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, 267 insertions, 0 deletions

diff --git a/drivers/misc/cardreader/rts5209.c b/drivers/misc/cardreader/rts5209.c
new file mode 100644
index 000000000..52b0a476b
--- /dev/null
+++ b/drivers/misc/cardreader/rts5209.c
@@ -0,0 +1,267 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Driver for Realtek PCI-Express card reader
+ *
+ * Copyright(c) 2009-2013 Realtek Semiconductor Corp. All rights reserved.
+ *
+ * Author:
+ *   Wei WANG <wei_wang@realsil.com.cn>
+ */
+
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/rtsx_pci.h>
+
+#include "rtsx_pcr.h"
+
+static u8 rts5209_get_ic_version(struct rtsx_pcr *pcr)
+{
+	u8 val;
+
+	val = rtsx_pci_readb(pcr, 0x1C);
+	return val & 0x0F;
+}
+
+static void rts5209_fetch_vendor_settings(struct rtsx_pcr *pcr)
+{
+	struct pci_dev *pdev = pcr->pci;
+	u32 reg;
+
+	pci_read_config_dword(pdev, PCR_SETTING_REG1, &reg);
+	pcr_dbg(pcr, "Cfg 0x%x: 0x%x\n", PCR_SETTING_REG1, reg);
+
+	if (rts5209_vendor_setting1_valid(reg)) {
+		if (rts5209_reg_check_ms_pmos(reg))
+			pcr->flags |= PCR_MS_PMOS;
+		pcr->aspm_en = rts5209_reg_to_aspm(reg);
+	}
+
+	pci_read_config_dword(pdev, PCR_SETTING_REG2, &reg);
+	pcr_dbg(pcr, "Cfg 0x%x: 0x%x\n", PCR_SETTING_REG2, reg);
+
+	if (rts5209_vendor_setting2_valid(reg)) {
+		pcr->sd30_drive_sel_1v8 =
+			rts5209_reg_to_sd30_drive_sel_1v8(reg);
+		pcr->sd30_drive_sel_3v3 =
+			rts5209_reg_to_sd30_drive_sel_3v3(reg);
+		pcr->card_drive_sel = rts5209_reg_to_card_drive_sel(reg);
+	}
+}
+
+static void rts5209_force_power_down(struct rtsx_pcr *pcr, u8 pm_state, bool runtime)
+{
+	rtsx_pci_write_register(pcr, FPDCTL, 0x07, 0x07);
+}
+
+static int rts5209_extra_init_hw(struct rtsx_pcr *pcr)
+{
+	rtsx_pci_init_cmd(pcr);
+
+	/* Turn off LED */
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, CARD_GPIO, 0xFF, 0x03);
+	/* Reset ASPM state to default value */
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, ASPM_FORCE_CTL, 0x3F, 0);
+	/* Force CLKREQ# PIN to drive 0 to request clock */
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, PETXCFG, 0x08, 0x08);
+	/* Configure GPIO as output */
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, CARD_GPIO_DIR, 0xFF, 0x03);
+	/* Configure driving */
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, SD30_DRIVE_SEL,
+			0xFF, pcr->sd30_drive_sel_3v3);
+
+	return rtsx_pci_send_cmd(pcr, 100);
+}
+
+static int rts5209_optimize_phy(struct rtsx_pcr *pcr)
+{
+	return rtsx_pci_write_phy_register(pcr, 0x00, 0xB966);
+}
+
+static int rts5209_turn_on_led(struct rtsx_pcr *pcr)
+{
+	return rtsx_pci_write_register(pcr, CARD_GPIO, 0x01, 0x00);
+}
+
+static int rts5209_turn_off_led(struct rtsx_pcr *pcr)
