/*
   * (C) Copyright 2002 Linus Torvalds
   * Portions based on the vdso-randomization code from exec-shield:
   * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
   *
   * This file contains the needed initializations to support sysenter.
   */
  
  #include <linux/init.h>
  #include <linux/smp.h>
  #include <linux/thread_info.h>
  #include <linux/sched.h>
  #include <linux/gfp.h>
  #include <linux/string.h>
  #include <linux/elf.h>
  #include <linux/mm.h>
  #include <linux/err.h>
  #include <linux/module.h>
  
  #include <asm/cpufeature.h>
  #include <asm/msr.h>
  #include <asm/pgtable.h>
  #include <asm/unistd.h>
  #include <asm/elf.h>
  #include <asm/tlbflush.h>
  #include <asm/vdso.h>
  #include <asm/proto.h>
  
  enum {
  	VDSO_DISABLED = 0,
  	VDSO_ENABLED = 1,
  	VDSO_COMPAT = 2,
  };
  
  #ifdef CONFIG_COMPAT_VDSO
  #define VDSO_DEFAULT	VDSO_COMPAT
  #else
  #define VDSO_DEFAULT	VDSO_ENABLED
  #endif
  
  #ifdef CONFIG_X86_64
  #define vdso_enabled			sysctl_vsyscall32
  #define arch_setup_additional_pages	syscall32_setup_pages
  #endif
  
  /*
   * This is the difference between the prelinked addresses in the vDSO images
   * and the VDSO_HIGH_BASE address where CONFIG_COMPAT_VDSO places the vDSO
   * in the user address space.
   */
  #define VDSO_ADDR_ADJUST	(VDSO_HIGH_BASE - (unsigned long)VDSO32_PRELINK)
  
  /*
   * Should the kernel map a VDSO page into processes and pass its
   * address down to glibc upon exec()?
   */
  unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
  
  static int __init vdso_setup(char *s)
  {
  	vdso_enabled = simple_strtoul(s, NULL, 0);
  
  	return 1;
  }
  
  /*
   * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
   * behavior on both 64-bit and 32-bit kernels.
   * On 32-bit kernels, vdso=[012] means the same thing.
   */
  __setup("vdso32=", vdso_setup);
  
  #ifdef CONFIG_X86_32
  __setup_param("vdso=", vdso32_setup, vdso_setup, 0);
  
  EXPORT_SYMBOL_GPL(vdso_enabled);
  #endif
  
  static __init void reloc_symtab(Elf32_Ehdr *ehdr,
  				unsigned offset, unsigned size)
  {
  	Elf32_Sym *sym = (void *)ehdr + offset;
  	unsigned nsym = size / sizeof(*sym);
  	unsigned i;
  
  	for(i = 0; i < nsym; i++, sym++) {
  		if (sym->st_shndx == SHN_UNDEF ||
  		    sym->st_shndx == SHN_ABS)
  			continue;  /* skip */
  
  		if (sym->st_shndx > SHN_LORESERVE) {
  			printk(KERN_INFO "VDSO: unexpected st_shndx %x
  ",
  			       sym->st_shndx);
  			continue;
  		}
  
  		switch(ELF_ST_TYPE(sym->st_info)) {
  		case STT_OBJECT:
  		case STT_FUNC:
  		case STT_SECTION:
  		case STT_FILE:
  			sym->st_value += VDSO_ADDR_ADJUST;
  		}
  	}
  }
  
  static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
  {
  	Elf32_Dyn *dyn = (void *)ehdr + offset;
  
  	for(; dyn->d_tag != DT_NULL; dyn++)
  		switch(dyn->d_tag) {
  		case DT_PLTGOT:
  		case DT_HASH:
  		case DT_STRTAB:
  		case DT_SYMTAB:
  		case DT_RELA:
  		case DT_INIT:
  		case DT_FINI:
  		case DT_REL:
  		case DT_DEBUG:
  		case DT_JMPREL:
  		case DT_VERSYM:
  		case DT_VERDEF:
  		case DT_VERNEED:
  		case DT_ADDRRNGLO ... DT_ADDRRNGHI:
  			/* definitely pointers needing relocation */
  			dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
  			break;
  
