linux/arch/x86/vdso/vdso32-setup.c
Jeremy Fitzhardinge 6a52e4b1cd x86_64: further cleanup of 32-bit compat syscall mechanisms
AMD only supports "syscall" from 32-bit compat usermode.
Intel and Centaur(?) only support "sysenter" from 32-bit compat usermode.

Set the X86 feature bits accordingly, and set up the vdso in
accordance with those bits.  On the offchance we run on in a 64-bit
environment which supports neither syscall nor sysenter from 32-bit
mode, then fall back to the int $0x80 vdso.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2008-07-16 11:08:27 +02:00

440 lines
9.7 KiB
C

/*
* (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\n",
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\n",
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. */
checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
checking_wrmsrl(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;
/*
* Make sure the vDSO gets into every core dump.
* Dumping its contents makes post-mortem fully interpretable later
* without matching up the same kernel and hardware config to see
* what PC values meant.
*/
gate_vma.vm_flags |= VM_ALWAYSDUMP;
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 exstack)
{
struct mm_struct *mm = current->mm;
unsigned long addr;
int ret = 0;
bool compat;
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;
}
}
if (compat_uses_vma || !compat) {
/*
* MAYWRITE to allow gdb to COW and set breakpoints
*
* Make sure the vDSO gets into every core dump.
* Dumping its contents makes post-mortem fully
* interpretable later without matching up the same
* kernel and hardware config to see what PC values
* meant.
*/
ret = install_special_mapping(mm, addr, PAGE_SIZE,
VM_READ|VM_EXEC|
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
VM_ALWAYSDUMP,
vdso32_pages);
if (ret)
goto up_fail;
}
current->mm->context.vdso = (void *)addr;
current_thread_info()->sysenter_return =
VDSO32_SYMBOL(addr, SYSENTER_RETURN);
up_fail:
up_write(&mm->mmap_sem);
return ret;
}
#ifdef CONFIG_X86_64
__initcall(sysenter_setup);
#ifdef CONFIG_SYSCTL
/* Register vsyscall32 into the ABI table */
#include <linux/sysctl.h>
static ctl_table abi_table2[] = {
{
.procname = "vsyscall32",
.data = &sysctl_vsyscall32,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
},
{}
};
static ctl_table abi_root_table2[] = {
{
.ctl_name = CTL_ABI,
.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 task_struct *tsk)
{
struct mm_struct *mm = tsk->mm;
/* Check to see if this 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 task_struct *task, unsigned long addr)
{
const struct vm_area_struct *vma = get_gate_vma(task);
return vma && addr >= vma->vm_start && addr < vma->vm_end;
}
int in_gate_area_no_task(unsigned long addr)
{
return 0;
}
#endif /* CONFIG_X86_64 */