kernel/linux.git/include/linux/thread_info.h, branch v6.6.132

thread_info: move function declarations to linux/thread_info.h

2023-06-10T00:44:16+00:00

There are a few __weak functions in kernel/fork.c, which architectures can override. If there is no prototype, the compiler warns about them: kernel/fork.c:164:13: error: no previous prototype for 'arch_release_task_struct' [-Werror=missing-prototypes] kernel/fork.c:991:20: error: no previous prototype for 'arch_task_cache_init' [-Werror=missing-prototypes] kernel/fork.c:1086:12: error: no previous prototype for 'arch_dup_task_struct' [-Werror=missing-prototypes] There are already prototypes in a number of architecture specific headers that have addressed those warnings before, but it's much better to have these in a single place so the warning no longer shows up anywhere. Link: https://lkml.kernel.org/r/20230517131102.934196-14-arnd@kernel.org Signed-off-by: Arnd Bergmann Cc: Boqun Feng Cc: Catalin Marinas Cc: Christoph Lameter Cc: Dennis Zhou Cc: Eric Paris Cc: Heiko Carstens Cc: Helge Deller Cc: Ingo Molnar Cc: Michael Ellerman Cc: Michal Simek Cc: Palmer Dabbelt Cc: Paul Moore Cc: Pavel Machek Cc: Peter Zijlstra Cc: Rafael J. Wysocki Cc: Russell King Cc: Tejun Heo Cc: Thomas Bogendoerfer Cc: Thomas Gleixner Cc: Waiman Long Cc: Will Deacon Signed-off-by: Andrew Morton

cpuidle, sched: Remove instrumentation from TIF_{POLLING_NRFLAG,NEED_RESCHED}

2023-01-13T10:48:16+00:00

objtool pointed out that various idle-TIF management methods have instrumentation: vmlinux.o: warning: objtool: mwait_idle+0x5: call to current_set_polling_and_test() leaves .noinstr.text section vmlinux.o: warning: objtool: acpi_processor_ffh_cstate_enter+0xc5: call to current_set_polling_and_test() leaves .noinstr.text section vmlinux.o: warning: objtool: cpu_idle_poll.isra.0+0x73: call to test_ti_thread_flag() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle+0xbc: call to current_set_polling_and_test() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle_irq+0xea: call to current_set_polling_and_test() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle_s2idle+0xb4: call to current_set_polling_and_test() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle+0xa6: call to current_clr_polling() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle_irq+0xbf: call to current_clr_polling() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle_s2idle+0xa1: call to current_clr_polling() leaves .noinstr.text section vmlinux.o: warning: objtool: mwait_idle+0xe: call to __current_set_polling() leaves .noinstr.text section vmlinux.o: warning: objtool: acpi_processor_ffh_cstate_enter+0xc5: call to __current_set_polling() leaves .noinstr.text section vmlinux.o: warning: objtool: cpu_idle_poll.isra.0+0x73: call to test_ti_thread_flag() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle+0xbc: call to __current_set_polling() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle_irq+0xea: call to __current_set_polling() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle_s2idle+0xb4: call to __current_set_polling() leaves .noinstr.text section vmlinux.o: warning: objtool: cpu_idle_poll.isra.0+0x73: call to test_ti_thread_flag() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle_s2idle+0x73: call to test_ti_thread_flag.constprop.0() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle_irq+0x91: call to test_ti_thread_flag.constprop.0() leaves .noinstr.text section vmlinux.o: warning: objtool: intel_idle+0x78: call to test_ti_thread_flag.constprop.0() leaves .noinstr.text section vmlinux.o: warning: objtool: acpi_safe_halt+0xf: call to test_ti_thread_flag.constprop.0() leaves .noinstr.text section Remove the instrumentation, because these methods are used in low-level cpuidle code moving between states, that should not be instrumented. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Tested-by: Tony Lindgren Tested-by: Ulf Hansson Acked-by: Rafael J. Wysocki Acked-by: Frederic Weisbecker Link: https://lore.kernel.org/r/20230112195540.988741683@infradead.org

mm: uninline copy_overflow()

