Commit c728762e authored by Linus Torvalds's avatar Linus Torvalds

Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 vdso fixes from Peter Anvin:
 "Fixes for x86/vdso.

  One is a simple build fix for bigendian hosts, one is to make "make
  vdso_install" work again, and the rest is about working around a bug
  in Google's Go language -- two are documentation patches that improves
  the sample code that the Go coders took, modified, and broke; the
  other two implements a workaround that keeps existing Go binaries from
  segfaulting at least"

* 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/vdso: Fix vdso_install
  x86/vdso: Hack to keep 64-bit Go programs working
  x86/vdso: Add PUT_LE to store little-endian values
  x86/vdso/doc: Make vDSO examples more portable
  x86/vdso/doc: Rename vdso_test.c to vdso_standalone_test_x86.c
  x86, vdso: Remove one final use of htole16()
parents 503698e1 a934fb5b
/*
* parse_vdso.c: Linux reference vDSO parser
* Written by Andrew Lutomirski, 2011.
* Written by Andrew Lutomirski, 2011-2014.
*
* This code is meant to be linked in to various programs that run on Linux.
* As such, it is available with as few restrictions as possible. This file
......@@ -11,13 +11,14 @@
* it starts a program. It works equally well in statically and dynamically
* linked binaries.
*
* This code is tested on x86_64. In principle it should work on any 64-bit
* This code is tested on x86. In principle it should work on any
* architecture that has a vDSO.
*/
#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include <limits.h>
#include <elf.h>
/*
......@@ -45,11 +46,18 @@ extern void *vdso_sym(const char *version, const char *name);
/* And here's the code. */
#ifndef __x86_64__
# error Not yet ported to non-x86_64 architectures
#ifndef ELF_BITS
# if ULONG_MAX > 0xffffffffUL
# define ELF_BITS 64
# else
# define ELF_BITS 32
# endif
#endif
#define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
#define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
#define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
static struct vdso_info
{
bool valid;
......@@ -59,14 +67,14 @@ static struct vdso_info
uintptr_t load_offset; /* load_addr - recorded vaddr */
/* Symbol table */
Elf64_Sym *symtab;
ELF(Sym) *symtab;
const char *symstrings;
Elf64_Word *bucket, *chain;
Elf64_Word nbucket, nchain;
ELF(Word) *bucket, *chain;
ELF(Word) nbucket, nchain;
/* Version table */
Elf64_Versym *versym;
Elf64_Verdef *verdef;
ELF(Versym) *versym;
ELF(Verdef) *verdef;
} vdso_info;
/* Straight from the ELF specification. */
......@@ -92,9 +100,14 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
vdso_info.load_addr = base;
Elf64_Ehdr *hdr = (Elf64_Ehdr*)base;
Elf64_Phdr *pt = (Elf64_Phdr*)(vdso_info.load_addr + hdr->e_phoff);
Elf64_Dyn *dyn = 0;
ELF(Ehdr) *hdr = (ELF(Ehdr)*)base;
if (hdr->e_ident[EI_CLASS] !=
(ELF_BITS == 32 ? ELFCLASS32 : ELFCLASS64)) {
return; /* Wrong ELF class -- check ELF_BITS */
}
ELF(Phdr) *pt = (ELF(Phdr)*)(vdso_info.load_addr + hdr->e_phoff);
ELF(Dyn) *dyn = 0;
/*
* We need two things from the segment table: the load offset
......@@ -108,7 +121,7 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
+ (uintptr_t)pt[i].p_offset
- (uintptr_t)pt[i].p_vaddr;
} else if (pt[i].p_type == PT_DYNAMIC) {
dyn = (Elf64_Dyn*)(base + pt[i].p_offset);
dyn = (ELF(Dyn)*)(base + pt[i].p_offset);
}
}
......@@ -118,7 +131,7 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
/*
* Fish out the useful bits of the dynamic table.
