5de253cc5b
We map a VMA for the 32-bit vDSO even when it's disabled, which is stupid. For the 32-bit kernel it's the vdso_enabled boot parameter/sysctl and for the 64-bit kernel it's the vdso32 boot parameter/syscall32 sysctl. When it's disabled, we don't pass AT_SYSINFO_EHDR so processes don't use the vDSO for anything, but we still map it. For the non-compat vDSO, this means we're always putting an extra VMA somewhere, maybe lousing up the control of the address space the user was hoping for. Honor the setting by doing nothing in arch_setup_additional_pages. [ also see: "x86 vDSO: don't use disabled vDSO for signal trampoline" ] Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
448 lines
9.9 KiB
C
448 lines
9.9 KiB
C
/*
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* (C) Copyright 2002 Linus Torvalds
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* Portions based on the vdso-randomization code from exec-shield:
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* Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
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*
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* This file contains the needed initializations to support sysenter.
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*/
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#include <linux/init.h>
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#include <linux/smp.h>
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#include <linux/thread_info.h>
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#include <linux/sched.h>
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#include <linux/gfp.h>
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#include <linux/string.h>
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#include <linux/elf.h>
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#include <linux/mm.h>
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#include <linux/err.h>
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#include <linux/module.h>
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#include <asm/cpufeature.h>
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#include <asm/msr.h>
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#include <asm/pgtable.h>
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#include <asm/unistd.h>
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#include <asm/elf.h>
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#include <asm/tlbflush.h>
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#include <asm/vdso.h>
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#include <asm/proto.h>
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enum {
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VDSO_DISABLED = 0,
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VDSO_ENABLED = 1,
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VDSO_COMPAT = 2,
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};
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#ifdef CONFIG_COMPAT_VDSO
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#define VDSO_DEFAULT VDSO_COMPAT
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#else
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#define VDSO_DEFAULT VDSO_ENABLED
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#endif
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#ifdef CONFIG_X86_64
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#define vdso_enabled sysctl_vsyscall32
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#define arch_setup_additional_pages syscall32_setup_pages
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#endif
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/*
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* This is the difference between the prelinked addresses in the vDSO images
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* and the VDSO_HIGH_BASE address where CONFIG_COMPAT_VDSO places the vDSO
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* in the user address space.
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*/
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#define VDSO_ADDR_ADJUST (VDSO_HIGH_BASE - (unsigned long)VDSO32_PRELINK)
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/*
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* Should the kernel map a VDSO page into processes and pass its
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* address down to glibc upon exec()?
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*/
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unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
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static int __init vdso_setup(char *s)
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{
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vdso_enabled = simple_strtoul(s, NULL, 0);
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return 1;
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}
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/*
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* For consistency, the argument vdso32=[012] affects the 32-bit vDSO
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* behavior on both 64-bit and 32-bit kernels.
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* On 32-bit kernels, vdso=[012] means the same thing.
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*/
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__setup("vdso32=", vdso_setup);
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#ifdef CONFIG_X86_32
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__setup_param("vdso=", vdso32_setup, vdso_setup, 0);
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EXPORT_SYMBOL_GPL(vdso_enabled);
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#endif
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static __init void reloc_symtab(Elf32_Ehdr *ehdr,
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unsigned offset, unsigned size)
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{
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Elf32_Sym *sym = (void *)ehdr + offset;
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unsigned nsym = size / sizeof(*sym);
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unsigned i;
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for(i = 0; i < nsym; i++, sym++) {
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if (sym->st_shndx == SHN_UNDEF ||
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sym->st_shndx == SHN_ABS)
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continue; /* skip */
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if (sym->st_shndx > SHN_LORESERVE) {
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printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
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sym->st_shndx);
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continue;
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}
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switch(ELF_ST_TYPE(sym->st_info)) {
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case STT_OBJECT:
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case STT_FUNC:
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case STT_SECTION:
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case STT_FILE:
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sym->st_value += VDSO_ADDR_ADJUST;
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}
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}
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}
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static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
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{
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Elf32_Dyn *dyn = (void *)ehdr + offset;
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for(; dyn->d_tag != DT_NULL; dyn++)
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switch(dyn->d_tag) {
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case DT_PLTGOT:
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case DT_HASH:
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case DT_STRTAB:
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case DT_SYMTAB:
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case DT_RELA:
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case DT_INIT:
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case DT_FINI:
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case DT_REL:
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case DT_DEBUG:
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case DT_JMPREL:
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case DT_VERSYM:
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case DT_VERDEF:
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case DT_VERNEED:
