x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 666 insertions, 0 deletions

diff --git a/arch/m68k/mac/misc.c b/arch/m68k/mac/misc.c
new file mode 100644
index 000000000..e7f0f72c1
--- /dev/null
+++ b/arch/m68k/mac/misc.c
@@ -0,0 +1,666 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Miscellaneous Mac68K-specific stuff
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+#include <linux/rtc.h>
+#include <linux/mm.h>
+
+#include <linux/adb.h>
+#include <linux/cuda.h>
+#include <linux/pmu.h>
+
+#include <linux/uaccess.h>
+#include <asm/io.h>
+#include <asm/setup.h>
+#include <asm/macintosh.h>
+#include <asm/mac_via.h>
+#include <asm/mac_oss.h>
+
+#include <asm/machdep.h>
+
+#include "mac.h"
+
+/*
+ * Offset between Unix time (1970-based) and Mac time (1904-based). Cuda and PMU
+ * times wrap in 2040. If we need to handle later times, the read_time functions
+ * need to be changed to interpret wrapped times as post-2040.
+ */
+
+#define RTC_OFFSET 2082844800
+
+static void (*rom_reset)(void);
+
+#if IS_ENABLED(CONFIG_NVRAM)
+#ifdef CONFIG_ADB_CUDA
+static unsigned char cuda_pram_read_byte(int offset)
+{
+	struct adb_request req;
+
+	if (cuda_request(&req, NULL, 4, CUDA_PACKET, CUDA_GET_PRAM,
+			 (offset >> 8) & 0xFF, offset & 0xFF) < 0)
+		return 0;
+	while (!req.complete)
+		cuda_poll();
+	return req.reply[3];
+}
+
+static void cuda_pram_write_byte(unsigned char data, int offset)
+{
+	struct adb_request req;
+
+	if (cuda_request(&req, NULL, 5, CUDA_PACKET, CUDA_SET_PRAM,
+			 (offset >> 8) & 0xFF, offset & 0xFF, data) < 0)
+		return;
+	while (!req.complete)
+		cuda_poll();
+}
+#endif /* CONFIG_ADB_CUDA */
+
+#ifdef CONFIG_ADB_PMU
+static unsigned char pmu_pram_read_byte(int offset)
+{
+	struct adb_request req;
+
+	if (pmu_request(&req, NULL, 3, PMU_READ_XPRAM,
+	                offset & 0xFF, 1) < 0)
+		return 0;
+	pmu_wait_complete(&req);
+
+	return req.reply[0];
+}
+
+static void pmu_pram_write_byte(unsigned char data, int offset)
+{
+	struct adb_request req;
+
+	if (pmu_request(&req, NULL, 4, PMU_WRITE_XPRAM,
+	                offset & 0xFF, 1, data) < 0)
+		return;
+	pmu_wait_complete(&req);
+}
+#endif /* CONFIG_ADB_PMU */
+#endif /* CONFIG_NVRAM */
+
+/*
+ * VIA PRAM/RTC access routines
+ *
+ * Must be called with interrupts disabled and
+ * the RTC should be enabled.
+ */
+
+static __u8 via_rtc_recv(void)
+{
+	int i, reg;
+	__u8 data;
+
+	reg = via1[vBufB] & ~VIA1B_vRTCClk;
+
+	/* Set the RTC data line to be an input. */
+
+	via1[vDirB] &= ~VIA1B_vRTCData;
+
+	/* The bits of the byte come out in MSB order */
+
+	data = 0;
+	for (i = 0 ; i < 8 ; i++) {
+		via1[vBufB] = reg;
+		via1[vBufB] = reg | VIA1B_vRTCClk;
+		data = (data << 1) | (via1[vBufB] & VIA1B_vRTCData);
+	}
+
+	/* Return RTC data line to output state */
+
+	via1[vDirB] |= VIA1B_vRTCData;
+
+	return data;
+}
+
+static void via_rtc_send(__u8 data)
+{
+	int i, reg, bit;
+
+	reg = via1[vBufB] & ~(VIA1B_vRTCClk | VIA1B_vRTCData);
+
+	/* The bits of the byte go into the RTC in MSB order */
+
+	for (i = 0 ; i < 8 ; i++) {
+		bit = data & 0x80? 1 : 0;
+		data <<= 1;
+		via1[vBufB] = reg | bit;
+		via1[vBufB] = reg | bit | VIA1B_vRTCClk;
+	}
+}
+
+/*
+ * These values can be found in Inside Macintosh vol. III ch. 2
+ * which has a description of the RTC chip in the original Mac.
