linux.git/kernel/entry/common.c, branch v6.12.80

treewide: context_tracking: Rename CONTEXT_* into CT_STATE_*

2024-07-29T02:03:10+00:00

Context tracking state related symbols currently use a mix of the
CONTEXT_ (e.g. CONTEXT_KERNEL) and CT_SATE_ (e.g. CT_STATE_MASK) prefixes.

Clean up the naming and make the ctx_state enum use the CT_STATE_ prefix.

Suggested-by: Frederic Weisbecker 
Signed-off-by: Valentin Schneider 
Acked-by: Frederic Weisbecker 
Acked-by: Thomas Gleixner 
Signed-off-by: Neeraj Upadhyay

entry: Respect changes to system call number by trace_sys_enter()

2024-03-12T12:23:32+00:00

When a probe is registered at the trace_sys_enter() tracepoint, and that
probe changes the system call number, the old system call still gets
executed.  This worked correctly until commit b6ec41346103 ("core/entry:
Report syscall correctly for trace and audit"), which removed the
re-evaluation of the syscall number after the trace point.

Restore the original semantics by re-evaluating the system call number
after trace_sys_enter(). 

The performance impact of this re-evaluation is minimal because it only
takes place when a trace point is active, and compared to the actual trace
point overhead the read from a cache hot variable is negligible.

Fixes: b6ec41346103 ("core/entry: Report syscall correctly for trace and audit")
Signed-off-by: André Rösti 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240311211704.7262-1-an.roesti@gmail.com

entry: Move syscall_enter_from_user_mode() to header file

2023-12-21T22:12:18+00:00

To allow inlining of syscall_enter_from_user_mode(), move it
to entry-common.h.

Signed-off-by: Sven Schnelle 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20231218074520.1998026-4-svens@linux.ibm.com

entry: Move enter_from_user_mode() to header file

2023-12-21T22:12:18+00:00

To allow inlining of enter_from_user_mode(), move it to
entry-common.h.

Signed-off-by: Sven Schnelle 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20231218074520.1998026-3-svens@linux.ibm.com

entry: Move exit to usermode functions to header file

2023-12-21T22:12:18+00:00

To allow inlining, move exit_to_user_mode() to
entry-common.h.

Signed-off-by: Sven Schnelle 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20231218074520.1998026-2-svens@linux.ibm.com

entry: Remove empty addr_limit_user_check()

2023-08-23T08:32:39+00:00

Back when set_fs() was a generic API for altering the address limit,
addr_limit_user_check() was a safety measure to prevent userspace being
able to issue syscalls with an unbound limit.

With the the removal of set_fs() as a generic API, the last user of
addr_limit_user_check() was removed in commit:

  b5a5a01d8e9a44ec ("arm64: uaccess: remove addr_limit_user_check()")

... as since that commit, no architecture defines TIF_FSCHECK, and hence
addr_limit_user_check() always expands to nothing.

Remove addr_limit_user_check(), updating the comment in
exit_to_user_mode_prepare() to no longer refer to it. At the same time,
the comment is reworded to be a little more generic so as to cover
kmap_assert_nomap() in addition to lockdep_sys_exit().

No functional change.

Signed-off-by: Mark Rutland 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20230821163526.2319443-1-mark.rutland@arm.com

entry/rcu: Check TIF_RESCHED _after_ delayed RCU wake-up

2023-03-21T14:13:15+00:00

RCU sometimes needs to perform a delayed wake up for specific kthreads
handling offloaded callbacks (RCU_NOCB).  These wakeups are performed
by timers and upon entry to idle (also to guest and to user on nohz_full).

However the delayed wake-up on kernel exit is actually performed after
the thread flags are fetched towards the fast path check for work to
do on exit to user. As a result, and if there is no other pending work
to do upon that kernel exit, the current task will resume to userspace
with TIF_RESCHED set and the pending wake up ignored.

Fix this with fetching the thread flags _after_ the delayed RCU-nocb
kthread wake-up.

