cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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vsyscall.c (2110B)

      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 */
     23unsigned int __read_mostly vdso_enabled = 1;
     24EXPORT_SYMBOL_GPL(vdso_enabled);
     25
     26static 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 */
     37extern const char vsyscall_trapa_start, vsyscall_trapa_end;
     38static struct page *syscall_pages[1];
     39
     40int __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 */
     58int 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 (mmap_write_lock_killable(mm))
     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
     82up_fail:
     83	mmap_write_unlock(mm);
     84	return ret;
     85}
     86
     87const 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}