+ */
+
+#define RTC_FLG_READ            BIT(7)
+#define RTC_FLG_WRITE_PROTECT   BIT(7)
+#define RTC_CMD_READ(r)         (RTC_FLG_READ | (r << 2))
+#define RTC_CMD_WRITE(r)        (r << 2)
+#define RTC_REG_SECONDS_0       0
+#define RTC_REG_SECONDS_1       1
+#define RTC_REG_SECONDS_2       2
+#define RTC_REG_SECONDS_3       3
+#define RTC_REG_WRITE_PROTECT   13
+
+/*
+ * Inside Mac has no information about two-byte RTC commands but
+ * the MAME/MESS source code has the essentials.
+ */
+
+#define RTC_REG_XPRAM           14
+#define RTC_CMD_XPRAM_READ      (RTC_CMD_READ(RTC_REG_XPRAM) << 8)
+#define RTC_CMD_XPRAM_WRITE     (RTC_CMD_WRITE(RTC_REG_XPRAM) << 8)
+#define RTC_CMD_XPRAM_ARG(a)    (((a & 0xE0) << 3) | ((a & 0x1F) << 2))
+
+/*
+ * Execute a VIA PRAM/RTC command. For read commands
+ * data should point to a one-byte buffer for the
+ * resulting data. For write commands it should point
+ * to the data byte to for the command.
+ *
+ * This function disables all interrupts while running.
+ */
+
+static void via_rtc_command(int command, __u8 *data)
+{
+	unsigned long flags;
+	int is_read;
+
+	local_irq_save(flags);
+
+	/* The least significant bits must be 0b01 according to Inside Mac */
+
+	command = (command & ~3) | 1;
+
+	/* Enable the RTC and make sure the strobe line is high */
+
+	via1[vBufB] = (via1[vBufB] | VIA1B_vRTCClk) & ~VIA1B_vRTCEnb;
+
+	if (command & 0xFF00) {		/* extended (two-byte) command */
+		via_rtc_send((command & 0xFF00) >> 8);
+		via_rtc_send(command & 0xFF);
+		is_read = command & (RTC_FLG_READ << 8);
+	} else {			/* one-byte command */
+		via_rtc_send(command);
+		is_read = command & RTC_FLG_READ;
+	}
+	if (is_read) {
+		*data = via_rtc_recv();
+	} else {
+		via_rtc_send(*data);
+	}
+
+	/* All done, disable the RTC */
+
+	via1[vBufB] |= VIA1B_vRTCEnb;
+
+	local_irq_restore(flags);
+}
+
+#if IS_ENABLED(CONFIG_NVRAM)
+static unsigned char via_pram_read_byte(int offset)
+{
+	unsigned char temp;
+
+	via_rtc_command(RTC_CMD_XPRAM_READ | RTC_CMD_XPRAM_ARG(offset), &temp);
+
+	return temp;
+}
+
+static void via_pram_write_byte(unsigned char data, int offset)
+{
+	unsigned char temp;
+
+	temp = 0x55;
+	via_rtc_command(RTC_CMD_WRITE(RTC_REG_WRITE_PROTECT), &temp);
+
+	temp = data;
+	via_rtc_command(RTC_CMD_XPRAM_WRITE | RTC_CMD_XPRAM_ARG(offset), &temp);
+
+	temp = 0x55 | RTC_FLG_WRITE_PROTECT;
+	via_rtc_command(RTC_CMD_WRITE(RTC_REG_WRITE_PROTECT), &temp);
+}
+#endif /* CONFIG_NVRAM */
+
+/*
+ * Return the current time in seconds since January 1, 1904.
