git: 203bcad73164 - stable/13 - amd64: wrap 64bit sigtramp into vdso
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Date: Sun, 02 Jan 2022 19:08:10 UTC
The branch stable/13 has been updated by kib:
URL: https://cgit.FreeBSD.org/src/commit/?id=203bcad73164bf6e4f51edc4ffda7f2a3885b413
commit 203bcad73164bf6e4f51edc4ffda7f2a3885b413
Author: Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2021-11-05 08:07:24 +0000
Commit: Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2022-01-02 16:43:01 +0000
amd64: wrap 64bit sigtramp into vdso
(cherry picked from commit ab4524b3d7fba872a143b03c9346cb04c3670efa)
---
sys/amd64/amd64/elf_machdep.c | 20 +++++++---
sys/amd64/amd64/sigtramp.S | 18 +++------
sys/compat/linux/linux_vdso.c | 4 +-
sys/conf/files.amd64 | 7 +++-
sys/conf/vdso_amd64.ldscript | 89 +++++++++++++++++++++++++++++++++++++++++++
sys/kern/kern_proc.c | 7 +++-
sys/kern/kern_sharedpage.c | 18 ++++++++-
sys/sys/sysent.h | 4 +-
sys/tools/amd64_vdso.sh | 59 ++++++++++++++++++++++++++++
sys/tools/vdso_wrap.S | 48 +++++++++++++++++++++++
10 files changed, 247 insertions(+), 27 deletions(-)
diff --git a/sys/amd64/amd64/elf_machdep.c b/sys/amd64/amd64/elf_machdep.c
index 445efa883fd2..6a4c25072962 100644
--- a/sys/amd64/amd64/elf_machdep.c
+++ b/sys/amd64/amd64/elf_machdep.c
@@ -49,14 +49,21 @@ __FBSDID("$FreeBSD$");
#include <machine/fpu.h>
#include <machine/md_var.h>
+#include "vdso_offsets.h"
+
+extern const char _binary_elf_vdso_so_1_start[];
+extern const char _binary_elf_vdso_so_1_end[];
+extern char _binary_elf_vdso_so_1_size;
+
struct sysentvec elf64_freebsd_sysvec_la48 = {
.sv_size = SYS_MAXSYSCALL,
.sv_table = sysent,
.sv_transtrap = NULL,
.sv_fixup = __elfN(freebsd_fixup),
.sv_sendsig = sendsig,
- .sv_sigcode = sigcode,
- .sv_szsigcode = &szsigcode,
+ .sv_sigcode = _binary_elf_vdso_so_1_start,
+ .sv_szsigcode = (int *)&_binary_elf_vdso_so_1_size,
+ .sv_sigcodeoff = VDSO_SIGCODE_OFFSET,
.sv_name = "FreeBSD ELF64",
.sv_coredump = __elfN(coredump),
.sv_imgact_try = NULL,
@@ -72,7 +79,7 @@ struct sysentvec elf64_freebsd_sysvec_la48 = {
.sv_fixlimit = NULL,
.sv_maxssiz = NULL,
.sv_flags = SV_ABI_FREEBSD | SV_ASLR | SV_LP64 | SV_SHP |
- SV_TIMEKEEP | SV_RNG_SEED_VER,
+ SV_TIMEKEEP | SV_RNG_SEED_VER | SV_DSO_SIG,
.sv_set_syscall_retval = cpu_set_syscall_retval,
.sv_fetch_syscall_args = cpu_fetch_syscall_args,
.sv_syscallnames = syscallnames,
@@ -92,8 +99,9 @@ struct sysentvec elf64_freebsd_sysvec_la57 = {
.sv_transtrap = NULL,
.sv_fixup = __elfN(freebsd_fixup),
