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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vdso.c (3058B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 *  Copyright (c) 2022 Helge Deller <deller@gmx.de>
      4 *
      5 *  based on arch/s390/kernel/vdso.c which is
      6 *  Copyright IBM Corp. 2008
      7 *  Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
      8 */
      9
     10#include <linux/kernel.h>
     11#include <linux/mm.h>
     12#include <linux/slab.h>
     13#include <linux/elf.h>
     14#include <linux/timekeeper_internal.h>
     15#include <linux/compat.h>
     16#include <linux/nsproxy.h>
     17#include <linux/time_namespace.h>
     18#include <linux/random.h>
     19
     20#include <asm/pgtable.h>
     21#include <asm/page.h>
     22#include <asm/sections.h>
     23#include <asm/vdso.h>
     24#include <asm/cacheflush.h>
     25
     26extern char vdso32_start, vdso32_end;
     27extern char vdso64_start, vdso64_end;
     28
     29static int vdso_mremap(const struct vm_special_mapping *sm,
     30		       struct vm_area_struct *vma)
     31{
     32	current->mm->context.vdso_base = vma->vm_start;
     33	return 0;
     34}
     35
     36#ifdef CONFIG_64BIT
     37static struct vm_special_mapping vdso64_mapping = {
     38	.name = "[vdso]",
     39	.mremap = vdso_mremap,
     40};
     41#endif
     42
     43static struct vm_special_mapping vdso32_mapping = {
     44	.name = "[vdso]",
     45	.mremap = vdso_mremap,
     46};
     47
     48/*
     49 * This is called from binfmt_elf, we create the special vma for the
     50 * vDSO and insert it into the mm struct tree
     51 */
     52int arch_setup_additional_pages(struct linux_binprm *bprm,
     53				int executable_stack)
     54{
     55
     56	unsigned long vdso_text_start, vdso_text_len, map_base;
     57	struct vm_special_mapping *vdso_mapping;
     58	struct mm_struct *mm = current->mm;
     59	struct vm_area_struct *vma;
     60	int rc;
     61
     62	if (mmap_write_lock_killable(mm))
     63		return -EINTR;
     64
     65#ifdef CONFIG_64BIT
     66	if (!is_compat_task()) {
     67		vdso_text_len = &vdso64_end - &vdso64_start;
     68		vdso_mapping = &vdso64_mapping;
     69	} else
     70#endif
     71	{
     72		vdso_text_len = &vdso32_end - &vdso32_start;
     73		vdso_mapping = &vdso32_mapping;
     74	}
     75
     76	map_base = mm->mmap_base;
     77	if (current->flags & PF_RANDOMIZE)
     78		map_base -= (get_random_int() & 0x1f) * PAGE_SIZE;
     79
     80	vdso_text_start = get_unmapped_area(NULL, map_base, vdso_text_len, 0, 0);
     81
     82	/* VM_MAYWRITE for COW so gdb can set breakpoints */
     83	vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len,
     84				       VM_READ|VM_EXEC|
     85				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
     86				       vdso_mapping);
     87	if (IS_ERR(vma)) {
     88		do_munmap(mm, vdso_text_start, PAGE_SIZE, NULL);
     89		rc = PTR_ERR(vma);
     90	} else {
     91		current->mm->context.vdso_base = vdso_text_start;
     92		rc = 0;
     93	}
     94
     95	mmap_write_unlock(mm);
     96	return rc;
     97}
     98
     99static struct page ** __init vdso_setup_pages(void *start, void *end)
    100{
    101	int pages = (end - start) >> PAGE_SHIFT;
    102	struct page **pagelist;
    103	int i;
    104
    105	pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
    106	if (!pagelist)
    107		panic("%s: Cannot allocate page list for VDSO", __func__);
    108	for (i = 0; i < pages; i++)
    109		pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
    110	return pagelist;
    111}
    112
    113static int __init vdso_init(void)
    114{
    115#ifdef CONFIG_64BIT
    116	vdso64_mapping.pages = vdso_setup_pages(&vdso64_start, &vdso64_end);
    117#endif
    118	if (IS_ENABLED(CONFIG_COMPAT) || !IS_ENABLED(CONFIG_64BIT))
    119		vdso32_mapping.pages = vdso_setup_pages(&vdso32_start, &vdso32_end);
    120	return 0;
    121}
    122arch_initcall(vdso_init);