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Linux/arch/sh/kernel/vsyscall/vsyscall.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * arch/sh/kernel/vsyscall/vsyscall.c
  4  *
  5  *  Copyright (C) 2006 Paul Mundt
  6  *
  7  * vDSO randomization
  8  * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
  9  */
 10 #include <linux/mm.h>
 11 #include <linux/kernel.h>
 12 #include <linux/init.h>
 13 #include <linux/gfp.h>
 14 #include <linux/module.h>
 15 #include <linux/elf.h>
 16 #include <linux/sched.h>
 17 #include <linux/err.h>
 18 
 19 /*
 20  * Should the kernel map a VDSO page into processes and pass its
 21  * address down to glibc upon exec()?
 22  */
 23 unsigned int __read_mostly vdso_enabled = 1;
 24 EXPORT_SYMBOL_GPL(vdso_enabled);
 25 
 26 static int __init vdso_setup(char *s)
 27 {
 28         vdso_enabled = simple_strtoul(s, NULL, 0);
 29         return 1;
 30 }
 31 __setup("vdso=", vdso_setup);
 32 
 33 /*
 34  * These symbols are defined by vsyscall.o to mark the bounds
 35  * of the ELF DSO images included therein.
 36  */
 37 extern const char vsyscall_trapa_start, vsyscall_trapa_end;
 38 static struct page *syscall_pages[1];
 39 
 40 int __init vsyscall_init(void)
 41 {
 42         void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
 43         syscall_pages[0] = virt_to_page(syscall_page);
 44 
 45         /*
 46          * XXX: Map this page to a fixmap entry if we get around
 47          * to adding the page to ELF core dumps
 48          */
 49 
 50         memcpy(syscall_page,
 51                &vsyscall_trapa_start,
 52                &vsyscall_trapa_end - &vsyscall_trapa_start);
 53 
 54         return 0;
 55 }
 56 
 57 /* Setup a VMA at program startup for the vsyscall page */
 58 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 59 {
 60         struct mm_struct *mm = current->mm;
 61         unsigned long addr;
 62         int ret;
 63 
 64         if (down_write_killable(&mm->mmap_sem))
 65                 return -EINTR;
 66 
 67         addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 68         if (IS_ERR_VALUE(addr)) {
 69                 ret = addr;
 70                 goto up_fail;
 71         }
 72 
 73         ret = install_special_mapping(mm, addr, PAGE_SIZE,
 74                                       VM_READ | VM_EXEC |
 75                                       VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 76                                       syscall_pages);
 77         if (unlikely(ret))
 78                 goto up_fail;
 79 
 80         current->mm->context.vdso = (void *)addr;
 81 
 82 up_fail:
 83         up_write(&mm->mmap_sem);
 84         return ret;
 85 }
 86 
 87 const char *arch_vma_name(struct vm_area_struct *vma)
 88 {
 89         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 90                 return "[vdso]";
 91 
 92         return NULL;
 93 }
 94 

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