arch/riscv/kernel/patch.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2020 SiFive
  */

 #include <linux/spinlock.h>
 #include <linux/mm.h>
 #include <linux/memory.h>
 #include <linux/string.h>
 #include <linux/uaccess.h>
 #include <linux/stop_machine.h>
 #include <asm/kprobes.h>
 #include <asm/cacheflush.h>
 #include <asm/fixmap.h>
 #include <asm/ftrace.h>
 #include <asm/patch.h>

 struct patch_insn {
 	void *addr;
 	u32 *insns;
 	int ninsns;
 	atomic_t cpu_count;
 };

 int riscv_patch_in_stop_machine = false;

 #ifdef CONFIG_MMU
 /*
  * The fix_to_virt(, idx) needs a const value (not a dynamic variable of
  * reg-a0) or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".
  * So use '__always_inline' and 'const unsigned int fixmap' here.
  */
 static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
 {
 	uintptr_t uintaddr = (uintptr_t) addr;
 	struct page *page;

 	if (core_kernel_text(uintaddr))
 		page = phys_to_page(__pa_symbol(addr));
 	else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
 		page = vmalloc_to_page(addr);
 	else
 		return addr;

 	BUG_ON(!page);

 	return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
 					 (uintaddr & ~PAGE_MASK));
 }

 static void patch_unmap(int fixmap)
 {
 	clear_fixmap(fixmap);
 }
 NOKPROBE_SYMBOL(patch_unmap);

 static int __patch_insn_set(void *addr, u8 c, size_t len)
 {
 	void *waddr = addr;
 	bool across_pages = (((uintptr_t)addr & ~PAGE_MASK) + len) > PAGE_SIZE;

 	/*
 	 * Only two pages can be mapped at a time for writing.
 	 */
 	if (len + offset_in_page(addr) > 2 * PAGE_SIZE)
 		return -EINVAL;
 	/*
 	 * Before reaching here, it was expected to lock the text_mutex
 	 * already, so we don't need to give another lock here and could
 	 * ensure that it was safe between each cores.
 	 */
 	lockdep_assert_held(&text_mutex);

 	if (across_pages)
 		patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1);

 	waddr = patch_map(addr, FIX_TEXT_POKE0);

 	memset(waddr, c, len);

 	patch_unmap(FIX_TEXT_POKE0);

 	if (across_pages)
 		patch_unmap(FIX_TEXT_POKE1);

 	return 0;
 }
 NOKPROBE_SYMBOL(__patch_insn_set);

 static int __patch_insn_write(void *addr, const void *insn, size_t len)
 {
 	void *waddr = addr;
 	bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE;
 	int ret;

 	/*
 	 * Only two pages can be mapped at a time for writing.
 	 */
 	if (len + offset_in_page(addr) > 2 * PAGE_SIZE)
 		return -EINVAL;

 	/*
 	 * Before reaching here, it was expected to lock the text_mutex
 	 * already, so we don't need to give another lock here and could
 	 * ensure that it was safe between each cores.
 	 *
 	 * We're currently using stop_machine() for ftrace & kprobes, and while
 	 * that ensures text_mutex is held before installing the mappings it
 	 * does not ensure text_mutex is held by the calling thread.  That's
 	 * safe but triggers a lockdep failure, so just elide it for that
 	 * specific case.
 	 */
 	if (!riscv_patch_in_stop_machine)
 		lockdep_assert_held(&text_mutex);

 	if (across_pages)
 		patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1);

 	waddr = patch_map(addr, FIX_TEXT_POKE0);

 	ret = copy_to_kernel_nofault(waddr, insn, len);

 	patch_unmap(FIX_TEXT_POKE0);

 	if (across_pages)
 		patch_unmap(FIX_TEXT_POKE1);

 	return ret;
 }
 NOKPROBE_SYMBOL(__patch_insn_write);
 #else
 static int __patch_insn_set(void *addr, u8 c, size_t len)
 {
 	memset(addr, c, len);

 	return 0;
 }
 NOKPROBE_SYMBOL(__patch_insn_set);

 static int __patch_insn_write(void *addr, const void *insn, size_t len)
 {
 	return copy_to_kernel_nofault(addr, insn, len);
 }
 NOKPROBE_SYMBOL(__patch_insn_write);
 #endif /* CONFIG_MMU */

 static int patch_insn_set(void *addr, u8 c, size_t len)
 {
 	size_t patched = 0;
 	size_t size;
 	int ret = 0;

 	/*
 	 * __patch_insn_set() can only work on 2 pages at a time so call it in a
 	 * loop with len <= 2 * PAGE_SIZE.
 	 */
 	while (patched < len && !ret) {
 		size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched);
 		ret = __patch_insn_set(addr + patched, c, size);

 		patched += size;
 	}

 	return ret;
 }
 NOKPROBE_SYMBOL(patch_insn_set);

 int patch_text_set_nosync(void *addr, u8 c, size_t len)
 {
 	u32 *tp = addr;
 	int ret;

 	ret = patch_insn_set(tp, c, len);

 	if (!ret)
 		flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len);

 	return ret;
 }
 NOKPROBE_SYMBOL(patch_text_set_nosync);

 static int patch_insn_write(void *addr, const void *insn, size_t len)
 {
 	size_t patched = 0;
 	size_t size;
 	int ret = 0;