.sv_sendsig = sendsig,
- .sv_sigcode = sigcode,
- .sv_szsigcode = &szsigcode,
+ .sv_sigcode = _binary_elf_vdso_so_1_start,
+ .sv_szsigcode = (int *)&_binary_elf_vdso_so_1_size,
+ .sv_sigcodeoff = VDSO_SIGCODE_OFFSET,
.sv_name = "FreeBSD ELF64",
.sv_coredump = __elfN(coredump),
.sv_imgact_try = NULL,
@@ -109,7 +117,7 @@ struct sysentvec elf64_freebsd_sysvec_la57 = {
.sv_fixlimit = NULL,
.sv_maxssiz = NULL,
.sv_flags = SV_ABI_FREEBSD | SV_ASLR | SV_LP64 | SV_SHP |
- SV_TIMEKEEP | SV_RNG_SEED_VER,
+ SV_TIMEKEEP | SV_RNG_SEED_VER | SV_DSO_SIG,
.sv_set_syscall_retval = cpu_set_syscall_retval,
.sv_fetch_syscall_args = cpu_fetch_syscall_args,
.sv_syscallnames = syscallnames,
diff --git a/sys/amd64/amd64/sigtramp.S b/sys/amd64/amd64/sigtramp.S
index a249a1a646f2..05bf30293a9a 100644
--- a/sys/amd64/amd64/sigtramp.S
+++ b/sys/amd64/amd64/sigtramp.S
@@ -27,18 +27,15 @@
*/
#include <sys/syscall.h>
-
#include <machine/asmacros.h>
#include "assym.inc"
.text
-/**********************************************************************
- *
- * Signal trampoline, copied to top of user stack
- *
+/*
+ * Signal trampoline, mapped as vdso into shared page.
*/
-NON_GPROF_ENTRY(sigcode)
+ENTRY(__vdso_sigcode)
call *SIGF_HANDLER(%rsp) /* call signal handler */
lea SIGF_UC(%rsp),%rdi /* get ucontext_t */
pushq $0 /* junk to fake return addr. */
@@ -46,11 +43,6 @@ NON_GPROF_ENTRY(sigcode)
syscall /* enter kernel with args */
0: hlt /* trap priviliged instruction */
jmp 0b
+END(__vdso_sigcode)
- ALIGN_TEXT
-esigcode:
-
- .data
- .globl szsigcode
-szsigcode:
- .long esigcode-sigcode
+ .section .note.GNU-stack,"",%progbits
diff --git a/sys/compat/linux/linux_vdso.c b/sys/compat/linux/linux_vdso.c
index a05c0b01ff40..ba828c1b6816 100644
--- a/sys/compat/linux/linux_vdso.c
+++ b/sys/compat/linux/linux_vdso.c
@@ -110,7 +110,7 @@ __elfN(linux_vdso_fixup)(struct sysentvec *sv)
Elf_Shdr *shdr;
int i;
- ehdr = (Elf_Ehdr *) sv->sv_sigcode;
+ ehdr = __DECONST(Elf_Ehdr *, sv->sv_sigcode);
if (!IS_ELF(*ehdr) ||
ehdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
@@ -153,7 +153,7 @@ __elfN(linux_vdso_reloc)(struct sysentvec *sv)
Elf_Sym *sym;
int i, j, symcnt;
- ehdr = (Elf_Ehdr *) sv->sv_sigcode;
+ ehdr = __DECONST(Elf_Ehdr *, sv->sv_sigcode);
/* Adjust our so relative to the sigcode_base */
if (sv->sv_shared_page_base != 0) {
diff --git a/sys/conf/files.amd64 b/sys/conf/files.amd64
index 633d9125398c..f529ffeba7e8 100644
--- a/sys/conf/files.amd64
+++ b/sys/conf/files.amd64
@@ -12,6 +12,12 @@ include "conf/files.x86"