*/
Elf64_Word *hash = 0;
ELF(Word) *hash = 0;
vdso_info.symstrings = 0;
vdso_info.symtab = 0;
vdso_info.versym = 0;
......@@ -131,22 +144,22 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
+ vdso_info.load_offset);
break;
case DT_SYMTAB:
vdso_info.symtab = (Elf64_Sym *)
vdso_info.symtab = (ELF(Sym) *)
((uintptr_t)dyn[i].d_un.d_ptr
+ vdso_info.load_offset);
break;
case DT_HASH:
hash = (Elf64_Word *)
hash = (ELF(Word) *)
((uintptr_t)dyn[i].d_un.d_ptr
+ vdso_info.load_offset);
break;
case DT_VERSYM:
vdso_info.versym = (Elf64_Versym *)
vdso_info.versym = (ELF(Versym) *)
((uintptr_t)dyn[i].d_un.d_ptr
+ vdso_info.load_offset);
break;
case DT_VERDEF:
vdso_info.verdef = (Elf64_Verdef *)
vdso_info.verdef = (ELF(Verdef) *)
((uintptr_t)dyn[i].d_un.d_ptr
+ vdso_info.load_offset);
break;
......@@ -168,8 +181,8 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
vdso_info.valid = true;
}
static bool vdso_match_version(Elf64_Versym ver,
const char *name, Elf64_Word hash)
static bool vdso_match_version(ELF(Versym) ver,
const char *name, ELF(Word) hash)
{
/*
* This is a helper function to check if the version indexed by
......@@ -188,7 +201,7 @@ static bool vdso_match_version(Elf64_Versym ver,
/* First step: find the version definition */
ver &= 0x7fff; /* Apparently bit 15 means "hidden" */
Elf64_Verdef *def = vdso_info.verdef;
ELF(Verdef) *def = vdso_info.verdef;
while(true) {
if ((def->vd_flags & VER_FLG_BASE) == 0
&& (def->vd_ndx & 0x7fff) == ver)
......@@ -197,11 +210,11 @@ static bool vdso_match_version(Elf64_Versym ver,
if (def->vd_next == 0)
return false; /* No definition. */
def = (Elf64_Verdef *)((char *)def + def->vd_next);
def = (ELF(Verdef) *)((char *)def + def->vd_next);
}
/* Now figure out whether it matches. */
Elf64_Verdaux *aux = (Elf64_Verdaux*)((char *)def + def->vd_aux);
ELF(Verdaux) *aux = (ELF(Verdaux)*)((char *)def + def->vd_aux);
return def->vd_hash == hash
&& !strcmp(name, vdso_info.symstrings + aux->vda_name);
}
......@@ -213,10 +226,10 @@ void *vdso_sym(const char *version, const char *name)
return 0;
ver_hash = elf_hash(version);
Elf64_Word chain = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket];
ELF(Word) chain = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket];
for (; chain != STN_UNDEF; chain = vdso_info.chain[chain]) {
Elf64_Sym *sym = &vdso_info.symtab[chain];
ELF(Sym) *sym = &vdso_info.symtab[chain];
/* Check for a defined global or weak function w/ right name. */
if (ELF64_ST_TYPE(sym->st_info) != STT_FUNC)
......@@ -243,7 +256,7 @@ void *vdso_sym(const char *version, const char *name)
void vdso_init_from_auxv(void *auxv)
{
Elf64_auxv_t *elf_auxv = auxv;
ELF(auxv_t) *elf_auxv = auxv;
for (int i = 0; elf_auxv[i].a_type != AT_NULL; i++)
{
if (elf_auxv[i].a_type == AT_SYSINFO_EHDR) {
......
/*
* vdso_test.c: Sample code to test parse_vdso.c on x86
* Copyright (c) 2011-2014 Andy Lutomirski
* Subject to the GNU General Public License, version 2
*
* You can amuse yourself by compiling with:
* gcc -std=gnu99 -nostdlib
* -Os -fno-asynchronous-unwind-tables -flto -lgcc_s
* vdso_standalone_test_x86.c parse_vdso.c
* to generate a small binary. On x86_64, you can omit -lgcc_s
* if you want the binary to be completely standalone.
