forked from rubenslte/android_kernel_samsung_msm8226
Greg Reid
cf10549454
Expose a read-only timer page to user-space to allow for a more efficient implementation of gettimeofday in user-space. Change-Id: Ibd6ce41f5f4ff9435e4bf4582ef5de721283d56b Signed-off-by: Brent DeGraaf <bdegraaf@codeaurora.org>
133 lines
3.6 KiB
C
133 lines
3.6 KiB
C
/* Copyright (c) 2012, The Linux Foundation. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 and
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* only version 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/export.h>
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <asm/user_accessible_timer.h>
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#include <asm/traps.h>
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#define USER_ACCESS_TIMER_OFFSET 0xf30
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#define USER_ACCESS_FEATURE_OFFSET 0xf34
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#define USER_ACCESS_FEATURE_FLAG 0xffff0f20
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static struct vm_area_struct user_timers_vma;
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static int __init user_timers_vma_init(void)
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{
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user_timers_vma.vm_start = CONFIG_ARM_USER_ACCESSIBLE_TIMER_BASE;
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user_timers_vma.vm_end = CONFIG_ARM_USER_ACCESSIBLE_TIMER_BASE
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+ PAGE_SIZE;
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user_timers_vma.vm_page_prot = PAGE_READONLY;
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user_timers_vma.vm_flags = VM_READ | VM_MAYREAD;
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return 0;
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}
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arch_initcall(user_timers_vma_init);
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int in_user_timers_area(struct mm_struct *mm, unsigned long addr)
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{
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return (addr >= user_timers_vma.vm_start) &&
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(addr < user_timers_vma.vm_end);
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}
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EXPORT_SYMBOL(in_user_timers_area);
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struct vm_area_struct *get_user_timers_vma(struct mm_struct *mm)
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{
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return &user_timers_vma;
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}
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EXPORT_SYMBOL(get_user_timers_vma);
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int get_user_timer_page(struct vm_area_struct *vma,
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struct mm_struct *mm, unsigned long start, unsigned int gup_flags,
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struct page **pages, int idx, int *goto_next_page)
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{
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/* Replicates the earlier work done in mm/memory.c */
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unsigned long pg = start & PAGE_MASK;
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte;
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/* Unset this flag -- this only gets activated if the
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* caller should go straight to the next_page label on
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* return.
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*/
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*goto_next_page = 0;
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/* user gate pages are read-only */
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if (gup_flags & FOLL_WRITE)
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return idx ? : -EFAULT;
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if (pg > TASK_SIZE)
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pgd = pgd_offset_k(pg);
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else
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pgd = pgd_offset_gate(mm, pg);
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BUG_ON(pgd_none(*pgd));
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pud = pud_offset(pgd, pg);
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BUG_ON(pud_none(*pud));
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pmd = pmd_offset(pud, pg);
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if (pmd_none(*pmd))
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return idx ? : -EFAULT;
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VM_BUG_ON(pmd_trans_huge(*pmd));
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pte = pte_offset_map(pmd, pg);
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if (pte_none(*pte)) {
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pte_unmap(pte);
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return idx ? : -EFAULT;
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}
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vma = get_user_timers_vma(mm);
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if (pages) {
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struct page *page;
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page = vm_normal_page(vma, start, *pte);
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if (!page) {
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if (!(gup_flags & FOLL_DUMP) &&
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zero_pfn == pte_pfn(*pte))
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page = pte_page(*pte);
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else {
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pte_unmap(pte);
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return idx ? : -EFAULT;
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}
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}
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pages[idx] = page;
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get_page(page);
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}
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pte_unmap(pte);
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/* In this case, set the next page */
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*goto_next_page = 1;
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return 0;
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}
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EXPORT_SYMBOL(get_user_timer_page);
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void setup_user_timer_offset(unsigned long addr)
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{
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#if defined(CONFIG_CPU_USE_DOMAINS)
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unsigned long vectors = CONFIG_VECTORS_BASE;
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#else
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unsigned long vectors = (unsigned long)vectors_page;
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#endif
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unsigned long *timer_offset = (unsigned long *)(vectors +
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USER_ACCESS_TIMER_OFFSET);
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*timer_offset = addr;
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}
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EXPORT_SYMBOL(setup_user_timer_offset);
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void set_user_accessible_timer_flag(bool flag)
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{
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#if defined(CONFIG_CPU_USE_DOMAINS)
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unsigned long vectors = CONFIG_VECTORS_BASE;
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#else
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unsigned long vectors = (unsigned long)vectors_page;
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#endif
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unsigned long *timer_offset = (unsigned long *)(vectors +
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USER_ACCESS_FEATURE_OFFSET);
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*timer_offset = (flag ? USER_ACCESS_FEATURE_FLAG : 0);
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}
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EXPORT_SYMBOL(set_user_accessible_timer_flag);
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