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linux/arch/x86_64/kernel/vmlinux.lds.S
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

238 lines
6.1 KiB
ArmAsm

/* ld script to make x86-64 Linux kernel
* Written by Martin Mares <mj@atrey.karlin.mff.cuni.cz>;
*/
#define LOAD_OFFSET __START_KERNEL_map
#include <asm-generic/vmlinux.lds.h>
#include <asm/page.h>
#undef i386 /* in case the preprocessor is a 32bit one */
OUTPUT_FORMAT("elf64-x86-64", "elf64-x86-64", "elf64-x86-64")
OUTPUT_ARCH(i386:x86-64)
ENTRY(phys_startup_64)
jiffies_64 = jiffies;
_proxy_pda = 1;
PHDRS {
text PT_LOAD FLAGS(5); /* R_E */
data PT_LOAD FLAGS(7); /* RWE */
user PT_LOAD FLAGS(7); /* RWE */
data.init PT_LOAD FLAGS(7); /* RWE */
note PT_NOTE FLAGS(4); /* R__ */
}
SECTIONS
{
. = __START_KERNEL;
phys_startup_64 = startup_64 - LOAD_OFFSET;
_text = .; /* Text and read-only data */
.text : AT(ADDR(.text) - LOAD_OFFSET) {
/* First the code that has to be first for bootstrapping */
*(.bootstrap.text)
_stext = .;
/* Then the rest */
TEXT_TEXT
SCHED_TEXT
LOCK_TEXT
KPROBES_TEXT
*(.fixup)
*(.gnu.warning)
} :text = 0x9090
/* out-of-line lock text */
.text.lock : AT(ADDR(.text.lock) - LOAD_OFFSET) { *(.text.lock) }
_etext = .; /* End of text section */
. = ALIGN(16); /* Exception table */
__start___ex_table = .;
__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { *(__ex_table) }
__stop___ex_table = .;
NOTES :text :note
BUG_TABLE :text
RODATA
. = ALIGN(PAGE_SIZE); /* Align data segment to page size boundary */
/* Data */
.data : AT(ADDR(.data) - LOAD_OFFSET) {
DATA_DATA
CONSTRUCTORS
} :data
_edata = .; /* End of data section */
. = ALIGN(PAGE_SIZE);
. = ALIGN(CONFIG_X86_L1_CACHE_BYTES);
.data.cacheline_aligned : AT(ADDR(.data.cacheline_aligned) - LOAD_OFFSET) {
*(.data.cacheline_aligned)
}
. = ALIGN(CONFIG_X86_INTERNODE_CACHE_BYTES);
.data.read_mostly : AT(ADDR(.data.read_mostly) - LOAD_OFFSET) {
*(.data.read_mostly)
}
#define VSYSCALL_ADDR (-10*1024*1024)
#define VSYSCALL_PHYS_ADDR ((LOADADDR(.data.read_mostly) + SIZEOF(.data.read_mostly) + 4095) & ~(4095))
#define VSYSCALL_VIRT_ADDR ((ADDR(.data.read_mostly) + SIZEOF(.data.read_mostly) + 4095) & ~(4095))
#define VLOAD_OFFSET (VSYSCALL_ADDR - VSYSCALL_PHYS_ADDR)
#define VLOAD(x) (ADDR(x) - VLOAD_OFFSET)
#define VVIRT_OFFSET (VSYSCALL_ADDR - VSYSCALL_VIRT_ADDR)
#define VVIRT(x) (ADDR(x) - VVIRT_OFFSET)
. = VSYSCALL_ADDR;
.vsyscall_0 : AT(VSYSCALL_PHYS_ADDR) { *(.vsyscall_0) } :user
__vsyscall_0 = VSYSCALL_VIRT_ADDR;
. = ALIGN(CONFIG_X86_L1_CACHE_BYTES);
.vsyscall_fn : AT(VLOAD(.vsyscall_fn)) { *(.vsyscall_fn) }
. = ALIGN(CONFIG_X86_L1_CACHE_BYTES);
.vsyscall_gtod_data : AT(VLOAD(.vsyscall_gtod_data))
{ *(.vsyscall_gtod_data) }
vsyscall_gtod_data = VVIRT(.vsyscall_gtod_data);
.vsyscall_clock : AT(VLOAD(.vsyscall_clock))
{ *(.vsyscall_clock) }
vsyscall_clock = VVIRT(.vsyscall_clock);
.vsyscall_1 ADDR(.vsyscall_0) + 1024: AT(VLOAD(.vsyscall_1))
{ *(.vsyscall_1) }
.vsyscall_2 ADDR(.vsyscall_0) + 2048: AT(VLOAD(.vsyscall_2))
{ *(.vsyscall_2) }
