arch/powerpc/lib/code-patching.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  Copyright 2008 Michael Ellerman, IBM Corporation.
  */

 #include <linux/kprobes.h>
 #include <linux/vmalloc.h>
 #include <linux/init.h>
 #include <linux/cpuhotplug.h>
 #include <linux/uaccess.h>
 #include <linux/jump_label.h>

 #include <asm/tlbflush.h>
 #include <asm/page.h>
 #include <asm/code-patching.h>
 #include <asm/inst.h>

 static int __patch_instruction(u32 *exec_addr, ppc_inst_t instr, u32 *patch_addr)
 {
 	if (!ppc_inst_prefixed(instr)) {
 		u32 val = ppc_inst_val(instr);

 		__put_kernel_nofault(patch_addr, &val, u32, failed);
 	} else {
 		u64 val = ppc_inst_as_ulong(instr);

 		__put_kernel_nofault(patch_addr, &val, u64, failed);
 	}

 	asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
 							    "r" (exec_addr));

 	return 0;

 failed:
 	return -EPERM;
 }

 int raw_patch_instruction(u32 *addr, ppc_inst_t instr)
 {
 	return __patch_instruction(addr, instr, addr);
 }

 #ifdef CONFIG_STRICT_KERNEL_RWX
 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);

 static int map_patch_area(void *addr, unsigned long text_poke_addr);
 static void unmap_patch_area(unsigned long addr);

 static int text_area_cpu_up(unsigned int cpu)
 {
 	struct vm_struct *area;
 	unsigned long addr;
 	int err;

 	area = get_vm_area(PAGE_SIZE, VM_ALLOC);
 	if (!area) {
 		WARN_ONCE(1, "Failed to create text area for cpu %d\n",
 			cpu);
 		return -1;
 	}

 	// Map/unmap the area to ensure all page tables are pre-allocated
 	addr = (unsigned long)area->addr;
 	err = map_patch_area(empty_zero_page, addr);
 	if (err)
 		return err;

 	unmap_patch_area(addr);

 	this_cpu_write(text_poke_area, area);

 	return 0;
 }

 static int text_area_cpu_down(unsigned int cpu)
 {
 	free_vm_area(this_cpu_read(text_poke_area));
 	return 0;
 }

 static __ro_after_init DEFINE_STATIC_KEY_FALSE(poking_init_done);

 /*
  * Although BUG_ON() is rude, in this case it should only happen if ENOMEM, and
  * we judge it as being preferable to a kernel that will crash later when
  * someone tries to use patch_instruction().
  */
 void __init poking_init(void)
 {
 	BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
 		"powerpc/text_poke:online", text_area_cpu_up,
 		text_area_cpu_down));
 	static_branch_enable(&poking_init_done);
 }

 /*
  * This can be called for kernel text or a module.
  */
 static int map_patch_area(void *addr, unsigned long text_poke_addr)
 {
 	unsigned long pfn;

 	if (IS_ENABLED(CONFIG_MODULES) && is_vmalloc_or_module_addr(addr))
 		pfn = vmalloc_to_pfn(addr);
 	else
 		pfn = __pa_symbol(addr) >> PAGE_SHIFT;

 	return map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL);
 }

 static void unmap_patch_area(unsigned long addr)
 {
 	pte_t *ptep;
 	pmd_t *pmdp;
 	pud_t *pudp;
 	p4d_t *p4dp;
 	pgd_t *pgdp;

 	pgdp = pgd_offset_k(addr);
 	if (WARN_ON(pgd_none(*pgdp)))
 		return;

 	p4dp = p4d_offset(pgdp, addr);
 	if (WARN_ON(p4d_none(*p4dp)))
 		return;

 	pudp = pud_offset(p4dp, addr);
 	if (WARN_ON(pud_none(*pudp)))
 		return;

 	pmdp = pmd_offset(pudp, addr);
 	if (WARN_ON(pmd_none(*pmdp)))
 		return;

 	ptep = pte_offset_kernel(pmdp, addr);
 	if (WARN_ON(pte_none(*ptep)))
 		return;

 	/*
 	 * In hash, pte_clear flushes the tlb, in radix, we have to
 	 */
 	pte_clear(&init_mm, addr, ptep);
 	flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
 }

 static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
 {
 	int err;
 	u32 *patch_addr;
 	unsigned long text_poke_addr;

 	text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
 	patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr));

 	err = map_patch_area(addr, text_poke_addr);
 	if (err)
 		return err;

 	err = __patch_instruction(addr, instr, patch_addr);

 	unmap_patch_area(text_poke_addr);

 	return err;
 }

 static int do_patch_instruction(u32 *addr, ppc_inst_t instr)
 {
 	int err;
 	unsigned long flags;

