From: Dmitry Safonov <dima@arista.com>
To: linux-kernel@vger.kernel.org
Cc: Dmitry Safonov <dima@arista.com>, Adrian Reber <adrian@lisas.de>,
Andrei Vagin <avagin@openvz.org>, Andrei Vagin <avagin@gmail.com>,
Andy Lutomirski <luto@kernel.org>,
Andy Tucker <agtucker@google.com>, Arnd Bergmann <arnd@arndb.de>,
Christian Brauner <christian.brauner@ubuntu.com>,
Cyrill Gorcunov <gorcunov@openvz.org>,
Dmitry Safonov <0x7f454c46@gmail.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Jeff Dike <jdike@addtoit.com>, Oleg Nesterov <oleg@redhat.com>,
Pavel Emelyanov <xemul@virtuozzo.com>,
Shuah Khan <shuah@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
containers@lists.linux-foundation.org, criu@openvz.org,
linux-api@vger.kernel.org, x86@kernel.org
Subject: [PATCH 14/32] x86/VDSO: Build VDSO with -ffunction-sections
Date: Wed, 6 Feb 2019 00:10:48 +0000 [thread overview]
Message-ID: <20190206001107.16488-15-dima@arista.com> (raw)
In-Reply-To: <20190206001107.16488-1-dima@arista.com>
As it has been discussed on timens RFC, adding a new conditional branch
`if (inside_time_ns)` on VDSO for all processes is undesirable.
It will add a penalty for everybody as branch predictor may mispredict
the jump. Also there are instruction cache lines wasted on cmp/jmp.
Those effects of introducing time namespace are very much unwanted
having in mind how much work have been spent on micro-optimisation
vdso code.
Addressing those problems, there are two versions of VDSO's .so:
for host tasks (without any penalty) and for processes inside of time
namespace with clk_to_ns() that subtracts offsets from host's time.
Unfortunately, to allow changing VDSO VMA on a running process,
the entry points to VDSO should have the same offsets (addresses).
That's needed as i.e. application that calls setns() may have already
resolved VDSO symbols in GOT/PLT.
Compile VDSO images with -ffunction-sections so that VDSO entries can be
aligned on the same addresses with linker script magic.
Put ia32 functions those are written in assembly into corresponding
sections.
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
arch/x86/entry/vdso/Makefile | 2 +-
arch/x86/entry/vdso/vdso32/sigreturn.S | 2 ++
arch/x86/entry/vdso/vdso32/system_call.S | 2 +-
3 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 2433ed9342fd..55ba81d4415c 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -3,7 +3,7 @@
# Building vDSO images for x86.
#
-KBUILD_CFLAGS += $(DISABLE_LTO)
+KBUILD_CFLAGS += $(DISABLE_LTO) -ffunction-sections
KASAN_SANITIZE := n
UBSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y
diff --git a/arch/x86/entry/vdso/vdso32/sigreturn.S b/arch/x86/entry/vdso/vdso32/sigreturn.S
index c3233ee98a6b..b641ccf8d664 100644
--- a/arch/x86/entry/vdso/vdso32/sigreturn.S
+++ b/arch/x86/entry/vdso/vdso32/sigreturn.S
@@ -11,6 +11,7 @@
.globl __kernel_sigreturn
.type __kernel_sigreturn,@function
nop /* this guy is needed for .LSTARTFDEDLSI1 below (watch for HACK) */
+ .section .text.__kernel_sigreturn, "ax"
ALIGN
__kernel_sigreturn:
.LSTART_sigreturn:
@@ -21,6 +22,7 @@ __kernel_sigreturn:
nop
.size __kernel_sigreturn,.-.LSTART_sigreturn
+ .section .text.__kernel_rt_sigreturn, "ax"
.globl __kernel_rt_sigreturn
.type __kernel_rt_sigreturn,@function
ALIGN
diff --git a/arch/x86/entry/vdso/vdso32/system_call.S b/arch/x86/entry/vdso/vdso32/system_call.S
index 263d7433dea8..13ec05287f63 100644
--- a/arch/x86/entry/vdso/vdso32/system_call.S
+++ b/arch/x86/entry/vdso/vdso32/system_call.S
@@ -8,7 +8,7 @@
#include <asm/cpufeatures.h>
#include <asm/alternative-asm.h>
- .text
+ .section .text.__kernel_vsyscall, "ax"
.globl __kernel_vsyscall
.type __kernel_vsyscall,@function
ALIGN
--
2.20.1
