linux/arch/riscv/kernel/vdso.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
 *                    <benh@kernel.crashing.org>
 * Copyright (C) 2012 ARM Limited
 * Copyright (C) 2015 Regents of the University of California
 */

#include <linux/elf.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/binfmts.h>
#include <linux/err.h>
#include <asm/page.h>
#include <asm/vdso.h>
#include <linux/vdso_datastore.h>
#include <vdso/datapage.h>
#include <vdso/vsyscall.h>

#define VVAR_SIZE  (VDSO_NR_PAGES << PAGE_SHIFT)

struct __vdso_info {
	const char *name;
	const char *vdso_code_start;
	const char *vdso_code_end;
	unsigned long vdso_pages;
	/* Code Mapping */
	struct vm_special_mapping *cm;
};

static struct __vdso_info vdso_info;
#ifdef CONFIG_COMPAT
static struct __vdso_info compat_vdso_info;
#endif

static int vdso_mremap(const struct vm_special_mapping *sm,
		       struct vm_area_struct *new_vma)
{
	current->mm->context.vdso = (void *)new_vma->vm_start;

	return 0;
}

static void __init __vdso_init(struct __vdso_info *vdso_info)
{
	unsigned int i;
	struct page **vdso_pagelist;
	unsigned long pfn;

	if (memcmp(vdso_info->vdso_code_start, "\177ELF", 4))
		panic("vDSO is not a valid ELF object!\n");

	vdso_info->vdso_pages = (
		vdso_info->vdso_code_end -
		vdso_info->vdso_code_start) >>
		PAGE_SHIFT;

	vdso_pagelist = kcalloc(vdso_info->vdso_pages,
				sizeof(struct page *),
				GFP_KERNEL);
	if (vdso_pagelist == NULL)
		panic("vDSO kcalloc failed!\n");

	/* Grab the vDSO code pages. */
	pfn = sym_to_pfn(vdso_info->vdso_code_start);

	for (i = 0; i < vdso_info->vdso_pages; i++)
		vdso_pagelist[i] = pfn_to_page(pfn + i);

	vdso_info->cm->pages = vdso_pagelist;
}

static struct vm_special_mapping rv_vdso_map __ro_after_init = {
	.name   = "[vdso]",
	.mremap = vdso_mremap,
};

static struct __vdso_info vdso_info __ro_after_init = {
	.name = "vdso",
	.vdso_code_start = vdso_start,
	.vdso_code_end = vdso_end,
	.cm = &rv_vdso_map,
};

#ifdef CONFIG_COMPAT
static struct vm_special_mapping rv_compat_vdso_map __ro_after_init = {
	.name   = "[vdso]",
	.mremap = vdso_mremap,
};

static struct __vdso_info compat_vdso_info __ro_after_init = {
	.name = "compat_vdso",
	.vdso_code_start = compat_vdso_start,
	.vdso_code_end = compat_vdso_end,
	.cm = &rv_compat_vdso_map,
};
#endif

static int __init vdso_init(void)
{
	/* Hart implements zimop, expose cfi compiled vdso */
	if (IS_ENABLED(CONFIG_RISCV_USER_CFI) &&
	    riscv_has_extension_unlikely(RISCV_ISA_EXT_ZIMOP)) {
		vdso_info.vdso_code_start = vdso_cfi_start;
		vdso_info.vdso_code_end = vdso_cfi_end;
	}

	__vdso_init(&vdso_info);
#ifdef CONFIG_COMPAT
	__vdso_init(&compat_vdso_info);
#endif

	return 0;
}
arch_initcall(vdso_init);

static int __setup_additional_pages(struct mm_struct *mm,
				    struct linux_binprm *bprm,
				    int uses_interp,
				    struct __vdso_info *vdso_info)
{
	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
	void *ret;

	BUILD_BUG_ON(VDSO_NR_PAGES != __VDSO_PAGES);

	vdso_text_len = vdso_info->vdso_pages << PAGE_SHIFT;
	/* Be sure to map the data page */
	vdso_mapping_len = vdso_text_len + VVAR_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 = vdso_install_vvar_mapping(mm, vdso_base);
	if (IS_ERR(ret))
		goto up_fail;

	vdso_base += VVAR_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 | VM_SEALED_SYSMAP),
		vdso_info->cm);

	if (IS_ERR(ret))
		goto up_fail;

	return 0;

up_fail:
	mm->context.vdso = NULL;
	return PTR_ERR(ret);
}

#ifdef CONFIG_COMPAT
int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
				       int uses_interp)
{
	struct mm_struct *mm = current->mm;
	int ret;

	if (mmap_write_lock_killable(mm))
		return -EINTR;

	ret = __setup_additional_pages(mm, bprm, uses_interp,
							&compat_vdso_info);
	mmap_write_unlock(mm);

	return ret;
}
#endif

int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
	struct mm_struct *mm = current->mm;
	int ret;

	if (mmap_write_lock_killable(mm))
		return -EINTR;

	ret = __setup_additional_pages(mm, bprm, uses_interp, &vdso_info);
	mmap_write_unlock(mm);

	return ret;
}