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[PATCH] i386: Relocate VDSO ELF headers to match mapped location with COMPAT_VDSO 

Some versions of libc can't deal with a VDSO which doesn't have its
ELF headers matching its mapped address.  COMPAT_VDSO maps the VDSO at
a specific system-wide fixed address.  Previously this was all done at
build time, on the grounds that the fixed VDSO address is always at
the top of the address space.  However, a hypervisor may reserve some
of that address space, pushing the fixmap address down.

This patch does the adjustment dynamically at runtime, depending on
the runtime location of the VDSO fixmap.

[ Patch has been through several hands: Jan Beulich wrote the orignal
  version; Zach reworked it, and Jeremy converted it to relocate phdrs
  as well as sections. ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Zachary Amsden <zach@vmware.com>
Cc: "Jan Beulich" <JBeulich@novell.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>
This commit is contained in:
Jeremy Fitzhardinge 2007-05-02 19:27:12 +02:00 committed by Andi Kleen
parent a6c4e076ee
commit d4f7a2c18e
6 changed files with 178 additions and 43 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/i386/kernel/entry.S
View File

@ -305,16 +305,12 @@ sysenter_past_esp:
pushl $(__USER_CS)
CFI_ADJUST_CFA_OFFSET 4
/*CFI_REL_OFFSET cs, 0*/
#ifndef CONFIG_COMPAT_VDSO
/*
* Push current_thread_info()->sysenter_return to the stack.
* A tiny bit of offset fixup is necessary - 4*4 means the 4 words
* pushed above; +8 corresponds to copy_thread's esp0 setting.
*/
pushl (TI_sysenter_return-THREAD_SIZE+8+4*4)(%esp)
#else
pushl $SYSENTER_RETURN
#endif
CFI_ADJUST_CFA_OFFSET 4
CFI_REL_OFFSET eip, 0

158
arch/i386/kernel/sysenter.c
View File

@ -22,6 +22,7 @@
#include <asm/msr.h>
#include <asm/pgtable.h>
#include <asm/unistd.h>
#include <asm/elf.h>
/*
* Should the kernel map a VDSO page into processes and pass its
@ -46,6 +47,129 @@ __setup("vdso=", vdso_setup);
extern asmlinkage void sysenter_entry(void);
#ifdef CONFIG_COMPAT_VDSO
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_HIGH_BASE;
}
}
}
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_HIGH_BASE;
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_HIGH_BASE;
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, 4) != 0 ||
!elf_check_arch(ehdr) ||
ehdr->e_type != ET_DYN);
ehdr->e_entry += VDSO_HIGH_BASE;
/* rebase phdrs */
phdr = (void *)ehdr + ehdr->e_phoff;
for (i = 0; i < ehdr->e_phnum; i++) {
phdr[i].p_vaddr += VDSO_HIGH_BASE;
/* 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_HIGH_BASE;
if (shdr[i].sh_type == SHT_SYMTAB ||
shdr[i].sh_type == SHT_DYNSYM)
reloc_symtab(ehdr, shdr[i].sh_offset,
shdr[i].sh_size);
}
}
#else
static inline void relocate_vdso(Elf32_Ehdr *ehdr)
{
}
#endif /* COMPAT_VDSO */
void enable_sep_cpu(void)
{
int cpu = get_cpu();
@ -75,6 +199,9 @@ static struct page *syscall_pages[1];
int __init sysenter_setup(void)
{
void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
const void *vsyscall;
size_t vsyscall_len;
syscall_pages[0] = virt_to_page(syscall_page);
#ifdef CONFIG_COMPAT_VDSO
@ -83,23 +210,23 @@ int __init sysenter_setup(void)
#endif
if (!boot_cpu_has(X86_FEATURE_SEP)) {
memcpy(syscall_page,
&vsyscall_int80_start,
&vsyscall_int80_end - &vsyscall_int80_start);
return 0;
vsyscall = &vsyscall_int80_start;
vsyscall_len = &vsyscall_int80_end - &vsyscall_int80_start;
} else {
vsyscall = &vsyscall_sysenter_start;
vsyscall_len = &vsyscall_sysenter_end - &vsyscall_sysenter_start;
}
memcpy(syscall_page,
&vsyscall_sysenter_start,
&vsyscall_sysenter_end - &vsyscall_sysenter_start);
memcpy(syscall_page, vsyscall, vsyscall_len);
relocate_vdso(syscall_page);
return 0;
}
#ifndef CONFIG_COMPAT_VDSO
/* Defined in vsyscall-sysenter.S */
extern void SYSENTER_RETURN;
#ifdef __HAVE_ARCH_GATE_AREA
/* Setup a VMA at program startup for the vsyscall page */
int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
{
@ -159,4 +286,17 @@ int in_gate_area_no_task(unsigned long addr)
{
return 0;
}
#endif
#else /* !__HAVE_ARCH_GATE_AREA */
int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
{
/*
* If not creating userspace VMA, simply set vdso to point to
* fixmap page.
*/
current->mm->context.vdso = (void *)VDSO_HIGH_BASE;
current_thread_info()->sysenter_return =
(void *)VDSO_SYM(&SYSENTER_RETURN);
return 0;
}
#endif /* __HAVE_ARCH_GATE_AREA */