*/
#include <sys/syscall.h>
#include <sys/time.h>
#include <unistd.h>
#include <stdint.h>
extern void *vdso_sym(const char *version, const char *name);
extern void vdso_init_from_sysinfo_ehdr(uintptr_t base);
extern void vdso_init_from_auxv(void *auxv);
/* We need a libc functions... */
int strcmp(const char *a, const char *b)
{
/* This implementation is buggy: it never returns -1. */
while (*a || *b) {
if (*a != *b)
return 1;
if (*a == 0 || *b == 0)
return 1;
a++;
b++;
}
return 0;
}
/* ...and two syscalls. This is x86-specific. */
static inline long x86_syscall3(long nr, long a0, long a1, long a2)
{
long ret;
#ifdef __x86_64__
asm volatile ("syscall" : "=a" (ret) : "a" (nr),
"D" (a0), "S" (a1), "d" (a2) :
"cc", "memory", "rcx",
"r8", "r9", "r10", "r11" );
#else
asm volatile ("int $0x80" : "=a" (ret) : "a" (nr),
"b" (a0), "c" (a1), "d" (a2) :
"cc", "memory" );
#endif
return ret;
}
static inline long linux_write(int fd, const void *data, size_t len)
{
return x86_syscall3(__NR_write, fd, (long)data, (long)len);
}
static inline void linux_exit(int code)
{
x86_syscall3(__NR_exit, code, 0, 0);
}
void to_base10(char *lastdig, uint64_t n)
{
while (n) {
*lastdig = (n % 10) + '0';
n /= 10;
lastdig--;
}
}
__attribute__((externally_visible)) void c_main(void **stack)
{
/* Parse the stack */
long argc = (long)*stack;
stack += argc + 2;
/* Now we're pointing at the environment. Skip it. */
while(*stack)
stack++;
stack++;
/* Now we're pointing at auxv. Initialize the vDSO parser. */
vdso_init_from_auxv((void *)stack);
/* Find gettimeofday. */
typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
gtod_t gtod = (gtod_t)vdso_sym("LINUX_2.6", "__vdso_gettimeofday");
if (!gtod)
linux_exit(1);
struct timeval tv;
long ret = gtod(&tv, 0);
if (ret == 0) {
char buf[] = "The time is .000000\n";
to_base10(buf + 31, tv.tv_sec);
to_base10(buf + 38, tv.tv_usec);
linux_write(1, buf, sizeof(buf) - 1);
} else {
linux_exit(ret);
}
linux_exit(0);
}
/*
* This is the real entry point. It passes the initial stack into
* the C entry point.
*/
asm (
".text\n"
".global _start\n"
".type _start,@function\n"
"_start:\n\t"
#ifdef __x86_64__
"mov %rsp,%rdi\n\t"
"jmp c_main"
#else
"push %esp\n\t"
"call c_main\n\t"
"int $3"
#endif
);
/*
* vdso_test.c: Sample code to test parse_vdso.c on x86_64
* Copyright (c) 2011 Andy Lutomirski
* vdso_test.c: Sample code to test parse_vdso.c
* Copyright (c) 2014 Andy Lutomirski
* Subject to the GNU General Public License, version 2
*
* You can amuse yourself by compiling with:
* gcc -std=gnu99 -nostdlib
* -Os -fno-asynchronous-unwind-tables -flto
* vdso_test.c parse_vdso.c -o vdso_test
* to generate a small binary with no dependencies at all.
* Compile with:
* gcc -std=gnu99 vdso_test.c parse_vdso.c
*
* Tested on x86, 32-bit and 64-bit. It may work on other architectures, too.
*/
#include <sys/syscall.h>
#include <sys/time.h>
#include <unistd.h>
#include <stdint.h>
#include <elf.h>
#include <stdio.h>
#include <sys/auxv.h>
#include <sys/time.h>
extern void *vdso_sym(const char *version, const char *name);
extern void vdso_init_from_sysinfo_ehdr(uintptr_t base);
extern void vdso_init_from_auxv(void *auxv);
/* We need a libc functions... */
int strcmp(const char *a, const char *b)
int main(int argc, char **argv)
{
/* This implementation is buggy: it never returns -1. */
while (*a || *b) {
if (*a != *b)
return 1;
if (*a == 0 || *b == 0)
return 1;
a++;
b++;
}
unsigned long sysinfo_ehdr = getauxval(AT_SYSINFO_EHDR);
if (!sysinfo_ehdr) {
printf("AT_SYSINFO_EHDR is not present!\n");
return 0;
}
/* ...and two syscalls. This is x86_64-specific. */
static inline long linux_write(int fd, const void *data, size_t len)
{
long ret;
asm volatile ("syscall" : "=a" (ret) : "a" (__NR_write),
"D" (fd), "S" (data), "d" (len) :
"cc", "memory", "rcx",
"r8", "r9", "r10", "r11" );
return ret;
}
static inline void linux_exit(int code)
{
asm volatile ("syscall" : : "a" (__NR_exit), "D" (code));
}
void to_base10(char *lastdig, uint64_t n)
{
while (n) {
*lastdig = (n % 10) + '0';
n /= 10;
lastdig--;
}
}
__attribute__((externally_visible)) void c_main(void **stack)
{
/* Parse the stack */
long argc = (long)*stack;
stack += argc + 2;
/* Now we're pointing at the environment. Skip it. */
while(*stack)
stack++;
stack++;
/* Now we're pointing at auxv. Initialize the vDSO parser. */
vdso_init_from_auxv((void *)stack);
vdso_init_from_sysinfo_ehdr(getauxval(AT_SYSINFO_EHDR));
/* Find gettimeofday. */
typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
gtod_t gtod = (gtod_t)vdso_sym("LINUX_2.6", "__vdso_gettimeofday");
if (!gtod)
linux_exit(1);
if (!gtod) {
printf("Could not find __vdso_gettimeofday\n");
return 1;
}
struct timeval tv;
long ret = gtod(&tv, 0);
if (ret == 0) {
char buf[] = "The time is .000000\n";
to_base10(buf + 31, tv.tv_sec);
to_base10(buf + 38, tv.tv_usec);
linux_write(1, buf, sizeof(buf) - 1);
printf("The time is %lld.%06lld\n",
(long long)tv.tv_sec, (long long)tv.tv_usec);
} else {
linux_exit(ret);
printf("__vdso_gettimeofday failed\n");
}
linux_exit(0);
return 0;
}
/*
* This is the real entry point. It passes the initial stack into
* the C entry point.
