[GIT PULL] fork cleanup for v5.9
From: Christian Brauner
Date: Tue Aug 04 2020 - 07:28:37 EST
Hi Linus,
/* Summary */
This is a series announced some time back (cf. [2]) when we reworked a chunk of
the process creation paths in the kernel and switched to struct
{kernel_}clone_args.
High-level this does two main things:
1. Remove the double export of both do_fork() and _do_fork() where do_fork()
used the incosistent legacy clone calling convention. Now we only export
_do_fork() which is based on struct kernel_clone_args.
2. Remove the copy_thread_tls()/copy_thread() split making the
architecture specific HAVE_COYP_THREAD_TLS config option obsolete.
This switches all remaining architectures to select HAVE_COPY_THREAD_TLS and
thus to the copy_thread_tls() calling convention. The current split makes the
process creation codepaths more convoluted than they need to be. Each
architecture has their own copy_thread() function unless it selects
HAVE_COPY_THREAD_TLS then it has a copy_thread_tls() function. The split is not
needed anymore nowadays, all architectures support CLONE_SETTLS but quite a few
of them never bothered to select HAVE_COPY_THREAD_TLS and instead simply
continued to use copy_thread() and use the old calling convention.
Removing this split cleans up the process creation codepaths and paves the way
for implementing clone3() on such architectures since it requires the
copy_thread_tls() calling convention.
After having made each architectures support copy_thread_tls() this series
simply renames that function back to copy_thread().
It also switches all architectures that call do_fork() directly over to
_do_fork() and the struct kernel_clone_args calling convention. This is a
corollary of switching the architectures that did not yet support it over to
copy_thread_tls() since do_fork() is conditional on not supporting
copy_thread_tls() (Mostly because it lacks a separate argument for tls which is
trivial to fix but there's no need for this function to exist.).
The do_fork() removal is in itself already useful as it allows to to remove the
export of both do_fork() and _do_fork() we currently have in favor of only
_do_fork(). This has already been discussed back when we added clone3(). The
legacy clone() calling convention is - as is probably well-known - somewhat odd
or as Al once put it in arch/Kconfig (cf. [1]):
#
# ABI hall of shame
#
config CLONE_BACKWARDS
config CLONE_BACKWARDS2
config CLONE_BACKWARDS3
that is aggravated by the fact that some architectures such as sparc follow the
CLONE_BACKWARDSx calling convention but don't really select the corresponding
config option since they call do_fork() directly.
So do_fork() enforces a somewhat arbitrary calling convention in the first place
that doesn't really help the individual architectures that deviate from it. They
can thus simply be switched to _do_fork() enforcing a single calling convention.
(I really hope that any new architectures will __not__ try to implement their
own calling conventions...) Most architectures already have made a similar
switch (m68k comes to mind).
Overall this removes more code then it adds even with a good portion of added
comments. It simplifies a chunk of arch specific assembly either by moving the
code into C or by simply rewriting the assembly.
Architectures that have been touched in non-trivial ways have all been actually
boot and stress tested: sparc and ia64 have been tested with Debian 9 images.
They are the two architectures which have been touched the most. All non-trivial
changes to architectures have seen acks from the relevant maintainers.
nios2 with a custom built buildroot image. h8300 I couldn't get something
bootable to test on but the changes have been fairly automatic and I'm sure
we'll hear people yell if I broke something there. All other architectures that
have been touched in trivial ways have been compile tested for each single patch
of the series via git rebase -x "make ..." v5.8-rc2. arm{64} and x86{_64} have
been boot tested even though they have just been trivially touched (removal of
the HAVE_COPY_THREAD_TLS macro from their Kconfig) because well they are
basically "core architectures" and since it is trivial to get your hands on a
useable image.
/* Testing */
All patches are based on v5.8-rc2 and have been sitting in linux-next. No build
failures or warnings were observed. All old and new tests of relevant
test-suites are passing.