next prev parent reply other threads:[~2019-02-06 0:11 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-06 0:10 [PATCH 00/32] kernel: Introduce Time Namespace Dmitry Safonov
2019-02-06 0:10 ` [PATCH 01/32] ns: " Dmitry Safonov
2019-02-06 0:10 ` [PATCH 02/32] timens: Add timens_offsets Dmitry Safonov
2019-02-06 0:10 ` [PATCH 03/32] timens: Introduce CLOCK_MONOTONIC offsets Dmitry Safonov
2019-02-07 21:40 ` Thomas Gleixner
2019-02-08 9:02 ` Andrei Vagin
2019-02-08 9:46 ` Thomas Gleixner
2019-02-06 0:10 ` [PATCH 04/32] timens: Introduce CLOCK_BOOTTIME offset Dmitry Safonov
2019-02-06 0:10 ` [PATCH 05/32] timerfd/timens: Take into account ns clock offsets Dmitry Safonov
2019-02-06 8:52 ` Cyrill Gorcunov
2019-02-06 8:55 ` Cyrill Gorcunov
2019-02-07 6:38 ` Andrei Vagin
2019-02-06 0:10 ` [PATCH 06/32] posix-timers/timens: Take into account " Dmitry Safonov
2019-02-06 0:10 ` [PATCH 07/32] timens/kernel: Take into account timens clock offsets in clock_nanosleep Dmitry Safonov
2019-02-08 7:56 ` Thomas Gleixner
2019-02-06 0:10 ` [PATCH 08/32] timens: Shift /proc/uptime Dmitry Safonov
2019-02-06 0:10 ` [PATCH 09/32] x86/vdso2c: Correct err messages on file opening Dmitry Safonov
2019-02-06 0:10 ` [PATCH 10/32] x86/vdso2c: Convert iterator to unsigned Dmitry Safonov
2019-02-06 0:10 ` [PATCH 11/32] x86/vdso/Makefile: Add vobjs32 Dmitry Safonov
2019-02-06 0:10 ` [PATCH 12/32] x86/vdso/timens: Add offsets page in vvar Dmitry Safonov
2019-02-06 0:10 ` [PATCH 13/32] x86/vdso: Build timens .so(s) Dmitry Safonov
2019-02-06 0:10 ` Dmitry Safonov [this message]
2019-02-06 0:10 ` [PATCH 15/32] x86/vdso2c: Optionally produce linker script for vdso entries Dmitry Safonov
2019-02-06 0:10 ` [PATCH 16/32] x86/vdso: Generate vdso{,32}-timens.lds Dmitry Safonov
2019-02-07 8:31 ` Rasmus Villemoes
2019-02-07 16:11 ` Dmitry Safonov
2019-02-08 9:57 ` Thomas Gleixner
2019-02-08 15:18 ` Dmitry Safonov
2019-03-27 18:00 ` Andrei Vagin
2019-03-27 18:06 ` [PATCH RFC] x86/asm: Introduce static_retcall(s) Andrei Vagin
2019-03-27 18:06 ` [PATCH RFC] vdso: introduce timens_static_branch Andrei Vagin
2019-02-06 0:10 ` [PATCH 17/32] x86/vdso2c: Sort vdso entries by addresses for linker script Dmitry Safonov
2019-02-06 0:10 ` [PATCH 18/32] x86/vdso.lds: Align !timens (host's) vdso.so entries Dmitry Safonov
2019-02-06 0:10 ` [PATCH 19/32] x86/vdso2c: Align LOCAL symbols between vdso{-timens,}.so Dmitry Safonov
2019-02-06 0:10 ` [PATCH 20/32] x86/vdso: Initialize timens 64-bit vdso Dmitry Safonov
2019-02-06 0:10 ` [PATCH 21/32] x86/vdso: Switch image on setns()/unshare()/clone() Dmitry Safonov
2019-02-06 0:10 ` [PATCH 22/32] timens: Add align for timens_offsets Dmitry Safonov
2019-02-06 0:10 ` [PATCH 23/32] timens/fs/proc: Introduce /proc/pid/timens_offsets Dmitry Safonov
2019-02-06 0:10 ` [PATCH 24/32] selftest/timens: Add Time Namespace test for supported clocks Dmitry Safonov
2019-02-06 0:10 ` [PATCH 25/32] selftest/timens: Add a test for timerfd Dmitry Safonov
2019-02-06 0:11 ` [PATCH 26/32] selftest/timens: Add a test for clock_nanosleep() Dmitry Safonov
2019-02-06 0:11 ` [PATCH 27/32] selftest/timens: Add procfs selftest Dmitry Safonov
2019-02-06 0:11 ` [PATCH 28/32] selftest/timens: Add timer offsets test Dmitry Safonov
2019-02-06 0:11 ` [PATCH 29/32] selftests: Add a simple perf test for clock_gettime() Dmitry Safonov
2019-02-06 0:11 ` [PATCH 30/32] selftest/timens: Check that a right vdso is mapped after fork and exec Dmitry Safonov
2019-02-06 0:11 ` [PATCH 31/32] x86/vdso: Align VDSO functions by CPU L1 cache line Dmitry Safonov
2019-02-06 0:11 ` [PATCH 32/32] x86/vdso: Restrict splitting VVAR VMA Dmitry Safonov
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