text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * VDSO implementations.
   *
   * Copyright (C) 2012 ARM Limited
   *
   * Author: Will Deacon <will.deacon@arm.com>
   */
  
  #include <linux/cache.h>
  #include <linux/clocksource.h>
  #include <linux/elf.h>
  #include <linux/err.h>
  #include <linux/errno.h>
  #include <linux/gfp.h>
  #include <linux/kernel.h>
  #include <linux/mm.h>
  #include <linux/sched.h>
  #include <linux/signal.h>
  #include <linux/slab.h>
  #include <linux/timekeeper_internal.h>
  #include <linux/vmalloc.h>
  #include <vdso/datapage.h>
  #include <vdso/helpers.h>
  #include <vdso/vsyscall.h>
  
  #include <asm/cacheflush.h>
  #include <asm/signal32.h>
  #include <asm/vdso.h>
  
  extern char vdso_start[], vdso_end[];
  #ifdef CONFIG_COMPAT_VDSO
  extern char vdso32_start[], vdso32_end[];
  #endif /* CONFIG_COMPAT_VDSO */
  
  /* vdso_lookup arch_index */
  enum arch_vdso_type {
  	ARM64_VDSO = 0,
  #ifdef CONFIG_COMPAT_VDSO
  	ARM64_VDSO32 = 1,
  #endif /* CONFIG_COMPAT_VDSO */
  };
  #ifdef CONFIG_COMPAT_VDSO
  #define VDSO_TYPES		(ARM64_VDSO32 + 1)
  #else
  #define VDSO_TYPES		(ARM64_VDSO + 1)
  #endif /* CONFIG_COMPAT_VDSO */
  
  struct __vdso_abi {
  	const char *name;
  	const char *vdso_code_start;
  	const char *vdso_code_end;
  	unsigned long vdso_pages;
  	/* Data Mapping */
  	struct vm_special_mapping *dm;
  	/* Code Mapping */
  	struct vm_special_mapping *cm;
  };
  
  static struct __vdso_abi vdso_lookup[VDSO_TYPES] __ro_after_init = {
  	{
  		.name = "vdso",
  		.vdso_code_start = vdso_start,
  		.vdso_code_end = vdso_end,
  	},
  #ifdef CONFIG_COMPAT_VDSO
  	{
  		.name = "vdso32",
  		.vdso_code_start = vdso32_start,
  		.vdso_code_end = vdso32_end,
  	},
  #endif /* CONFIG_COMPAT_VDSO */
  };
  
  /*
   * The vDSO data page.
   */
  static union {
  	struct vdso_data	data[CS_BASES];
  	u8			page[PAGE_SIZE];
  } vdso_data_store __page_aligned_data;
  struct vdso_data *vdso_data = vdso_data_store.data;
  
  static int __vdso_remap(enum arch_vdso_type arch_index,
  			const struct vm_special_mapping *sm,
  			struct vm_area_struct *new_vma)
  {
  	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
  	unsigned long vdso_size = vdso_lookup[arch_index].vdso_code_end -
  				  vdso_lookup[arch_index].vdso_code_start;
  
  	if (vdso_size != new_size)
  		return -EINVAL;
  
  	current->mm->context.vdso = (void *)new_vma->vm_start;
  
  	return 0;
  }
  
  static int __vdso_init(enum arch_vdso_type arch_index)
  {
  	int i;
  	struct page **vdso_pagelist;
  	unsigned long pfn;
  
  	if (memcmp(vdso_lookup[arch_index].vdso_code_start, "\177ELF", 4)) {
  		pr_err("vDSO is not a valid ELF object!\n");
  		return -EINVAL;
  	}
  
  	vdso_lookup[arch_index].vdso_pages = (
  			vdso_lookup[arch_index].vdso_code_end -
  			vdso_lookup[arch_index].vdso_code_start) >>
  			PAGE_SHIFT;
  
  	/* Allocate the vDSO pagelist, plus a page for the data. */
  	vdso_pagelist = kcalloc(vdso_lookup[arch_index].vdso_pages + 1,
  				sizeof(struct page *),
  				GFP_KERNEL);
  	if (vdso_pagelist == NULL)
  		return -ENOMEM;
  
  	/* Grab the vDSO data page. */
  	vdso_pagelist[0] = phys_to_page(__pa_symbol(vdso_data));
  
