Commit f1c2bb8b authored by Richard Weinberger's avatar Richard Weinberger Committed by Linus Torvalds

um: implement a x86_64 vDSO

Until now UML had no x86_64 vDSO.  So glibc always used the vsyscall page
for gettimeday() and friends.  Calls to gettimeday() returned falsely the
host time and confused some programs.

This patch adds a vDSO which turns all __vdso_* calls into a system call
so that UML can trap them.

As glibc still uses the vsyscall page for static binaries this patch
improves the situation only for dynamic binaries.
Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fc9a0018
......@@ -8,6 +8,8 @@ obj-y = bug.o bugs.o delay.o fault.o ldt.o ptrace.o ptrace_user.o mem.o \
setjmp.o signal.o stub.o stub_segv.o syscalls.o syscall_table.o \
sysrq.o ksyms.o tls.o
obj-y += vdso/
subarch-obj-y = lib/csum-partial_64.o lib/memcpy_64.o lib/thunk_64.o \
lib/rwsem.o
subarch-obj-$(CONFIG_MODULES) += kernel/module.o
......
#
# Building vDSO images for x86.
#
VDSO64-y := y
vdso-install-$(VDSO64-y) += vdso.so
# files to link into the vdso
vobjs-y := vdso-note.o um_vdso.o
# files to link into kernel
obj-$(VDSO64-y) += vdso.o vma.o
vobjs := $(foreach F,$(vobjs-y),$(obj)/$F)
$(obj)/vdso.o: $(obj)/vdso.so
targets += vdso.so vdso.so.dbg vdso.lds $(vobjs-y)
export CPPFLAGS_vdso.lds += -P -C
VDSO_LDFLAGS_vdso.lds = -m64 -Wl,-soname=linux-vdso.so.1 \
-Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096
$(obj)/vdso.o: $(src)/vdso.S $(obj)/vdso.so
$(obj)/vdso.so.dbg: $(src)/vdso.lds $(vobjs) FORCE
$(call if_changed,vdso)
$(obj)/%.so: OBJCOPYFLAGS := -S
$(obj)/%.so: $(obj)/%.so.dbg FORCE
$(call if_changed,objcopy)
#
# Don't omit frame pointers for ease of userspace debugging, but do
# optimize sibling calls.
#
CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
$(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
-fno-omit-frame-pointer -foptimize-sibling-calls
$(vobjs): KBUILD_CFLAGS += $(CFL)
#
# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
#
CFLAGS_REMOVE_vdso-note.o = -pg
CFLAGS_REMOVE_um_vdso.o = -pg
targets += vdso-syms.lds
obj-$(VDSO64-y) += vdso-syms.lds
#
# Match symbols in the DSO that look like VDSO*; produce a file of constants.
#
sed-vdsosym := -e 's/^00*/0/' \
-e 's/^\([0-9a-fA-F]*\) . \(VDSO[a-zA-Z0-9_]*\)$$/\2 = 0x\1;/p'
quiet_cmd_vdsosym = VDSOSYM $@
define cmd_vdsosym
$(NM) $< | LC_ALL=C sed -n $(sed-vdsosym) | LC_ALL=C sort > $@
endef
$(obj)/%-syms.lds: $(obj)/%.so.dbg FORCE
$(call if_changed,vdsosym)
#
# The DSO images are built using a special linker script.
#
quiet_cmd_vdso = VDSO $@
cmd_vdso = $(CC) -nostdlib -o $@ \
$(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \
-Wl,-T,$(filter %.lds,$^) $(filter %.o,$^) && \
sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@'
VDSO_LDFLAGS = -fPIC -shared $(call cc-ldoption, -Wl$(comma)--hash-style=sysv)
GCOV_PROFILE := n
#
# Install the unstripped copy of vdso*.so listed in $(vdso-install-y).
#
quiet_cmd_vdso_install = INSTALL $@
cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
$(vdso-install-y): %.so: $(obj)/%.so.dbg FORCE
@mkdir -p $(MODLIB)/vdso
$(call cmd,vdso_install)
PHONY += vdso_install $(vdso-install-y)
vdso_install: $(vdso-install-y)
#!/bin/sh
nm="$1"
file="$2"
$nm "$file" | grep '^ *U' > /dev/null 2>&1
if [ $? -eq 1 ]; then
exit 0
else
echo "$file: undefined symbols found" >&2
exit 1
fi
/*
* Copyright (C) 2011 Richard Weinberger <richrd@nod.at>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This vDSO turns all calls into a syscall so that UML can trap them.
*/
/* Disable profiling for userspace code */
#define DISABLE_BRANCH_PROFILING
#include <linux/time.h>
#include <linux/getcpu.h>
#include <asm/unistd.h>
int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
{
long ret;
asm("syscall" : "=a" (ret) :
"0" (__NR_clock_gettime), "D" (clock), "S" (ts) : "memory");
return ret;
}
int clock_gettime(clockid_t, struct timespec *)
__attribute__((weak, alias("__vdso_clock_gettime")));
int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
{
long ret;
asm("syscall" : "=a" (ret) :
"0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
return ret;
}
int gettimeofday(struct timeval *, struct timezone *)
__attribute__((weak, alias("__vdso_gettimeofday")));
time_t __vdso_time(time_t *t)
