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

10 files changed, 552 insertions, 0 deletions

diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
new file mode 100644
index 000000000..02a7a3335
--- /dev/null
+++ b/arch/riscv/errata/Makefile
@@ -0,0 +1,18 @@
+ifdef CONFIG_RELOCATABLE
+# We can't use PIC/PIE when handling early-boot errata parsing, as the kernel
+# doesn't have a GOT setup at that point.  So instead just use medany: it's
+# usually position-independent, so it should be good enough for the errata
+# handling.
+KBUILD_CFLAGS += -fno-pie -mcmodel=medany
+endif
+
+ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
+ifdef CONFIG_FORTIFY_SOURCE
+KBUILD_CFLAGS += -D__NO_FORTIFY
+endif
+endif
+
+obj-$(CONFIG_ERRATA_ANDES) += andes/
+obj-$(CONFIG_ERRATA_MIPS) += mips/
+obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
+obj-$(CONFIG_ERRATA_THEAD) += thead/
diff --git a/arch/riscv/errata/andes/Makefile b/arch/riscv/errata/andes/Makefile
new file mode 100644
index 000000000..6278c389b
--- /dev/null
+++ b/arch/riscv/errata/andes/Makefile
@@ -0,0 +1,5 @@
+ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
+CFLAGS_errata.o := -mcmodel=medany
+endif
+
+obj-y += errata.o
diff --git a/arch/riscv/errata/andes/errata.c b/arch/riscv/errata/andes/errata.c
new file mode 100644
index 000000000..dcc9d1ee5
--- /dev/null
+++ b/arch/riscv/errata/andes/errata.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Erratas to be applied for Andes CPU cores
+ *
+ *  Copyright (C) 2023 Renesas Electronics Corporation.
+ *
+ * Author: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
+ */
+
+#include <linux/memory.h>
+#include <linux/module.h>
+
+#include <asm/alternative.h>
+#include <asm/cacheflush.h>
+#include <asm/errata_list.h>
+#include <asm/text-patching.h>
+#include <asm/processor.h>
+#include <asm/sbi.h>
+#include <asm/vendorid_list.h>
+#include <asm/vendor_extensions.h>
+
+#define ANDES_AX45MP_MARCHID		0x8000000000008a45UL
+#define ANDES_AX45MP_MIMPID		0x500UL
+#define ANDES_SBI_EXT_ANDES		0x0900031E
+
+#define ANDES_SBI_EXT_IOCP_SW_WORKAROUND	1
+
+static long ax45mp_iocp_sw_workaround(void)
+{
+	struct sbiret ret;
+
+	/*
+	 * ANDES_SBI_EXT_IOCP_SW_WORKAROUND SBI EXT checks if the IOCP is missing and
+	 * cache is controllable only then CMO will be applied to the platform.
+	 */
+	ret = sbi_ecall(ANDES_SBI_EXT_ANDES, ANDES_SBI_EXT_IOCP_SW_WORKAROUND,
+			0, 0, 0, 0, 0, 0);
+
+	return ret.error ? 0 : ret.value;
+}
+
+static void errata_probe_iocp(unsigned int stage, unsigned long arch_id, unsigned long impid)
+{
+	static bool done;
+
+	if (!IS_ENABLED(CONFIG_ERRATA_ANDES_CMO))
+		return;
+
+	if (done)
+		return;
+
+	done = true;
+
+	if (arch_id != ANDES_AX45MP_MARCHID || impid != ANDES_AX45MP_MIMPID)
+		return;
+
+	if (!ax45mp_iocp_sw_workaround())
+		return;
+
+	/* Set this just to make core cbo code happy */
+	riscv_cbom_block_size = 1;
+	riscv_noncoherent_supported();
+}
+
+void __init_or_module andes_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+					      unsigned long archid, unsigned long impid,
+					      unsigned int stage)
+{
+	BUILD_BUG_ON(ERRATA_ANDES_NUMBER >= RISCV_VENDOR_EXT_ALTERNATIVES_BASE);
+
+	if (stage == RISCV_ALTERNATIVES_BOOT)
+		errata_probe_iocp(stage, archid, impid);
+
+	/* we have nothing to patch here ATM so just return back */
+}
diff --git a/arch/riscv/errata/mips/Makefile b/arch/riscv/errata/mips/Makefile
new file mode 100644
index 000000000..6278c389b
--- /dev/null
+++ b/arch/riscv/errata/mips/Makefile
@@ -0,0 +1,5 @@
+ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
+CFLAGS_errata.o := -mcmodel=medany
+endif
+
+obj-y += errata.o
diff --git a/arch/riscv/errata/mips/errata.c b/arch/riscv/errata/mips/errata.c
new file mode 100644
index 000000000..2c3dc2259
--- /dev/null
+++ b/arch/riscv/errata/mips/errata.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 MIPS.