+ *
+ * This only works on machines with the VIA-based PRAM/RTC, which
+ * is basically any machine with Mac II-style ADB.
+ */
+
+static time64_t via_read_time(void)
+{
+	union {
+		__u8 cdata[4];
+		__u32 idata;
+	} result, last_result;
+	int count = 1;
+
+	via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_0), &last_result.cdata[3]);
+	via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_1), &last_result.cdata[2]);
+	via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_2), &last_result.cdata[1]);
+	via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_3), &last_result.cdata[0]);
+
+	/*
+	 * The NetBSD guys say to loop until you get the same reading
+	 * twice in a row.
+	 */
+
+	while (1) {
+		via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_0),
+		                &result.cdata[3]);
+		via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_1),
+		                &result.cdata[2]);
+		via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_2),
+		                &result.cdata[1]);
+		via_rtc_command(RTC_CMD_READ(RTC_REG_SECONDS_3),
+		                &result.cdata[0]);
+
+		if (result.idata == last_result.idata)
+			return (time64_t)result.idata - RTC_OFFSET;
+
+		if (++count > 10)
+			break;
+
+		last_result.idata = result.idata;
+	}
+
+	pr_err("%s: failed to read a stable value; got 0x%08x then 0x%08x\n",
+	       __func__, last_result.idata, result.idata);
+
+	return 0;
+}
+
+/*
+ * Set the current time to a number of seconds since January 1, 1904.
+ *
+ * This only works on machines with the VIA-based PRAM/RTC, which
+ * is basically any machine with Mac II-style ADB.
+ */
+
+static void via_set_rtc_time(struct rtc_time *tm)
+{
+	union {
+		__u8 cdata[4];
+		__u32 idata;
+	} data;
+	__u8 temp;
+	time64_t time;
+
+	time = mktime64(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
+	                tm->tm_hour, tm->tm_min, tm->tm_sec);
+
+	/* Clear the write protect bit */
+
+	temp = 0x55;
+	via_rtc_command(RTC_CMD_WRITE(RTC_REG_WRITE_PROTECT), &temp);
+
+	data.idata = lower_32_bits(time + RTC_OFFSET);
+	via_rtc_command(RTC_CMD_WRITE(RTC_REG_SECONDS_0), &data.cdata[3]);
+	via_rtc_command(RTC_CMD_WRITE(RTC_REG_SECONDS_1), &data.cdata[2]);
+	via_rtc_command(RTC_CMD_WRITE(RTC_REG_SECONDS_2), &data.cdata[1]);
+	via_rtc_command(RTC_CMD_WRITE(RTC_REG_SECONDS_3), &data.cdata[0]);
+
+	/* Set the write protect bit */
+
+	temp = 0x55 | RTC_FLG_WRITE_PROTECT;
+	via_rtc_command(RTC_CMD_WRITE(RTC_REG_WRITE_PROTECT), &temp);
+}
+
+static void via_shutdown(void)
+{
+	if (rbv_present) {
+		via2[rBufB] &= ~0x04;
+	} else {
+		/* Direction of vDirB is output */
+		via2[vDirB] |= 0x04;
+		/* Send a value of 0 on that line */
+		via2[vBufB] &= ~0x04;
+		mdelay(1000);
+	}
+}
+
+static void oss_shutdown(void)
+{
+	oss->rom_ctrl = OSS_POWEROFF;
+}
+
+#ifdef CONFIG_ADB_CUDA
+static void cuda_restart(void)
+{
+	struct adb_request req;
+
+	if (cuda_request(&req, NULL, 2, CUDA_PACKET, CUDA_RESET_SYSTEM) < 0)
+		return;
+	while (!req.complete)
+		cuda_poll();
+}
+
+static void cuda_shutdown(void)
+{
+	struct adb_request req;
+
+	if (cuda_request(&req, NULL, 2, CUDA_PACKET, CUDA_POWERDOWN) < 0)
+		return;
+
+	/* Avoid infinite polling loop when PSU is not under Cuda control */
+	switch (macintosh_config->ident) {
+	case MAC_MODEL_C660:
+	case MAC_MODEL_Q605:
+	case MAC_MODEL_Q605_ACC:
+	case MAC_MODEL_P475:
+	case MAC_MODEL_P475F:
+		return;
+	}
+
+	while (!req.complete)
+		cuda_poll();
+}
+#endif /* CONFIG_ADB_CUDA */
+
+/*
+ *-------------------------------------------------------------------
+ * Below this point are the generic routines; they'll dispatch to the
+ * correct routine for the hardware on which we're running.
