linux-toradex.git/include/linux/thread_info.h, branch v5.14-rc6

kernel.h: split out panic and oops helpers

2021-07-01T18:06:04+00:00

kernel.h is being used as a dump for all kinds of stuff for a long time.
Here is the attempt to start cleaning it up by splitting out panic and
oops helpers.

There are several purposes of doing this:
- dropping dependency in bug.h
- dropping a loop by moving out panic_notifier.h
- unload kernel.h from something which has its own domain

At the same time convert users tree-wide to use new headers, although for
the time being include new header back to kernel.h to avoid twisted
indirected includes for existing users.

[akpm@linux-foundation.org: thread_info.h needs limits.h]
[andriy.shevchenko@linux.intel.com: ia64 fix]
  Link: https://lkml.kernel.org/r/20210520130557.55277-1-andriy.shevchenko@linux.intel.com

Link: https://lkml.kernel.org/r/20210511074137.33666-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko 
Reviewed-by: Bjorn Andersson 
Co-developed-by: Andrew Morton 
Acked-by: Mike Rapoport 
Acked-by: Corey Minyard 
Acked-by: Christian Brauner 
Acked-by: Arnd Bergmann 
Acked-by: Kees Cook 
Acked-by: Wei Liu 
Acked-by: Rasmus Villemoes 
Signed-off-by: Andrew Morton 
Acked-by: Sebastian Reichel 
Acked-by: Luis Chamberlain 
Acked-by: Stephen Boyd 
Acked-by: Thomas Bogendoerfer 
Acked-by: Helge Deller  # parisc
Signed-off-by: Linus Torvalds

kernel, fs: Introduce and use set_restart_fn() and arch_set_restart_data()

2021-03-16T21:13:10+00:00

Preparation for fixing get_nr_restart_syscall() on X86 for COMPAT.

Add a new helper which sets restart_block->fn and calls a dummy
arch_set_restart_data() helper.

Fixes: 609c19a385c8 ("x86/ptrace: Stop setting TS_COMPAT in ptrace code")
Signed-off-by: Oleg Nesterov 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210201174641.GA17871@redhat.com

entry: Ensure trap after single-step on system call return

2021-02-05T23:21:42+00:00

Commit 299155244770 ("entry: Drop usage of TIF flags in the generic syscall
code") introduced a bug on architectures using the generic syscall entry
code, in which processes stopped by PTRACE_SYSCALL do not trap on syscall
return after receiving a TIF_SINGLESTEP.

The reason is that the meaning of TIF_SINGLESTEP flag is overloaded to
cause the trap after a system call is executed, but since the above commit,
the syscall call handler only checks for the SYSCALL_WORK flags on the exit
work.

Split the meaning of TIF_SINGLESTEP such that it only means single-step
mode, and create a new type of SYSCALL_WORK to request a trap immediately
after a syscall in single-step mode.  In the current implementation, the
SYSCALL_WORK flag shadows the TIF_SINGLESTEP flag for simplicity.

Update x86 to flip this bit when a tracer enables single stepping.

Fixes: 299155244770 ("entry: Drop usage of TIF flags in the generic syscall code")
Suggested-by: Linus Torvalds 
Signed-off-by: Gabriel Krisman Bertazi 
Signed-off-by: Thomas Gleixner 
Tested-by: Kyle Huey 
Link: https://lore.kernel.org/r/87h7mtc9pr.fsf_-_@collabora.com

kernel: Implement selective syscall userspace redirection

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

Introduce a mechanism to quickly disable/enable syscall handling for a
specific process and redirect to userspace via SIGSYS.  This is useful
for processes with parts that require syscall redirection and parts that
don't, but who need to perform this boundary crossing really fast,
without paying the cost of a system call to reconfigure syscall handling
on each boundary transition.  This is particularly important for Windows
games running over Wine.

The proposed interface looks like this:

  prctl(PR_SET_SYSCALL_USER_DISPATCH, , , , [selector])

The range [,+) is a part of the process memory
map that is allowed to by-pass the redirection code and dispatch
syscalls directly, such that in fast paths a process doesn't need to
disable the trap nor the kernel has to check the selector.  This is
essential to return from SIGSYS to a blocked area without triggering
another SIGSYS from rt_sigreturn.

selector is an optional pointer to a char-sized userspace memory region
that has a key switch for the mechanism. This key switch is set to
either PR_SYS_DISPATCH_ON, PR_SYS_DISPATCH_OFF to enable and disable the
redirection without calling the kernel.

The feature is meant to be set per-thread and it is disabled on
fork/clone/execv.

Internally, this doesn't add overhead to the syscall hot path, and it
requires very little per-architecture support.  I avoided using seccomp,
even though it duplicates some functionality, due to previous feedback
that maybe it shouldn't mix with seccomp since it is not a security
mechanism.  And obviously, this should never be considered a security
mechanism, since any part of the program can by-pass it by using the
syscall dispatcher.

For the sysinfo benchmark, which measures the overhead added to
executing a native syscall that doesn't require interception, the
overhead using only the direct dispatcher region to issue syscalls is
pretty much irrelevant.  The overhead of using the selector goes around
40ns for a native (unredirected) syscall in my system, and it is (as
expected) dominated by the supervisor-mode user-address access.  In
fact, with SMAP off, the overhead is consistently less than 5ns on my
test box.

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/20201127193238.821364-4-krisman@collabora.com

entry: Fix boot for !CONFIG_GENERIC_ENTRY

2020-11-25T01:20:09+00:00

A copy-pasta mistake tries to set SYSCALL_WORK flags instead of TIF
flags for !CONFIG_GENERIC_ENTRY.  Also, add safeguards to catch this at
compilation time.

Fixes: 3136b93c3fb2 ("entry: Expose helpers to migrate TIF to SYSCALL_WORK flags")
Reported-by: Naresh Kamboju 
Suggested-by: Jann Horn 
Signed-off-by: Gabriel Krisman Bertazi 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Kees Cook 
Link: https://lore.kernel.org/r/87a6v8qd9p.fsf_-_@collabora.com

audit: Migrate 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_AUDIT, 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/20201116174206.2639648-9-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

ptrace: Migrate to use SYSCALL_TRACE 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_TRACE, 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/20201116174206.2639648-7-krisman@collabora.com

tracepoints: Migrate to use SYSCALL_WORK flag

2020-11-16T20:53:15+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_TRACEPOINT, 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/20201116174206.2639648-6-krisman@collabora.com

seccomp: Migrate to use SYSCALL_WORK flag

2020-11-16T20:53:15+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_SECCOMP, 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/20201116174206.2639648-5-krisman@collabora.com