 	/*
 	 * During early early boot patch_instruction is called
 	 * when text_poke_area is not ready, but we still need
 	 * to allow patching. We just do the plain old patching
 	 */
 	if (!static_branch_likely(&poking_init_done))
 		return raw_patch_instruction(addr, instr);

 	local_irq_save(flags);
 	err = __do_patch_instruction(addr, instr);
 	local_irq_restore(flags);

 	return err;
 }
 #else /* !CONFIG_STRICT_KERNEL_RWX */

 static int do_patch_instruction(u32 *addr, ppc_inst_t instr)
 {
 	return raw_patch_instruction(addr, instr);
 }

 #endif /* CONFIG_STRICT_KERNEL_RWX */

 __ro_after_init DEFINE_STATIC_KEY_FALSE(init_mem_is_free);

 int patch_instruction(u32 *addr, ppc_inst_t instr)
 {
 	/* Make sure we aren't patching a freed init section */
 	if (static_branch_likely(&init_mem_is_free) && init_section_contains(addr, 4))
 		return 0;

 	return do_patch_instruction(addr, instr);
 }
 NOKPROBE_SYMBOL(patch_instruction);

 int patch_branch(u32 *addr, unsigned long target, int flags)
 {
 	ppc_inst_t instr;

 	if (create_branch(&instr, addr, target, flags))
 		return -ERANGE;

 	return patch_instruction(addr, instr);
 }

 /*
  * Helper to check if a given instruction is a conditional branch
  * Derived from the conditional checks in analyse_instr()
  */
 bool is_conditional_branch(ppc_inst_t instr)
 {
 	unsigned int opcode = ppc_inst_primary_opcode(instr);

 	if (opcode == 16)       /* bc, bca, bcl, bcla */
 		return true;
 	if (opcode == 19) {
 		switch ((ppc_inst_val(instr) >> 1) & 0x3ff) {
 		case 16:        /* bclr, bclrl */
 		case 528:       /* bcctr, bcctrl */
 		case 560:       /* bctar, bctarl */
 			return true;
 		}
 	}
 	return false;
 }
 NOKPROBE_SYMBOL(is_conditional_branch);

 int create_cond_branch(ppc_inst_t *instr, const u32 *addr,
 		       unsigned long target, int flags)
 {
 	long offset;

 	offset = target;
 	if (! (flags & BRANCH_ABSOLUTE))
 		offset = offset - (unsigned long)addr;

 	/* Check we can represent the target in the instruction format */
 	if (!is_offset_in_cond_branch_range(offset))
 		return 1;

 	/* Mask out the flags and target, so they don't step on each other. */
 	*instr = ppc_inst(0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC));

 	return 0;
 }

 int instr_is_relative_branch(ppc_inst_t instr)
 {
 	if (ppc_inst_val(instr) & BRANCH_ABSOLUTE)
 		return 0;

 	return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
 }

 int instr_is_relative_link_branch(ppc_inst_t instr)
 {
 	return instr_is_relative_branch(instr) && (ppc_inst_val(instr) & BRANCH_SET_LINK);
 }

 static unsigned long branch_iform_target(const u32 *instr)
 {
 	signed long imm;

 	imm = ppc_inst_val(ppc_inst_read(instr)) & 0x3FFFFFC;

 	/* If the top bit of the immediate value is set this is negative */
 	if (imm & 0x2000000)
 		imm -= 0x4000000;

 	if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0)
 		imm += (unsigned long)instr;

 	return (unsigned long)imm;
 }

 static unsigned long branch_bform_target(const u32 *instr)
 {
 	signed long imm;

 	imm = ppc_inst_val(ppc_inst_read(instr)) & 0xFFFC;

 	/* If the top bit of the immediate value is set this is negative */
 	if (imm & 0x8000)
 		imm -= 0x10000;

 	if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0)
 		imm += (unsigned long)instr;

 	return (unsigned long)imm;
 }

 unsigned long branch_target(const u32 *instr)
 {
 	if (instr_is_branch_iform(ppc_inst_read(instr)))
 		return branch_iform_target(instr);
 	else if (instr_is_branch_bform(ppc_inst_read(instr)))
 		return branch_bform_target(instr);

 	return 0;
 }

 int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src)
 {
 	unsigned long target;
 	target = branch_target(src);

 	if (instr_is_branch_iform(ppc_inst_read(src)))
 		return create_branch(instr, dest, target,
 				     ppc_inst_val(ppc_inst_read(src)));
 	else if (instr_is_branch_bform(ppc_inst_read(src)))
 		return create_cond_branch(instr, dest, target,
 					  ppc_inst_val(ppc_inst_read(src)));

 	return 1;
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Copyright 2008 Michael Ellerman, IBM Corporation.
	*/

