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linux/include/asm-x86_64/elf.h
Andi Kleen 2aae950b21 x86_64: Add vDSO for x86-64 with gettimeofday/clock_gettime/getcpu 
This implements new vDSO for x86-64.  The concept is similar
to the existing vDSOs on i386 and PPC.  x86-64 has had static
vsyscalls before,  but these are not flexible enough anymore.

A vDSO is a ELF shared library supplied by the kernel that is mapped into
user address space.  The vDSO mapping is randomized for each process
for security reasons.

Doing this was needed for clock_gettime, because clock_gettime
always needs a syscall fallback and having one at a fixed
address would have made buffer overflow exploits too easy to write.

The vdso can be disabled with vdso=0

It currently includes a new gettimeofday implemention and optimized
clock_gettime(). The gettimeofday implementation is slightly faster
than the one in the old vsyscall.  clock_gettime is significantly faster
than the syscall for CLOCK_MONOTONIC and CLOCK_REALTIME.

The new calls are generally faster than the old vsyscall.

Advantages over the old x86-64 vsyscalls:
- Extensible
- Randomized
- Cleaner
- Easier to virtualize (the old static address range previously causes
overhead e.g. for Xen because it has to create special page tables for it)

Weak points:
- glibc support still to be written

The VM interface is partly based on Ingo Molnar's i386 version.

