arch/x86/entry/vdso/vma.c - linux - Git at Google

 /*
  * Copyright 2007 Andi Kleen, SUSE Labs.
  * Subject to the GPL, v.2
  *
  * This contains most of the x86 vDSO kernel-side code.
  */
 #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 <linux/cpu.h>
 #include <asm/pvclock.h>
 #include <asm/vgtod.h>
 #include <asm/proto.h>
 #include <asm/vdso.h>
 #include <asm/vvar.h>
 #include <asm/page.h>
 #include <asm/hpet.h>
 #include <asm/desc.h>

 #if defined(CONFIG_X86_64)
 unsigned int __read_mostly vdso64_enabled = 1;
 #endif

 void __init init_vdso_image(const struct vdso_image *image)
 {
 	int i;
 	int npages = (image->size) / PAGE_SIZE;

 	BUG_ON(image->size % PAGE_SIZE != 0);
 	for (i = 0; i < npages; i++)
 		image->text_mapping.pages[i] =
 			virt_to_page(image->data + i*PAGE_SIZE);

 	apply_alternatives((struct alt_instr *)(image->data + image->alt),
 			   (struct alt_instr *)(image->data + image->alt +
 						image->alt_len));
 }

 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.
  *
  * Note that this algorithm is imperfect: the distribution of the vdso
  * start address within a PMD is biased toward the end.
  *
  * Only used for the 64-bit and x32 vdsos.
  */
 static unsigned long vdso_addr(unsigned long start, unsigned len)
 {
 #ifdef CONFIG_X86_32
 	return 0;
 #else
 	unsigned long addr, end;
 	unsigned offset;

 	/*
 	 * Round up the start address.  It can start out unaligned as a result
 	 * of stack start randomization.
 	 */
 	start = PAGE_ALIGN(start);

 	/* Round the lowest possible end address up to a PMD boundary. */
 	end = (start + len + PMD_SIZE - 1) & PMD_MASK;
 	if (end >= TASK_SIZE_MAX)
 		end = TASK_SIZE_MAX;
 	end -= len;

 	if (end > start) {
 		offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
 		addr = start + (offset << PAGE_SHIFT);
 	} else {
 		addr = start;
 	}

 	/*
 	 * Forcibly align the final address in case we have a hardware
 	 * issue that requires alignment for performance reasons.
 	 */
 	addr = align_vdso_addr(addr);

 	return addr;
 #endif
 }

 static int map_vdso(const struct vdso_image *image, bool calculate_addr)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	unsigned long addr, text_start;
 	int ret = 0;
 	static struct page *no_pages[] = {NULL};
 	static struct vm_special_mapping vvar_mapping = {
 		.name = "[vvar]",
 		.pages = no_pages,
 	};
 	struct pvclock_vsyscall_time_info *pvti;

 	if (calculate_addr) {
 		addr = vdso_addr(current->mm->start_stack,
 				 image->size - image->sym_vvar_start);
 	} else {
 		addr = 0;
 	}

 	down_write(&mm->mmap_sem);

 	addr = get_unmapped_area(NULL, addr,
 				 image->size - image->sym_vvar_start, 0, 0);
 	if (IS_ERR_VALUE(addr)) {
 		ret = addr;
 		goto up_fail;
 	}

 	text_start = addr - image->sym_vvar_start;
 	current->mm->context.vdso = (void __user *)text_start;

 	/*
 	 * MAYWRITE to allow gdb to COW and set breakpoints
 	 */
 	vma = _install_special_mapping(mm,
 				       text_start,
 				       image->size,
 				       VM_READ|VM_EXEC|
 				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 				       &image->text_mapping);

 	if (IS_ERR(vma)) {
 		ret = PTR_ERR(vma);
 		goto up_fail;
 	}

 	vma = _install_special_mapping(mm,
 				       addr,
 				       -image->sym_vvar_start,
 				       VM_READ|VM_MAYREAD,
 				       &vvar_mapping);

 	if (IS_ERR(vma)) {
 		ret = PTR_ERR(vma);
 		goto up_fail;
 	}

 	if (image->sym_vvar_page)
 		ret = remap_pfn_range(vma,
 				      text_start + image->sym_vvar_page,
 				      __pa_symbol(&__vvar_page) >> PAGE_SHIFT,
 				      PAGE_SIZE,
 				      PAGE_READONLY);

 	if (ret)
 		goto up_fail;