.vgetcpu_mode : AT(VLOAD(.vgetcpu_mode)) { *(.vgetcpu_mode) }
vgetcpu_mode = VVIRT(.vgetcpu_mode);
. = ALIGN(CONFIG_X86_L1_CACHE_BYTES);
.jiffies : AT(VLOAD(.jiffies)) { *(.jiffies) }
jiffies = VVIRT(.jiffies);
.vsyscall_3 ADDR(.vsyscall_0) + 3072: AT(VLOAD(.vsyscall_3))
{ *(.vsyscall_3) }
. = VSYSCALL_VIRT_ADDR + 4096;
#undef VSYSCALL_ADDR
#undef VSYSCALL_PHYS_ADDR
#undef VSYSCALL_VIRT_ADDR
#undef VLOAD_OFFSET
#undef VLOAD
#undef VVIRT_OFFSET
#undef VVIRT
. = ALIGN(8192); /* init_task */
.data.init_task : AT(ADDR(.data.init_task) - LOAD_OFFSET) {
*(.data.init_task)
}:data.init
. = ALIGN(4096);
.data.page_aligned : AT(ADDR(.data.page_aligned) - LOAD_OFFSET) {
*(.data.page_aligned)
}
/* might get freed after init */
. = ALIGN(4096);
__smp_alt_begin = .;
__smp_alt_instructions = .;
.smp_altinstructions : AT(ADDR(.smp_altinstructions) - LOAD_OFFSET) {
*(.smp_altinstructions)
}
__smp_alt_instructions_end = .;
. = ALIGN(8);
__smp_locks = .;
.smp_locks : AT(ADDR(.smp_locks) - LOAD_OFFSET) {
*(.smp_locks)
}
__smp_locks_end = .;
.smp_altinstr_replacement : AT(ADDR(.smp_altinstr_replacement) - LOAD_OFFSET) {
*(.smp_altinstr_replacement)
}
. = ALIGN(4096);
__smp_alt_end = .;
. = ALIGN(4096); /* Init code and data */
__init_begin = .;
.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
_sinittext = .;
*(.init.text)
_einittext = .;
}
__initdata_begin = .;
.init.data : AT(ADDR(.init.data) - LOAD_OFFSET) { *(.init.data) }
__initdata_end = .;
. = ALIGN(16);
__setup_start = .;
.init.setup : AT(ADDR(.init.setup) - LOAD_OFFSET) { *(.init.setup) }
__setup_end = .;
__initcall_start = .;
.initcall.init : AT(ADDR(.initcall.init) - LOAD_OFFSET) {
INITCALLS
}
__initcall_end = .;
__con_initcall_start = .;
.con_initcall.init : AT(ADDR(.con_initcall.init) - LOAD_OFFSET) {
*(.con_initcall.init)
}
__con_initcall_end = .;
SECURITY_INIT
. = ALIGN(8);
__alt_instructions = .;
.altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {
*(.altinstructions)
}
__alt_instructions_end = .;
.altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) {
*(.altinstr_replacement)
}
/* .exit.text is discard at runtime, not link time, to deal with references
from .altinstructions and .eh_frame */
.exit.text : AT(ADDR(.exit.text) - LOAD_OFFSET) { *(.exit.text) }
.exit.data : AT(ADDR(.exit.data) - LOAD_OFFSET) { *(.exit.data) }
/* vdso blob that is mapped into user space */
vdso_start = . ;
.vdso : AT(ADDR(.vdso) - LOAD_OFFSET) { *(.vdso) }
. = ALIGN(4096);
vdso_end = .;
#ifdef CONFIG_BLK_DEV_INITRD
. = ALIGN(4096);
__initramfs_start = .;
.init.ramfs : AT(ADDR(.init.ramfs) - LOAD_OFFSET) { *(.init.ramfs) }
__initramfs_end = .;
#endif
PERCPU(4096)
. = ALIGN(4096);
__init_end = .;
. = ALIGN(4096);
__nosave_begin = .;
.data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) { *(.data.nosave) }
. = ALIGN(4096);
__nosave_end = .;
__bss_start = .; /* BSS */
.bss : AT(ADDR(.bss) - LOAD_OFFSET) {
*(.bss.page_aligned)
*(.bss)
}
__bss_stop = .;
_end = . ;
/* Sections to be discarded */
/DISCARD/ : {
*(.exitcall.exit)
*(.eh_frame)
}
STABS_DEBUG
DWARF_DEBUG
}