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case DT_ADDRRNGLO ... DT_ADDRRNGHI:
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/* definitely pointers needing relocation */
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dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
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break;
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case DT_ENCODING ... OLD_DT_LOOS-1:
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case DT_LOOS ... DT_HIOS-1:
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/* Tags above DT_ENCODING are pointers if
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they're even */
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if (dyn->d_tag >= DT_ENCODING &&
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(dyn->d_tag & 1) == 0)
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dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
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break;
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case DT_VERDEFNUM:
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case DT_VERNEEDNUM:
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case DT_FLAGS_1:
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case DT_RELACOUNT:
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case DT_RELCOUNT:
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case DT_VALRNGLO ... DT_VALRNGHI:
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/* definitely not pointers */
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break;
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case OLD_DT_LOOS ... DT_LOOS-1:
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case DT_HIOS ... DT_VALRNGLO-1:
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default:
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if (dyn->d_tag > DT_ENCODING)
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printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
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dyn->d_tag);
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break;
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}
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}
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static __init void relocate_vdso(Elf32_Ehdr *ehdr)
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{
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Elf32_Phdr *phdr;
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Elf32_Shdr *shdr;
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int i;
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BUG_ON(memcmp(ehdr->e_ident, ELFMAG, 4) != 0 ||
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!elf_check_arch_ia32(ehdr) ||
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ehdr->e_type != ET_DYN);
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ehdr->e_entry += VDSO_ADDR_ADJUST;
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/* rebase phdrs */
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phdr = (void *)ehdr + ehdr->e_phoff;
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for (i = 0; i < ehdr->e_phnum; i++) {
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phdr[i].p_vaddr += VDSO_ADDR_ADJUST;
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/* relocate dynamic stuff */
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if (phdr[i].p_type == PT_DYNAMIC)
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reloc_dyn(ehdr, phdr[i].p_offset);
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}
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/* rebase sections */
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shdr = (void *)ehdr + ehdr->e_shoff;
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for(i = 0; i < ehdr->e_shnum; i++) {
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if (!(shdr[i].sh_flags & SHF_ALLOC))
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continue;
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shdr[i].sh_addr += VDSO_ADDR_ADJUST;
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if (shdr[i].sh_type == SHT_SYMTAB ||
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shdr[i].sh_type == SHT_DYNSYM)
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reloc_symtab(ehdr, shdr[i].sh_offset,
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shdr[i].sh_size);
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}
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}
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/*
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* These symbols are defined by vdso32.S to mark the bounds
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* of the ELF DSO images included therein.
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*/
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extern const char vdso32_default_start, vdso32_default_end;
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extern const char vdso32_sysenter_start, vdso32_sysenter_end;
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static struct page *vdso32_pages[1];
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#ifdef CONFIG_X86_64
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static int use_sysenter __read_mostly = -1;
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#define vdso32_sysenter() (use_sysenter > 0)
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/* May not be __init: called during resume */
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void syscall32_cpu_init(void)
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{
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if (use_sysenter < 0)
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use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);
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/* Load these always in case some future AMD CPU supports
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SYSENTER from compat mode too. */
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checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
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checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
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checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
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wrmsrl(MSR_CSTAR, ia32_cstar_target);
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}
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#define compat_uses_vma 1
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static inline void map_compat_vdso(int map)
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{
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}
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#else /* CONFIG_X86_32 */
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#define vdso32_sysenter() (boot_cpu_has(X86_FEATURE_SEP))
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void enable_sep_cpu(void)
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{
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int cpu = get_cpu();
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struct tss_struct *tss = &per_cpu(init_tss, cpu);
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if (!boot_cpu_has(X86_FEATURE_SEP)) {
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put_cpu();
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return;
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}
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tss->x86_tss.ss1 = __KERNEL_CS;
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tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
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wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
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wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
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wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
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put_cpu();
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}
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static struct vm_area_struct gate_vma;
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static int __init gate_vma_init(void)
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{
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gate_vma.vm_mm = NULL;
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gate_vma.vm_start = FIXADDR_USER_START;
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gate_vma.vm_end = FIXADDR_USER_END;
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gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
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gate_vma.vm_page_prot = __P101;
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/*
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* Make sure the vDSO gets into every core dump.