  
  	/* Grab the vDSO code pages. */
  	pfn = sym_to_pfn(vdso_lookup[arch_index].vdso_code_start);
  
  	for (i = 0; i < vdso_lookup[arch_index].vdso_pages; i++)
  		vdso_pagelist[i + 1] = pfn_to_page(pfn + i);
  
  	vdso_lookup[arch_index].dm->pages = &vdso_pagelist[0];
  	vdso_lookup[arch_index].cm->pages = &vdso_pagelist[1];
  
  	return 0;
  }
  
  static int __setup_additional_pages(enum arch_vdso_type arch_index,
  				    struct mm_struct *mm,
  				    struct linux_binprm *bprm,
  				    int uses_interp)
  {
  	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
  	void *ret;
  
  	vdso_text_len = vdso_lookup[arch_index].vdso_pages << PAGE_SHIFT;
  	/* Be sure to map the data page */
  	vdso_mapping_len = vdso_text_len + PAGE_SIZE;
  
  	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
  	if (IS_ERR_VALUE(vdso_base)) {
  		ret = ERR_PTR(vdso_base);
  		goto up_fail;
  	}
  
  	ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
  				       VM_READ|VM_MAYREAD,
  				       vdso_lookup[arch_index].dm);
  	if (IS_ERR(ret))
  		goto up_fail;
  
  	vdso_base += PAGE_SIZE;
  	mm->context.vdso = (void *)vdso_base;
  	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
  				       VM_READ|VM_EXEC|
  				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
  				       vdso_lookup[arch_index].cm);
  	if (IS_ERR(ret))
  		goto up_fail;
  
  	return 0;
  
  up_fail:
  	mm->context.vdso = NULL;
  	return PTR_ERR(ret);
  }
  
  #ifdef CONFIG_COMPAT
  /*
   * Create and map the vectors page for AArch32 tasks.
   */
  #ifdef CONFIG_COMPAT_VDSO
  static int aarch32_vdso_mremap(const struct vm_special_mapping *sm,
  		struct vm_area_struct *new_vma)
  {
  	return __vdso_remap(ARM64_VDSO32, sm, new_vma);
  }
  #endif /* CONFIG_COMPAT_VDSO */
  
  /*
   * aarch32_vdso_pages:
   * 0 - kuser helpers
   * 1 - sigreturn code
   * or (CONFIG_COMPAT_VDSO):
   * 0 - kuser helpers
   * 1 - vdso data
   * 2 - vdso code
   */
  #define C_VECTORS	0
  #ifdef CONFIG_COMPAT_VDSO
  #define C_VVAR		1
  #define C_VDSO		2
  #define C_PAGES		(C_VDSO + 1)
  #else
  #define C_SIGPAGE	1
  #define C_PAGES		(C_SIGPAGE + 1)
  #endif /* CONFIG_COMPAT_VDSO */
  static struct page *aarch32_vdso_pages[C_PAGES] __ro_after_init;
  static struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = {
  	{
  		.name	= "[vectors]", /* ABI */
  		.pages	= &aarch32_vdso_pages[C_VECTORS],
  	},
  #ifdef CONFIG_COMPAT_VDSO
  	{
  		.name = "[vvar]",
  	},
  	{
  		.name = "[vdso]",
  		.mremap = aarch32_vdso_mremap,
  	},
  #else
  	{
  		.name	= "[sigpage]", /* ABI */
  		.pages	= &aarch32_vdso_pages[C_SIGPAGE],
  	},
  #endif /* CONFIG_COMPAT_VDSO */
  };
  
  static int aarch32_alloc_kuser_vdso_page(void)
  {
  	extern char __kuser_helper_start[], __kuser_helper_end[];
  	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
  	unsigned long vdso_page;
  
  	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
  		return 0;
  
  	vdso_page = get_zeroed_page(GFP_ATOMIC);
  	if (!vdso_page)
  		return -ENOMEM;
  
  	memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
  	       kuser_sz);
  	aarch32_vdso_pages[C_VECTORS] = virt_to_page(vdso_page);
  	flush_dcache_page(aarch32_vdso_pages[C_VECTORS]);
  	return 0;
  }
  
  #ifdef CONFIG_COMPAT_VDSO
  static int __aarch32_alloc_vdso_pages(void)
  {
  	int ret;
  
  	vdso_lookup[ARM64_VDSO32].dm = &aarch32_vdso_spec[C_VVAR];
  	vdso_lookup[ARM64_VDSO32].cm = &aarch32_vdso_spec[C_VDSO];
  
  	ret = __vdso_init(ARM64_VDSO32);
  	if (ret)
  		return ret;
  
  	ret = aarch32_alloc_kuser_vdso_page();
  	if (ret) {
  		unsigned long c_vvar =
  			(unsigned long)page_to_virt(aarch32_vdso_pages[C_VVAR]);
  		unsigned long c_vdso =
  			(unsigned long)page_to_virt(aarch32_vdso_pages[C_VDSO]);
  