# dependency lines other than the first are silently ignored.
#
#
+elf-vdso.so.o standard \
+ dependency "$S/amd64/amd64/sigtramp.S assym.inc $S/tools/amd64_vdso.sh" \
+ compile-with "env AWK='${AWK}' NM='${NM}' LD='${LD}' CC='${CC}' OBJCOPY='${OBJCOPY}' S='${S}' sh $S/tools/amd64_vdso.sh" \
+ no-implicit-rule before-depend \
+ clean "elf-vdso.so.o elf-vdso.so.1 vdso_offsets.h sigtramp.pico"
+#
cloudabi32_vdso.o optional compat_cloudabi32 \
dependency "$S/contrib/cloudabi/cloudabi_vdso_i686_on_64bit.S" \
compile-with "${CC} -x assembler-with-cpp -m32 -shared -nostdinc -nostdlib -Wl,-T$S/compat/cloudabi/cloudabi_vdso.lds $S/contrib/cloudabi/cloudabi_vdso_i686_on_64bit.S -o ${.TARGET}" \
@@ -124,7 +130,6 @@ amd64/amd64/mpboot.S optional smp
amd64/amd64/pmap.c standard
amd64/amd64/prof_machdep.c optional profiling-routine
amd64/amd64/ptrace_machdep.c standard
-amd64/amd64/sigtramp.S standard
amd64/amd64/support.S standard
amd64/amd64/sys_machdep.c standard
amd64/amd64/trap.c standard
diff --git a/sys/conf/vdso_amd64.ldscript b/sys/conf/vdso_amd64.ldscript
new file mode 100644
index 000000000000..d412abd4cd02
--- /dev/null
+++ b/sys/conf/vdso_amd64.ldscript
@@ -0,0 +1,89 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software was developed by Konstantin Belousov <kib@FreeBSD.org>
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Linker script for amd64 vdso.
+ */
+
+PHDRS
+{
+ text PT_LOAD FILEHDR PHDRS FLAGS(5); /* PF_R|PF_X */
+ dynamic PT_DYNAMIC FLAGS(5);
+ eh_frame_hdr PT_GNU_EH_FRAME FLAGS(5);
+}
+
+SECTIONS
+{
+ . = . + SIZEOF_HEADERS;
+
+ .hash : { *(.hash) } :text
+ .gnu.hash : { *(.gnu.hash) } :text
+ .dynsym : { *(.dynsym) } :text
+ .dynstr : { *(.dynstr) } :text
+ .gnu.version : { *(.gnu.version) } :text
+ .gnu.version_d : { *(.gnu.version_d) } :text
+ .gnu.version_r : { *(.gnu.version_r) } :text
+ .eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
+ .eh_frame : { KEEP (*(.eh_frame)) } :text
+ .dynamic : { *(.dynamic) } :text :dynamic
+ .rodata : { *(.rodata*) } :text
+ .data : {
+ *(.got.plt) *(.got)
+ } :text
+ /DISCARD/ /* .data */: {
+ *(.data*)
+ *(.sdata*)
+ *(.gnu.linkonce.d.*)
+ *(.bss*)
+ *(.dynbss*)
+ *(.gnu.linkonce.b.*)
+ *(.ctors)
+ *(.dtors)
+ *(.jcr)
+ *(.init_array)
+ *(.init)
+ *(.fini)
+ *(.debug*)
+ *(.comment)
+ }
+
+ . = ALIGN(0x10);
+ .text : { *(.text .text*) } :text =0x90909090
+}
+
+VERSION
+{
+ FBSD_1.7 {
+ global:
+ __vdso_sigcode;
+ local:
+ *;
+ };
+}
diff --git a/sys/kern/kern_proc.c b/sys/kern/kern_proc.c
index 21af09265dd2..dc3068c29514 100644
--- a/sys/kern/kern_proc.c
+++ b/sys/kern/kern_proc.c
@@ -3100,7 +3100,9 @@ sysctl_kern_proc_sigtramp(SYSCTL_HANDLER_ARGS)
if (sv->sv_sigcode_base != 0) {
kst32.ksigtramp_start = sv->sv_sigcode_base;
kst32.ksigtramp_end = sv->sv_sigcode_base +
- *sv->sv_szsigcode;
+ ((sv->sv_flags & SV_DSO_SIG) == 0 ?
