* filled at runtime */
+		.end		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		.start		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+	{
+		.start		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+	{
+		.start		= -1, /* filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct bcm63xx_enet_platform_data enet1_pd;
+
+static struct platform_device bcm63xx_enet1_device = {
+	.name		= "bcm63xx_enet",
+	.id		= 1,
+	.num_resources	= ARRAY_SIZE(enet1_res),
+	.resource	= enet1_res,
+	.dev		= {
+		.platform_data = &enet1_pd,
+		.dma_mask = &enet_dmamask,
+		.coherent_dma_mask = DMA_BIT_MASK(32),
+	},
+};
+
+static struct resource enetsw_res[] = {
+	{
+		/* start & end filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		/* start filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+	{
+		/* start filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct bcm63xx_enetsw_platform_data enetsw_pd;
+
+static struct platform_device bcm63xx_enetsw_device = {
+	.name		= "bcm63xx_enetsw",
+	.num_resources	= ARRAY_SIZE(enetsw_res),
+	.resource	= enetsw_res,
+	.dev		= {
+		.platform_data = &enetsw_pd,
+		.dma_mask = &enet_dmamask,
+		.coherent_dma_mask = DMA_BIT_MASK(32),
+	},
+};
+
+static int __init register_shared(void)
+{
+	int ret, chan_count;
+
+	if (shared_device_registered)
+		return 0;
+
+	bcm63xx_enetdmac_regs_init();
+
+	shared_res[0].start = bcm63xx_regset_address(RSET_ENETDMA);
+	shared_res[0].end = shared_res[0].start;
+	if (BCMCPU_IS_6345())
+		shared_res[0].end += (RSET_6345_ENETDMA_SIZE) - 1;
+	else
+		shared_res[0].end += (RSET_ENETDMA_SIZE)  - 1;
+
+	if (BCMCPU_IS_6328() || BCMCPU_IS_6362() || BCMCPU_IS_6368())
+		chan_count = 32;
+	else if (BCMCPU_IS_6345())
+		chan_count = 8;
+	else
+		chan_count = 16;
+
+	shared_res[1].start = bcm63xx_regset_address(RSET_ENETDMAC);
+	shared_res[1].end = shared_res[1].start;
+	shared_res[1].end += RSET_ENETDMAC_SIZE(chan_count)  - 1;
+
+	shared_res[2].start = bcm63xx_regset_address(RSET_ENETDMAS);
+	shared_res[2].end = shared_res[2].start;
+	shared_res[2].end += RSET_ENETDMAS_SIZE(chan_count)  - 1;
+
+	ret = platform_device_register(&bcm63xx_enet_shared_device);
+	if (ret)
+		return ret;
+	shared_device_registered = 1;
+
+	return 0;
+}
+
+int __init bcm63xx_enet_register(int unit,
+				 const struct bcm63xx_enet_platform_data *pd)
+{
+	struct platform_device *pdev;
+	struct bcm63xx_enet_platform_data *dpd;
+	int ret;
+
+	if (unit > 1)
+		return -ENODEV;
+
+	if (unit == 1 && (BCMCPU_IS_6338() || BCMCPU_IS_6345()))
+		return -ENODEV;
+
+	ret = register_shared();
+	if (ret)
+		return ret;
+
+	if (unit == 0) {
+		enet0_res[0].start = bcm63xx_regset_address(RSET_ENET0);
+		enet0_res[0].end = enet0_res[0].start;
+		enet0_res[0].end += RSET_ENET_SIZE - 1;
+		enet0_res[1].start = bcm63xx_get_irq_number(IRQ_ENET0);