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* Dumping its contents makes post-mortem fully interpretable later
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* without matching up the same kernel and hardware config to see
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* what PC values meant.
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*/
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gate_vma.vm_flags |= VM_ALWAYSDUMP;
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return 0;
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}
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#define compat_uses_vma 0
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static void map_compat_vdso(int map)
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{
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static int vdso_mapped;
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if (map == vdso_mapped)
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return;
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vdso_mapped = map;
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__set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
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map ? PAGE_READONLY_EXEC : PAGE_NONE);
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/* flush stray tlbs */
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flush_tlb_all();
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}
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#endif /* CONFIG_X86_64 */
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int __init sysenter_setup(void)
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{
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void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
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const void *vsyscall;
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size_t vsyscall_len;
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vdso32_pages[0] = virt_to_page(syscall_page);
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#ifdef CONFIG_X86_32
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gate_vma_init();
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printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
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#endif
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if (!vdso32_sysenter()) {
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vsyscall = &vdso32_default_start;
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vsyscall_len = &vdso32_default_end - &vdso32_default_start;
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} else {
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vsyscall = &vdso32_sysenter_start;
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vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
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}
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memcpy(syscall_page, vsyscall, vsyscall_len);
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relocate_vdso(syscall_page);
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return 0;
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}
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/* Setup a VMA at program startup for the vsyscall page */
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int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
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{
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struct mm_struct *mm = current->mm;
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unsigned long addr;
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int ret = 0;
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bool compat;
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if (vdso_enabled == VDSO_DISABLED)
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return 0;
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down_write(&mm->mmap_sem);
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/* Test compat mode once here, in case someone
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changes it via sysctl */
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compat = (vdso_enabled == VDSO_COMPAT);
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map_compat_vdso(compat);
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if (compat)
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addr = VDSO_HIGH_BASE;
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else {
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addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
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if (IS_ERR_VALUE(addr)) {
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ret = addr;
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goto up_fail;
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}
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}
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if (compat_uses_vma || !compat) {
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/*
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* MAYWRITE to allow gdb to COW and set breakpoints
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*
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* Make sure the vDSO gets into every core dump.
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* Dumping its contents makes post-mortem fully
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* interpretable later without matching up the same
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* kernel and hardware config to see what PC values
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* meant.
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*/
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ret = install_special_mapping(mm, addr, PAGE_SIZE,
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VM_READ|VM_EXEC|
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VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
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VM_ALWAYSDUMP,
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vdso32_pages);
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if (ret)
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goto up_fail;
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}
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current->mm->context.vdso = (void *)addr;
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current_thread_info()->sysenter_return =
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VDSO32_SYMBOL(addr, SYSENTER_RETURN);
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up_fail:
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up_write(&mm->mmap_sem);
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return ret;
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}
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#ifdef CONFIG_X86_64
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__initcall(sysenter_setup);
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#ifdef CONFIG_SYSCTL
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/* Register vsyscall32 into the ABI table */
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#include <linux/sysctl.h>
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static ctl_table abi_table2[] = {
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{
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.procname = "vsyscall32",
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.data = &sysctl_vsyscall32,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{}
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};
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static ctl_table abi_root_table2[] = {
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{
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.ctl_name = CTL_ABI,
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.procname = "abi",
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.mode = 0555,
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.child = abi_table2
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},
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{}
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};
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static __init int ia32_binfmt_init(void)
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{
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register_sysctl_table(abi_root_table2);
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return 0;
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}
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__initcall(ia32_binfmt_init);
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#endif
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#else /* CONFIG_X86_32 */
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const char *arch_vma_name(struct vm_area_struct *vma)
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{
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if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
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return "[vdso]";
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return NULL;
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}
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struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
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{
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struct mm_struct *mm = tsk->mm;
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/* Check to see if this task was created in compat vdso mode */
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if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
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return &gate_vma;
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return NULL;
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}
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int in_gate_area(struct task_struct *task, unsigned long addr)
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{
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const struct vm_area_struct *vma = get_gate_vma(task);
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return vma && addr >= vma->vm_start && addr < vma->vm_end;
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}
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int in_gate_area_no_task(unsigned long addr)
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{
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return 0;
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}
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#endif /* CONFIG_X86_64 */
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