+ *-------------------------------------------------------------------
+ */
+
+#if IS_ENABLED(CONFIG_NVRAM)
+unsigned char mac_pram_read_byte(int addr)
+{
+	switch (macintosh_config->adb_type) {
+	case MAC_ADB_IOP:
+	case MAC_ADB_II:
+	case MAC_ADB_PB1:
+		return via_pram_read_byte(addr);
+#ifdef CONFIG_ADB_CUDA
+	case MAC_ADB_EGRET:
+	case MAC_ADB_CUDA:
+		return cuda_pram_read_byte(addr);
+#endif
+#ifdef CONFIG_ADB_PMU
+	case MAC_ADB_PB2:
+		return pmu_pram_read_byte(addr);
+#endif
+	default:
+		return 0xFF;
+	}
+}
+
+void mac_pram_write_byte(unsigned char val, int addr)
+{
+	switch (macintosh_config->adb_type) {
+	case MAC_ADB_IOP:
+	case MAC_ADB_II:
+	case MAC_ADB_PB1:
+		via_pram_write_byte(val, addr);
+		break;
+#ifdef CONFIG_ADB_CUDA
+	case MAC_ADB_EGRET:
+	case MAC_ADB_CUDA:
+		cuda_pram_write_byte(val, addr);
+		break;
+#endif
+#ifdef CONFIG_ADB_PMU
+	case MAC_ADB_PB2:
+		pmu_pram_write_byte(val, addr);
+		break;
+#endif
+	default:
+		break;
+	}
+}
+
+ssize_t mac_pram_get_size(void)
+{
+	return 256;
+}
+#endif /* CONFIG_NVRAM */
+
+void mac_poweroff(void)
+{
+	if (oss_present) {
+		oss_shutdown();
+	} else if (macintosh_config->adb_type == MAC_ADB_II) {
+		via_shutdown();
+#ifdef CONFIG_ADB_CUDA
+	} else if (macintosh_config->adb_type == MAC_ADB_EGRET ||
+	           macintosh_config->adb_type == MAC_ADB_CUDA) {
+		cuda_shutdown();
+#endif
+#ifdef CONFIG_ADB_PMU
+	} else if (macintosh_config->adb_type == MAC_ADB_PB2) {
+		pmu_shutdown();
+#endif
+	}
+
+	pr_crit("It is now safe to turn off your Macintosh.\n");
+	local_irq_disable();
+	while(1);
+}
+
+void mac_reset(void)
+{
+#ifdef CONFIG_ADB_CUDA
+	if (macintosh_config->adb_type == MAC_ADB_EGRET ||
+	    macintosh_config->adb_type == MAC_ADB_CUDA) {
+		cuda_restart();
+	} else
+#endif
+#ifdef CONFIG_ADB_PMU
+	if (macintosh_config->adb_type == MAC_ADB_PB2) {
+		pmu_restart();
+	} else
+#endif
+	if (CPU_IS_030) {
+		/* 030-specific reset routine.  The idea is general, but the
+		 * specific registers to reset are '030-specific.  Until I
+		 * have a non-030 machine, I can't test anything else.