*/
asm (
".text\n"
".global _start\n"
".type _start,@function\n"
"_start:\n\t"
"mov %rsp,%rdi\n\t"
"jmp c_main"
);
......@@ -9,18 +9,9 @@ VDSOX32-$(CONFIG_X86_X32_ABI) := y
VDSO32-$(CONFIG_X86_32) := y
VDSO32-$(CONFIG_COMPAT) := y
vdso-install-$(VDSO64-y) += vdso.so
vdso-install-$(VDSOX32-y) += vdsox32.so
vdso-install-$(VDSO32-y) += $(vdso32-images)
# files to link into the vdso
vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o
vobjs-$(VDSOX32-y) += $(vobjx32s-compat)
# Filter out x32 objects.
vobj64s := $(filter-out $(vobjx32s-compat),$(vobjs-y))
vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o vdso-fakesections.o
vobjs-nox32 := vdso-fakesections.o
# files to link into kernel
obj-y += vma.o
......@@ -34,7 +25,7 @@ vdso_img-$(VDSO32-y) += 32-sysenter
obj-$(VDSO32-y) += vdso32-setup.o
vobjs := $(foreach F,$(vobj64s),$(obj)/$F)
vobjs := $(foreach F,$(vobjs-y),$(obj)/$F)
$(obj)/vdso.o: $(obj)/vdso.so
......@@ -104,7 +95,13 @@ VDSO_LDFLAGS_vdsox32.lds = -Wl,-m,elf32_x86_64 \
-Wl,-z,max-page-size=4096 \
-Wl,-z,common-page-size=4096
vobjx32s-y := $(vobj64s:.o=-x32.o)
# 64-bit objects to re-brand as x32
vobjs64-for-x32 := $(filter-out $(vobjs-nox32),$(vobjs-y))
# x32-rebranded versions
vobjx32s-y := $(vobjs64-for-x32:.o=-x32.o)
# same thing, but in the output directory
vobjx32s := $(foreach F,$(vobjx32s-y),$(obj)/$F)
# Convert 64bit object file to x32 for x32 vDSO.
......@@ -176,15 +173,20 @@ 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).
# Install the unstripped copies of vdso*.so.
#
quiet_cmd_vdso_install = INSTALL $@
cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
$(vdso-install-y): %.so: $(obj)/%.so.dbg FORCE
quiet_cmd_vdso_install = INSTALL $(@:install_%=%)
cmd_vdso_install = cp $< $(MODLIB)/vdso/$(@:install_%=%)
vdso_img_insttargets := $(vdso_img_sodbg:%.dbg=install_%)
$(MODLIB)/vdso: FORCE
@mkdir -p $(MODLIB)/vdso
$(vdso_img_insttargets): install_%: $(obj)/%.dbg $(MODLIB)/vdso FORCE
$(call cmd,vdso_install)
PHONY += vdso_install $(vdso-install-y)
vdso_install: $(vdso-install-y)
PHONY += vdso_install $(vdso_img_insttargets)
vdso_install: $(vdso_img_insttargets) FORCE
clean-files := vdso32-syscall* vdso32-sysenter* vdso32-int80*
/*
* Copyright 2014 Andy Lutomirski
* Subject to the GNU Public License, v.2
*
* Hack to keep broken Go programs working.