	#include <linux/kprobes.h>
	#include <linux/vmalloc.h>
	#include <linux/init.h>
	#include <linux/cpuhotplug.h>
	#include <linux/uaccess.h>
	#include <linux/jump_label.h>

	#include <asm/tlbflush.h>
	#include <asm/page.h>
	#include <asm/code-patching.h>
	#include <asm/inst.h>

	static int __patch_instruction(u32 exec_addr, ppc_inst_t instr, u32 patch_addr)
	{
	if (!ppc_inst_prefixed(instr)) {
	u32 val = ppc_inst_val(instr);

	__put_kernel_nofault(patch_addr, &val, u32, failed);
	} else {
	u64 val = ppc_inst_as_ulong(instr);

	__put_kernel_nofault(patch_addr, &val, u64, failed);
	}

	asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
	"r" (exec_addr));

	return 0;

	failed:
	return -EPERM;
	}

	int raw_patch_instruction(u32 *addr, ppc_inst_t instr)
	{
	return __patch_instruction(addr, instr, addr);
	}

	#ifdef CONFIG_STRICT_KERNEL_RWX
	static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);

	static int map_patch_area(void *addr, unsigned long text_poke_addr);
	static void unmap_patch_area(unsigned long addr);

	static int text_area_cpu_up(unsigned int cpu)
	{
	struct vm_struct *area;
	unsigned long addr;
	int err;

	area = get_vm_area(PAGE_SIZE, VM_ALLOC);
	if (!area) {
	WARN_ONCE(1, "Failed to create text area for cpu %d\n",
	cpu);
	return -1;
	}

	// Map/unmap the area to ensure all page tables are pre-allocated
	addr = (unsigned long)area->addr;
	err = map_patch_area(empty_zero_page, addr);
	if (err)
	return err;

	unmap_patch_area(addr);

	this_cpu_write(text_poke_area, area);

	return 0;
	}

	static int text_area_cpu_down(unsigned int cpu)
	{
	free_vm_area(this_cpu_read(text_poke_area));
	return 0;
	}

	static __ro_after_init DEFINE_STATIC_KEY_FALSE(poking_init_done);

	/*
	* Although BUG_ON() is rude, in this case it should only happen if ENOMEM, and
	* we judge it as being preferable to a kernel that will crash later when
	* someone tries to use patch_instruction().
	*/
	void __init poking_init(void)
	{
	BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
	"powerpc/text_poke:online", text_area_cpu_up,
	text_area_cpu_down));
	static_branch_enable(&poking_init_done);
	}

	/*
	* This can be called for kernel text or a module.
	*/
	static int map_patch_area(void *addr, unsigned long text_poke_addr)
	{
	unsigned long pfn;

	if (IS_ENABLED(CONFIG_MODULES) && is_vmalloc_or_module_addr(addr))
	pfn = vmalloc_to_pfn(addr);
	else
	pfn = __pa_symbol(addr) >> PAGE_SHIFT;

	return map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL);
	}

	static void unmap_patch_area(unsigned long addr)
	{
	pte_t *ptep;
	pmd_t *pmdp;
	pud_t *pudp;
	p4d_t *p4dp;
	pgd_t *pgdp;

	pgdp = pgd_offset_k(addr);
	if (WARN_ON(pgd_none(*pgdp)))
	return;

	p4dp = p4d_offset(pgdp, addr);
	if (WARN_ON(p4d_none(*p4dp)))
	return;

	pudp = pud_offset(p4dp, addr);
	if (WARN_ON(pud_none(*pudp)))
	return;

	pmdp = pmd_offset(pudp, addr);
	if (WARN_ON(pmd_none(*pmdp)))
	return;

	ptep = pte_offset_kernel(pmdp, addr);
	if (WARN_ON(pte_none(*ptep)))
	return;

	/*
	* In hash, pte_clear flushes the tlb, in radix, we have to
	*/
	pte_clear(&init_mm, addr, ptep);
	flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
	}

	static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
	{
	int err;
	u32 *patch_addr;
	unsigned long text_poke_addr;

	text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
	patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr));

	err = map_patch_area(addr, text_poke_addr);
	if (err)
	return err;

	err = __patch_instruction(addr, instr, patch_addr);

	unmap_patch_area(text_poke_addr);

	return err;
	}

	static int do_patch_instruction(u32 *addr, ppc_inst_t instr)
	{
	int err;
	unsigned long flags;