2022-03-22T22:57:11+00:00

While building a small config with CONFIG_CC_OPTIMISE_FOR_SIZE, I ended up with more than 50 times the following function in vmlinux because GCC doesn't honor the 'inline' keyword: c00243bc : c00243bc: 94 21 ff f0 stwu r1,-16(r1) c00243c0: 7c 85 23 78 mr r5,r4 c00243c4: 7c 64 1b 78 mr r4,r3 c00243c8: 3c 60 c0 62 lis r3,-16286 c00243cc: 7c 08 02 a6 mflr r0 c00243d0: 38 63 5e e5 addi r3,r3,24293 c00243d4: 90 01 00 14 stw r0,20(r1) c00243d8: 4b ff 82 45 bl c001c61c <__warn_printk> c00243dc: 0f e0 00 00 twui r0,0 c00243e0: 80 01 00 14 lwz r0,20(r1) c00243e4: 38 21 00 10 addi r1,r1,16 c00243e8: 7c 08 03 a6 mtlr r0 c00243ec: 4e 80 00 20 blr With -Winline, GCC tells: /include/linux/thread_info.h:212:20: warning: inlining failed in call to 'copy_overflow': call is unlikely and code size would grow [-Winline] copy_overflow() is a non conditional warning called by check_copy_size() on an error path. check_copy_size() have to remain inlined in order to benefit from constant folding, but copy_overflow() is not worth inlining. Uninline the warning when CONFIG_BUG is selected. When CONFIG_BUG is not selected, WARN() does nothing so skip it. This reduces the size of vmlinux by almost 4kbytes. Link: https://lkml.kernel.org/r/e1723b9cfa924bcefcd41f69d0025b38e4c9364e.1644819985.git.christophe.leroy@csgroup.eu Signed-off-by: Christophe Leroy Cc: David Laight Cc: Anshuman Khandual Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

thread_info: Add helpers to snapshot thread flags

2021-11-30T23:06:43+00:00

In there are helpers to manipulate individual thread flags, but where code wants to check several flags at once, it must open code reading current_thread_info()->flags and operating on a snapshot. As some flags can be set remotely it's necessary to use READ_ONCE() to get a consistent snapshot even when IRQs are disabled, but some code forgets to do this. Generally this is unlike to cause a problem in practice, but it is somewhat unsound, and KCSAN will legitimately warn that there is a data race. To make it easier to do the right thing, and to highlight that concurrent modification is possible, add new helpers to snapshot the flags, which should be used in preference to plain reads. Subsequent patches will move existing code to use the new helpers. Signed-off-by: Mark Rutland Signed-off-by: Thomas Gleixner Reviewed-by: Thomas Gleixner Acked-by: Marco Elver Acked-by: Paul E. McKenney Cc: Boqun Feng Cc: Dmitry Vyukov Cc: Peter Zijlstra Cc: Will Deacon Link: https://lore.kernel.org/r/20211129130653.2037928-2-mark.rutland@arm.com

compiler_types.h: Remove __compiletime_object_size()

2021-09-25T15:20:49+00:00

Since all compilers support __builtin_object_size(), and there is only one user of __compiletime_object_size, remove it to avoid the needless indirection. This lets Clang reason about check_copy_size() correctly. Link: https://github.com/ClangBuiltLinux/linux/issues/1179 Suggested-by: Nick Desaulniers Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Sedat Dilek Cc: Will Deacon Cc: Marco Elver Cc: Arvind Sankar Cc: Masahiro Yamada Cc: Luc Van Oostenryck Cc: Andrew Morton Cc: Sami Tolvanen Cc: Thomas Gleixner Cc: Gabriel Krisman Bertazi Cc: Andy Lutomirski Cc: Oleg Nesterov Reviewed-by: Miguel Ojeda Signed-off-by: Kees Cook

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