+		enet0_res[2].start = bcm63xx_get_irq_number(IRQ_ENET0_RXDMA);
+		enet0_res[3].start = bcm63xx_get_irq_number(IRQ_ENET0_TXDMA);
+		pdev = &bcm63xx_enet0_device;
+	} else {
+		enet1_res[0].start = bcm63xx_regset_address(RSET_ENET1);
+		enet1_res[0].end = enet1_res[0].start;
+		enet1_res[0].end += RSET_ENET_SIZE - 1;
+		enet1_res[1].start = bcm63xx_get_irq_number(IRQ_ENET1);
+		enet1_res[2].start = bcm63xx_get_irq_number(IRQ_ENET1_RXDMA);
+		enet1_res[3].start = bcm63xx_get_irq_number(IRQ_ENET1_TXDMA);
+		pdev = &bcm63xx_enet1_device;
+	}
+
+	/* copy given platform data */
+	dpd = pdev->dev.platform_data;
+	memcpy(dpd, pd, sizeof(*pd));
+
+	/* adjust them in case internal phy is used */
+	if (dpd->use_internal_phy) {
+
+		/* internal phy only exists for enet0 */
+		if (unit == 1)
+			return -ENODEV;
+
+		dpd->phy_id = 1;
+		dpd->has_phy_interrupt = 1;
+		dpd->phy_interrupt = bcm63xx_get_irq_number(IRQ_ENET_PHY);
+	}
+
+	dpd->dma_chan_en_mask = ENETDMAC_CHANCFG_EN_MASK;
+	dpd->dma_chan_int_mask = ENETDMAC_IR_PKTDONE_MASK;
+	if (BCMCPU_IS_6345()) {
+		dpd->dma_chan_en_mask |= ENETDMAC_CHANCFG_CHAINING_MASK;
+		dpd->dma_chan_en_mask |= ENETDMAC_CHANCFG_WRAP_EN_MASK;
+		dpd->dma_chan_en_mask |= ENETDMAC_CHANCFG_FLOWC_EN_MASK;
+		dpd->dma_chan_int_mask |= ENETDMA_IR_BUFDONE_MASK;
+		dpd->dma_chan_int_mask |= ENETDMA_IR_NOTOWNER_MASK;
+		dpd->dma_chan_width = ENETDMA_6345_CHAN_WIDTH;
+		dpd->dma_desc_shift = ENETDMA_6345_DESC_SHIFT;
+	} else {
+		dpd->dma_has_sram = true;
+		dpd->dma_chan_width = ENETDMA_CHAN_WIDTH;
+	}
+
+	if (unit == 0) {
+		dpd->rx_chan = 0;
+		dpd->tx_chan = 1;
+	} else {
+		dpd->rx_chan = 2;
+		dpd->tx_chan = 3;
+	}
+
+	ret = platform_device_register(pdev);
+	if (ret)
+		return ret;
+	return 0;
+}
+
+int __init
+bcm63xx_enetsw_register(const struct bcm63xx_enetsw_platform_data *pd)
+{
+	int ret;
+
+	if (!BCMCPU_IS_6328() && !BCMCPU_IS_6362() && !BCMCPU_IS_6368())
+		return -ENODEV;
+
+	ret = register_shared();
+	if (ret)
+		return ret;
+
+	enetsw_res[0].start = bcm63xx_regset_address(RSET_ENETSW);
+	enetsw_res[0].end = enetsw_res[0].start;
+	enetsw_res[0].end += RSET_ENETSW_SIZE - 1;
+	enetsw_res[1].start = bcm63xx_get_irq_number(IRQ_ENETSW_RXDMA0);
+	enetsw_res[2].start = bcm63xx_get_irq_number(IRQ_ENETSW_TXDMA0);
+	if (!enetsw_res[2].start)
+		enetsw_res[2].start = -1;
+
+	memcpy(bcm63xx_enetsw_device.dev.platform_data, pd, sizeof(*pd));
+
+	if (BCMCPU_IS_6328())
+		enetsw_pd.num_ports = ENETSW_PORTS_6328;
+	else if (BCMCPU_IS_6362() || BCMCPU_IS_6368())
+		enetsw_pd.num_ports = ENETSW_PORTS_6368;
+
+	enetsw_pd.dma_has_sram = true;
+	enetsw_pd.dma_chan_width = ENETDMA_CHAN_WIDTH;
+	enetsw_pd.dma_chan_en_mask = ENETDMAC_CHANCFG_EN_MASK;
+	enetsw_pd.dma_chan_int_mask = ENETDMAC_IR_PKTDONE_MASK;
+
+	ret = platform_device_register(&bcm63xx_enetsw_device);
+	if (ret)
+		return ret;
+
+	return 0;
+}