linux.git/kernel/entry/common.c, branch v5.11-rc2

Merge tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-12-15T02:35:53+00:00

Pull kmap updates from Thomas Gleixner:
 "The new preemtible kmap_local() implementation:

   - Consolidate all kmap_atomic() internals into a generic
     implementation which builds the base for the kmap_local() API and
     make the kmap_atomic() interface wrappers which handle the
     disabling/enabling of preemption and pagefaults.

   - Switch the storage from per-CPU to per task and provide scheduler
     support for clearing mapping when scheduling out and restoring them
     when scheduling back in.

   - Merge the migrate_disable/enable() code, which is also part of the
     scheduler pull request. This was required to make the kmap_local()
     interface available which does not disable preemption when a
     mapping is established. It has to disable migration instead to
     guarantee that the virtual address of the mapped slot is the same
     across preemption.

   - Provide better debug facilities: guard pages and enforced
     utilization of the mapping mechanics on 64bit systems when the
     architecture allows it.

   - Provide the new kmap_local() API which can now be used to cleanup
     the kmap_atomic() usage sites all over the place. Most of the usage
     sites do not require the implicit disabling of preemption and
     pagefaults so the penalty on 64bit and 32bit non-highmem systems is
     removed and quite some of the code can be simplified. A wholesale
     conversion is not possible because some usage depends on the
     implicit side effects and some need to be cleaned up because they
     work around these side effects.

     The migrate disable side effect is only effective on highmem
     systems and when enforced debugging is enabled. On 64bit and 32bit
     non-highmem systems the overhead is completely avoided"

* tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits)
  ARM: highmem: Fix cache_is_vivt() reference
  x86/crashdump/32: Simplify copy_oldmem_page()
  io-mapping: Provide iomap_local variant
  mm/highmem: Provide kmap_local*
  sched: highmem: Store local kmaps in task struct
  x86: Support kmap_local() forced debugging
  mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP
  mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL
  microblaze/mm/highmem: Add dropped #ifdef back
  xtensa/mm/highmem: Make generic kmap_atomic() work correctly
  mm/highmem: Take kmap_high_get() properly into account
  highmem: High implementation details and document API
  Documentation/io-mapping: Remove outdated blurb
  io-mapping: Cleanup atomic iomap
  mm/highmem: Remove the old kmap_atomic cruft
  highmem: Get rid of kmap_types.h
  xtensa/mm/highmem: Switch to generic kmap atomic
  sparc/mm/highmem: Switch to generic kmap atomic
  powerpc/mm/highmem: Switch to generic kmap atomic
  nds32/mm/highmem: Switch to generic kmap atomic
  ...

entry: Add syscall_exit_to_user_mode_work()

2020-12-02T14:07:58+00:00

This is the same as syscall_exit_to_user_mode() but without calling
exit_to_user_mode(). This can be used if there is an architectural reason
to avoid the combo function, e.g. restarting a syscall without returning to
userspace. Before returning to user space the caller has to invoke
exit_to_user_mode().

[ tglx: Amended comments ]

Signed-off-by: Sven Schnelle 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20201201142755.31931-6-svens@linux.ibm.com

entry: Add exit_to_user_mode() wrapper

2020-12-02T14:07:57+00:00

Called from architecture specific code when syscall_exit_to_user_mode() is
not suitable. It simply calls __exit_to_user_mode().

This way __exit_to_user_mode() can still be inlined because it is declared
static __always_inline.

[ tglx: Amended comments and moved it to a different place in the header ]

Signed-off-by: Sven Schnelle 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20201201142755.31931-5-svens@linux.ibm.com

entry_Add_enter_from_user_mode_wrapper

2020-12-02T14:07:57+00:00

To be called from architecture specific code if the combo interfaces are
not suitable. It simply calls __enter_from_user_mode(). This way
__enter_from_user_mode will still be inlined because it is declared static
__always_inline.

[ tglx: Amend comments and move it to a different location in the header ]

Signed-off-by: Sven Schnelle 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20201201142755.31931-4-svens@linux.ibm.com

entry: Rename exit_to_user_mode()

2020-12-02T14:07:57+00:00

In order to make this function publicly available rename it so it can still
be inlined. An additional exit_to_user_mode() function will be added with
a later commit.

Signed-off-by: Sven Schnelle 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20201201142755.31931-3-svens@linux.ibm.com

entry: Rename enter_from_user_mode()

2020-12-02T14:07:57+00:00

In order to make this function publicly available rename it so it can still
be inlined. An additional enter_from_user_mode() function will be added with
a later commit.

Signed-off-by: Sven Schnelle 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20201201142755.31931-2-svens@linux.ibm.com

entry: Support Syscall User Dispatch on common syscall entry

2020-12-02T14:07:56+00:00

Syscall User Dispatch (SUD) must take precedence over seccomp and
ptrace, since the use case is emulation (it can be invoked with a
different ABI) such that seccomp filtering by syscall number doesn't
make sense in the first place.  In addition, either the syscall is
dispatched back to userspace, in which case there is no resource for to
trace, or the syscall will be executed, and seccomp/ptrace will execute
next.

Since SUD runs before tracepoints, it needs to be a SYSCALL_WORK_EXIT as
well, just to prevent a trace exit event when dispatch was triggered.
For that, the on_syscall_dispatch() examines context to skip the
tracepoint, audit and other work.

[ tglx: Add a comment on the exit side ]

Signed-off-by: Gabriel Krisman Bertazi 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Andy Lutomirski 
Acked-by: Peter Zijlstra (Intel) 
Acked-by: Kees Cook 
Link: https://lore.kernel.org/r/20201127193238.821364-5-krisman@collabora.com

sched: highmem: Store local kmaps in task struct

2020-11-24T13:42:09+00:00

Instead of storing the map per CPU provide and use per task storage. That
prepares for local kmaps which are preemptible.

The context switch code is preparatory and not yet in use because
kmap_atomic() runs with preemption disabled. Will be made usable in the
next step.

The context switch logic is safe even when an interrupt happens after
clearing or before restoring the kmaps. The kmap index in task struct is
not modified so any nesting kmap in an interrupt will use unused indices
and on return the counter is the same as before.

Also add an assert into the return to user space code. Going back to user
space with an active kmap local is a nono.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20201118204007.372935758@linutronix.de

entry: Drop usage of TIF flags in the generic syscall code

2020-11-16T20:53:16+00:00

Now that the flags migration in the common syscall entry code is complete
and the code relies exclusively on thread_info::syscall_work, clean up the
accesses to TI flags in that path.

Signed-off-by: Gabriel Krisman Bertazi 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Andy Lutomirski 
Link: https://lore.kernel.org/r/20201116174206.2639648-10-krisman@collabora.com

ptrace: Migrate TIF_SYSCALL_EMU to use SYSCALL_WORK flag

2020-11-16T20:53:16+00:00

On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.

Define SYSCALL_WORK_SYSCALL_EMU, use it in the generic entry code and
convert the code which uses the TIF specific helper functions to use the
new *_syscall_work() helpers which either resolve to the new mode for users
of the generic entry code or to the TIF based functions for the other
architectures.

Signed-off-by: Gabriel Krisman Bertazi 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Andy Lutomirski 
Link: https://lore.kernel.org/r/20201116174206.2639648-8-krisman@collabora.com