Fixes: 47b8ff194c1f ("entry: Explicitly flush pending rcuog wakeup before last rescheduling point")
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Joel Fernandes (Google) 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20230315194349.10798-3-joel@joelfernandes.org

entry: Fix noinstr warning in __enter_from_user_mode()

2023-03-21T10:53:16+00:00

__enter_from_user_mode() is triggering noinstr warnings with
CONFIG_DEBUG_PREEMPT due to its call of preempt_count_add() via
ct_state().

The preemption disable isn't needed as interrupts are already disabled.
And the context_tracking_enabled() check in ct_state() also isn't needed
as that's already being done by the CT_WARN_ON().

Just use __ct_state() instead.

Fixes the following warnings:

  vmlinux.o: warning: objtool: enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section
  vmlinux.o: warning: objtool: syscall_enter_from_user_mode+0xf9: call to preempt_count_add() leaves .noinstr.text section
  vmlinux.o: warning: objtool: syscall_enter_from_user_mode_prepare+0xc7: call to preempt_count_add() leaves .noinstr.text section
  vmlinux.o: warning: objtool: irqentry_enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section

Fixes: 171476775d32 ("context_tracking: Convert state to atomic_t")
Signed-off-by: Josh Poimboeuf 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/d8955fa6d68dc955dda19baf13ae014ae27926f5.1677369694.git.jpoimboe@kernel.org

entry: kmsan: introduce kmsan_unpoison_entry_regs()

2022-10-03T21:03:25+00:00

struct pt_regs passed into IRQ entry code is set up by uninstrumented asm
functions, therefore KMSAN may not notice the registers are initialized.

kmsan_unpoison_entry_regs() unpoisons the contents of struct pt_regs,
preventing potential false positives.  Unlike kmsan_unpoison_memory(), it
can be called under kmsan_in_runtime(), which is often the case in IRQ
entry code.

Link: https://lkml.kernel.org/r/20220915150417.722975-41-glider@google.com
Signed-off-by: Alexander Potapenko 
Cc: Alexander Viro 
Cc: Alexei Starovoitov 
Cc: Andrey Konovalov 
Cc: Andrey Konovalov 
Cc: Andy Lutomirski 
Cc: Arnd Bergmann 
Cc: Borislav Petkov 
Cc: Christoph Hellwig 
Cc: Christoph Lameter 
Cc: David Rientjes 
Cc: Dmitry Vyukov 
Cc: Eric Biggers 
Cc: Eric Biggers 
Cc: Eric Dumazet 
Cc: Greg Kroah-Hartman 
Cc: Herbert Xu 
Cc: Ilya Leoshkevich 
Cc: Ingo Molnar 
Cc: Jens Axboe 
Cc: Joonsoo Kim 
Cc: Kees Cook 
Cc: Marco Elver 
Cc: Mark Rutland 
Cc: Matthew Wilcox 
Cc: Michael S. Tsirkin 
Cc: Pekka Enberg 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: Stephen Rothwell 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Cc: Vasily Gorbik 
Cc: Vegard Nossum 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

context_tracking: Take NMI eqs entrypoints over RCU

2022-07-05T20:32:59+00:00

The RCU dynticks counter is going to be merged into the context tracking
subsystem. Prepare with moving the NMI extended quiescent states
entrypoints to context tracking. For now those are dumb redirection to
existing RCU calls.

Acked-by: Paul E. McKenney 
Signed-off-by: Frederic Weisbecker 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Neeraj Upadhyay 
Cc: Uladzislau Rezki 
Cc: Joel Fernandes 
Cc: Boqun Feng 
Cc: Nicolas Saenz Julienne 
Cc: Marcelo Tosatti 
Cc: Xiongfeng Wang 
Cc: Yu Liao 
Cc: Phil Auld 
Cc: Paul Gortmaker
Cc: Alex Belits 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Nicolas Saenz Julienne 
Tested-by: Nicolas Saenz Julienne