+ */
+
+#include <linux/memory.h>
+#include <linux/module.h>
+#include <asm/text-patching.h>
+#include <asm/alternative.h>
+#include <asm/errata_list.h>
+#include <asm/vendorid_list.h>
+#include <asm/vendor_extensions.h>
+#include <asm/vendor_extensions/mips.h>
+
+static inline bool errata_probe_pause(void)
+{
+	if (!IS_ENABLED(CONFIG_ERRATA_MIPS_P8700_PAUSE_OPCODE))
+		return false;
+
+	if (!riscv_isa_vendor_extension_available(MIPS_VENDOR_ID, XMIPSEXECTL))
+		return false;
+
+	return true;
+}
+
+static u32 mips_errata_probe(void)
+{
+	u32 cpu_req_errata = 0;
+
+	if (errata_probe_pause())
+		cpu_req_errata |= BIT(ERRATA_MIPS_P8700_PAUSE_OPCODE);
+
+	return cpu_req_errata;
+}
+
+void mips_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+			    unsigned long archid, unsigned long impid,
+			    unsigned int stage)
+{
+	struct alt_entry *alt;
+	u32 cpu_req_errata = mips_errata_probe();
+	u32 tmp;
+
+	BUILD_BUG_ON(ERRATA_MIPS_NUMBER >= RISCV_VENDOR_EXT_ALTERNATIVES_BASE);
+
+	if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+		return;
+
+	for (alt = begin; alt < end; alt++) {
+		if (alt->vendor_id != MIPS_VENDOR_ID)
+			continue;
+
+		if (alt->patch_id >= ERRATA_MIPS_NUMBER) {
+			WARN(1, "MIPS errata id:%d not in kernel errata list\n",
+			     alt->patch_id);
+			continue;
+		}
+
+		tmp = (1U << alt->patch_id);
+		if (cpu_req_errata & tmp) {
+			mutex_lock(&text_mutex);
+			patch_text_nosync(ALT_OLD_PTR(alt), ALT_ALT_PTR(alt),
+					  alt->alt_len);
+			mutex_unlock(&text_mutex);
+		}
+	}
+}
diff --git a/arch/riscv/errata/sifive/Makefile b/arch/riscv/errata/sifive/Makefile
new file mode 100644
index 000000000..2fde48db0
--- /dev/null
+++ b/arch/riscv/errata/sifive/Makefile
@@ -0,0 +1,2 @@
+obj-$(CONFIG_ERRATA_SIFIVE_CIP_453) += errata_cip_453.o
+obj-y += errata.o
diff --git a/arch/riscv/errata/sifive/errata.c b/arch/riscv/errata/sifive/errata.c
new file mode 100644
index 000000000..df80c9614
--- /dev/null
+++ b/arch/riscv/errata/sifive/errata.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Sifive.
