From: Dmitry Safonov <dima@arista.com>
To: linux-kernel@vger.kernel.org
Cc: Andrei Vagin <avagin@gmail.com>, Dmitry Safonov <dima@arista.com>,
Adrian Reber <adrian@lisas.de>, Andrei Vagin <avagin@openvz.org>,
Andy Lutomirski <luto@kernel.org>, 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>,
Jann Horn <jannh@google.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>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
containers@lists.linux-foundation.org, criu@openvz.org,
linux-api@vger.kernel.org, x86@kernel.org
Subject: [PATCHv4 18/28] vdso: introduce timens_static_branch
Date: Wed, 12 Jun 2019 20:26:17 +0100 [thread overview]
Message-ID: <20190612192628.23797-19-dima@arista.com> (raw)
In-Reply-To: <20190612192628.23797-1-dima@arista.com>
From: Andrei Vagin <avagin@gmail.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.
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.
This patch introduces timens_static_branch(), which is similar with
static_branch_unlikely.
The timens code in vdso looks like this:
if (timens_static_branch()) {
clk_to_ns(clk, ts);
}
The version of vdso which is compiled from sources will never execute
clk_to_ns(). And then we can patch the 'no-op' in the straight-line
codepath with a 'jump' instruction to the out-of-line true branch and
get the timens version of the vdso library.
While cooking the patch, an alternative approach has being considered:
to omit no-ops - memcpy() the following asm ret sequience on the place of
a function call: https://github.com/0x7f454c46/linux/commit/4cc0180f6d65
Having in mind possible issues with different toolchains, the usual
static_branch() approach was choosen.
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Co-developed-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
arch/x86/entry/vdso/vclock_gettime.c | 9 +++++--
arch/x86/entry/vdso/vdso-layout.lds.S | 1 +
arch/x86/entry/vdso/vdso2c.h | 11 +++++++-
arch/x86/entry/vdso/vma.c | 37 ++++++++++++++++++++++-----
arch/x86/include/asm/jump_label.h | 14 ++++++++++
arch/x86/include/asm/vdso.h | 1 +
include/linux/jump_label.h | 5 ++++
7 files changed, 69 insertions(+), 9 deletions(-)
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index e2d93628c0dd..21b7153cf2b0 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -18,6 +18,7 @@
#include <asm/msr.h>
#include <asm/pvclock.h>
#include <asm/mshyperv.h>
+#include <asm/jump_label.h>
#include <linux/math64.h>
#include <linux/time.h>
#include <linux/kernel.h>
@@ -174,8 +175,10 @@ notrace static __always_inline void clk_to_ns(clockid_t clk, struct timespec *ts
ts->tv_sec--;
}
}
+#define _timens_static_branch_unlikely timens_static_branch_unlikely
#else
notrace static __always_inline void clk_to_ns(clockid_t clk, struct timespec *ts) {}
+notrace static __always_inline bool _timens_static_branch_unlikely(void) { return false; }
#endif
notrace static int do_hres(clockid_t clk, struct timespec *ts)
@@ -204,7 +207,8 @@ notrace static int do_hres(clockid_t clk, struct timespec *ts)
ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
ts->tv_nsec = ns;
- clk_to_ns(clk, ts);
+ if (_timens_static_branch_unlikely())
+ clk_to_ns(clk, ts);
return 0;
}
@@ -220,7 +224,8 @@ notrace static void do_coarse(clockid_t clk, struct timespec *ts)
ts->tv_nsec = base->nsec;
} while (unlikely(gtod_read_retry(gtod, seq)));
- clk_to_ns(clk, ts);
+ if (_timens_static_branch_unlikely())
+ clk_to_ns(clk, ts);
}
notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
diff --git a/arch/x86/entry/vdso/vdso-layout.lds.S b/arch/x86/entry/vdso/vdso-layout.lds.S
index ba216527e59f..69dbe4821aa5 100644
--- a/arch/x86/entry/vdso/vdso-layout.lds.S
+++ b/arch/x86/entry/vdso/vdso-layout.lds.S
@@ -45,6 +45,7 @@ SECTIONS
.gnu.version : { *(.gnu.version) }
.gnu.version_d : { *(.gnu.version_d) }
.gnu.version_r : { *(.gnu.version_r) }
+ __jump_table : { *(__jump_table) } :text
.dynamic : { *(.dynamic) } :text :dynamic
diff --git a/arch/x86/entry/vdso/vdso2c.h b/arch/x86/entry/vdso/vdso2c.h
index 885b988aea19..392031258315 100644
--- a/arch/x86/entry/vdso/vdso2c.h
+++ b/arch/x86/entry/vdso/vdso2c.h
@@ -16,7 +16,7 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
unsigned int i, syms_nr;
unsigned long j;
ELF(Shdr) *symtab_hdr = NULL, *strtab_hdr, *secstrings_hdr,
