[PATCH v2 00/28] Unify vDSOs across more architectures

Vincenzo Frascino
2018-11-29T17:06:48Z

vDSO (virtual dynamic shared object) is a mechanism that the Linux
kernel provides as an alternative to system calls to reduce where
possible the costs in terms of cycles.
This is possible because certain syscalls like gettimeofday() do
not write any data and return one or more values that are stored
in the kernel, which makes relatively safe calling them directly
as a library function.

Even if the mechanism is pretty much standard, every architecture
in the last few years ended up implementing their own vDSO library
in the architectural code.

The purpose of this patch-set is to identify the commonalities in
between the architectures and try to consolidate the common code
paths, starting with gettimeofday().

This implementation contains the following design choices:
* Every architecture defines the arch specific code in an header in
"asm/vdso/".
* The generic implementation includes the arch specific one and lives
in "lib/vdso".
* The arch specific code for gettimeofday lives in
"<arch path>/vdso/gettimeofday.c" and includes the generic code only.
* This approach allows to consolidate the common code in a single place
with the benefit of avoiding code duplication.

This implementation contains the portings to the common library for: arm64,
compat mode for arm64, arm and mips.

The mips porting has been tested on qemu for mips32el. A configuration to
repeat the tests can be found at [4].

Last but not least from this porting arm64, compat arm64, arm and mips gain
the support for:
* CLOCK_BOOTTIME that can be useful in certain scenarios since it keeps
track of the time during sleep as well.
* CLOCK_TAI that is like CLOCK_REALTIME, but uses the International
Atomic Time (TAI) reference instead of UTC to avoid jumping on leap
second updates.
for both clock_gettime and clock_getres.

The porting has been validated using the vdsotest test-suite [1] extended
to cover all the clock ids [2].

To simplify the testing, a copy of the patchset on top of a recent linux tree
can be found at [3].

[1] https://github.com/nlynch-mentor/vdsotest
[2] https://github.com/fvincenzo/vdsotest
[3] git://linux-arm.org/linux-vf.git vdso/v2
[4] git://linux-arm.org/linux-vf.git vdso-mips/v2

Changes:
--------
v2:
- Added -ffixed-x18 to arm64
- Repleced occurrences of timeval and timespec
- Modified datapage.h to be compliant with y2038 on all the architectures
- Removed __u_vdso type

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

Peter Collingbourne (1):
arm64: Build vDSO with -ffixed-x18

Vincenzo Frascino (27):
kernel: Standardize vdso_datapage
kernel: Add Monotonic boot time support
kernel: Add International Atomic Time support
kernel: Add masks support for Raw and NTP time
kernel: Add clock_mode support
kernel: Define gettimeofday vdso common code
arm64: Substitute gettimeofday with C implementation
arm64: compat: Alloc separate pages for vectors and sigpage
arm64: compat: Split kuser32
arm64: compat: Refactor aarch32_alloc_vdso_pages()
arm64: compat: Add KUSER_HELPERS config option
arm64: compat: Add missing syscall numbers
arm64: compat: Expose signal related structures
arm64: compat: Generate asm offsets for signals
lib: vdso: Add compat support
arm64: compat: Add vDSO
arm64: Refactor vDSO code
arm64: compat: vDSO setup for compat layer
arm64: elf: vDSO code page discovery
arm64: compat: Get sigreturn trampolines from vDSO
arm64: Add vDSO compat support
arm64: Enable compat vDSO support
arm: Add support for generic vDSO
mips: Introduce vdso_direct
clock: csrc-4k: Add support for vdso_direct
clock: gic-timer: Add support for vdso_direct
mips: Add support for generic vDSO

