From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- arch/powerpc/lib/vmx-helper.c | 84 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) create mode 100644 arch/powerpc/lib/vmx-helper.c (limited to 'arch/powerpc/lib/vmx-helper.c') diff --git a/arch/powerpc/lib/vmx-helper.c b/arch/powerpc/lib/vmx-helper.c new file mode 100644 index 000000000..cc9fb72cb --- /dev/null +++ b/arch/powerpc/lib/vmx-helper.c @@ -0,0 +1,84 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * + * Copyright (C) IBM Corporation, 2011 + * + * Authors: Sukadev Bhattiprolu + * Anton Blanchard + */ +#include +#include +#include + +int enter_vmx_usercopy(void) +{ + if (in_interrupt()) + return 0; + + preempt_disable(); + /* + * We need to disable page faults as they can call schedule and + * thus make us lose the VMX context. So on page faults, we just + * fail which will cause a fallback to the normal non-vmx copy. + */ + pagefault_disable(); + + enable_kernel_altivec(); + + return 1; +} +EXPORT_SYMBOL(enter_vmx_usercopy); + +/* + * This function must return 0 because we tail call optimise when calling + * from __copy_tofrom_user_power7 which returns 0 on success. + */ +int exit_vmx_usercopy(void) +{ + disable_kernel_altivec(); + pagefault_enable(); + preempt_enable_no_resched(); + /* + * Must never explicitly call schedule (including preempt_enable()) + * while in a kuap-unlocked user copy, because the AMR register will + * not be saved and restored across context switch. However preempt + * kernels need to be preempted as soon as possible if need_resched is + * set and we are preemptible. The hack here is to schedule a + * decrementer to fire here and reschedule for us if necessary. + */ + if (need_resched()) + set_dec(1); + return 0; +} +EXPORT_SYMBOL(exit_vmx_usercopy); + +/* + * Can be called from kexec copy_page() path with MMU off. The kexec + * code sets preempt_count to HARDIRQ_OFFSET so we return early here. + * Since in_interrupt() is always inline, __no_sanitize_address on this + * function is sufficient to avoid KASAN shadow memory accesses in real + * mode. + */ +int __no_sanitize_address enter_vmx_ops(void) +{ + if (in_interrupt()) + return 0; + + preempt_disable(); + + enable_kernel_altivec(); + + return 1; +} + +/* + * All calls to this function will be optimised into tail calls. We are + * passed a pointer to the destination which we return as required by a + * memcpy implementation. + */ +void *exit_vmx_ops(void *dest) +{ + disable_kernel_altivec(); + preempt_enable(); + return dest; +} -- cgit v1.3.1