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