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67850b7bdc
linux/arch/um/kernel
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Linus Torvalds 67850b7bdc While looking at the ptrace problems with PREEMPT_RT and the problems 
of Peter Zijlstra was encountering with ptrace in his freezer rewrite
 I identified some cleanups to ptrace_stop that make sense on their own
 and move make resolving the other problems much simpler.
 
 The biggest issue is the habbit of the ptrace code to change task->__state
 from the tracer to suppress TASK_WAKEKILL from waking up the tracee.  No
 other code in the kernel does that and it is straight forward to update
 signal_wake_up and friends to make that unnecessary.
 
 Peter's task freezer sets frozen tasks to a new state TASK_FROZEN and
 then it stores them by calling "wake_up_state(t, TASK_FROZEN)" relying
 on the fact that all stopped states except the special stop states can
 tolerate spurious wake up and recover their state.
 
 The state of stopped and traced tasked is changed to be stored in
 task->jobctl as well as in task->__state.  This makes it possible for
 the freezer to recover tasks in these special states, as well as
 serving as a general cleanup.  With a little more work in that
 direction I believe TASK_STOPPED can learn to tolerate spurious wake
 ups and become an ordinary stop state.
 
 The TASK_TRACED state has to remain a special state as the registers for
 a process are only reliably available when the process is stopped in
 the scheduler.  Fundamentally ptrace needs acess to the saved
 register values of a task.
 
 There are bunch of semi-random ptrace related cleanups that were found
 while looking at these issues.
 
 One cleanup that deserves to be called out is from commit 57b6de08b5
 ("ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs").  This
 makes a change that is technically user space visible, in the handling
 of what happens to a tracee when a tracer dies unexpectedly.
 According to our testing and our understanding of userspace nothing
 cares that spurious SIGTRAPs can be generated in that case.
 
 The entire discussion can be found at:
   https://lkml.kernel.org/r/87a6bv6dl6.fsf_-_@email.froward.int.ebiederm.org
 
 Eric W. Biederman (11):
       signal: Rename send_signal send_signal_locked
       signal: Replace __group_send_sig_info with send_signal_locked
       ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP
       ptrace/xtensa: Replace PT_SINGLESTEP with TIF_SINGLESTEP
       ptrace: Remove arch_ptrace_attach
       signal: Use lockdep_assert_held instead of assert_spin_locked
       ptrace: Reimplement PTRACE_KILL by always sending SIGKILL
       ptrace: Document that wait_task_inactive can't fail
       ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs
       ptrace: Don't change __state
       ptrace: Always take siglock in ptrace_resume
 
 Peter Zijlstra (1):
       sched,signal,ptrace: Rework TASK_TRACED, TASK_STOPPED state
 
  arch/ia64/include/asm/ptrace.h    |   4 --
  arch/ia64/kernel/ptrace.c         |  57 ----------------
  arch/um/include/asm/thread_info.h |   2 +
  arch/um/kernel/exec.c             |   2 +-
  arch/um/kernel/process.c          |   2 +-
  arch/um/kernel/ptrace.c           |   8 +--
  arch/um/kernel/signal.c           |   4 +-
  arch/x86/kernel/step.c            |   3 +-
  arch/xtensa/kernel/ptrace.c       |   4 +-
  arch/xtensa/kernel/signal.c       |   4 +-
  drivers/tty/tty_jobctrl.c         |   4 +-
  include/linux/ptrace.h            |   7 --
  include/linux/sched.h             |  10 ++-
  include/linux/sched/jobctl.h      |   8 +++
  include/linux/sched/signal.h      |  20 ++++--
  include/linux/signal.h            |   3 +-
  kernel/ptrace.c                   |  87 ++++++++---------------
  kernel/sched/core.c               |   5 +-
  kernel/signal.c                   | 140 +++++++++++++++++---------------------
  kernel/time/posix-cpu-timers.c    |   6 +-
  20 files changed, 140 insertions(+), 240 deletions(-)
 
 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Merge tag 'ptrace_stop-cleanup-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull ptrace_stop cleanups from Eric Biederman:
 "While looking at the ptrace problems with PREEMPT_RT and the problems
  Peter Zijlstra was encountering with ptrace in his freezer rewrite I
  identified some cleanups to ptrace_stop that make sense on their own
  and move make resolving the other problems much simpler.

  The biggest issue is the habit of the ptrace code to change
  task->__state from the tracer to suppress TASK_WAKEKILL from waking up
  the tracee. No other code in the kernel does that and it is straight
  forward to update signal_wake_up and friends to make that unnecessary.

  Peter's task freezer sets frozen tasks to a new state TASK_FROZEN and
  then it stores them by calling "wake_up_state(t, TASK_FROZEN)" relying
  on the fact that all stopped states except the special stop states can
  tolerate spurious wake up and recover their state.

