swh:1:snp:c3bf2749e3476071fa748f67b0ffa2fdc5fe49d9
Tip revision: a102a9ece5489e1718cd7543aa079082450ac3a2 authored by Linus Torvalds on 27 September 2011, 22:48:34 UTC
Linux 3.1-rc8
Linux 3.1-rc8
Tip revision: a102a9e
vma.c
/*
* Set up the VMAs to tell the VM about the vDSO.
* Copyright 2007 Andi Kleen, SUSE Labs.
* Subject to the GPL, v.2
*/
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/random.h>
#include <linux/elf.h>
#include <asm/vsyscall.h>
#include <asm/vgtod.h>
#include <asm/proto.h>
#include <asm/vdso.h>
#include <asm/page.h>
unsigned int __read_mostly vdso_enabled = 1;
extern char vdso_start[], vdso_end[];
extern unsigned short vdso_sync_cpuid;
extern struct page *vdso_pages[];
static unsigned vdso_size;
static void __init patch_vdso(void *vdso, size_t len)
{
Elf64_Ehdr *hdr = vdso;
Elf64_Shdr *sechdrs, *alt_sec = 0;
char *secstrings;
void *alt_data;
int i;
BUG_ON(len < sizeof(Elf64_Ehdr));
BUG_ON(memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0);
sechdrs = (void *)hdr + hdr->e_shoff;
secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
for (i = 1; i < hdr->e_shnum; i++) {
Elf64_Shdr *shdr = &sechdrs[i];
if (!strcmp(secstrings + shdr->sh_name, ".altinstructions")) {
alt_sec = shdr;
goto found;
}
}
/* If we get here, it's probably a bug. */
pr_warning("patch_vdso: .altinstructions not found\n");
return; /* nothing to patch */
found:
alt_data = (void *)hdr + alt_sec->sh_offset;
apply_alternatives(alt_data, alt_data + alt_sec->sh_size);
}
static int __init init_vdso(void)
{
int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
int i;
patch_vdso(vdso_start, vdso_end - vdso_start);
vdso_size = npages << PAGE_SHIFT;
for (i = 0; i < npages; i++)
vdso_pages[i] = virt_to_page(vdso_start + i*PAGE_SIZE);
return 0;
}
subsys_initcall(init_vdso);
struct linux_binprm;
/* Put the vdso above the (randomized) stack with another randomized offset.
This way there is no hole in the middle of address space.
To save memory make sure it is still in the same PTE as the stack top.
This doesn't give that many random bits */
static unsigned long vdso_addr(unsigned long start, unsigned len)
{
unsigned long addr, end;
unsigned offset;
end = (start + PMD_SIZE - 1) & PMD_MASK;
if (end >= TASK_SIZE_MAX)
end = TASK_SIZE_MAX;
end -= len;
/* This loses some more bits than a modulo, but is cheaper */
offset = get_random_int() & (PTRS_PER_PTE - 1);
addr = start + (offset << PAGE_SHIFT);
if (addr >= end)
addr = end;
return addr;
}
/* Setup a VMA at program startup for the vsyscall page.
Not called for compat tasks */
int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
struct mm_struct *mm = current->mm;
unsigned long addr;
int ret;
if (!vdso_enabled)
return 0;
down_write(&mm->mmap_sem);
addr = vdso_addr(mm->start_stack, vdso_size);
addr = get_unmapped_area(NULL, addr, vdso_size, 0, 0);
if (IS_ERR_VALUE(addr)) {
ret = addr;
goto up_fail;
}
current->mm->context.vdso = (void *)addr;
ret = install_special_mapping(mm, addr, vdso_size,
VM_READ|VM_EXEC|
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
VM_ALWAYSDUMP,
vdso_pages);
if (ret) {
current->mm->context.vdso = NULL;
goto up_fail;
}
up_fail:
up_write(&mm->mmap_sem);
return ret;
}
static __init int vdso_setup(char *s)
{
vdso_enabled = simple_strtoul(s, NULL, 0);
return 0;
}
__setup("vdso=", vdso_setup);