+		 *  -- C. Scott Ananian <cananian@alumni.princeton.edu>
+		 */
+
+		unsigned long rombase = 0x40000000;
+
+		/* make a 1-to-1 mapping, using the transparent tran. reg. */
+		unsigned long virt = (unsigned long) mac_reset;
+		unsigned long phys = virt_to_phys(mac_reset);
+		unsigned long addr = (phys&0xFF000000)|0x8777;
+		unsigned long offset = phys-virt;
+
+		local_irq_disable(); /* lets not screw this up, ok? */
+		__asm__ __volatile__(".chip 68030\n\t"
+				     "pmove %0,%/tt0\n\t"
+				     ".chip 68k"
+				     : : "m" (addr));
+		/* Now jump to physical address so we can disable MMU */
+		__asm__ __volatile__(
+		    ".chip 68030\n\t"
+		    "lea %/pc@(1f),%/a0\n\t"
+		    "addl %0,%/a0\n\t"/* fixup target address and stack ptr */
+		    "addl %0,%/sp\n\t"
+		    "pflusha\n\t"
+		    "jmp %/a0@\n\t" /* jump into physical memory */
+		    "0:.long 0\n\t" /* a constant zero. */
+		    /* OK.  Now reset everything and jump to reset vector. */
+		    "1:\n\t"
+		    "lea %/pc@(0b),%/a0\n\t"
+		    "pmove %/a0@, %/tc\n\t" /* disable mmu */
+		    "pmove %/a0@, %/tt0\n\t" /* disable tt0 */
+		    "pmove %/a0@, %/tt1\n\t" /* disable tt1 */
+		    "movel #0, %/a0\n\t"
+		    "movec %/a0, %/vbr\n\t" /* clear vector base register */
+		    "movec %/a0, %/cacr\n\t" /* disable caches */
+		    "movel #0x0808,%/a0\n\t"
+		    "movec %/a0, %/cacr\n\t" /* flush i&d caches */
+		    "movew #0x2700,%/sr\n\t" /* set up status register */
+		    "movel %1@(0x0),%/a0\n\t"/* load interrupt stack pointer */
+		    "movec %/a0, %/isp\n\t"
+		    "movel %1@(0x4),%/a0\n\t" /* load reset vector */
+		    "reset\n\t" /* reset external devices */
+		    "jmp %/a0@\n\t" /* jump to the reset vector */
+		    ".chip 68k"
+		    : : "r" (offset), "a" (rombase) : "a0");
+	} else {
+		/* need ROMBASE in booter */
+		/* indeed, plus need to MAP THE ROM !! */
+
+		if (mac_bi_data.rombase == 0)
+			mac_bi_data.rombase = 0x40800000;
+
+		/* works on some */
+		rom_reset = (void *)(mac_bi_data.rombase + 0xa);
+
+		local_irq_disable();
+		rom_reset();
+	}
+
+	/* should never get here */
+	pr_crit("Restart failed. Please restart manually.\n");
+	local_irq_disable();
+	while(1);
+}
+
+/*
+ * This function translates seconds since 1970 into a proper date.
+ *
+ * Algorithm cribbed from glibc2.1, __offtime().
+ *
+ * This is roughly same as rtc_time64_to_tm(), which we should probably
+ * use here, but it's only available when CONFIG_RTC_LIB is enabled.