+{
+	return rtsx_pci_write_register(pcr, CARD_GPIO, 0x01, 0x01);
+}
+
+static int rts5209_enable_auto_blink(struct rtsx_pcr *pcr)
+{
+	return rtsx_pci_write_register(pcr, CARD_AUTO_BLINK, 0xFF, 0x0D);
+}
+
+static int rts5209_disable_auto_blink(struct rtsx_pcr *pcr)
+{
+	return rtsx_pci_write_register(pcr, CARD_AUTO_BLINK, 0x08, 0x00);
+}
+
+static int rts5209_card_power_on(struct rtsx_pcr *pcr, int card)
+{
+	int err;
+	u8 pwr_mask, partial_pwr_on, pwr_on;
+
+	pwr_mask = SD_POWER_MASK;
+	partial_pwr_on = SD_PARTIAL_POWER_ON;
+	pwr_on = SD_POWER_ON;
+
+	if ((pcr->flags & PCR_MS_PMOS) && (card == RTSX_MS_CARD)) {
+		pwr_mask = MS_POWER_MASK;
+		partial_pwr_on = MS_PARTIAL_POWER_ON;
+		pwr_on = MS_POWER_ON;
+	}
+
+	rtsx_pci_init_cmd(pcr);
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, CARD_PWR_CTL,
+			pwr_mask, partial_pwr_on);
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, PWR_GATE_CTRL,
+			LDO3318_PWR_MASK, 0x04);
+	err = rtsx_pci_send_cmd(pcr, 100);
+	if (err < 0)
+		return err;
+
+	/* To avoid too large in-rush current */
+	udelay(150);
+
+	rtsx_pci_init_cmd(pcr);
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, CARD_PWR_CTL, pwr_mask, pwr_on);
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, PWR_GATE_CTRL,
+			LDO3318_PWR_MASK, 0x00);
+	return rtsx_pci_send_cmd(pcr, 100);
+}
+
+static int rts5209_card_power_off(struct rtsx_pcr *pcr, int card)
+{
+	u8 pwr_mask, pwr_off;
+
+	pwr_mask = SD_POWER_MASK;
+	pwr_off = SD_POWER_OFF;
+
+	if ((pcr->flags & PCR_MS_PMOS) && (card == RTSX_MS_CARD)) {
+		pwr_mask = MS_POWER_MASK;
+		pwr_off = MS_POWER_OFF;
+	}
+
+	rtsx_pci_init_cmd(pcr);
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, CARD_PWR_CTL,
+			pwr_mask | PMOS_STRG_MASK, pwr_off | PMOS_STRG_400mA);
+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, PWR_GATE_CTRL,
+			LDO3318_PWR_MASK, 0x06);
+	return rtsx_pci_send_cmd(pcr, 100);
+}
+
+static int rts5209_switch_output_voltage(struct rtsx_pcr *pcr, u8 voltage)
+{
+	int err;
+
+	if (voltage == OUTPUT_3V3) {
+		err = rtsx_pci_write_register(pcr,
+				SD30_DRIVE_SEL, 0x07, pcr->sd30_drive_sel_3v3);
+		if (err < 0)
+			return err;
+		err = rtsx_pci_write_phy_register(pcr, 0x08, 0x4FC0 | 0x24);
+		if (err < 0)
+			return err;
+	} else if (voltage == OUTPUT_1V8) {
+		err = rtsx_pci_write_register(pcr,
+				SD30_DRIVE_SEL, 0x07, pcr->sd30_drive_sel_1v8);
+		if (err < 0)
+			return err;
+		err = rtsx_pci_write_phy_register(pcr, 0x08, 0x4C40 | 0x24);
+		if (err < 0)
+			return err;
+	} else {
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct pcr_ops rts5209_pcr_ops = {
+	.fetch_vendor_settings = rts5209_fetch_vendor_settings,