 	/*
 	 * Copy the instructions to the destination address, two pages at a time
 	 * because __patch_insn_write() can only handle len <= 2 * PAGE_SIZE.
 	 */
 	while (patched < len && !ret) {
 		size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched);
 		ret = __patch_insn_write(addr + patched, insn + patched, size);

 		patched += size;
 	}

 	return ret;
 }
 NOKPROBE_SYMBOL(patch_insn_write);

 int patch_text_nosync(void *addr, const void *insns, size_t len)
 {
 	u32 *tp = addr;
 	int ret;

 	ret = patch_insn_write(tp, insns, len);

 	if (!ret)
 		flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len);

 	return ret;
 }
 NOKPROBE_SYMBOL(patch_text_nosync);

 static int patch_text_cb(void *data)
 {
 	struct patch_insn *patch = data;
 	unsigned long len;
 	int i, ret = 0;

 	if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
 		for (i = 0; ret == 0 && i < patch->ninsns; i++) {
 			len = GET_INSN_LENGTH(patch->insns[i]);
 			ret = patch_text_nosync(patch->addr + i * len,
 						&patch->insns[i], len);
 		}
 		atomic_inc(&patch->cpu_count);
 	} else {
 		while (atomic_read(&patch->cpu_count) <= num_online_cpus())
 			cpu_relax();
 		smp_mb();
 	}

 	return ret;
 }
 NOKPROBE_SYMBOL(patch_text_cb);

 int patch_text(void *addr, u32 *insns, int ninsns)
 {
 	int ret;
 	struct patch_insn patch = {
 		.addr = addr,
 		.insns = insns,
 		.ninsns = ninsns,
 		.cpu_count = ATOMIC_INIT(0),
 	};

 	/*
 	 * kprobes takes text_mutex, before calling patch_text(), but as we call
 	 * calls stop_machine(), the lockdep assertion in patch_insn_write()
 	 * gets confused by the context in which the lock is taken.
 	 * Instead, ensure the lock is held before calling stop_machine(), and
 	 * set riscv_patch_in_stop_machine to skip the check in
 	 * patch_insn_write().
 	 */
 	lockdep_assert_held(&text_mutex);
 	riscv_patch_in_stop_machine = true;
 	ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask);
 	riscv_patch_in_stop_machine = false;
 	return ret;
 }
 NOKPROBE_SYMBOL(patch_text);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2020 SiFive
	*/

	#include <linux/spinlock.h>
	#include <linux/mm.h>
	#include <linux/memory.h>
	#include <linux/string.h>
	#include <linux/uaccess.h>
	#include <linux/stop_machine.h>
	#include <asm/kprobes.h>
	#include <asm/cacheflush.h>
	#include <asm/fixmap.h>
	#include <asm/ftrace.h>
	#include <asm/patch.h>

	struct patch_insn {
	void *addr;
	u32 *insns;
	int ninsns;
	atomic_t cpu_count;
	};

	int riscv_patch_in_stop_machine = false;

	#ifdef CONFIG_MMU
	/*
	* The fix_to_virt(, idx) needs a const value (not a dynamic variable of
	* reg-a0) or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".
	* So use '__always_inline' and 'const unsigned int fixmap' here.
	*/
	static __always_inline void patch_map(void addr, const unsigned int fixmap)
	{
	uintptr_t uintaddr = (uintptr_t) addr;
	struct page *page;

	if (core_kernel_text(uintaddr))
	page = phys_to_page(__pa_symbol(addr));
	else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
	page = vmalloc_to_page(addr);
	else
	return addr;

	BUG_ON(!page);

	return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
	(uintaddr & ~PAGE_MASK));
	}

	static void patch_unmap(int fixmap)
	{
	clear_fixmap(fixmap);
	}
	NOKPROBE_SYMBOL(patch_unmap);

	static int __patch_insn_set(void *addr, u8 c, size_t len)
	{
	void *waddr = addr;
	bool across_pages = (((uintptr_t)addr & ~PAGE_MASK) + len) > PAGE_SIZE;

	/*
	* Only two pages can be mapped at a time for writing.
	*/
	if (len + offset_in_page(addr) > 2 * PAGE_SIZE)
	return -EINVAL;
	/*
	* Before reaching here, it was expected to lock the text_mutex
	* already, so we don't need to give another lock here and could
	* ensure that it was safe between each cores.
	*/
	lockdep_assert_held(&text_mutex);

	if (across_pages)
	patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1);

	waddr = patch_map(addr, FIX_TEXT_POKE0);

	memset(waddr, c, len);

	patch_unmap(FIX_TEXT_POKE0);

	if (across_pages)
	patch_unmap(FIX_TEXT_POKE1);

	return 0;
	}
	NOKPROBE_SYMBOL(__patch_insn_set);

	static int __patch_insn_write(void addr, const void insn, size_t len)
	{
	void *waddr = addr;
	bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE;
	int ret;

