ftrace: Synchronize the initialization of ftrace_opsgrafted

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 <rostedt@goodmis.org>

1 files changed, 95 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/timing.h b/arch/powerpc/kvm/timing.h
new file mode 100644
index 000000000..14b0e23f6
--- /dev/null
+++ b/arch/powerpc/kvm/timing.h
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *
+ * Copyright IBM Corp. 2008
+ *
+ * Authors: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
+ */
+
+#ifndef __POWERPC_KVM_EXITTIMING_H__
+#define __POWERPC_KVM_EXITTIMING_H__
+
+#include <linux/kvm_host.h>
+
+#ifdef CONFIG_KVM_EXIT_TIMING
+void kvmppc_init_timing_stats(struct kvm_vcpu *vcpu);
+void kvmppc_update_timing_stats(struct kvm_vcpu *vcpu);
+int kvmppc_create_vcpu_debugfs_e500(struct kvm_vcpu *vcpu,
+				    struct dentry *debugfs_dentry);
+
+static inline void kvmppc_set_exit_type(struct kvm_vcpu *vcpu, int type)
+{
+	vcpu->arch.last_exit_type = type;
+}
+
+#else
+/* if exit timing is not configured there is no need to build the c file */
+static inline void kvmppc_init_timing_stats(struct kvm_vcpu *vcpu) {}
+static inline void kvmppc_update_timing_stats(struct kvm_vcpu *vcpu) {}
+static inline int kvmppc_create_vcpu_debugfs_e500(struct kvm_vcpu *vcpu,
+						  struct dentry *debugfs_dentry)
+{
+	return 0;
+}
+static inline void kvmppc_set_exit_type(struct kvm_vcpu *vcpu, int type) {}
+#endif /* CONFIG_KVM_EXIT_TIMING */
+
+/* account the exit in kvm_stats */
+static inline void kvmppc_account_exit_stat(struct kvm_vcpu *vcpu, int type)
+{
+	/* type has to be known at build time for optimization */
+	BUILD_BUG_ON(!__builtin_constant_p(type));
+	switch (type) {
+	case EXT_INTR_EXITS:
+		vcpu->stat.ext_intr_exits++;
+		break;
+	case DEC_EXITS:
+		vcpu->stat.dec_exits++;
+		break;
+	case EMULATED_INST_EXITS:
+		vcpu->stat.emulated_inst_exits++;
+		break;
+	case DSI_EXITS:
+		vcpu->stat.dsi_exits++;
+		break;
+	case ISI_EXITS:
+		vcpu->stat.isi_exits++;
+		break;
+	case SYSCALL_EXITS:
+		vcpu->stat.syscall_exits++;
+		break;
+	case DTLB_REAL_MISS_EXITS:
+		vcpu->stat.dtlb_real_miss_exits++;
+		break;
+	case DTLB_VIRT_MISS_EXITS:
+		vcpu->stat.dtlb_virt_miss_exits++;
+		break;
+	case MMIO_EXITS:
+		vcpu->stat.mmio_exits++;
+		break;
+	case ITLB_REAL_MISS_EXITS:
+		vcpu->stat.itlb_real_miss_exits++;
+		break;
+	case ITLB_VIRT_MISS_EXITS:
+		vcpu->stat.itlb_virt_miss_exits++;
+		break;
+	case SIGNAL_EXITS:
+		vcpu->stat.signal_exits++;
+		break;
+	case DBELL_EXITS:
+		vcpu->stat.dbell_exits++;
+		break;
+	case GDBELL_EXITS:
+		vcpu->stat.gdbell_exits++;
+		break;
+	}
+}
+
+/* wrapper to set exit time and account for it in kvm_stats */
+static inline void kvmppc_account_exit(struct kvm_vcpu *vcpu, int type)
+{
+	kvmppc_set_exit_type(vcpu, type);
+	kvmppc_account_exit_stat(vcpu, type);
+}
+
+#endif /* __POWERPC_KVM_EXITTIMING_H__ */