Includes compile fix from Joachim Deguara

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-21 18:37:08 -07:00

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#ifndef __ASM_X86_64_ELF_H
#define __ASM_X86_64_ELF_H
/*
* ELF register definitions..
*/
#include <asm/ptrace.h>
#include <asm/user.h>
/* x86-64 relocation types */
#define R_X86_64_NONE 0 /* No reloc */
#define R_X86_64_64 1 /* Direct 64 bit */
#define R_X86_64_PC32 2 /* PC relative 32 bit signed */
#define R_X86_64_GOT32 3 /* 32 bit GOT entry */
#define R_X86_64_PLT32 4 /* 32 bit PLT address */
#define R_X86_64_COPY 5 /* Copy symbol at runtime */
#define R_X86_64_GLOB_DAT 6 /* Create GOT entry */
#define R_X86_64_JUMP_SLOT 7 /* Create PLT entry */
#define R_X86_64_RELATIVE 8 /* Adjust by program base */
#define R_X86_64_GOTPCREL 9 /* 32 bit signed pc relative
offset to GOT */
#define R_X86_64_32 10 /* Direct 32 bit zero extended */
#define R_X86_64_32S 11 /* Direct 32 bit sign extended */
#define R_X86_64_16 12 /* Direct 16 bit zero extended */
#define R_X86_64_PC16 13 /* 16 bit sign extended pc relative */
#define R_X86_64_8 14 /* Direct 8 bit sign extended */
#define R_X86_64_PC8 15 /* 8 bit sign extended pc relative */
#define R_X86_64_NUM 16
typedef unsigned long elf_greg_t;
#define ELF_NGREG (sizeof (struct user_regs_struct) / sizeof(elf_greg_t))
typedef elf_greg_t elf_gregset_t[ELF_NGREG];
typedef struct user_i387_struct elf_fpregset_t;
/*
* These are used to set parameters in the core dumps.
*/
#define ELF_CLASS ELFCLASS64
#define ELF_DATA ELFDATA2LSB
#define ELF_ARCH EM_X86_64
#ifdef __KERNEL__
#include <asm/processor.h>
/*
* This is used to ensure we don't load something for the wrong architecture.
*/
#define elf_check_arch(x) \
((x)->e_machine == EM_X86_64)
/* SVR4/i386 ABI (pages 3-31, 3-32) says that when the program starts %edx
contains a pointer to a function which might be registered using `atexit'.
This provides a mean for the dynamic linker to call DT_FINI functions for
shared libraries that have been loaded before the code runs.
A value of 0 tells we have no such handler.
We might as well make sure everything else is cleared too (except for %esp),
just to make things more deterministic.
*/
#define ELF_PLAT_INIT(_r, load_addr) do { \
struct task_struct *cur = current; \
(_r)->rbx = 0; (_r)->rcx = 0; (_r)->rdx = 0; \
(_r)->rsi = 0; (_r)->rdi = 0; (_r)->rbp = 0; \
(_r)->rax = 0; \
(_r)->r8 = 0; \
(_r)->r9 = 0; \
(_r)->r10 = 0; \
(_r)->r11 = 0; \
(_r)->r12 = 0; \
(_r)->r13 = 0; \
(_r)->r14 = 0; \
(_r)->r15 = 0; \
cur->thread.fs = 0; cur->thread.gs = 0; \
cur->thread.fsindex = 0; cur->thread.gsindex = 0; \
cur->thread.ds = 0; cur->thread.es = 0; \
clear_thread_flag(TIF_IA32); \
} while (0)
#define USE_ELF_CORE_DUMP
#define ELF_EXEC_PAGESIZE 4096
/* This is the location that an ET_DYN program is loaded if exec'ed. Typical
use of this is to invoke "./ld.so someprog" to test out a new version of
the loader. We need to make sure that it is out of the way of the program
that it will "exec", and that there is sufficient room for the brk. */
#define ELF_ET_DYN_BASE (2 * TASK_SIZE / 3)
/* regs is struct pt_regs, pr_reg is elf_gregset_t (which is
now struct_user_regs, they are different). Assumes current is the process
getting dumped. */
#define ELF_CORE_COPY_REGS(pr_reg, regs) do { \
unsigned v; \
(pr_reg)[0] = (regs)->r15; \
(pr_reg)[1] = (regs)->r14; \
(pr_reg)[2] = (regs)->r13; \
(pr_reg)[3] = (regs)->r12; \
(pr_reg)[4] = (regs)->rbp; \
(pr_reg)[5] = (regs)->rbx; \
(pr_reg)[6] = (regs)->r11; \
(pr_reg)[7] = (regs)->r10; \
(pr_reg)[8] = (regs)->r9; \
(pr_reg)[9] = (regs)->r8; \
(pr_reg)[10] = (regs)->rax; \
(pr_reg)[11] = (regs)->rcx; \
(pr_reg)[12] = (regs)->rdx; \
(pr_reg)[13] = (regs)->rsi; \
(pr_reg)[14] = (regs)->rdi; \
(pr_reg)[15] = (regs)->orig_rax; \
(pr_reg)[16] = (regs)->rip; \
(pr_reg)[17] = (regs)->cs; \
(pr_reg)[18] = (regs)->eflags; \
(pr_reg)[19] = (regs)->rsp; \
(pr_reg)[20] = (regs)->ss; \
(pr_reg)[21] = current->thread.fs; \
(pr_reg)[22] = current->thread.gs; \
asm("movl %%ds,%0" : "=r" (v)); (pr_reg)[23] = v; \
asm("movl %%es,%0" : "=r" (v)); (pr_reg)[24] = v; \
asm("movl %%fs,%0" : "=r" (v)); (pr_reg)[25] = v; \
asm("movl %%gs,%0" : "=r" (v)); (pr_reg)[26] = v; \
} while(0);
/* This yields a mask that user programs can use to figure out what
instruction set this CPU supports. This could be done in user space,
but it's not easy, and we've already done it here. */
#define ELF_HWCAP (boot_cpu_data.x86_capability[0])
/* This yields a string that ld.so will use to load implementation
specific libraries for optimization. This is more specific in
intent than poking at uname or /proc/cpuinfo.
For the moment, we have only optimizations for the Intel generations,
but that could change... */
/* I'm not sure if we can use '-' here */
#define ELF_PLATFORM ("x86_64")
extern void set_personality_64bit(void);
#define SET_PERSONALITY(ex, ibcs2) set_personality_64bit()
/*
* An executable for which elf_read_implies_exec() returns TRUE will
* have the READ_IMPLIES_EXEC personality flag set automatically.
*/
#define elf_read_implies_exec(ex, executable_stack) (executable_stack != EXSTACK_DISABLE_X)
struct task_struct;
extern int dump_task_regs (struct task_struct *, elf_gregset_t *);
extern int dump_task_fpu (struct task_struct *, elf_fpregset_t *);
#define ELF_CORE_COPY_TASK_REGS(tsk, elf_regs) dump_task_regs(tsk, elf_regs)
#define ELF_CORE_COPY_FPREGS(tsk, elf_fpregs) dump_task_fpu(tsk, elf_fpregs)
/* 1GB for 64bit, 8MB for 32bit */
#define STACK_RND_MASK (test_thread_flag(TIF_IA32) ? 0x7ff : 0x3fffff)
#define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
struct linux_binprm;
extern int arch_setup_additional_pages(struct linux_binprm *bprm,
int executable_stack);
extern int vdso_enabled;
#define ARCH_DLINFO \
do if (vdso_enabled) { \
NEW_AUX_ENT(AT_SYSINFO_EHDR,(unsigned long)current->mm->context.vdso);\
} while (0)
#endif
#endif
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