+ *sv->sv_szsigcode :
+ (uintptr_t)sv->sv_szsigcode);
} else {
kst32.ksigtramp_start = sv->sv_psstrings -
*sv->sv_szsigcode;
@@ -3116,7 +3118,8 @@ sysctl_kern_proc_sigtramp(SYSCTL_HANDLER_ARGS)
if (sv->sv_sigcode_base != 0) {
kst.ksigtramp_start = (char *)sv->sv_sigcode_base;
kst.ksigtramp_end = (char *)sv->sv_sigcode_base +
- *sv->sv_szsigcode;
+ ((sv->sv_flags & SV_DSO_SIG) == 0 ? *sv->sv_szsigcode :
+ (uintptr_t)sv->sv_szsigcode);
} else {
kst.ksigtramp_start = (char *)sv->sv_psstrings -
*sv->sv_szsigcode;
diff --git a/sys/kern/kern_sharedpage.c b/sys/kern/kern_sharedpage.c
index e47fbbe62bb7..98f7b619e0b7 100644
--- a/sys/kern/kern_sharedpage.c
+++ b/sys/kern/kern_sharedpage.c
@@ -305,10 +305,12 @@ void
exec_sysvec_init(void *param)
{
struct sysentvec *sv;
+ vm_offset_t sb;
#ifdef RANDOM_FENESTRASX
ptrdiff_t base;
#endif
u_int flags;
+ int res;
sv = param;
flags = sv->sv_flags;
@@ -319,8 +321,20 @@ exec_sysvec_init(void *param)
sv->sv_shared_page_obj = shared_page_obj;
if ((flags & SV_ABI_MASK) == SV_ABI_FREEBSD) {
- sv->sv_sigcode_base = sv->sv_shared_page_base +
- shared_page_fill(*(sv->sv_szsigcode), 16, sv->sv_sigcode);
+ if ((flags & SV_DSO_SIG) != 0) {
+ sb = sv->sv_shared_page_base;
+ res = shared_page_fill((uintptr_t)sv->sv_szsigcode,
+ 16, sv->sv_sigcode);
+ if (res == -1)
+ panic("copying sigtramp to shared page");
+ sb += res;
+ sb += sv->sv_sigcodeoff;
+ sv->sv_sigcode_base = sb;
+ } else {
+ sv->sv_sigcode_base = sv->sv_shared_page_base +
+ shared_page_fill(*(sv->sv_szsigcode), 16,
+ sv->sv_sigcode);
+ }
}
if ((flags & SV_TIMEKEEP) != 0) {
#ifdef COMPAT_FREEBSD32
diff --git a/sys/sys/sysent.h b/sys/sys/sysent.h
index d95ea5cd9038..cc3f183ff7cd 100644
--- a/sys/sys/sysent.h
+++ b/sys/sys/sysent.h
@@ -108,8 +108,9 @@ struct sysentvec {
/* stack fixup function */
void (*sv_sendsig)(void (*)(int), struct ksiginfo *, struct __sigset *);
/* send signal */
- char *sv_sigcode; /* start of sigtramp code */
+ const char *sv_sigcode; /* start of sigtramp code */
int *sv_szsigcode; /* size of sigtramp code */
+ int sv_sigcodeoff;
char *sv_name; /* name of binary type */
int (*sv_coredump)(struct thread *, struct vnode *, off_t, int);
/* function to dump core, or NULL */
@@ -164,6 +165,7 @@ struct sysentvec {
#define SV_RNG_SEED_VER 0x100000 /* random(4) reseed generation. */
#define SV_SIG_DISCIGN 0x200000 /* Do not discard ignored signals */
#define SV_SIG_WAITNDQ 0x400000 /* Wait does not dequeue SIGCHLD */
+#define SV_DSO_SIG 0x800000 /* Signal trampoline packed in dso */
#define SV_ABI_MASK 0xff
#define SV_PROC_FLAG(p, x) ((p)->p_sysent->sv_flags & (x))
diff --git a/sys/tools/amd64_vdso.sh b/sys/tools/amd64_vdso.sh
new file mode 100644
index 000000000000..39406eccd2ef
--- /dev/null
+++ b/sys/tools/amd64_vdso.sh
@@ -0,0 +1,59 @@
+#!/bin/sh
+# SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+#
+# Copyright (c) 2021 The FreeBSD Foundation
+# All rights reserved.