/* Conflicts */
There are a few smaller conflicts that linux-next reported:
1. csky tree: https://lore.kernel.org/lkml/20200803182550.4c7df8ae@xxxxxxxxxxxxxxxx
Stephen's suggestion to fix it seems correct:
diff --cc arch/csky/Kconfig
index af238739811e,902f1142d550..000000000000
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@@ -39,11 -38,6 +39,10 @@@ config CSK
select GX6605S_TIMER if CPU_CK610
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_AUDITSYSCALL
+ select HAVE_ARCH_MMAP_RND_BITS
+ select HAVE_ARCH_SECCOMP_FILTER
- select HAVE_COPY_THREAD_TLS
+ select HAVE_CONTEXT_TRACKING
+ select HAVE_VIRT_CPU_ACCOUNTING_GEN
select HAVE_DEBUG_BUGVERBOSE
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_REGS
2. sh tree: https://lore.kernel.org/lkml/20200722203812.6ca23e0d@xxxxxxxxxxxxxxxx
Stephen's suggestion to fix it seems correct:
diff --cc arch/um/Kconfig
index 32c1d1945033,ef69be17ff70..000000000000
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@@ -14,8 -14,6 +14,7 @@@ config UM
select HAVE_FUTEX_CMPXCHG if FUTEX
select HAVE_DEBUG_KMEMLEAK
select HAVE_DEBUG_BUGVERBOSE
- select HAVE_COPY_THREAD_TLS
+ select NO_DMA
select GENERIC_IRQ_SHOW
select GENERIC_CPU_DEVICES
select GENERIC_CLOCKEVENTS
3. riscv tree: https://lore.kernel.org/lkml/20200713165846.5166ff82@xxxxxxxxxxxxxxxx
Stephen's suggestion to fix it seems correct:
diff --cc arch/riscv/Kconfig
index 76a0cfad3367,f6a3a2bea3d8..000000000000
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@@ -57,9 -52,6 +57,8 @@@ config RISC
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TRACEHOOK
select HAVE_ASM_MODVERSIONS
+ select HAVE_CONTEXT_TRACKING
- select HAVE_COPY_THREAD_TLS
+ select HAVE_DEBUG_KMEMLEAK
select HAVE_DMA_CONTIGUOUS if MMU
select HAVE_EBPF_JIT if MMU
select HAVE_FUTEX_CMPXCHG if FUTEX
4. memlock tree: https://lore.kernel.org/lkml/20200706155811.7928b30d@xxxxxxxxxxxxxxxx
The conflict is in arch/unicore32/kernel/process.c and it seems that the
unicore32 port is about to be removed. So if that tree lands than the changes
in 8496da092a53 ("unicore: switch to copy_thread_tls()") can just be dropped
similar to what Stephen did for linux-next.
Fwiw, doing a test-merge with current mainline bcf876870b95 ("Linux 5.8") shows me:
brauner@wittgenstein|~/src/git/linux/linux|master $%=
> git pull git@xxxxxxxxxxxxxxxxxxx:pub/scm/linux/kernel/git/brauner/linux tags/fork-v5.9
>From gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux
* tag fork-v5.9 -> FETCH_HEAD
Auto-merging kernel/fork.c
Auto-merging arch/x86/kernel/process.c
Auto-merging arch/x86/Kconfig
Auto-merging arch/riscv/Kconfig
Auto-merging arch/arm64/Kconfig
Auto-merging arch/arc/Kconfig
Merge made by the 'recursive' strategy.
And nothing looks suspicious afterwards.
The following changes since commit 48778464bb7d346b47157d21ffde2af6b2d39110:
Linux 5.8-rc2 (2020-06-21 15:45:29 -0700)
are available in the Git repository at:
git@xxxxxxxxxxxxxxxxxxx:pub/scm/linux/kernel/git/brauner/linux tags/fork-v5.9
for you to fetch changes up to 714acdbd1c94e7e3ab90f6b6938f1ccb27b662f0:
arch: rename copy_thread_tls() back to copy_thread() (2020-07-04 23:41:37 +0200)
Please consider pulling these changes from the signed fork-v5.9 tag.
Thanks!