+ */
+
+#include <linux/kernel.h>
+#include <linux/memory.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/bug.h>
+#include <asm/text-patching.h>
+#include <asm/alternative.h>
+#include <asm/vendorid_list.h>
+#include <asm/errata_list.h>
+#include <asm/vendor_extensions.h>
+
+struct errata_info_t {
+	char name[32];
+	bool (*check_func)(unsigned long  arch_id, unsigned long impid);
+};
+
+static bool errata_cip_453_check_func(unsigned long  arch_id, unsigned long impid)
+{
+	/*
+	 * Affected cores:
+	 * Architecture ID: 0x8000000000000007
+	 * Implement ID: 0x20181004 <= impid <= 0x20191105
+	 */
+	if (arch_id != 0x8000000000000007 ||
+	    (impid < 0x20181004 || impid > 0x20191105))
+		return false;
+	return true;
+}
+
+static bool errata_cip_1200_check_func(unsigned long  arch_id, unsigned long impid)
+{
+	/*
+	 * Affected cores:
+	 * Architecture ID: 0x8000000000000007 or 0x1
+	 * Implement ID: mimpid[23:0] <= 0x200630 and mimpid != 0x01200626
+	 */
+	if (arch_id != 0x8000000000000007 && arch_id != 0x1)
+		return false;
+	if ((impid & 0xffffff) > 0x200630 || impid == 0x1200626)
+		return false;
+
+#ifdef CONFIG_MMU
+	tlb_flush_all_threshold = 0;
+#endif
+
+	return true;
+}
+
+static struct errata_info_t errata_list[ERRATA_SIFIVE_NUMBER] = {
+	{
+		.name = "cip-453",
+		.check_func = errata_cip_453_check_func
+	},
+	{
+		.name = "cip-1200",
+		.check_func = errata_cip_1200_check_func
+	},
+};
+
+static u32 __init_or_module sifive_errata_probe(unsigned long archid,
+						unsigned long impid)
+{
+	int idx;
+	u32 cpu_req_errata = 0;
+
+	for (idx = 0; idx < ERRATA_SIFIVE_NUMBER; idx++)
+		if (errata_list[idx].check_func(archid, impid))
+			cpu_req_errata |= (1U << idx);
+
+	return cpu_req_errata;
+}
+
+void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+			      unsigned long archid, unsigned long impid,
+			      unsigned int stage)
+{
+	struct alt_entry *alt;
+	u32 cpu_req_errata;
+	u32 tmp;
+
+	BUILD_BUG_ON(ERRATA_SIFIVE_NUMBER >= RISCV_VENDOR_EXT_ALTERNATIVES_BASE);
+
+	if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+		return;
+
+	cpu_req_errata = sifive_errata_probe(archid, impid);
+
+	for (alt = begin; alt < end; alt++) {
+		if (alt->vendor_id != SIFIVE_VENDOR_ID)
+			continue;
+		if (alt->patch_id >= ERRATA_SIFIVE_NUMBER)
+			continue;
+
+		tmp = (1U << alt->patch_id);
+		if (cpu_req_errata & tmp) {
+			mutex_lock(&text_mutex);
+			patch_text_nosync(ALT_OLD_PTR(alt), ALT_ALT_PTR(alt),
+					  alt->alt_len);
+			mutex_unlock(&text_mutex);
+		}
+	}
+}
diff --git a/arch/riscv/errata/sifive/errata_cip_453.S b/arch/riscv/errata/sifive/errata_cip_453.S
new file mode 100644
index 000000000..b1f7b636f
--- /dev/null
+++ b/arch/riscv/errata/sifive/errata_cip_453.S
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 SiFive
+ */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/alternative.h>
+
+.macro ADD_SIGN_EXT pt_reg badaddr tmp_reg
+	REG_L \badaddr, PT_BADADDR(\pt_reg)
+	li \tmp_reg,1
+	slli \tmp_reg,\tmp_reg,0x26
+	and \tmp_reg,\tmp_reg,\badaddr
+	beqz \tmp_reg, 1f
+	li \tmp_reg,-1
+	slli \tmp_reg,\tmp_reg,0x27
+	or \badaddr,\tmp_reg,\badaddr
+	REG_S \badaddr, PT_BADADDR(\pt_reg)
+1:
+.endm
+
+SYM_FUNC_START(sifive_cip_453_page_fault_trp)
+	ADD_SIGN_EXT a0, t0, t1
+#ifdef CONFIG_MMU
+	la t0, do_page_fault
+#else
+	la t0, do_trap_unknown
+#endif
+	jr t0
+SYM_FUNC_END(sifive_cip_453_page_fault_trp)
+
+SYM_FUNC_START(sifive_cip_453_insn_fault_trp)
+	ADD_SIGN_EXT a0, t0, t1
+	la t0, do_trap_insn_fault