	/*
	* Only two pages can be mapped at a time for writing.
	*/
	if (len + offset_in_page(addr) > 2 * PAGE_SIZE)
	return -EINVAL;

	/*
	* Before reaching here, it was expected to lock the text_mutex
	* already, so we don't need to give another lock here and could
	* ensure that it was safe between each cores.
	*
	* We're currently using stop_machine() for ftrace & kprobes, and while
	* that ensures text_mutex is held before installing the mappings it
	* does not ensure text_mutex is held by the calling thread. That's
	* safe but triggers a lockdep failure, so just elide it for that
	* specific case.
	*/
	if (!riscv_patch_in_stop_machine)
	lockdep_assert_held(&text_mutex);

	if (across_pages)
	patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1);

	waddr = patch_map(addr, FIX_TEXT_POKE0);

	ret = copy_to_kernel_nofault(waddr, insn, len);

	patch_unmap(FIX_TEXT_POKE0);

	if (across_pages)
	patch_unmap(FIX_TEXT_POKE1);

	return ret;
	}
	NOKPROBE_SYMBOL(__patch_insn_write);
	#else
	static int __patch_insn_set(void *addr, u8 c, size_t len)
	{
	memset(addr, c, len);

	return 0;
	}
	NOKPROBE_SYMBOL(__patch_insn_set);

	static int __patch_insn_write(void addr, const void insn, size_t len)
	{
	return copy_to_kernel_nofault(addr, insn, len);
	}
	NOKPROBE_SYMBOL(__patch_insn_write);
	#endif /* CONFIG_MMU */

	static int patch_insn_set(void *addr, u8 c, size_t len)
	{
	size_t patched = 0;
	size_t size;
	int ret = 0;

	/*
	* __patch_insn_set() can only work on 2 pages at a time so call it in a
	* loop with len <= 2 * PAGE_SIZE.
	*/
	while (patched < len && !ret) {
	size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched);
	ret = __patch_insn_set(addr + patched, c, size);

	patched += size;
	}

	return ret;
	}
	NOKPROBE_SYMBOL(patch_insn_set);

	int patch_text_set_nosync(void *addr, u8 c, size_t len)
	{
	u32 *tp = addr;
	int ret;

	ret = patch_insn_set(tp, c, len);

	if (!ret)
	flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len);

	return ret;
	}
	NOKPROBE_SYMBOL(patch_text_set_nosync);

	static int patch_insn_write(void addr, const void insn, size_t len)
	{
	size_t patched = 0;
	size_t size;
	int ret = 0;

	/*
	* Copy the instructions to the destination address, two pages at a time
	* because __patch_insn_write() can only handle len <= 2 * PAGE_SIZE.
	*/
	while (patched < len && !ret) {
	size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched);
	ret = __patch_insn_write(addr + patched, insn + patched, size);

	patched += size;
	}

	return ret;
	}
	NOKPROBE_SYMBOL(patch_insn_write);

	int patch_text_nosync(void addr, const void insns, size_t len)
	{
	u32 *tp = addr;
	int ret;

	ret = patch_insn_write(tp, insns, len);

	if (!ret)
	flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len);

	return ret;
	}
	NOKPROBE_SYMBOL(patch_text_nosync);

	static int patch_text_cb(void *data)
	{
	struct patch_insn *patch = data;
	unsigned long len;
	int i, ret = 0;

	if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
	for (i = 0; ret == 0 && i < patch->ninsns; i++) {
	len = GET_INSN_LENGTH(patch->insns[i]);
	ret = patch_text_nosync(patch->addr + i * len,
	&patch->insns[i], len);
	}
	atomic_inc(&patch->cpu_count);
	} else {
	while (atomic_read(&patch->cpu_count) <= num_online_cpus())
	cpu_relax();
	smp_mb();
	}

	return ret;
	}
	NOKPROBE_SYMBOL(patch_text_cb);

	int patch_text(void addr, u32 insns, int ninsns)
	{
	int ret;
	struct patch_insn patch = {
	.addr = addr,
	.insns = insns,
	.ninsns = ninsns,
	.cpu_count = ATOMIC_INIT(0),
	};

	/*
	* kprobes takes text_mutex, before calling patch_text(), but as we call
	* calls stop_machine(), the lockdep assertion in patch_insn_write()
	* gets confused by the context in which the lock is taken.
	* Instead, ensure the lock is held before calling stop_machine(), and
	* set riscv_patch_in_stop_machine to skip the check in
	* patch_insn_write().
	*/
	lockdep_assert_held(&text_mutex);
	riscv_patch_in_stop_machine = true;
	ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask);
	riscv_patch_in_stop_machine = false;
	return ret;
	}
	NOKPROBE_SYMBOL(patch_text);