+	.extra_init_hw = rts5209_extra_init_hw,
+	.optimize_phy = rts5209_optimize_phy,
+	.turn_on_led = rts5209_turn_on_led,
+	.turn_off_led = rts5209_turn_off_led,
+	.enable_auto_blink = rts5209_enable_auto_blink,
+	.disable_auto_blink = rts5209_disable_auto_blink,
+	.card_power_on = rts5209_card_power_on,
+	.card_power_off = rts5209_card_power_off,
+	.switch_output_voltage = rts5209_switch_output_voltage,
+	.cd_deglitch = NULL,
+	.conv_clk_and_div_n = NULL,
+	.force_power_down = rts5209_force_power_down,
+};
+
+/* SD Pull Control Enable:
+ *     SD_DAT[3:0] ==> pull up
+ *     SD_CD       ==> pull up
+ *     SD_WP       ==> pull up
+ *     SD_CMD      ==> pull up
+ *     SD_CLK      ==> pull down
+ */
+static const u32 rts5209_sd_pull_ctl_enable_tbl[] = {
+	RTSX_REG_PAIR(CARD_PULL_CTL1, 0xAA),
+	RTSX_REG_PAIR(CARD_PULL_CTL2, 0xAA),
+	RTSX_REG_PAIR(CARD_PULL_CTL3, 0xE9),
+	0,
+};
+
+/* SD Pull Control Disable:
+ *     SD_DAT[3:0] ==> pull down
+ *     SD_CD       ==> pull up
+ *     SD_WP       ==> pull down
+ *     SD_CMD      ==> pull down
+ *     SD_CLK      ==> pull down
+ */
+static const u32 rts5209_sd_pull_ctl_disable_tbl[] = {
+	RTSX_REG_PAIR(CARD_PULL_CTL1, 0x55),
+	RTSX_REG_PAIR(CARD_PULL_CTL2, 0x55),
+	RTSX_REG_PAIR(CARD_PULL_CTL3, 0xD5),
+	0,
+};
+
+/* MS Pull Control Enable:
+ *     MS CD       ==> pull up
+ *     others      ==> pull down
+ */
+static const u32 rts5209_ms_pull_ctl_enable_tbl[] = {
+	RTSX_REG_PAIR(CARD_PULL_CTL4, 0x55),
+	RTSX_REG_PAIR(CARD_PULL_CTL5, 0x55),
+	RTSX_REG_PAIR(CARD_PULL_CTL6, 0x15),
+	0,
+};
+
+/* MS Pull Control Disable:
+ *     MS CD       ==> pull up
+ *     others      ==> pull down
+ */
+static const u32 rts5209_ms_pull_ctl_disable_tbl[] = {
+	RTSX_REG_PAIR(CARD_PULL_CTL4, 0x55),
+	RTSX_REG_PAIR(CARD_PULL_CTL5, 0x55),
+	RTSX_REG_PAIR(CARD_PULL_CTL6, 0x15),
+	0,
+};
+
+void rts5209_init_params(struct rtsx_pcr *pcr)
+{
+	pcr->extra_caps = EXTRA_CAPS_SD_SDR50 |
+		EXTRA_CAPS_SD_SDR104 | EXTRA_CAPS_MMC_8BIT;
+	pcr->num_slots = 2;
+	pcr->ops = &rts5209_pcr_ops;
+
+	pcr->flags = 0;
+	pcr->card_drive_sel = RTS5209_CARD_DRIVE_DEFAULT;
+	pcr->sd30_drive_sel_1v8 = DRIVER_TYPE_B;
+	pcr->sd30_drive_sel_3v3 = DRIVER_TYPE_D;
+	pcr->aspm_en = ASPM_L1_EN;
+	pcr->aspm_mode = ASPM_MODE_CFG;
+	pcr->tx_initial_phase = SET_CLOCK_PHASE(27, 27, 16);
+	pcr->rx_initial_phase = SET_CLOCK_PHASE(24, 6, 5);
+
+	pcr->ic_version = rts5209_get_ic_version(pcr);
+	pcr->sd_pull_ctl_enable_tbl = rts5209_sd_pull_ctl_enable_tbl;
+	pcr->sd_pull_ctl_disable_tbl = rts5209_sd_pull_ctl_disable_tbl;
+	pcr->ms_pull_ctl_enable_tbl = rts5209_ms_pull_ctl_enable_tbl;
+	pcr->ms_pull_ctl_disable_tbl = rts5209_ms_pull_ctl_disable_tbl;
+}