  		case DT_ENCODING ... OLD_DT_LOOS-1:
  		case DT_LOOS ... DT_HIOS-1:
  			/* Tags above DT_ENCODING are pointers if
  			   they're even */
  			if (dyn->d_tag >= DT_ENCODING &&
  			    (dyn->d_tag & 1) == 0)
  				dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
  			break;
  
  		case DT_VERDEFNUM:
  		case DT_VERNEEDNUM:
  		case DT_FLAGS_1:
  		case DT_RELACOUNT:
  		case DT_RELCOUNT:
  		case DT_VALRNGLO ... DT_VALRNGHI:
  			/* definitely not pointers */
  			break;
  
  		case OLD_DT_LOOS ... DT_LOOS-1:
  		case DT_HIOS ... DT_VALRNGLO-1:
  		default:
  			if (dyn->d_tag > DT_ENCODING)
  				printk(KERN_INFO "VDSO: unexpected DT_tag %x
  ",
  				       dyn->d_tag);
  			break;
  		}
  }
  
  static __init void relocate_vdso(Elf32_Ehdr *ehdr)
  {
  	Elf32_Phdr *phdr;
  	Elf32_Shdr *shdr;
  	int i;
  
  	BUG_ON(memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0 ||
  	       !elf_check_arch_ia32(ehdr) ||
  	       ehdr->e_type != ET_DYN);
  
  	ehdr->e_entry += VDSO_ADDR_ADJUST;
  
  	/* rebase phdrs */
  	phdr = (void *)ehdr + ehdr->e_phoff;
  	for (i = 0; i < ehdr->e_phnum; i++) {
  		phdr[i].p_vaddr += VDSO_ADDR_ADJUST;
  
  		/* relocate dynamic stuff */
  		if (phdr[i].p_type == PT_DYNAMIC)
  			reloc_dyn(ehdr, phdr[i].p_offset);
  	}
  
  	/* rebase sections */
  	shdr = (void *)ehdr + ehdr->e_shoff;
  	for(i = 0; i < ehdr->e_shnum; i++) {
  		if (!(shdr[i].sh_flags & SHF_ALLOC))
  			continue;
  
  		shdr[i].sh_addr += VDSO_ADDR_ADJUST;
  
  		if (shdr[i].sh_type == SHT_SYMTAB ||
  		    shdr[i].sh_type == SHT_DYNSYM)
  			reloc_symtab(ehdr, shdr[i].sh_offset,
  				     shdr[i].sh_size);
  	}
  }
  
  static struct page *vdso32_pages[1];
  
  #ifdef CONFIG_X86_64
  
  #define	vdso32_sysenter()	(boot_cpu_has(X86_FEATURE_SYSENTER32))
  #define	vdso32_syscall()	(boot_cpu_has(X86_FEATURE_SYSCALL32))
  
  /* May not be __init: called during resume */
  void syscall32_cpu_init(void)
  {
  	/* Load these always in case some future AMD CPU supports
  	   SYSENTER from compat mode too. */
  	wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
  	wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL);
  	wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
  
  	wrmsrl(MSR_CSTAR, ia32_cstar_target);
  }
  
  #define compat_uses_vma		1
  
  static inline void map_compat_vdso(int map)
  {
  }
  
  #else  /* CONFIG_X86_32 */
  
  #define vdso32_sysenter()	(boot_cpu_has(X86_FEATURE_SEP))
  #define vdso32_syscall()	(0)
  
  void enable_sep_cpu(void)
  {
  	int cpu = get_cpu();
  	struct tss_struct *tss = &per_cpu(init_tss, cpu);
  
  	if (!boot_cpu_has(X86_FEATURE_SEP)) {
  		put_cpu();
  		return;
  	}
  
  	tss->x86_tss.ss1 = __KERNEL_CS;
  	tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
  	wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
  	wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
  	wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
  	put_cpu();	
  }
  
  static struct vm_area_struct gate_vma;
  
  static int __init gate_vma_init(void)
  {
  	gate_vma.vm_mm = NULL;
  	gate_vma.vm_start = FIXADDR_USER_START;
  	gate_vma.vm_end = FIXADDR_USER_END;
  	gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
  	gate_vma.vm_page_prot = __P101;
  
  	return 0;
  }
  
  #define compat_uses_vma		0
  
  static void map_compat_vdso(int map)
  {
  	static int vdso_mapped;
  
  	if (map == vdso_mapped)
  		return;
  
  	vdso_mapped = map;
  