Christian
----------------------------------------------------------------
fork-v5.9
----------------------------------------------------------------
Christian Brauner (17):
fork: fold legacy_clone_args_valid() into _do_fork()
sparc64: enable HAVE_COPY_THREAD_TLS
sparc: share process creation helpers between sparc and sparc64
sparc: unconditionally enable HAVE_COPY_THREAD_TLS
ia64: enable HAVE_COPY_THREAD_TLS, switch to kernel_clone_args
nios2: enable HAVE_COPY_THREAD_TLS, switch to kernel_clone_args
h8300: select HAVE_COPY_THREAD_TLS, switch to kernel_clone_args
fork: remove do_fork()
alpha: switch to copy_thread_tls()
c6x: switch to copy_thread_tls()
hexagon: switch to copy_thread_tls()
microblaze: switch to copy_thread_tls()
nds32: switch to copy_thread_tls()
sh: switch to copy_thread_tls()
unicore: switch to copy_thread_tls()
arch: remove HAVE_COPY_THREAD_TLS
arch: rename copy_thread_tls() back to copy_thread()
arch/Kconfig | 7 ---
arch/alpha/kernel/process.c | 9 ++--
arch/arc/Kconfig | 1 -
arch/arc/kernel/process.c | 5 +-
arch/arm/Kconfig | 1 -
arch/arm/kernel/process.c | 5 +-
arch/arm64/Kconfig | 1 -
arch/arm64/kernel/process.c | 2 +-
arch/c6x/kernel/process.c | 4 +-
arch/csky/Kconfig | 1 -
arch/csky/kernel/process.c | 2 +-
arch/h8300/kernel/process.c | 17 ++++--
arch/hexagon/kernel/process.c | 6 +--
arch/ia64/kernel/entry.S | 32 +++++------
arch/ia64/kernel/process.c | 29 +++++++---
arch/m68k/Kconfig | 1 -
arch/m68k/kernel/process.c | 8 +--
arch/microblaze/kernel/process.c | 6 +--
arch/mips/Kconfig | 1 -
arch/mips/kernel/process.c | 5 +-
arch/nds32/kernel/process.c | 4 +-
arch/nios2/kernel/entry.S | 7 +--
arch/nios2/kernel/process.c | 23 ++++++--
arch/openrisc/Kconfig | 1 -
arch/openrisc/kernel/process.c | 6 +--
arch/parisc/Kconfig | 1 -
arch/parisc/kernel/process.c | 2 +-
arch/powerpc/Kconfig | 1 -
arch/powerpc/kernel/process.c | 2 +-
arch/riscv/Kconfig | 1 -
arch/riscv/kernel/process.c | 4 +-
arch/s390/Kconfig | 1 -
arch/s390/kernel/process.c | 4 +-
arch/sh/kernel/process_32.c | 6 +--
arch/sparc/include/asm/syscalls.h | 7 ++-
arch/sparc/kernel/Makefile | 1 +
arch/sparc/kernel/entry.S | 29 +++-------
arch/sparc/kernel/kernel.h | 11 ++--
arch/sparc/kernel/process.c | 110 ++++++++++++++++++++++++++++++++++++++
arch/sparc/kernel/process_32.c | 33 ++----------
arch/sparc/kernel/process_64.c | 40 ++------------
arch/sparc/kernel/syscalls.S | 23 ++++----
arch/um/Kconfig | 1 -
arch/um/kernel/process.c | 2 +-
arch/unicore32/kernel/process.c | 7 ++-
arch/x86/Kconfig | 1 -
arch/x86/kernel/process.c | 4 +-
arch/x86/kernel/sys_ia32.c | 3 --
arch/x86/kernel/unwind_frame.c | 2 +-
arch/xtensa/Kconfig | 1 -
arch/xtensa/kernel/process.c | 2 +-
include/linux/sched/task.h | 17 +-----
kernel/fork.c | 67 ++++++-----------------
53 files changed, 277 insertions(+), 290 deletions(-)
create mode 100644 arch/sparc/kernel/process.c