Changes in Makefile

2cbb20b0 - tracing: Disable branch profiling in noinstr code

Fri, 21 Mar 2025 19:53:32 +0000

tracing: Disable branch profiling in noinstr codeCONFIG_TRACE_BRANCH_PROFILING inserts a call to ftrace_likely_update()for each use of likely() or unlikely(). That breaks noinstr rules ifthe affected function is annotated as noinstr.Disable branch profiling for files with noinstr functions. In additionto some individual files, this also includes the entire arch/x86subtree, as well as the kernel/entry, drivers/cpuidle, and drivers/idledirectories, all of which are noinstr-heavy.Due to the nature of how sched binaries are built by combining multiple.c files into one, branch profiling is disabled more broadly across thesched code than would otherwise be needed.This fixes many warnings like the following: vmlinux.o: warning: objtool: do_syscall_64+0x40: call to ftrace_likely_update() leaves .noinstr.text section vmlinux.o: warning: objtool: __rdgsbase_inactive+0x33: call to ftrace_likely_update() leaves .noinstr.text section vmlinux.o: warning: objtool: handle_bug.isra.0+0x198: call to ftrace_likely_update() leaves .noinstr.text section ...Reported-by: Ingo Molnar Suggested-by: Steven Rostedt Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Acked-by: Thomas Gleixner Cc: Linus Torvalds Link: https://lore.kernel.org/r/fb94fc9303d48a5ed370498f54500cc4c338eb6d.1742586676.git.jpoimboe@kernel.org List of files: /linux-6.15/kernel/entry/Makefile

1446e1df - kernel: Implement selective syscall userspace redirection

Fri, 27 Nov 2020 19:32:34 +0000

kernel: Implement selective syscall userspace redirectionIntroduce a mechanism to quickly disable/enable syscall handling for aspecific process and redirect to userspace via SIGSYS. This is usefulfor processes with parts that require syscall redirection and parts thatdon't, but who need to perform this boundary crossing really fast,without paying the cost of a system call to reconfigure syscall handlingon each boundary transition. This is particularly important for Windowsgames running over Wine.The proposed interface looks like this: prctl(PR_SET_SYSCALL_USER_DISPATCH, , , , [selector])The range [,+) is a part of the process memorymap that is allowed to by-pass the redirection code and dispatchsyscalls directly, such that in fast paths a process doesn't need todisable the trap nor the kernel has to check the selector. This isessential to return from SIGSYS to a blocked area without triggeringanother SIGSYS from rt_sigreturn.selector is an optional pointer to a char-sized userspace memory regionthat has a key switch for the mechanism. This key switch is set toeither PR_SYS_DISPATCH_ON, PR_SYS_DISPATCH_OFF to enable and disable theredirection without calling the kernel.The feature is meant to be set per-thread and it is disabled onfork/clone/execv.Internally, this doesn't add overhead to the syscall hot path, and itrequires very little per-architecture support. I avoided using seccomp,even though it duplicates some functionality, due to previous feedbackthat maybe it shouldn't mix with seccomp since it is not a securitymechanism. And obviously, this should never be considered a securitymechanism, since any part of the program can by-pass it by using thesyscall dispatcher.For the sysinfo benchmark, which measures the overhead added toexecuting a native syscall that doesn't require interception, theoverhead using only the direct dispatcher region to issue syscalls ispretty much irrelevant. The overhead of using the selector goes around40ns for a native (unredirected) syscall in my system, and it is (asexpected) dominated by the supervisor-mode user-address access. Infact, with SMAP off, the overhead is consistently less than 5ns on mytest 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 List of files: /linux-6.15/kernel/entry/Makefile

935ace2f - entry: Provide infrastructure for work before transitioning to guest mode

Wed, 22 Jul 2020 21:59:59 +0000

entry: Provide infrastructure for work before transitioning to guest modeEntering a guest is similar to exiting to user space. Pending work likehandling signals, rescheduling, task work etc. needs to be handled beforethat.Provide generic infrastructure to avoid duplication of the same handlingcode all over the place.The transfer to guest mode handling is different from the exit to usermodehandling, e.g. vs. rseq and live patching, so a separate function is used.The initial list of work items handled is: TIF_SIGPENDING, TIF_NEED_RESCHED, TIF_NOTIFY_RESUMEArchitecture specific TIF flags can be added via defines in thearchitecture specific include files.The calling convention is also different from the syscall/interrupt entryfunctions as KVM invokes this from the outer vcpu_run() loop withinterrupts and preemption enabled. To prevent missing a pending work itemit invokes a check for pending TIF work from interrupt disabled code rightbefore transitioning to guest mode. The lockdep, RCU and tracing statehandling is also done directly around the switch to and from guest mode.Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200722220519.833296398@linutronix.de List of files: /linux-6.15/kernel/entry/Makefile

142781e1 - entry: Provide generic syscall entry functionality

Wed, 22 Jul 2020 21:59:56 +0000

entry: Provide generic syscall entry functionalityOn syscall entry certain work needs to be done: - Establish state (lockdep, context tracking, tracing) - Conditional work (ptrace, seccomp, audit...)This code is needlessly duplicated and different in allarchitectures.Provide a generic version based on the x86 implementation which has all theRCU and instrumentation bits right.As interrupt/exception entry from user space needs parts of the samefunctionality, provide a function for this as well.syscall_enter_from_user_mode() and irqentry_enter_from_user_mode() must becalled right after the low level ASM entry. The calling code must benon-instrumentable. After the functions returns state is correct and thesubsequent functions can be instrumented.Signed-off-by: Thomas Gleixner Acked-by: Kees Cook Link: https://lkml.kernel.org/r/20200722220519.513463269@linutronix.de List of files: /linux-6.15/kernel/entry/Makefile