  	__set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
  		     map ? PAGE_READONLY_EXEC : PAGE_NONE);
  
  	/* flush stray tlbs */
  	flush_tlb_all();
  }
  
  #endif	/* CONFIG_X86_64 */
  
  int __init sysenter_setup(void)
  {
  	void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
  	const void *vsyscall;
  	size_t vsyscall_len;
  
  	vdso32_pages[0] = virt_to_page(syscall_page);
  
  #ifdef CONFIG_X86_32
  	gate_vma_init();
  #endif
  
  	if (vdso32_syscall()) {
  		vsyscall = &vdso32_syscall_start;
  		vsyscall_len = &vdso32_syscall_end - &vdso32_syscall_start;
  	} else if (vdso32_sysenter()){
  		vsyscall = &vdso32_sysenter_start;
  		vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
  	} else {
  		vsyscall = &vdso32_int80_start;
  		vsyscall_len = &vdso32_int80_end - &vdso32_int80_start;
  	}
  
  	memcpy(syscall_page, vsyscall, vsyscall_len);
  	relocate_vdso(syscall_page);
  
  	return 0;
  }
  
  /* Setup a VMA at program startup for the vsyscall page */
  int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  {
  	struct mm_struct *mm = current->mm;
  	unsigned long addr;
  	int ret = 0;
  	bool compat;
  
  #ifdef CONFIG_X86_X32_ABI
  	if (test_thread_flag(TIF_X32))
  		return x32_setup_additional_pages(bprm, uses_interp);
  #endif
  
  	if (vdso_enabled == VDSO_DISABLED)
  		return 0;
  
  	down_write(&mm->mmap_sem);
  
  	/* Test compat mode once here, in case someone
  	   changes it via sysctl */
  	compat = (vdso_enabled == VDSO_COMPAT);
  
  	map_compat_vdso(compat);
  
  	if (compat)
  		addr = VDSO_HIGH_BASE;
  	else {
  		addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
  		if (IS_ERR_VALUE(addr)) {
  			ret = addr;
  			goto up_fail;
  		}
  	}
  
  	current->mm->context.vdso = (void *)addr;
  
  	if (compat_uses_vma || !compat) {
  		/*
  		 * MAYWRITE to allow gdb to COW and set breakpoints
  		 */
  		ret = install_special_mapping(mm, addr, PAGE_SIZE,
  					      VM_READ|VM_EXEC|
  					      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
  					      vdso32_pages);
  
  		if (ret)
  			goto up_fail;
  	}
  
  	current_thread_info()->sysenter_return =
  		VDSO32_SYMBOL(addr, SYSENTER_RETURN);
  
    up_fail:
  	if (ret)
  		current->mm->context.vdso = NULL;
  
  	up_write(&mm->mmap_sem);
  
  	return ret;
  }
  
  #ifdef CONFIG_X86_64
  
  subsys_initcall(sysenter_setup);
  
  #ifdef CONFIG_SYSCTL
  /* Register vsyscall32 into the ABI table */
  #include <linux/sysctl.h>
  
  static struct ctl_table abi_table2[] = {
  	{
  		.procname	= "vsyscall32",
  		.data		= &sysctl_vsyscall32,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec
  	},
  	{}
  };
  
  static struct ctl_table abi_root_table2[] = {
  	{
  		.procname = "abi",
  		.mode = 0555,
  		.child = abi_table2
  	},
  	{}
  };
  
  static __init int ia32_binfmt_init(void)
  {
  	register_sysctl_table(abi_root_table2);
  	return 0;
  }
  __initcall(ia32_binfmt_init);
  #endif
  
  #else  /* CONFIG_X86_32 */
  
  const char *arch_vma_name(struct vm_area_struct *vma)
  {
  	if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
  		return "[vdso]";
  	return NULL;
  }
  
  struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
  {
  	/*
  	 * Check to see if the corresponding task was created in compat vdso
  	 * mode.
  	 */
  	if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
  		return &gate_vma;
  	return NULL;
  }
  
  int in_gate_area(struct mm_struct *mm, unsigned long addr)
  {
  	const struct vm_area_struct *vma = get_gate_vma(mm);
  
  	return vma && addr >= vma->vm_start && addr < vma->vm_end;
  }
  
  int in_gate_area_no_mm(unsigned long addr)
  {
  	return 0;
  }
  
  #endif	/* CONFIG_X86_64 */