+	jr t0
+SYM_FUNC_END(sifive_cip_453_insn_fault_trp)
diff --git a/arch/riscv/errata/thead/Makefile b/arch/riscv/errata/thead/Makefile
new file mode 100644
index 000000000..137e700d9
--- /dev/null
+++ b/arch/riscv/errata/thead/Makefile
@@ -0,0 +1,11 @@
+ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
+CFLAGS_errata.o := -mcmodel=medany
+ifdef CONFIG_FTRACE
+CFLAGS_REMOVE_errata.o = $(CC_FLAGS_FTRACE)
+endif
+ifdef CONFIG_KASAN
+KASAN_SANITIZE_errata.o := n
+endif
+endif
+
+obj-y += errata.o
diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
new file mode 100644
index 000000000..6f1c683f0
--- /dev/null
+++ b/arch/riscv/errata/thead/errata.c
@@ -0,0 +1,224 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Heiko Stuebner <heiko@sntech.de>
+ */
+
+#include <linux/bug.h>
+#include <linux/kernel.h>
+#include <linux/memory.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/uaccess.h>
+#include <asm/alternative.h>
+#include <asm/bugs.h>
+#include <asm/cacheflush.h>
+#include <asm/cpufeature.h>
+#include <asm/dma-noncoherent.h>
+#include <asm/errata_list.h>
+#include <asm/hwprobe.h>
+#include <asm/io.h>
+#include <asm/text-patching.h>
+#include <asm/vendorid_list.h>
+#include <asm/vendor_extensions.h>
+
+#define CSR_TH_SXSTATUS		0x5c0
+#define SXSTATUS_MAEE		_AC(0x200000, UL)
+
+static bool errata_probe_mae(unsigned int stage,
+			     unsigned long arch_id, unsigned long impid)
+{
+	if (!IS_ENABLED(CONFIG_ERRATA_THEAD_MAE))
+		return false;
+
+	if (arch_id != 0 || impid != 0)
+		return false;
+
+	if (stage != RISCV_ALTERNATIVES_EARLY_BOOT &&
+	    stage != RISCV_ALTERNATIVES_MODULE)
+		return false;
+
+	if (!(csr_read(CSR_TH_SXSTATUS) & SXSTATUS_MAEE))
+		return false;
+
+	return true;
+}
+
+/*
+ * th.dcache.ipa rs1 (invalidate, physical address)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000001    01010      rs1       000      00000  0001011
+ * th.dcache.iva rs1 (invalidate, virtual address)
+ *   0000001    00110      rs1       000      00000  0001011
+ *
+ * th.dcache.cpa rs1 (clean, physical address)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000001    01001      rs1       000      00000  0001011
+ * th.dcache.cva rs1 (clean, virtual address)
+ *   0000001    00101      rs1       000      00000  0001011
+ *
+ * th.dcache.cipa rs1 (clean then invalidate, physical address)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000001    01011      rs1       000      00000  0001011
+ * th.dcache.civa rs1 (clean then invalidate, virtual address)
+ *   0000001    00111      rs1       000      00000  0001011
+ *
+ * th.sync.s (make sure all cache operations finished)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000000    11001     00000      000      00000  0001011
+ */
+#define THEAD_INVAL_A0	".long 0x02a5000b"
+#define THEAD_CLEAN_A0	".long 0x0295000b"
+#define THEAD_FLUSH_A0	".long 0x02b5000b"
+#define THEAD_SYNC_S	".long 0x0190000b"
+
+#define THEAD_CMO_OP(_op, _start, _size, _cachesize)			\
+asm volatile("mv a0, %1\n\t"						\
+	     "j 2f\n\t"							\
+	     "3:\n\t"							\
+	     THEAD_##_op##_A0 "\n\t"					\
+	     "add a0, a0, %0\n\t"					\
+	     "2:\n\t"							\
+	     "bltu a0, %2, 3b\n\t"					\
+	     THEAD_SYNC_S						\
+	     : : "r"(_cachesize),					\
+		 "r"((unsigned long)(_start) & ~((_cachesize) - 1UL)),	\
+		 "r"((unsigned long)(_start) + (_size))			\
+	     : "a0")
+
+static void thead_errata_cache_inv(phys_addr_t paddr, size_t size)
+{
+	THEAD_CMO_OP(INVAL, paddr, size, riscv_cbom_block_size);