 #ifdef CONFIG_HPET_TIMER
 	if (hpet_address && image->sym_hpet_page) {
 		ret = io_remap_pfn_range(vma,
 			text_start + image->sym_hpet_page,
 			hpet_address >> PAGE_SHIFT,
 			PAGE_SIZE,
 			pgprot_noncached(PAGE_READONLY));

 		if (ret)
 			goto up_fail;
 	}
 #endif

 	pvti = pvclock_pvti_cpu0_va();
 	if (pvti && image->sym_pvclock_page) {
 		ret = remap_pfn_range(vma,
 				      text_start + image->sym_pvclock_page,
 				      __pa(pvti) >> PAGE_SHIFT,
 				      PAGE_SIZE,
 				      PAGE_READONLY);

 		if (ret)
 			goto up_fail;
 	}

 up_fail:
 	if (ret)
 		current->mm->context.vdso = NULL;

 	up_write(&mm->mmap_sem);
 	return ret;
 }

 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 static int load_vdso32(void)
 {
 	if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
 		return 0;

 	return map_vdso(&vdso_image_32, false);
 }
 #endif

 #ifdef CONFIG_X86_64
 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {
 	if (!vdso64_enabled)
 		return 0;

 	return map_vdso(&vdso_image_64, true);
 }

 #ifdef CONFIG_COMPAT
 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
 				       int uses_interp)
 {
 #ifdef CONFIG_X86_X32_ABI
 	if (test_thread_flag(TIF_X32)) {
 		if (!vdso64_enabled)
 			return 0;

 		return map_vdso(&vdso_image_x32, true);
 	}
 #endif
 #ifdef CONFIG_IA32_EMULATION
 	return load_vdso32();
 #else
 	return 0;
 #endif
 }
 #endif
 #else
 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {
 	return load_vdso32();
 }
 #endif

 #ifdef CONFIG_X86_64
 static __init int vdso_setup(char *s)
 {
 	vdso64_enabled = simple_strtoul(s, NULL, 0);
 	return 0;
 }
 __setup("vdso=", vdso_setup);
 #endif

 #ifdef CONFIG_X86_64
 static void vgetcpu_cpu_init(void *arg)
 {
 	int cpu = smp_processor_id();
 	struct desc_struct d = { };
 	unsigned long node = 0;
 #ifdef CONFIG_NUMA
 	node = cpu_to_node(cpu);
 #endif
 	if (cpu_has(&cpu_data(cpu), X86_FEATURE_RDTSCP))
 		write_rdtscp_aux((node << 12) | cpu);

 	/*
 	 * Store cpu number in limit so that it can be loaded
 	 * quickly in user space in vgetcpu. (12 bits for the CPU
 	 * and 8 bits for the node)
 	 */
 	d.limit0 = cpu | ((node & 0xf) << 12);
 	d.limit = node >> 4;
 	d.type = 5;		/* RO data, expand down, accessed */
 	d.dpl = 3;		/* Visible to user code */
 	d.s = 1;		/* Not a system segment */
 	d.p = 1;		/* Present */
 	d.d = 1;		/* 32-bit */

 	write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
 }

 static int
 vgetcpu_cpu_notifier(struct notifier_block *n, unsigned long action, void *arg)
 {
 	long cpu = (long)arg;

 	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN)
 		smp_call_function_single(cpu, vgetcpu_cpu_init, NULL, 1);

 	return NOTIFY_DONE;
 }

 static int __init init_vdso(void)
 {
 	init_vdso_image(&vdso_image_64);