{
long secs;
asm volatile("syscall"
: "=a" (secs)
: "0" (__NR_time), "D" (t) : "cc", "r11", "cx", "memory");
return secs;
}
int time(time_t *t) __attribute__((weak, alias("__vdso_time")));
long
__vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
{
/*
* UML does not support SMP, we can cheat here. :)
*/
if (cpu)
*cpu = 0;
if (node)
*node = 0;
return 0;
}
long getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
__attribute__((weak, alias("__vdso_getcpu")));
/*
* Linker script for vDSO. This is an ELF shared object prelinked to
* its virtual address, and with only one read-only segment.
* This script controls its layout.
*/
SECTIONS
{
. = VDSO_PRELINK + SIZEOF_HEADERS;
.hash : { *(.hash) } :text
.gnu.hash : { *(.gnu.hash) }
.dynsym : { *(.dynsym) }
.dynstr : { *(.dynstr) }
.gnu.version : { *(.gnu.version) }
.gnu.version_d : { *(.gnu.version_d) }
.gnu.version_r : { *(.gnu.version_r) }
.note : { *(.note.*) } :text :note
.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
.eh_frame : { KEEP (*(.eh_frame)) } :text
.dynamic : { *(.dynamic) } :text :dynamic
.rodata : { *(.rodata*) } :text
.data : {
*(.data*)
*(.sdata*)
*(.got.plt) *(.got)
*(.gnu.linkonce.d.*)
*(.bss*)
*(.dynbss*)
*(.gnu.linkonce.b.*)
}
.altinstructions : { *(.altinstructions) }
.altinstr_replacement : { *(.altinstr_replacement) }
/*
* Align the actual code well away from the non-instruction data.
* This is the best thing for the I-cache.
*/
. = ALIGN(0x100);
.text : { *(.text*) } :text =0x90909090
}
/*
* Very old versions of ld do not recognize this name token; use the constant.
*/
#define PT_GNU_EH_FRAME 0x6474e550
/*
* We must supply the ELF program headers explicitly to get just one
* PT_LOAD segment, and set the flags explicitly to make segments read-only.
*/
PHDRS
{
text PT_LOAD FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
dynamic PT_DYNAMIC FLAGS(4); /* PF_R */
note PT_NOTE FLAGS(4); /* PF_R */
eh_frame_hdr PT_GNU_EH_FRAME;
}
/*
* This supplies .note.* sections to go into the PT_NOTE inside the vDSO text.
* Here we can supply some information useful to userland.
*/
#include <linux/uts.h>
#include <linux/version.h>
#include <linux/elfnote.h>
ELFNOTE_START(Linux, 0, "a")
.long LINUX_VERSION_CODE
ELFNOTE_END
#include <linux/init.h>
__INITDATA
.globl vdso_start, vdso_end
vdso_start:
.incbin "arch/um/sys-x86_64/vdso/vdso.so"
vdso_end:
__FINIT
/*
* Linker script for 64-bit vDSO.
* We #include the file to define the layout details.
* Here we only choose the prelinked virtual address.
*
* This file defines the version script giving the user-exported symbols in
* the DSO. We can define local symbols here called VDSO* to make their
* values visible using the asm-x86/vdso.h macros from the kernel proper.
*/
#define VDSO_PRELINK 0xffffffffff700000
#include "vdso-layout.lds.S"
/*
* This controls what userland symbols we export from the vDSO.
*/
VERSION {
LINUX_2.6 {
global:
clock_gettime;
__vdso_clock_gettime;
gettimeofday;
__vdso_gettimeofday;
getcpu;
__vdso_getcpu;
time;
__vdso_time;
local: *;
};
}
VDSO64_PRELINK = VDSO_PRELINK;
/*
* Copyright (C) 2011 Richard Weinberger <richrd@nod.at>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <asm/page.h>
#include <linux/init.h>
unsigned int __read_mostly vdso_enabled = 1;
unsigned long um_vdso_addr;
extern unsigned long task_size;
extern char vdso_start[], vdso_end[];
static struct page **vdsop;
static int __init init_vdso(void)
{
struct page *um_vdso;
BUG_ON(vdso_end - vdso_start > PAGE_SIZE);
um_vdso_addr = task_size - PAGE_SIZE;
vdsop = kmalloc(GFP_KERNEL, sizeof(struct page *));
if (!vdsop)
goto oom;
um_vdso = alloc_page(GFP_KERNEL);
if (!um_vdso) {
kfree(vdsop);
goto oom;
}
copy_page(page_address(um_vdso), vdso_start);
*vdsop = um_vdso;
return 0;
oom:
printk(KERN_ERR "Cannot allocate vdso\n");
vdso_enabled = 0;
return -ENOMEM;
}
subsys_initcall(init_vdso);
int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
int err;
struct mm_struct *mm = current->mm;
if (!vdso_enabled)
return 0;
down_write(&mm->mmap_sem);
err = install_special_mapping(mm, um_vdso_addr, PAGE_SIZE,
VM_READ|VM_EXEC|
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
VM_ALWAYSDUMP,
vdsop);
up_write(&mm->mmap_sem);
return err;
}
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