arch/arm/Kconfig | 4 +
arch/arm/include/asm/vdso/gettimeofday.h | 82 ++++
arch/arm/include/asm/vdso_datapage.h | 25 +-
arch/arm/kernel/vdso.c | 28 +-
arch/arm/vdso/Makefile | 13 +-
arch/arm/vdso/note.c | 15 +
arch/arm/vdso/vdso.lds.S | 1 +
arch/arm/vdso/vgettimeofday.c | 267 +----------
arch/arm64/Kconfig | 25 +
arch/arm64/Makefile | 21 +-
arch/arm64/configs/defconfig | 1 +
arch/arm64/include/asm/elf.h | 20 +-
arch/arm64/include/asm/processor.h | 4 +-
arch/arm64/include/asm/signal32.h | 58 ++-
arch/arm64/include/asm/unistd.h | 3 +
arch/arm64/include/asm/vdso.h | 3 +
arch/arm64/include/asm/vdso/compat_barrier.h | 36 ++
.../include/asm/vdso/compat_gettimeofday.h | 111 +++++
arch/arm64/include/asm/vdso/gettimeofday.h | 85 ++++
arch/arm64/kernel/Makefile | 7 +-
arch/arm64/kernel/asm-offsets.c | 13 +-
arch/arm64/kernel/kuser32.S | 65 +--
arch/arm64/kernel/signal32.c | 76 ++-
arch/arm64/kernel/sigreturn32.S | 46 ++
arch/arm64/kernel/vdso.c | 413 +++++++++++++----
arch/arm64/kernel/vdso/Makefile | 28 +-
arch/arm64/kernel/vdso/gettimeofday.S | 328 -------------
arch/arm64/kernel/vdso/vgettimeofday.c | 28 ++
arch/arm64/kernel/vdso32/.gitignore | 2 +
arch/arm64/kernel/vdso32/Makefile | 184 ++++++++
arch/arm64/kernel/vdso32/note.c | 15 +
arch/arm64/kernel/vdso32/sigreturn.S | 62 +++
arch/arm64/kernel/vdso32/vdso.S | 19 +
arch/arm64/kernel/vdso32/vdso.lds.S | 81 ++++
arch/arm64/kernel/vdso32/vgettimeofday.c | 41 ++
arch/mips/Kconfig | 3 +
arch/mips/include/asm/clocksource.h | 1 +
arch/mips/include/asm/vdso.h | 53 +--
arch/mips/include/asm/vdso/gettimeofday.h | 165 +++++++
arch/mips/{ => include/asm}/vdso/vdso.h | 6 +-
arch/mips/kernel/csrc-r4k.c | 4 +-
arch/mips/kernel/vdso.c | 56 ++-
arch/mips/vdso/Makefile | 23 +-
arch/mips/vdso/elf.S | 2 +-
arch/mips/vdso/gettimeofday.c | 273 -----------
arch/mips/vdso/sigreturn.S | 2 +-
arch/mips/vdso/vdso.lds.S | 1 +
arch/mips/vdso/vgettimeofday.c | 28 ++
drivers/clocksource/mips-gic-timer.c | 5 +-
.../vdso/datapage.h | 15 +-
include/vdso/types.h | 39 ++
lib/Kconfig | 5 +
lib/vdso/Kconfig | 41 ++
lib/vdso/Makefile | 22 +
lib/vdso/gettimeofday.c | 432 ++++++++++++++++++
55 files changed, 2192 insertions(+), 1194 deletions(-)
create mode 100644 arch/arm/include/asm/vdso/gettimeofday.h
create mode 100644 arch/arm/vdso/note.c
create mode 100644 arch/arm64/include/asm/vdso/compat_barrier.h
create mode 100644 arch/arm64/include/asm/vdso/compat_gettimeofday.h
create mode 100644 arch/arm64/include/asm/vdso/gettimeofday.h
create mode 100644 arch/arm64/kernel/sigreturn32.S
delete mode 100644 arch/arm64/kernel/vdso/gettimeofday.S
create mode 100644 arch/arm64/kernel/vdso/vgettimeofday.c
create mode 100644 arch/arm64/kernel/vdso32/.gitignore
create mode 100644 arch/arm64/kernel/vdso32/Makefile
create mode 100644 arch/arm64/kernel/vdso32/note.c
create mode 100644 arch/arm64/kernel/vdso32/sigreturn.S
create mode 100644 arch/arm64/kernel/vdso32/vdso.S
create mode 100644 arch/arm64/kernel/vdso32/vdso.lds.S
create mode 100644 arch/arm64/kernel/vdso32/vgettimeofday.c
create mode 100644 arch/mips/include/asm/vdso/gettimeofday.h
rename arch/mips/{ => include/asm}/vdso/vdso.h (90%)
delete mode 100644 arch/mips/vdso/gettimeofday.c
create mode 100644 arch/mips/vdso/vgettimeofday.c
rename arch/arm64/include/asm/vdso_datapage.h => include/vdso/datapage.h (79%)
create mode 100644 include/vdso/types.h
create mode 100644 lib/vdso/Kconfig
create mode 100644 lib/vdso/Makefile
create mode 100644 lib/vdso/gettimeofday.c