 #ifdef CONFIG_X86_X32_ABI
 	init_vdso_image(&vdso_image_x32);
 #endif

 	cpu_notifier_register_begin();

 	on_each_cpu(vgetcpu_cpu_init, NULL, 1);
 	/* notifier priority > KVM */
 	__hotcpu_notifier(vgetcpu_cpu_notifier, 30);

 	cpu_notifier_register_done();

 	return 0;
 }
 subsys_initcall(init_vdso);
 #endif /* CONFIG_X86_64 */
	/*
	* Copyright 2007 Andi Kleen, SUSE Labs.
	* Subject to the GPL, v.2
	*
	* This contains most of the x86 vDSO kernel-side code.
	*/
	#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 <linux/cpu.h>
	#include <asm/pvclock.h>
	#include <asm/vgtod.h>
	#include <asm/proto.h>
	#include <asm/vdso.h>
	#include <asm/vvar.h>
	#include <asm/page.h>
	#include <asm/hpet.h>
	#include <asm/desc.h>

	#if defined(CONFIG_X86_64)
	unsigned int __read_mostly vdso64_enabled = 1;
	#endif

	void __init init_vdso_image(const struct vdso_image *image)
	{
	int i;
	int npages = (image->size) / PAGE_SIZE;

	BUG_ON(image->size % PAGE_SIZE != 0);
	for (i = 0; i < npages; i++)
	image->text_mapping.pages[i] =
	virt_to_page(image->data + i*PAGE_SIZE);

	apply_alternatives((struct alt_instr *)(image->data + image->alt),
	(struct alt_instr *)(image->data + image->alt +
	image->alt_len));
	}

	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.
	*
	* Note that this algorithm is imperfect: the distribution of the vdso
	* start address within a PMD is biased toward the end.
	*
	* Only used for the 64-bit and x32 vdsos.
	*/
	static unsigned long vdso_addr(unsigned long start, unsigned len)
	{
	#ifdef CONFIG_X86_32
	return 0;
	#else
	unsigned long addr, end;
	unsigned offset;

	/*
	* Round up the start address. It can start out unaligned as a result
	* of stack start randomization.
	*/
	start = PAGE_ALIGN(start);

	/* Round the lowest possible end address up to a PMD boundary. */
	end = (start + len + PMD_SIZE - 1) & PMD_MASK;
	if (end >= TASK_SIZE_MAX)
	end = TASK_SIZE_MAX;
	end -= len;

	if (end > start) {
	offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
	addr = start + (offset << PAGE_SHIFT);
	} else {
	addr = start;
	}

	/*
	* Forcibly align the final address in case we have a hardware
	* issue that requires alignment for performance reasons.
	*/
	addr = align_vdso_addr(addr);

	return addr;
	#endif
	}

	static int map_vdso(const struct vdso_image *image, bool calculate_addr)
	{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long addr, text_start;
	int ret = 0;
	static struct page *no_pages[] = {NULL};
	static struct vm_special_mapping vvar_mapping = {
	.name = "[vvar]",
	.pages = no_pages,
	};
	struct pvclock_vsyscall_time_info *pvti;

	if (calculate_addr) {
	addr = vdso_addr(current->mm->start_stack,
	image->size - image->sym_vvar_start);
	} else {
	addr = 0;
	}

	down_write(&mm->mmap_sem);

	addr = get_unmapped_area(NULL, addr,
	image->size - image->sym_vvar_start, 0, 0);
	if (IS_ERR_VALUE(addr)) {
	ret = addr;
	goto up_fail;
	}

	text_start = addr - image->sym_vvar_start;
	current->mm->context.vdso = (void __user *)text_start;

	/*
	* MAYWRITE to allow gdb to COW and set breakpoints
	*/
	vma = _install_special_mapping(mm,
	text_start,
	image->size,
	VM_READ\|VM_EXEC\|
	VM_MAYREAD\|VM_MAYWRITE\|VM_MAYEXEC,
	&image->text_mapping);

	if (IS_ERR(vma)) {
	ret = PTR_ERR(vma);
	goto up_fail;
	}

	vma = _install_special_mapping(mm,
	addr,
	-image->sym_vvar_start,
	VM_READ\|VM_MAYREAD,
	&vvar_mapping);

	if (IS_ERR(vma)) {
	ret = PTR_ERR(vma);
	goto up_fail;
	}

	if (image->sym_vvar_page)
	ret = remap_pfn_range(vma,
	text_start + image->sym_vvar_page,
	__pa_symbol(&__vvar_page) >> PAGE_SHIFT,
	PAGE_SIZE,
	PAGE_READONLY);

	if (ret)
	goto up_fail;