+}
+
+static void thead_errata_cache_wback(phys_addr_t paddr, size_t size)
+{
+	THEAD_CMO_OP(CLEAN, paddr, size, riscv_cbom_block_size);
+}
+
+static void thead_errata_cache_wback_inv(phys_addr_t paddr, size_t size)
+{
+	THEAD_CMO_OP(FLUSH, paddr, size, riscv_cbom_block_size);
+}
+
+static const struct riscv_nonstd_cache_ops thead_errata_cmo_ops = {
+	.wback = &thead_errata_cache_wback,
+	.inv = &thead_errata_cache_inv,
+	.wback_inv = &thead_errata_cache_wback_inv,
+};
+
+static bool errata_probe_cmo(unsigned int stage,
+			     unsigned long arch_id, unsigned long impid)
+{
+	if (!IS_ENABLED(CONFIG_ERRATA_THEAD_CMO))
+		return false;
+
+	if (arch_id != 0 || impid != 0)
+		return false;
+
+	if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+		return false;
+
+	if (stage == RISCV_ALTERNATIVES_BOOT) {
+		riscv_cbom_block_size = L1_CACHE_BYTES;
+		riscv_noncoherent_supported();
+		riscv_noncoherent_register_cache_ops(&thead_errata_cmo_ops);
+	}
+
+	return true;
+}
+
+static bool errata_probe_pmu(unsigned int stage,
+			     unsigned long arch_id, unsigned long impid)
+{
+	if (!IS_ENABLED(CONFIG_ERRATA_THEAD_PMU))
+		return false;
+
+	/* target-c9xx cores report arch_id and impid as 0 */
+	if (arch_id != 0 || impid != 0)
+		return false;
+
+	if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+		return false;
+
+	return true;
+}
+
+static bool errata_probe_ghostwrite(unsigned int stage,
+				    unsigned long arch_id, unsigned long impid)
+{
+	if (!IS_ENABLED(CONFIG_ERRATA_THEAD_GHOSTWRITE))
+		return false;
+
+	/*
+	 * target-c9xx cores report arch_id and impid as 0
+	 *
+	 * While ghostwrite may not affect all c9xx cores that implement
+	 * xtheadvector, there is no further granularity than c9xx. Assume
+	 * vulnerable for this entire class of processors when xtheadvector is
+	 * enabled.
+	 */
+	if (arch_id != 0 || impid != 0)
+		return false;
+
+	if (stage != RISCV_ALTERNATIVES_EARLY_BOOT)
+		return false;
+
+	ghostwrite_set_vulnerable();
+
+	return true;
+}
+
+static u32 thead_errata_probe(unsigned int stage,
+			      unsigned long archid, unsigned long impid)
+{
+	u32 cpu_req_errata = 0;
+
+	if (errata_probe_mae(stage, archid, impid))
+		cpu_req_errata |= BIT(ERRATA_THEAD_MAE);
+
+	errata_probe_cmo(stage, archid, impid);
+
+	if (errata_probe_pmu(stage, archid, impid))
+		cpu_req_errata |= BIT(ERRATA_THEAD_PMU);
+
+	errata_probe_ghostwrite(stage, archid, impid);
+
+	return cpu_req_errata;
+}
+
+void thead_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+			     unsigned long archid, unsigned long impid,
+			     unsigned int stage)
+{
+	struct alt_entry *alt;
+	u32 cpu_req_errata = thead_errata_probe(stage, archid, impid);
+	u32 tmp;
+	void *oldptr, *altptr;
+
+	BUILD_BUG_ON(ERRATA_THEAD_NUMBER >= RISCV_VENDOR_EXT_ALTERNATIVES_BASE);
+
+	for (alt = begin; alt < end; alt++) {
+		if (alt->vendor_id != THEAD_VENDOR_ID)
+			continue;
+		if (alt->patch_id >= ERRATA_THEAD_NUMBER)
+			continue;
+
+		tmp = (1U << alt->patch_id);
+		if (cpu_req_errata & tmp) {
+			oldptr = ALT_OLD_PTR(alt);
+			altptr = ALT_ALT_PTR(alt);
+
+			/* On vm-alternatives, the mmu isn't running yet */
+			if (stage == RISCV_ALTERNATIVES_EARLY_BOOT) {
+				memcpy(oldptr, altptr, alt->alt_len);
+			} else {
+				mutex_lock(&text_mutex);
+				patch_text_nosync(oldptr, altptr, alt->alt_len);
+				mutex_unlock(&text_mutex);
+			}
+		}
+	}
+
+	if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+		local_flush_icache_all();
+}