linux-kernel - Re: [PATCHv6 23/36] x86/vdso: Allocate timens vdso

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Date:   Sun, 18 Aug 2019 18:24:18 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dmitry Safonov <0x7f454c46@...il.com>
cc:     Andy Lutomirski <luto@...nel.org>,
        Dmitry Safonov <dima@...sta.com>, linux-kernel@...r.kernel.org,
        Adrian Reber <adrian@...as.de>,
        Andrei Vagin <avagin@...nvz.org>,
        Arnd Bergmann <arnd@...db.de>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jann Horn <jannh@...gle.com>, Jeff Dike <jdike@...toit.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Shuah Khan <shuah@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        containers@...ts.linux-foundation.org, criu@...nvz.org,
        linux-api@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCHv6 23/36] x86/vdso: Allocate timens vdso

On Sun, 18 Aug 2019, Thomas Gleixner wrote:
> 
> Patch below. I tested this with the normal order and by installing a
> 'timens' page unconditionally for all processes. I'll reply with the timens
> testing hacks so you can see what I did.

First hack...

Thanks,

	tglx

8<-----------------

Subject: x86/vdso: Hack to enable time name space  for testing
From: Thomas Gleixner <tglx@...utronix.de>
Date: Sun, 18 Aug 2019 16:42:26 +0200

Select CONFIG_VDSO_TIMENS and prepare for the extra magic time namespace
vvar page. The fault handler is not handling it yet as the path is never
taken (hopefully)

Not-Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/Kconfig                         |    1 +
 arch/x86/entry/vdso/vdso-layout.lds.S    |    3 ++-
 arch/x86/entry/vdso/vdso2c.c             |    3 +++
 arch/x86/include/asm/vdso.h              |    1 +
 arch/x86/include/asm/vdso/gettimeofday.h |    9 +++++++++
 5 files changed, 16 insertions(+), 1 deletion(-)

--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -224,6 +224,7 @@ config X86
 	select VIRT_TO_BUS
 	select X86_FEATURE_NAMES		if PROC_FS
 	select PROC_PID_ARCH_STATUS		if PROC_FS
+	select VDSO_TIMENS
 
 config INSTRUCTION_DECODER
 	def_bool y
--- a/arch/x86/entry/vdso/vdso-layout.lds.S
+++ b/arch/x86/entry/vdso/vdso-layout.lds.S
@@ -16,7 +16,7 @@ SECTIONS
 	 * segment.
 	 */
 
-	vvar_start = . - 3 * PAGE_SIZE;
+	vvar_start = . - 4 * PAGE_SIZE;
 	vvar_page = vvar_start;
 
 	/* Place all vvars at the offsets in asm/vvar.h. */
@@ -28,6 +28,7 @@ SECTIONS
 
 	pvclock_page = vvar_start + PAGE_SIZE;
 	hvclock_page = vvar_start + 2 * PAGE_SIZE;
+	timens_page = vvar_start + 3 * PAGE_SIZE;
 
 	. = SIZEOF_HEADERS;
 
--- a/arch/x86/entry/vdso/vdso2c.c
+++ b/arch/x86/entry/vdso/vdso2c.c
@@ -75,12 +75,14 @@ enum {
 	sym_vvar_page,
 	sym_pvclock_page,
 	sym_hvclock_page,
+	sym_timens_page,
 };
 
 const int special_pages[] = {
 	sym_vvar_page,
 	sym_pvclock_page,
 	sym_hvclock_page,
+	sym_timens_page,
 };
 
 struct vdso_sym {
@@ -93,6 +95,7 @@ struct vdso_sym required_syms[] = {
 	[sym_vvar_page] = {"vvar_page", true},
 	[sym_pvclock_page] = {"pvclock_page", true},
 	[sym_hvclock_page] = {"hvclock_page", true},
+	[sym_timens_page] = {"timens_page", true},
 	{"VDSO32_NOTE_MASK", true},
 	{"__kernel_vsyscall", true},
 	{"__kernel_sigreturn", true},
--- a/arch/x86/include/asm/vdso.h
+++ b/arch/x86/include/asm/vdso.h
@@ -21,6 +21,7 @@ struct vdso_image {
 	long sym_vvar_page;
 	long sym_pvclock_page;
 	long sym_hvclock_page;
+	long sym_timens_page;
 	long sym_VDSO32_NOTE_MASK;
 	long sym___kernel_sigreturn;
 	long sym___kernel_rt_sigreturn;
--- a/arch/x86/include/asm/vdso/gettimeofday.h
+++ b/arch/x86/include/asm/vdso/gettimeofday.h
@@ -265,6 +265,15 @@ static __always_inline const struct vdso
 	return __vdso_data;
 }
 
+/* HACK .... */
+#define VDSO_TIMENS_PAGEOFFSET		(3 * PAGE_SIZE)
+
+static __always_inline
+const struct vdso_data *__arch_get_timens_vdso_data(const struct vdso_data *vd)
+{
+	return (void *)vd + VDSO_TIMENS_PAGEOFFSET;
+}
+
 /*
  * x86 specific delta calculation.
  *