linux/arch/x86/vdso/vma.c
Roland McGrath 7f3646aa16 x86 vDSO: use vdso-syms.lds
This patch changes the kernel's references to addresses in the vDSO image
to be based on the symbols defined by vdso-syms.lds instead of the old
vdso-syms.o symbols.  This is all wrapped up in a macro defined by the new
asm-x86/vdso.h header; that's the only place in the kernel source that has
to know the details of the scheme for getting vDSO symbol values.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30 13:30:41 +01:00

136 lines
3.1 KiB
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/init.h>
#include <linux/random.h>
#include <asm/vsyscall.h>
#include <asm/vgtod.h>
#include <asm/proto.h>
#include <asm/vdso.h>
#include "vextern.h" /* Just for VMAGIC. */
#undef VEXTERN
int vdso_enabled = 1;
extern char vdso_start[], vdso_end[];
extern unsigned short vdso_sync_cpuid;
struct page **vdso_pages;
static inline void *var_ref(void *p, char *name)
{
if (*(void **)p != (void *)VMAGIC) {
printk("VDSO: variable %s broken\n", name);
vdso_enabled = 0;
}
return p;
}
static int __init init_vdso_vars(void)
{
int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
int i;
char *vbase;
vdso_pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL);
if (!vdso_pages)
goto oom;
for (i = 0; i < npages; i++) {
struct page *p;
p = alloc_page(GFP_KERNEL);
if (!p)
goto oom;
vdso_pages[i] = p;
copy_page(page_address(p), vdso_start + i*PAGE_SIZE);
}
vbase = vmap(vdso_pages, npages, 0, PAGE_KERNEL);
if (!vbase)
goto oom;
if (memcmp(vbase, "\177ELF", 4)) {
printk("VDSO: I'm broken; not ELF\n");
vdso_enabled = 0;
}
#define VEXTERN(x) \
*(typeof(__ ## x) **) var_ref(VDSO64_SYMBOL(vbase, x), #x) = &__ ## x;
#include "vextern.h"
#undef VEXTERN
return 0;
oom:
printk("Cannot allocate vdso\n");
vdso_enabled = 0;
return -ENOMEM;
}
__initcall(init_vdso_vars);
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_SIZE64)
end = TASK_SIZE64;
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 exstack)
{
struct mm_struct *mm = current->mm;
unsigned long addr;
int ret;
unsigned len = round_up(vdso_end - vdso_start, PAGE_SIZE);
if (!vdso_enabled)
return 0;
down_write(&mm->mmap_sem);
addr = vdso_addr(mm->start_stack, len);
addr = get_unmapped_area(NULL, addr, len, 0, 0);
if (IS_ERR_VALUE(addr)) {
ret = addr;
goto up_fail;
}
ret = install_special_mapping(mm, addr, len,
VM_READ|VM_EXEC|
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
VM_ALWAYSDUMP,
vdso_pages);
if (ret)
goto up_fail;
current->mm->context.vdso = (void *)addr;
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);