  		free_page(c_vvar);
  		free_page(c_vdso);
  	}
  
  	return ret;
  }
  #else
  static int __aarch32_alloc_vdso_pages(void)
  {
  	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
  	int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
  	unsigned long sigpage;
  	int ret;
  
  	sigpage = get_zeroed_page(GFP_ATOMIC);
  	if (!sigpage)
  		return -ENOMEM;
  
  	memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz);
  	aarch32_vdso_pages[C_SIGPAGE] = virt_to_page(sigpage);
  	flush_dcache_page(aarch32_vdso_pages[C_SIGPAGE]);
  
  	ret = aarch32_alloc_kuser_vdso_page();
  	if (ret)
  		free_page(sigpage);
  
  	return ret;
  }
  #endif /* CONFIG_COMPAT_VDSO */
  
  static int __init aarch32_alloc_vdso_pages(void)
  {
  	return __aarch32_alloc_vdso_pages();
  }
  arch_initcall(aarch32_alloc_vdso_pages);
  
  static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
  {
  	void *ret;
  
  	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
  		return 0;
  
  	/*
  	 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
  	 * not safe to CoW the page containing the CPU exception vectors.
  	 */
  	ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
  				       VM_READ | VM_EXEC |
  				       VM_MAYREAD | VM_MAYEXEC,
  				       &aarch32_vdso_spec[C_VECTORS]);
  
  	return PTR_ERR_OR_ZERO(ret);
  }
  
  #ifndef CONFIG_COMPAT_VDSO
  static int aarch32_sigreturn_setup(struct mm_struct *mm)
  {
  	unsigned long addr;
  	void *ret;
  
  	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
  	if (IS_ERR_VALUE(addr)) {
  		ret = ERR_PTR(addr);
  		goto out;
  	}
  
  	/*
  	 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
  	 * set breakpoints.
  	 */
  	ret = _install_special_mapping(mm, addr, PAGE_SIZE,
  				       VM_READ | VM_EXEC | VM_MAYREAD |
  				       VM_MAYWRITE | VM_MAYEXEC,
  				       &aarch32_vdso_spec[C_SIGPAGE]);
  	if (IS_ERR(ret))
  		goto out;
  
  	mm->context.vdso = (void *)addr;
  
  out:
  	return PTR_ERR_OR_ZERO(ret);
  }
  #endif /* !CONFIG_COMPAT_VDSO */
  
  int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  {
  	struct mm_struct *mm = current->mm;
  	int ret;
  
  	if (down_write_killable(&mm->mmap_sem))
  		return -EINTR;
  
  	ret = aarch32_kuser_helpers_setup(mm);
  	if (ret)
  		goto out;
  
  #ifdef CONFIG_COMPAT_VDSO
  	ret = __setup_additional_pages(ARM64_VDSO32,
  				       mm,
  				       bprm,
  				       uses_interp);
  #else
  	ret = aarch32_sigreturn_setup(mm);
  #endif /* CONFIG_COMPAT_VDSO */
  
  out:
  	up_write(&mm->mmap_sem);
  	return ret;
  }
  #endif /* CONFIG_COMPAT */
  
  static int vdso_mremap(const struct vm_special_mapping *sm,
  		struct vm_area_struct *new_vma)
  {
  	return __vdso_remap(ARM64_VDSO, sm, new_vma);
  }
  
  /*
   * aarch64_vdso_pages:
   * 0 - vvar
   * 1 - vdso
   */
  #define A_VVAR		0
  #define A_VDSO		1
  #define A_PAGES		(A_VDSO + 1)
  static struct vm_special_mapping vdso_spec[A_PAGES] __ro_after_init = {
  	{
  		.name	= "[vvar]",
  	},
  	{
  		.name	= "[vdso]",
  		.mremap = vdso_mremap,
  	},
  };
  
  static int __init vdso_init(void)
  {
  	vdso_lookup[ARM64_VDSO].dm = &vdso_spec[A_VVAR];
  	vdso_lookup[ARM64_VDSO].cm = &vdso_spec[A_VDSO];
  
  	return __vdso_init(ARM64_VDSO);
  }
  arch_initcall(vdso_init);
  
  int arch_setup_additional_pages(struct linux_binprm *bprm,
  				int uses_interp)
  {
  	struct mm_struct *mm = current->mm;
  	int ret;
  
  	if (down_write_killable(&mm->mmap_sem))
  		return -EINTR;
  
  	ret = __setup_additional_pages(ARM64_VDSO,
  				       mm,
  				       bprm,
  				       uses_interp);
  
  	up_write(&mm->mmap_sem);
  
  	return ret;
  }
  