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

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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
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 */