*
* The Go runtime had a couple of bugs: it would read the section table to try
* to figure out how many dynamic symbols there were (it shouldn't have looked
* at the section table at all) and, if there were no SHT_SYNDYM section table
* entry, it would use an uninitialized value for the number of symbols. As a
* workaround, we supply a minimal section table. vdso2c will adjust the
* in-memory image so that "vdso_fake_sections" becomes the section table.
*
* The bug was introduced by:
* https://code.google.com/p/go/source/detail?r=56ea40aac72b (2012-08-31)
* and is being addressed in the Go runtime in this issue:
* https://code.google.com/p/go/issues/detail?id=8197
*/
#ifndef __x86_64__
#error This hack is specific to the 64-bit vDSO
#endif
#include <linux/elf.h>
extern const __visible struct elf64_shdr vdso_fake_sections[];
const __visible struct elf64_shdr vdso_fake_sections[] = {
{
.sh_type = SHT_DYNSYM,
.sh_entsize = sizeof(Elf64_Sym),
}
};
......@@ -54,7 +54,7 @@ static void fail(const char *format, ...)
}
/*
* Evil macros to do a little-endian read.
* Evil macros for little-endian reads and writes
*/
#define GLE(x, bits, ifnot) \
__builtin_choose_expr( \
......@@ -62,11 +62,24 @@ static void fail(const char *format, ...)
(__typeof__(*(x)))get_unaligned_le##bits(x), ifnot)
extern void bad_get_le(void);
#define LAST_LE(x) \
#define LAST_GLE(x) \
__builtin_choose_expr(sizeof(*(x)) == 1, *(x), bad_get_le())
#define GET_LE(x) \
GLE(x, 64, GLE(x, 32, GLE(x, 16, LAST_LE(x))))
GLE(x, 64, GLE(x, 32, GLE(x, 16, LAST_GLE(x))))
#define PLE(x, val, bits, ifnot) \
__builtin_choose_expr( \
(sizeof(*(x)) == bits/8), \
put_unaligned_le##bits((val), (x)), ifnot)
extern void bad_put_le(void);
#define LAST_PLE(x, val) \
__builtin_choose_expr(sizeof(*(x)) == 1, *(x) = (val), bad_put_le())
#define PUT_LE(x, val) \
PLE(x, val, 64, PLE(x, val, 32, PLE(x, val, 16, LAST_PLE(x, val))))
#define NSYMS (sizeof(required_syms) / sizeof(required_syms[0]))
......
......@@ -18,6 +18,8 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name)
const char *secstrings;
uint64_t syms[NSYMS] = {};
uint64_t fake_sections_value = 0, fake_sections_size = 0;
Elf_Phdr *pt = (Elf_Phdr *)(addr + GET_LE(&hdr->e_phoff));
/* Walk the segment table. */
......@@ -84,6 +86,7 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name)
GET_LE(&symtab_hdr->sh_entsize) * i;
const char *name = addr + GET_LE(&strtab_hdr->sh_offset) +
GET_LE(&sym->st_name);
for (k = 0; k < NSYMS; k++) {
if (!strcmp(name, required_syms[k])) {
if (syms[k]) {
......@@ -93,6 +96,13 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name)
syms[k] = GET_LE(&sym->st_value);
}
}
if (!strcmp(name, "vdso_fake_sections")) {
if (fake_sections_value)
fail("duplicate vdso_fake_sections\n");
fake_sections_value = GET_LE(&sym->st_value);
fake_sections_size = GET_LE(&sym->st_size);
}
}
/* Validate mapping addresses. */
......@@ -112,11 +122,14 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name)
if (syms[sym_end_mapping] % 4096)
fail("end_mapping must be a multiple of 4096\n");
/* Remove sections. */
hdr->e_shoff = 0;
hdr->e_shentsize = 0;
hdr->e_shnum = 0;
hdr->e_shstrndx = htole16(SHN_UNDEF);
/* Remove sections or use fakes */
if (fake_sections_size % sizeof(Elf_Shdr))
fail("vdso_fake_sections size is not a multiple of %ld\n",
(long)sizeof(Elf_Shdr));
PUT_LE(&hdr->e_shoff, fake_sections_value);
PUT_LE(&hdr->e_shentsize, fake_sections_value ? sizeof(Elf_Shdr) : 0);
PUT_LE(&hdr->e_shnum, fake_sections_size / sizeof(Elf_Shdr));
PUT_LE(&hdr->e_shstrndx, SHN_UNDEF);
if (!name) {
fwrite(addr, load_size, 1, outfile);
......
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