arch/arm64/kernel/vdso.c

/*
 * VDSO implementations.
 *
 * Copyright (C) 2012 ARM Limited
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * 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 <asm/cacheflush.h>
#include <asm/signal32.h>
#include <asm/vdso.h>
#include <asm/vdso_datapage.h>

extern char vdso_start[], vdso_end[];
static unsigned long vdso_pages __ro_after_init;

/*
 * The vDSO data page.
 */
static union {
	struct vdso_data	data;
	u8			page[PAGE_SIZE];
} vdso_data_store __page_aligned_data;
struct vdso_data *vdso_data = &vdso_data_store.data;

#ifdef CONFIG_COMPAT
/*
 * Create and map the vectors page for AArch32 tasks.
 */
#define C_VECTORS	0
#define C_SIGPAGE	1
#define C_PAGES		(C_SIGPAGE + 1)
static struct page *aarch32_vdso_pages[C_PAGES] __ro_after_init;
static const struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = {
	{
		.name	= "[vectors]", /* ABI */
		.pages	= &aarch32_vdso_pages[C_VECTORS],
	},
	{
		.name	= "[sigpage]", /* ABI */
		.pages	= &aarch32_vdso_pages[C_SIGPAGE],
	},
};

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;
}

static int __init 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;
}
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);
}

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);
}

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;

	ret = aarch32_sigreturn_setup(mm);

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)
{
	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
	unsigned long vdso_size = vdso_end - vdso_start;

	if (vdso_size != new_size)
		return -EINVAL;

	current->mm->context.vdso = (void *)new_vma->vm_start;

	return 0;
}

static struct vm_special_mapping vdso_spec[2] __ro_after_init = {
	{
		.name	= "[vvar]",
	},
	{
		.name	= "[vdso]",
		.mremap = vdso_mremap,
	},
};

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

	if (memcmp(vdso_start, "\177ELF", 4)) {
		pr_err("vDSO is not a valid ELF object!\n");
		return -EINVAL;
	}

	vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;

	/* Allocate the vDSO pagelist, plus a page for the data. */
	vdso_pagelist = kcalloc(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_start);

	for (i = 0; i < vdso_pages; i++)
		vdso_pagelist[i + 1] = pfn_to_page(pfn + i);

	vdso_spec[0].pages = &vdso_pagelist[0];
	vdso_spec[1].pages = &vdso_pagelist[1];

	return 0;
}
arch_initcall(vdso_init);

int arch_setup_additional_pages(struct linux_binprm *bprm,
				int uses_interp)
{
	struct mm_struct *mm = current->mm;
	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
	void *ret;

	vdso_text_len = vdso_pages << PAGE_SHIFT;
	/* Be sure to map the data page */
	vdso_mapping_len = vdso_text_len + PAGE_SIZE;

	if (down_write_killable(&mm->mmap_sem))
		return -EINTR;
	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_spec[0]);
	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_spec[1]);
	if (IS_ERR(ret))
		goto up_fail;


	up_write(&mm->mmap_sem);
	return 0;

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

/*
 * Update the vDSO data page to keep in sync with kernel timekeeping.
 */
void update_vsyscall(struct timekeeper *tk)
{
	u32 use_syscall = !tk->tkr_mono.clock->archdata.vdso_direct;

	++vdso_data->tb_seq_count;
	smp_wmb();

	vdso_data->use_syscall			= use_syscall;
	vdso_data->xtime_coarse_sec		= tk->xtime_sec;
	vdso_data->xtime_coarse_nsec		= tk->tkr_mono.xtime_nsec >>
							tk->tkr_mono.shift;
	vdso_data->wtm_clock_sec		= tk->wall_to_monotonic.tv_sec;
	vdso_data->wtm_clock_nsec		= tk->wall_to_monotonic.tv_nsec;

	/* Read without the seqlock held by clock_getres() */
	WRITE_ONCE(vdso_data->hrtimer_res, hrtimer_resolution);

	if (!use_syscall) {
		/* tkr_mono.cycle_last == tkr_raw.cycle_last */
		vdso_data->cs_cycle_last	= tk->tkr_mono.cycle_last;
		vdso_data->raw_time_sec         = tk->raw_sec;
		vdso_data->raw_time_nsec        = tk->tkr_raw.xtime_nsec;
		vdso_data->xtime_clock_sec	= tk->xtime_sec;
		vdso_data->xtime_clock_nsec	= tk->tkr_mono.xtime_nsec;
		vdso_data->cs_mono_mult		= tk->tkr_mono.mult;
		vdso_data->cs_raw_mult		= tk->tkr_raw.mult;
		/* tkr_mono.shift == tkr_raw.shift */
		vdso_data->cs_shift		= tk->tkr_mono.shift;
	}

	smp_wmb();
	++vdso_data->tb_seq_count;
}

void update_vsyscall_tz(void)
{
	vdso_data->tz_minuteswest	= sys_tz.tz_minuteswest;
	vdso_data->tz_dsttime		= sys_tz.tz_dsttime;
}