+ */
+#define SECS_PER_MINUTE (60)
+#define SECS_PER_HOUR  (SECS_PER_MINUTE * 60)
+#define SECS_PER_DAY   (SECS_PER_HOUR * 24)
+
+static void unmktime(time64_t time, long offset,
+		     int *yearp, int *monp, int *dayp,
+		     int *hourp, int *minp, int *secp)
+{
+        /* How many days come before each month (0-12).  */
+	static const unsigned short int __mon_yday[2][13] =
+	{
+		/* Normal years.  */
+		{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
+		/* Leap years.  */
+		{ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
+	};
+	int days, rem, y, wday;
+	const unsigned short int *ip;
+
+	days = div_u64_rem(time, SECS_PER_DAY, &rem);
+	rem += offset;
+	while (rem < 0) {
+		rem += SECS_PER_DAY;
+		--days;
+	}
+	while (rem >= SECS_PER_DAY) {
+		rem -= SECS_PER_DAY;
+		++days;
+	}
+	*hourp = rem / SECS_PER_HOUR;
+	rem %= SECS_PER_HOUR;
+	*minp = rem / SECS_PER_MINUTE;
+	*secp = rem % SECS_PER_MINUTE;
+	/* January 1, 1970 was a Thursday. */
+	wday = (4 + days) % 7; /* Day in the week. Not currently used */
+	if (wday < 0) wday += 7;
+	y = 1970;
+
+#define DIV(a, b) ((a) / (b) - ((a) % (b) < 0))
+#define LEAPS_THRU_END_OF(y) (DIV (y, 4) - DIV (y, 100) + DIV (y, 400))
+#define __isleap(year)	\
+  ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
+
+	while (days < 0 || days >= (__isleap (y) ? 366 : 365))
+	{
+		/* Guess a corrected year, assuming 365 days per year.  */
+		long int yg = y + days / 365 - (days % 365 < 0);
+
+		/* Adjust DAYS and Y to match the guessed year.  */
+		days -= (yg - y) * 365 +
+			LEAPS_THRU_END_OF(yg - 1) - LEAPS_THRU_END_OF(y - 1);
+		y = yg;
+	}
+	*yearp = y - 1900;
+	ip = __mon_yday[__isleap(y)];
+	for (y = 11; days < (long int) ip[y]; --y)
+		continue;
+	days -= ip[y];
+	*monp = y;
+	*dayp = days + 1; /* day in the month */
+	return;
+}
+
+/*
+ * Read/write the hardware clock.
+ */
+
+int mac_hwclk(int op, struct rtc_time *t)
+{
+	time64_t now;
+
+	if (!op) { /* read */
+		switch (macintosh_config->adb_type) {
+		case MAC_ADB_IOP:
+		case MAC_ADB_II:
+		case MAC_ADB_PB1:
+			now = via_read_time();
+			break;
+#ifdef CONFIG_ADB_CUDA
+		case MAC_ADB_EGRET:
+		case MAC_ADB_CUDA:
+			now = cuda_get_time();
+			break;
+#endif
+#ifdef CONFIG_ADB_PMU
+		case MAC_ADB_PB2:
+			now = pmu_get_time();
+			break;
+#endif
+		default:
+			now = 0;
+		}
+
+		t->tm_wday = 0;
+		unmktime(now, 0,
+			 &t->tm_year, &t->tm_mon, &t->tm_mday,
+			 &t->tm_hour, &t->tm_min, &t->tm_sec);
+		pr_debug("%s: read %ptR\n", __func__, t);
+	} else { /* write */
+		pr_debug("%s: tried to write %ptR\n", __func__, t);
+
+		switch (macintosh_config->adb_type) {
+		case MAC_ADB_IOP:
+		case MAC_ADB_II:
+		case MAC_ADB_PB1:
+			via_set_rtc_time(t);
+			break;
+#ifdef CONFIG_ADB_CUDA
+		case MAC_ADB_EGRET:
+		case MAC_ADB_CUDA:
+			cuda_set_rtc_time(t);
+			break;
+#endif
+#ifdef CONFIG_ADB_PMU
+		case MAC_ADB_PB2:
+			pmu_set_rtc_time(t);
+			break;
+#endif
+		default:
+			return -ENODEV;
+		}
+	}
+	return 0;
+}