[deliverable/linux.git] / arch / x86 / vdso / 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/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

unsigned int __read_mostly 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);
Commit	Line	Data
2aae950b AK	1	/*
	2	* Set up the VMAs to tell the VM about the vDSO.
	3	* Copyright 2007 Andi Kleen, SUSE Labs.
	4	* Subject to the GPL, v.2
	5	*/
	6	#include <linux/mm.h>
4e950f6f	7	#include <linux/err.h>
2aae950b AK	8	#include <linux/sched.h>
	9	#include <linux/init.h>
	10	#include <linux/random.h>
	11	#include <asm/vsyscall.h>
	12	#include <asm/vgtod.h>
	13	#include <asm/proto.h>
7f3646aa	14	#include <asm/vdso.h>
2aae950b	15
7f3646aa	16	#include "vextern.h" /* Just for VMAGIC. */
2aae950b AK	17	#undef VEXTERN
2aae950b AK	18
e6b0edef	19	unsigned int __read_mostly vdso_enabled = 1;
7f3646aa RM	20
7f3646aa RM	21	extern char vdso_start[], vdso_end[];
2aae950b AK	22	extern unsigned short vdso_sync_cpuid;
	23
	24	struct page **vdso_pages;
	25
7f3646aa	26	static inline void var_ref(void p, char *name)
2aae950b	27	{
2aae950b AK	28	if ((void )p != (void )VMAGIC) {
	29	printk("VDSO: variable %s broken\n", name);
	30	vdso_enabled = 0;
	31	}
	32	return p;
	33	}
	34
	35	static int __init init_vdso_vars(void)
	36	{
	37	int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
	38	int i;
	39	char *vbase;
	40
	41	vdso_pages = kmalloc(sizeof(struct page ) npages, GFP_KERNEL);
	42	if (!vdso_pages)
	43	goto oom;
	44	for (i = 0; i < npages; i++) {
	45	struct page *p;
	46	p = alloc_page(GFP_KERNEL);
	47	if (!p)
	48	goto oom;
	49	vdso_pages[i] = p;
	50	copy_page(page_address(p), vdso_start + i*PAGE_SIZE);
	51	}
	52
	53	vbase = vmap(vdso_pages, npages, 0, PAGE_KERNEL);
	54	if (!vbase)
	55	goto oom;
	56
	57	if (memcmp(vbase, "\177ELF", 4)) {
	58	printk("VDSO: I'm broken; not ELF\n");
	59	vdso_enabled = 0;
	60	}
	61
2aae950b	62	#define VEXTERN(x) \
7f3646aa	63	(typeof(__ ## x) *) var_ref(VDSO64_SYMBOL(vbase, x), #x) = &__ ## x;
2aae950b AK	64	#include "vextern.h"
	65	#undef VEXTERN
	66	return 0;
	67
	68	oom:
	69	printk("Cannot allocate vdso\n");
	70	vdso_enabled = 0;
	71	return -ENOMEM;
	72	}
	73	__initcall(init_vdso_vars);
	74
	75	struct linux_binprm;
	76
	77	/* Put the vdso above the (randomized) stack with another randomized offset.
	78	This way there is no hole in the middle of address space.
	79	To save memory make sure it is still in the same PTE as the stack top.
	80	This doesn't give that many random bits */
	81	static unsigned long vdso_addr(unsigned long start, unsigned len)
	82	{
	83	unsigned long addr, end;
	84	unsigned offset;
	85	end = (start + PMD_SIZE - 1) & PMD_MASK;
	86	if (end >= TASK_SIZE64)
	87	end = TASK_SIZE64;
	88	end -= len;
	89	/* This loses some more bits than a modulo, but is cheaper */
	90	offset = get_random_int() & (PTRS_PER_PTE - 1);
	91	addr = start + (offset << PAGE_SHIFT);
	92	if (addr >= end)
	93	addr = end;
	94	return addr;
	95	}
	96
	97	/* Setup a VMA at program startup for the vsyscall page.
	98	Not called for compat tasks */
	99	int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
	100	{
	101	struct mm_struct *mm = current->mm;
	102	unsigned long addr;
	103	int ret;
	104	unsigned len = round_up(vdso_end - vdso_start, PAGE_SIZE);
	105
	106	if (!vdso_enabled)
	107	return 0;
	108
	109	down_write(&mm->mmap_sem);
	110	addr = vdso_addr(mm->start_stack, len);
	111	addr = get_unmapped_area(NULL, addr, len, 0, 0);
	112	if (IS_ERR_VALUE(addr)) {
	113	ret = addr;
	114	goto up_fail;
	115	}
	116
	117	ret = install_special_mapping(mm, addr, len,
	118	VM_READ\|VM_EXEC\|
	119	VM_MAYREAD\|VM_MAYWRITE\|VM_MAYEXEC\|
	120	VM_ALWAYSDUMP,
	121	vdso_pages);
	122	if (ret)
	123	goto up_fail;
	124
	125	current->mm->context.vdso = (void *)addr;
	126	up_fail:
	127	up_write(&mm->mmap_sem);
128	return ret;
129	}
130
131	static __init int vdso_setup(char *s)
132	{
133	vdso_enabled = simple_strtoul(s, NULL, 0);
134	return 0;
135	}
136	__setup("vdso=", vdso_setup);