	#ifdef CONFIG_HPET_TIMER
	if (hpet_address && image->sym_hpet_page) {
	ret = io_remap_pfn_range(vma,
	text_start + image->sym_hpet_page,
	hpet_address >> PAGE_SHIFT,
	PAGE_SIZE,
	pgprot_noncached(PAGE_READONLY));

	if (ret)
	goto up_fail;
	}
	#endif

	pvti = pvclock_pvti_cpu0_va();
	if (pvti && image->sym_pvclock_page) {
	ret = remap_pfn_range(vma,
	text_start + image->sym_pvclock_page,
	__pa(pvti) >> PAGE_SHIFT,
	PAGE_SIZE,
	PAGE_READONLY);

	if (ret)
	goto up_fail;
	}

	up_fail:
	if (ret)
	current->mm->context.vdso = NULL;

	up_write(&mm->mmap_sem);
	return ret;
	}

	#if defined(CONFIG_X86_32) \|\| defined(CONFIG_IA32_EMULATION)
	static int load_vdso32(void)
	{
	if (vdso32_enabled != 1) /* Other values all mean "disabled" */
	return 0;

	return map_vdso(&vdso_image_32, false);
	}
	#endif

	#ifdef CONFIG_X86_64
	int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
	{
	if (!vdso64_enabled)
	return 0;

	return map_vdso(&vdso_image_64, true);
	}

	#ifdef CONFIG_COMPAT
	int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
	int uses_interp)
	{
	#ifdef CONFIG_X86_X32_ABI
	if (test_thread_flag(TIF_X32)) {
	if (!vdso64_enabled)
	return 0;

	return map_vdso(&vdso_image_x32, true);
	}
	#endif
	#ifdef CONFIG_IA32_EMULATION
	return load_vdso32();
	#else
	return 0;
	#endif
	}
	#endif
	#else
	int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
	{
	return load_vdso32();
	}
	#endif

	#ifdef CONFIG_X86_64
	static __init int vdso_setup(char *s)
	{
	vdso64_enabled = simple_strtoul(s, NULL, 0);
	return 0;
	}
	__setup("vdso=", vdso_setup);
	#endif

	#ifdef CONFIG_X86_64
	static void vgetcpu_cpu_init(void *arg)
	{
	int cpu = smp_processor_id();
	struct desc_struct d = { };
	unsigned long node = 0;
	#ifdef CONFIG_NUMA
	node = cpu_to_node(cpu);
	#endif
	if (cpu_has(&cpu_data(cpu), X86_FEATURE_RDTSCP))
	write_rdtscp_aux((node << 12) \| cpu);

	/*
	* Store cpu number in limit so that it can be loaded
	* quickly in user space in vgetcpu. (12 bits for the CPU
	* and 8 bits for the node)
	*/
	d.limit0 = cpu \| ((node & 0xf) << 12);
	d.limit = node >> 4;
	d.type = 5; /* RO data, expand down, accessed */
	d.dpl = 3; /* Visible to user code */
	d.s = 1; /* Not a system segment */
	d.p = 1; /* Present */
	d.d = 1; /* 32-bit */

	write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
	}

	static int
	vgetcpu_cpu_notifier(struct notifier_block n, unsigned long action, void arg)
	{
	long cpu = (long)arg;

	if (action == CPU_ONLINE \|\| action == CPU_ONLINE_FROZEN)
	smp_call_function_single(cpu, vgetcpu_cpu_init, NULL, 1);

	return NOTIFY_DONE;
	}

	static int __init init_vdso(void)
	{
	init_vdso_image(&vdso_image_64);

	#ifdef CONFIG_X86_X32_ABI
	init_vdso_image(&vdso_image_x32);
	#endif

	cpu_notifier_register_begin();

	on_each_cpu(vgetcpu_cpu_init, NULL, 1);
	/* notifier priority > KVM */
	__hotcpu_notifier(vgetcpu_cpu_notifier, 30);

	cpu_notifier_register_done();

	return 0;
	}
	subsys_initcall(init_vdso);
	#endif /* CONFIG_X86_64 */