  The state of stopped and traced tasked is changed to be stored in
  task->jobctl as well as in task->__state. This makes it possible for
  the freezer to recover tasks in these special states, as well as
  serving as a general cleanup. With a little more work in that
  direction I believe TASK_STOPPED can learn to tolerate spurious wake
  ups and become an ordinary stop state.

  The TASK_TRACED state has to remain a special state as the registers
  for a process are only reliably available when the process is stopped
  in the scheduler. Fundamentally ptrace needs acess to the saved
  register values of a task.

  There are bunch of semi-random ptrace related cleanups that were found
  while looking at these issues.

  One cleanup that deserves to be called out is from commit 57b6de08b5
  ("ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs"). This
  makes a change that is technically user space visible, in the handling
  of what happens to a tracee when a tracer dies unexpectedly. According
  to our testing and our understanding of userspace nothing cares that
  spurious SIGTRAPs can be generated in that case"

* tag 'ptrace_stop-cleanup-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  sched,signal,ptrace: Rework TASK_TRACED, TASK_STOPPED state
  ptrace: Always take siglock in ptrace_resume
  ptrace: Don't change __state
  ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs
  ptrace: Document that wait_task_inactive can't fail
  ptrace: Reimplement PTRACE_KILL by always sending SIGKILL
  signal: Use lockdep_assert_held instead of assert_spin_locked
  ptrace: Remove arch_ptrace_attach
  ptrace/xtensa: Replace PT_SINGLESTEP with TIF_SINGLESTEP
  ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP
  signal: Replace __group_send_sig_info with send_signal_locked
  signal: Rename send_signal send_signal_locked
2022-06-03 16:13:25 -07:00
..
skas Peter Zijlstra says: 2022-01-11 17:24:45 -08:00
asm-offsets.c um: get rid of pointless include "..." where include <...> will do 2012-10-09 22:28:45 +02:00
config.c.in um: Add SPDX headers to files in arch/um/kernel/ 2019-09-15 21:37:17 +02:00
dtb.c um: Fix order of dtb unflatten/early init 2022-03-11 10:44:43 +01:00
dyn.lds.S um: Mark all kernel symbols as local 2021-04-15 23:10:29 +02:00
early_printk.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
exec.c ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP 2022-05-11 14:33:33 -05:00
exitcode.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
gprof_syms.c um: Add SPDX headers to files in arch/um/kernel/ 2019-09-15 21:37:17 +02:00
initrd.c um: Extract load file helper from initrd.c 2021-12-22 20:32:36 +01:00
ioport.c um: add PCI over virtio emulation driver 2021-06-17 21:45:43 +02:00
irq.c um: add PCI over virtio emulation driver 2021-06-17 21:45:43 +02:00
kmsg_dump.c printk: introduce a kmsg_dump iterator 2021-03-08 11:43:27 +01:00
ksyms.c um: rename set_signals() to um_set_signals() 2021-12-21 21:13:44 +01:00
load_file.c um: Extract load file helper from initrd.c 2021-12-22 20:32:36 +01:00
maccess.c maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault 2020-06-17 10:57:41 -07:00
Makefile um: Add devicetree support 2021-12-22 20:35:01 +01:00
mem.c um: Replace if (cond) BUG() with BUG_ON() 2021-12-21 21:18:39 +01:00
physmem.c um: Add SPDX headers to files in arch/um/kernel/ 2019-09-15 21:37:17 +02:00
process.c While looking at the ptrace problems with PREEMPT_RT and the problems 2022-06-03 16:13:25 -07:00
ptrace.c ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP 2022-05-11 14:33:33 -05:00
reboot.c um: Add SPDX headers to files in arch/um/kernel/ 2019-09-15 21:37:17 +02:00
sigio.c um: Support dynamic IRQ allocation 2020-12-13 22:22:08 +01:00
signal.c ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP 2022-05-11 14:33:33 -05:00
stacktrace.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
sysrq.c um: Clean up stacktrace dump 2020-10-11 23:25:07 +02:00
time.c um: time-travel/signals: fix ndelay() in interrupt 2021-06-17 21:44:52 +02:00
tlb.c um: remove process stub VMA 2021-02-12 21:37:38 +01:00
trap.c Merge branch 'akpm' (patches from Andrew) 2022-01-15 20:37:06 +02:00
um_arch.c x86/alternative: Use .ibt_endbr_seal to seal indirect calls 2022-03-15 10:32:47 +01:00
um_arch.h um: Add devicetree support 2021-12-22 20:35:01 +01:00
umid.c um: Add SPDX headers to files in arch/um/kernel/ 2019-09-15 21:37:17 +02:00
uml.lds.S um: Mark all kernel symbols as local 2021-04-15 23:10:29 +02:00
vmlinux.lds.S