- *alt_sec = NULL;
+ *alt_sec = NULL, *jump_table_sec = NULL;
ELF(Dyn) *dyn = 0, *dyn_end = 0;
const char *secstrings;
INT_BITS syms[NSYMS] = {};
@@ -78,6 +78,9 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
if (!strcmp(secstrings + GET_LE(&sh->sh_name),
".altinstructions"))
alt_sec = sh;
+ if (!strcmp(secstrings + GET_LE(&sh->sh_name),
+ "__jump_table"))
+ jump_table_sec = sh;
}
if (!symtab_hdr)
@@ -166,6 +169,12 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
fprintf(outfile, "\t.alt_len = %lu,\n",
(unsigned long)GET_LE(&alt_sec->sh_size));
}
+ if (jump_table_sec) {
+ fprintf(outfile, "\t.jump_table = %lu,\n",
+ (unsigned long)GET_LE(&jump_table_sec->sh_offset));
+ fprintf(outfile, "\t.jump_table_len = %lu,\n",
+ (unsigned long)GET_LE(&jump_table_sec->sh_size));
+ }
for (i = 0; i < NSYMS; i++) {
if (required_syms[i].export && syms[i])
fprintf(outfile, "\t.sym_%s = %" PRIi64 ",\n",
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 3ed5bf4932af..12cf73aa0aec 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -15,6 +15,7 @@
#include <linux/cpu.h>
#include <linux/ptrace.h>
#include <linux/time_namespace.h>
+#include <linux/jump_label.h>
#include <asm/pvclock.h>
#include <asm/vgtod.h>
#include <asm/proto.h>
@@ -31,20 +32,44 @@
unsigned int __read_mostly vdso64_enabled = 1;
#endif
-void __init init_vdso_image(struct vdso_image *image)
+#ifdef CONFIG_TIME_NS
+static __init void apply_jump_tables(struct vdso_jump_entry *ent, unsigned long nr)
{
- BUG_ON(image->size % PAGE_SIZE != 0);
+ while (nr--) {
+ void *code_addr = (void *)ent + ent->code;
+ long target_addr = (long) ent->target - (ent->code + JUMP_LABEL_NOP_SIZE);
+ ((char *)code_addr)[0] = 0xe9; /* JMP rel32 */
+ *((long *)(code_addr + 1)) = (long)target_addr;
+
+ ent++;
+ }
+}
+
+static __init void init_timens(struct vdso_image *image)
+{
+ struct vdso_jump_entry *entries;
- apply_alternatives((struct alt_instr *)(image->text + image->alt),
- (struct alt_instr *)(image->text + image->alt +
- image->alt_len));
-#ifdef CONFIG_TIME_NS
image->text_timens = vmalloc_32(image->size);
if (WARN_ON(image->text_timens == NULL))
return;
memcpy(image->text_timens, image->text, image->size);
+
+ entries = image->text_timens + image->jump_table;
+ apply_jump_tables(entries, image->jump_table_len / sizeof(struct vdso_jump_entry));
+}
+#else
+static inline void init_timens(struct vdso_image *image) {}
#endif
+
+void __init init_vdso_image(struct vdso_image *image)
+{
+ BUG_ON(image->size % PAGE_SIZE != 0);
+
+ apply_alternatives((struct alt_instr *)(image->text + image->alt),
+ (struct alt_instr *)(image->text + image->alt +
+ image->alt_len));
+ init_timens(image);
}
struct linux_binprm;
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index 65191ce8e1cf..1784aa49cc82 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -51,6 +51,20 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool
return true;
}
+static __always_inline bool timens_static_branch_unlikely(void)
+{
+ asm_volatile_goto("1:\n\t"
+ ".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t"
+ ".pushsection __jump_table, \"aw\"\n\t"
+ "2: .word 1b - 2b, %l[l_yes] - 2b\n\t"
+ ".popsection\n\t"
+ : : : : l_yes);
+
+ return false;
+l_yes:
+ return true;
+}
+
#else /* __ASSEMBLY__ */
.macro STATIC_JUMP_IF_TRUE target, key, def
diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
index ccf89dedd04f..5e83bd3cda22 100644
--- a/arch/x86/include/asm/vdso.h
+++ b/arch/x86/include/asm/vdso.h
@@ -16,6 +16,7 @@ struct vdso_image {
unsigned long size; /* Always a multiple of PAGE_SIZE */
unsigned long alt, alt_len;
+ unsigned long jump_table, jump_table_len;
long sym_vvar_start; /* Negative offset to the vvar area */
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 3e113a1fa0f1..69854a05d2f2 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -125,6 +125,11 @@ struct jump_entry {
long key; // key may be far away from the core kernel under KASLR
};
+struct vdso_jump_entry {
+ u16 code;
+ u16 target;
+};
+
static inline unsigned long jump_entry_code(const struct jump_entry *entry)
{
return (unsigned long)&entry->code + entry->code;
--
2.22.0