6
arch/i386/mm/pgtable.c
View File

@ -144,10 +144,8 @@ void set_pmd_pfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags)
}
static int fixmaps;
#ifndef CONFIG_COMPAT_VDSO
unsigned long __FIXADDR_TOP = 0xfffff000;
EXPORT_SYMBOL(__FIXADDR_TOP);
#endif
void __set_fixmap (enum fixed_addresses idx, unsigned long phys, pgprot_t flags)
{
@ -173,12 +171,8 @@ void reserve_top_address(unsigned long reserve)
BUG_ON(fixmaps > 0);
printk(KERN_INFO "Reserving virtual address space above 0x%08x\n",
(int)-reserve);
#ifdef CONFIG_COMPAT_VDSO
BUG_ON(reserve != 0);
#else
__FIXADDR_TOP = -reserve - PAGE_SIZE;
__VMALLOC_RESERVE += reserve;
#endif
}
pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)

28
include/asm-i386/elf.h
View File

@ -133,39 +133,31 @@ extern int dump_task_extended_fpu (struct task_struct *, struct user_fxsr_struct
#define ELF_CORE_COPY_XFPREGS(tsk, elf_xfpregs) dump_task_extended_fpu(tsk, elf_xfpregs)
#define VDSO_HIGH_BASE (__fix_to_virt(FIX_VDSO))
#define VDSO_BASE ((unsigned long)current->mm->context.vdso)
#ifdef CONFIG_COMPAT_VDSO
# define VDSO_COMPAT_BASE VDSO_HIGH_BASE
# define VDSO_PRELINK VDSO_HIGH_BASE
#else
# define VDSO_COMPAT_BASE VDSO_BASE
# define VDSO_PRELINK 0
#endif
#define VDSO_CURRENT_BASE ((unsigned long)current->mm->context.vdso)
#define VDSO_PRELINK 0
#define VDSO_SYM(x) \
(VDSO_COMPAT_BASE + (unsigned long)(x) - VDSO_PRELINK)
(VDSO_CURRENT_BASE + (unsigned long)(x) - VDSO_PRELINK)
#define VDSO_HIGH_EHDR ((const struct elfhdr *) VDSO_HIGH_BASE)
#define VDSO_EHDR ((const struct elfhdr *) VDSO_COMPAT_BASE)
#define VDSO_EHDR ((const struct elfhdr *) VDSO_CURRENT_BASE)
extern void __kernel_vsyscall;
#define VDSO_ENTRY VDSO_SYM(&__kernel_vsyscall)
#ifndef CONFIG_COMPAT_VDSO
#define ARCH_HAS_SETUP_ADDITIONAL_PAGES
struct linux_binprm;
#define ARCH_HAS_SETUP_ADDITIONAL_PAGES
extern int arch_setup_additional_pages(struct linux_binprm *bprm,
int executable_stack);
#endif
extern unsigned int vdso_enabled;
#define ARCH_DLINFO \
do if (vdso_enabled) { \
NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY); \
NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_COMPAT_BASE); \
#define ARCH_DLINFO \
do if (vdso_enabled) { \
NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY); \
NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_CURRENT_BASE); \
} while (0)
#endif

8
include/asm-i386/fixmap.h
View File

@ -19,13 +19,9 @@
* Leave one empty page between vmalloc'ed areas and
* the start of the fixmap.
*/
#ifndef CONFIG_COMPAT_VDSO
extern unsigned long __FIXADDR_TOP;
#else
#define __FIXADDR_TOP 0xfffff000
#define FIXADDR_USER_START __fix_to_virt(FIX_VDSO)
#define FIXADDR_USER_END __fix_to_virt(FIX_VDSO - 1)
#endif
#define FIXADDR_USER_START __fix_to_virt(FIX_VDSO)
#define FIXADDR_USER_END __fix_to_virt(FIX_VDSO - 1)
#ifndef __ASSEMBLY__
#include <linux/kernel.h>

17
include/linux/elf.h
View File

@ -83,6 +83,23 @@ typedef __s64 Elf64_Sxword;
#define DT_DEBUG 21
#define DT_TEXTREL 22
#define DT_JMPREL 23
#define DT_ENCODING 32
#define OLD_DT_LOOS 0x60000000
#define DT_LOOS 0x6000000d
#define DT_HIOS 0x6ffff000
#define DT_VALRNGLO 0x6ffffd00
#define DT_VALRNGHI 0x6ffffdff
#define DT_ADDRRNGLO 0x6ffffe00
#define DT_ADDRRNGHI 0x6ffffeff
#define DT_VERSYM 0x6ffffff0
#define DT_RELACOUNT 0x6ffffff9
#define DT_RELCOUNT 0x6ffffffa
#define DT_FLAGS_1 0x6ffffffb
#define DT_VERDEF 0x6ffffffc
#define DT_VERDEFNUM 0x6ffffffd
#define DT_VERNEED 0x6ffffffe
#define DT_VERNEEDNUM 0x6fffffff
#define OLD_DT_HIOS 0x6fffffff
#define DT_LOPROC 0x70000000
#define DT_HIPROC 0x7fffffff