+#
+# This software was developed by Konstantin Belousov <kib@FreeBSD.org>
+# under sponsorship from the FreeBSD Foundation.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+set -e
+
+${CC} -x assembler-with-cpp -DLOCORE -fPIC -nostdinc -c \
+ -o sigtramp.pico -I. -I"${S}" -include opt_global.h \
+ "${S}"/amd64/amd64/sigtramp.S
+
+# We need to make vdso as compact as possible, for it to leave space
+# for other things in the shared page. For this, we pack everything
+# into single loadable segment.
+#
+# -z rodynamic is undocumented lld-specific option, seemingly required
+# for lld to avoid putting dynamic into dedicated writeable segment,
+# despite ldscript placement. It is ignored by ld.bfd but ldscript
+# alone is enough there.
+#
+${LD} --shared -Bsymbolic -soname="elf-vdso.so.1" \
+ -T "${S}"/conf/vdso_amd64.ldscript \
+ --eh-frame-hdr --no-undefined -z rodynamic -z norelro -nmagic \
+ --hash-style=sysv --fatal-warnings --strip-all \
+ -o elf-vdso.so.1 sigtramp.pico
+
+${CC} -x assembler-with-cpp -DLOCORE -fPIC -nostdinc -c \
+ -o elf-vdso.so.o -I. -I"${S}" -include opt_global.h \
+ -DVDSO_NAME=elf_vdso_so_1 -DVDSO_FILE=elf-vdso.so.1 \
+ "${S}"/tools/vdso_wrap.S
+
+${NM} -D elf-vdso.so.1 | \
+ awk '/__vdso_sigcode/{printf "#define VDSO_SIGCODE_OFFSET 0x%s\n",$1}' \
+ >vdso_offsets.h
diff --git a/sys/tools/vdso_wrap.S b/sys/tools/vdso_wrap.S
new file mode 100644
index 000000000000..807dcf9c06f4
--- /dev/null
+++ b/sys/tools/vdso_wrap.S
@@ -0,0 +1,48 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software was developed by Konstantin Belousov <kib@FreeBSD.org>
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+
+#define VDSO_BLOB_START(S) __CONCAT(_binary_, __CONCAT(S, _start))
+#define VDSO_BLOB_END(S) __CONCAT(_binary_, __CONCAT(S, _end))
+#define VDSO_BLOB_SIZE(S) __CONCAT(_binary_, __CONCAT(S, _size))
+
+ .section .rodata, "a", %progbits
+ .globl VDSO_BLOB_START(VDSO_NAME)
+ .type VDSO_BLOB_START(VDSO_NAME), %object
+ .size VDSO_BLOB_START(VDSO_NAME), 0
+VDSO_BLOB_START(VDSO_NAME):
+ .incbin __XSTRING(VDSO_FILE)
+ .globl VDSO_BLOB_END(VDSO_NAME)
+ .type VDSO_BLOB_END(VDSO_NAME), %object
+ .size VDSO_BLOB_END(VDSO_NAME), 0
+VDSO_BLOB_END(VDSO_NAME):
+ .globl VDSO_BLOB_SIZE(VDSO_NAME)
+ .set VDSO_BLOB_SIZE(VDSO_NAME), . - VDSO_BLOB_START(VDSO_NAME)