	/*
	* During early early boot patch_instruction is called
	* when text_poke_area is not ready, but we still need
	* to allow patching. We just do the plain old patching
	*/
	if (!static_branch_likely(&poking_init_done))
	return raw_patch_instruction(addr, instr);

	local_irq_save(flags);
	err = __do_patch_instruction(addr, instr);
	local_irq_restore(flags);

	return err;
	}
	#else /* !CONFIG_STRICT_KERNEL_RWX */

	static int do_patch_instruction(u32 *addr, ppc_inst_t instr)
	{
	return raw_patch_instruction(addr, instr);
	}

	#endif /* CONFIG_STRICT_KERNEL_RWX */

	__ro_after_init DEFINE_STATIC_KEY_FALSE(init_mem_is_free);

	int patch_instruction(u32 *addr, ppc_inst_t instr)
	{
	/* Make sure we aren't patching a freed init section */
	if (static_branch_likely(&init_mem_is_free) && init_section_contains(addr, 4))
	return 0;

	return do_patch_instruction(addr, instr);
	}
	NOKPROBE_SYMBOL(patch_instruction);

	int patch_branch(u32 *addr, unsigned long target, int flags)
	{
	ppc_inst_t instr;

	if (create_branch(&instr, addr, target, flags))
	return -ERANGE;

	return patch_instruction(addr, instr);
	}

	/*
	* Helper to check if a given instruction is a conditional branch
	* Derived from the conditional checks in analyse_instr()
	*/
	bool is_conditional_branch(ppc_inst_t instr)
	{
	unsigned int opcode = ppc_inst_primary_opcode(instr);

	if (opcode == 16) /* bc, bca, bcl, bcla */
	return true;
	if (opcode == 19) {
	switch ((ppc_inst_val(instr) >> 1) & 0x3ff) {
	case 16: /* bclr, bclrl */
	case 528: /* bcctr, bcctrl */
	case 560: /* bctar, bctarl */
	return true;
	}
	}
	return false;
	}
	NOKPROBE_SYMBOL(is_conditional_branch);

	int create_cond_branch(ppc_inst_t instr, const u32 addr,
	unsigned long target, int flags)
	{
	long offset;

	offset = target;
	if (! (flags & BRANCH_ABSOLUTE))
	offset = offset - (unsigned long)addr;

	/* Check we can represent the target in the instruction format */
	if (!is_offset_in_cond_branch_range(offset))
	return 1;

	/* Mask out the flags and target, so they don't step on each other. */
	*instr = ppc_inst(0x40000000 \| (flags & 0x3FF0003) \| (offset & 0xFFFC));

	return 0;
	}

	int instr_is_relative_branch(ppc_inst_t instr)
	{
	if (ppc_inst_val(instr) & BRANCH_ABSOLUTE)
	return 0;

	return instr_is_branch_iform(instr) \|\| instr_is_branch_bform(instr);
	}

	int instr_is_relative_link_branch(ppc_inst_t instr)
	{
	return instr_is_relative_branch(instr) && (ppc_inst_val(instr) & BRANCH_SET_LINK);
	}

	static unsigned long branch_iform_target(const u32 *instr)
	{
	signed long imm;

	imm = ppc_inst_val(ppc_inst_read(instr)) & 0x3FFFFFC;

	/* If the top bit of the immediate value is set this is negative */
	if (imm & 0x2000000)
	imm -= 0x4000000;

	if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0)
	imm += (unsigned long)instr;

	return (unsigned long)imm;
	}

	static unsigned long branch_bform_target(const u32 *instr)
	{
	signed long imm;

	imm = ppc_inst_val(ppc_inst_read(instr)) & 0xFFFC;

	/* If the top bit of the immediate value is set this is negative */
	if (imm & 0x8000)
	imm -= 0x10000;

	if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0)
	imm += (unsigned long)instr;

	return (unsigned long)imm;
	}

	unsigned long branch_target(const u32 *instr)
	{
	if (instr_is_branch_iform(ppc_inst_read(instr)))
	return branch_iform_target(instr);
	else if (instr_is_branch_bform(ppc_inst_read(instr)))
	return branch_bform_target(instr);

	return 0;
	}

	int translate_branch(ppc_inst_t instr, const u32 dest, const u32 *src)
	{
	unsigned long target;
	target = branch_target(src);

	if (instr_is_branch_iform(ppc_inst_read(src)))
	return create_branch(instr, dest, target,
	ppc_inst_val(ppc_inst_read(src)));
	else if (instr_is_branch_bform(ppc_inst_read(src)))
	return create_cond_branch(instr, dest, target,
	ppc_inst_val(ppc_inst_read(src)));

	return 1;
	}