next prev parent reply other threads:[~2019-06-12 19:27 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-12 19:25 [PATCHv4 00/28] kernel: Introduce Time Namespace Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 01/28] ns: " Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 02/28] timens: Add timens_offsets Dmitry Safonov
2019-06-14 13:11 ` Thomas Gleixner
2019-06-14 14:32 ` Dmitry Safonov
2019-07-29 22:26 ` Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 03/28] posix-clocks: add another call back to return clock time in ktime_t Dmitry Safonov
2019-06-14 13:32 ` Thomas Gleixner
2019-06-14 14:39 ` Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 04/28] timens: Introduce CLOCK_MONOTONIC offsets Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 05/28] timens: Introduce CLOCK_BOOTTIME offset Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 06/28] timerfd/timens: Take into account ns clock offsets Dmitry Safonov
2019-06-14 13:37 ` Thomas Gleixner
2019-06-16 17:43 ` Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 07/28] posix-timers/timens: Take into account " Dmitry Safonov
2019-06-14 13:42 ` Thomas Gleixner
2019-06-16 17:45 ` Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 08/28] timens/kernel: Take into account timens clock offsets in clock_nanosleep Dmitry Safonov
2019-06-14 13:49 ` Thomas Gleixner
2019-06-12 19:26 ` [PATCHv4 09/28] timens: Shift /proc/uptime Dmitry Safonov
2019-06-14 13:50 ` Thomas Gleixner
2019-06-16 17:48 ` Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 10/28] x86/vdso2c: Correct err messages on file opening Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 11/28] x86/vdso2c: Convert iterator to unsigned Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 12/28] x86/vdso/Makefile: Add vobjs32 Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 13/28] x86/vdso: Restrict splitting VVAR VMA Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 14/28] x86/vdso: Rename vdso_image {.data=>.text} Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 15/28] x86/vdso: Add offsets page in vvar Dmitry Safonov
2019-06-14 13:58 ` Thomas Gleixner
2019-06-16 17:49 ` Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 16/28] x86/vdso: Allocate timens vdso Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 17/28] x86/vdso: Switch image on setns()/unshare()/clone() Dmitry Safonov
2019-06-14 14:05 ` Thomas Gleixner
2019-06-16 17:51 ` Dmitry Safonov
2019-06-12 19:26 ` Dmitry Safonov [this message]
2019-06-12 19:26 ` [PATCHv4 19/28] timens: Add align for timens_offsets Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 20/28] timens/fs/proc: Introduce /proc/pid/timens_offsets Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 21/28] selftest/timens: Add Time Namespace test for supported clocks Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 22/28] selftest/timens: Add a test for timerfd Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 23/28] selftest/timens: Add a test for clock_nanosleep() Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 24/28] selftest/timens: Add procfs selftest Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 25/28] selftest/timens: Add timer offsets test Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 26/28] x86/vdso: Align VDSO functions by CPU L1 cache line Dmitry Safonov
2019-06-14 14:13 ` Thomas Gleixner
2019-06-23 5:26 ` Andrei Vagin
2019-06-12 19:26 ` [PATCHv4 27/28] selftests: Add a simple perf test for clock_gettime() Dmitry Safonov
2019-06-12 19:26 ` [PATCHv4 28/28] selftest/timens: Check that a right vdso is mapped after fork and exec Dmitry Safonov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190612192628.23797-19-dima@arista.com \
--to=dima@arista.com \
--cc=0x7f454c46@gmail.com \
--cc=adrian@lisas.de \
--cc=arnd@arndb.de \
--cc=avagin@gmail.com \
--cc=avagin@openvz.org \
--cc=christian.brauner@ubuntu.com \
--cc=containers@lists.linux-foundation.org \
--cc=criu@openvz.org \
--cc=ebiederm@xmission.com \
--cc=gorcunov@openvz.org \
--cc=hpa@zytor.com \
--cc=jannh@google.com \
--cc=jdike@addtoit.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=oleg@redhat.com \
--cc=shuah@kernel.org \
--cc=tglx@linutronix.de \
--cc=vincenzo.frascino@arm.com \
--cc=x86@kernel.org \
--cc=xemul@virtuozzo.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).