// SPDX-License-Identifier: GPL-2.0
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/*
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* arch/sh/kernel/vsyscall/vsyscall.c
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*
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* Copyright (C) 2006 Paul Mundt
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*
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* vDSO randomization
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* Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
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*/
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#include <linux/mm.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/gfp.h>
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#include <linux/module.h>
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#include <linux/elf.h>
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#include <linux/sched.h>
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#include <linux/err.h>
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/*
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* Should the kernel map a VDSO page into processes and pass its
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* address down to glibc upon exec()?
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*/
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unsigned int __read_mostly vdso_enabled = 1;
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EXPORT_SYMBOL_GPL(vdso_enabled);
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static int __init vdso_setup(char *s)
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{
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vdso_enabled = simple_strtoul(s, NULL, 0);
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return 1;
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}
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__setup("vdso=", vdso_setup);
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/*
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* These symbols are defined by vsyscall.o to mark the bounds
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* of the ELF DSO images included therein.
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*/
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extern const char vsyscall_trapa_start, vsyscall_trapa_end;
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static struct page *syscall_pages[1];
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int __init vsyscall_init(void)
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{
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void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
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syscall_pages[0] = virt_to_page(syscall_page);
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/*
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* XXX: Map this page to a fixmap entry if we get around
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* to adding the page to ELF core dumps
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*/
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memcpy(syscall_page,
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&vsyscall_trapa_start,
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&vsyscall_trapa_end - &vsyscall_trapa_start);
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return 0;
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}
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/* Setup a VMA at program startup for the vsyscall page */
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int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
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{
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struct mm_struct *mm = current->mm;
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unsigned long addr;
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int ret;
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if (mmap_write_lock_killable(mm))
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return -EINTR;
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addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
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if (IS_ERR_VALUE(addr)) {
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ret = addr;
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goto up_fail;
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}
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ret = install_special_mapping(mm, addr, PAGE_SIZE,
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VM_READ | VM_EXEC |
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VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
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syscall_pages);
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if (unlikely(ret))
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goto up_fail;
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current->mm->context.vdso = (void *)addr;
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up_fail:
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mmap_write_unlock(mm);
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return ret;
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}
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const char *arch_vma_name(struct vm_area_struct *vma)
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{
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if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
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return "[vdso]";
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return NULL;
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}
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