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, 167 insertions, 0 deletions

diff --git a/arch/powerpc/mm/init-common.c b/arch/powerpc/mm/init-common.c
new file mode 100644
index 000000000..745097554
--- /dev/null
+++ b/arch/powerpc/mm/init-common.c
@@ -0,0 +1,167 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  PowerPC version
+ *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
+ *
+ *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
+ *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
+ *    Copyright (C) 1996 Paul Mackerras
+ *
+ *  Derived from "arch/i386/mm/init.c"
+ *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ *
+ *  Dave Engebretsen <engebret@us.ibm.com>
+ *      Rework for PPC64 port.
+ */
+
+#undef DEBUG
+
+#include <linux/string.h>
+#include <linux/pgtable.h>
+#include <asm/pgalloc.h>
+#include <asm/kup.h>
+#include <asm/smp.h>
+
+phys_addr_t memstart_addr __ro_after_init = (phys_addr_t)~0ull;
+EXPORT_SYMBOL_GPL(memstart_addr);
+phys_addr_t kernstart_addr __ro_after_init;
+EXPORT_SYMBOL_GPL(kernstart_addr);
+unsigned long kernstart_virt_addr __ro_after_init = KERNELBASE;
+EXPORT_SYMBOL_GPL(kernstart_virt_addr);
+
+bool disable_kuep = !IS_ENABLED(CONFIG_PPC_KUEP);
+bool disable_kuap = !IS_ENABLED(CONFIG_PPC_KUAP);
+#ifdef CONFIG_KFENCE
+bool __ro_after_init kfence_disabled;
+bool __ro_after_init kfence_early_init = !!CONFIG_KFENCE_SAMPLE_INTERVAL;
+#endif
+
+static int __init parse_nosmep(char *p)
+{
+	if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64))
+		return 0;
+
+	disable_kuep = true;
+	pr_warn("Disabling Kernel Userspace Execution Prevention\n");
+	return 0;
+}
+early_param("nosmep", parse_nosmep);
+
+static int __init parse_nosmap(char *p)
+{
+	disable_kuap = true;
+	pr_warn("Disabling Kernel Userspace Access Protection\n");
+	return 0;
+}
+early_param("nosmap", parse_nosmap);
+
+void __weak setup_kuep(bool disabled)
+{
+	if (!IS_ENABLED(CONFIG_PPC_KUEP) || disabled)
+		return;
+
+	if (smp_processor_id() != boot_cpuid)
+		return;
+
+	pr_info("Activating Kernel Userspace Execution Prevention\n");
+}
+
+void setup_kup(void)
+{
+	setup_kuap(disable_kuap);
+	setup_kuep(disable_kuep);
+}
+
+#define CTOR(shift) static void ctor_##shift(void *addr) \
+{							\
+	memset(addr, 0, sizeof(pgd_t) << (shift));	\
+}
+
+CTOR(0); CTOR(1); CTOR(2); CTOR(3); CTOR(4); CTOR(5); CTOR(6); CTOR(7);
+CTOR(8); CTOR(9); CTOR(10); CTOR(11); CTOR(12); CTOR(13); CTOR(14); CTOR(15);
+
+static inline void (*ctor(int shift))(void *)
+{
+	BUILD_BUG_ON(MAX_PGTABLE_INDEX_SIZE != 15);
+
+	switch (shift) {
+	case 0: return ctor_0;
+	case 1: return ctor_1;
+	case 2: return ctor_2;
+	case 3: return ctor_3;
+	case 4: return ctor_4;
+	case 5: return ctor_5;
+	case 6: return ctor_6;
+	case 7: return ctor_7;
+	case 8: return ctor_8;
+	case 9: return ctor_9;
+	case 10: return ctor_10;
+	case 11: return ctor_11;
+	case 12: return ctor_12;
+	case 13: return ctor_13;
+	case 14: return ctor_14;
+	case 15: return ctor_15;
+	}
+	return NULL;
+}
+
+struct kmem_cache *pgtable_cache[MAX_PGTABLE_INDEX_SIZE + 1];
+EXPORT_SYMBOL_GPL(pgtable_cache);	/* used by kvm_hv module */
+
+/*
+ * Create a kmem_cache() for pagetables.  This is not used for PTE
+ * pages - they're linked to struct page, come from the normal free
+ * pages pool and have a different entry size (see real_pte_t) to
+ * everything else.  Caches created by this function are used for all
+ * the higher level pagetables, and for hugepage pagetables.
+ */
+void pgtable_cache_add(unsigned int shift)
+{
+	char *name;
+	unsigned long table_size = sizeof(pgd_t) << shift;
+	unsigned long align = table_size;
+
+	/* When batching pgtable pointers for RCU freeing, we store
+	 * the index size in the low bits.  Table alignment must be
+	 * big enough to fit it.
+	 */
+	unsigned long minalign = MAX_PGTABLE_INDEX_SIZE + 1;
+	struct kmem_cache *new = NULL;
+
+	/* It would be nice if this was a BUILD_BUG_ON(), but at the
+	 * moment, gcc doesn't seem to recognize is_power_of_2 as a
+	 * constant expression, so so much for that. */
+	BUG_ON(!is_power_of_2(minalign));
+	BUG_ON(shift > MAX_PGTABLE_INDEX_SIZE);
+
+	if (PGT_CACHE(shift))
+		return; /* Already have a cache of this size */
+
+	align = max_t(unsigned long, align, minalign);
+	name = kasprintf(GFP_KERNEL, "pgtable-2^%d", shift);
+	if (name)
+		new = kmem_cache_create(name, table_size, align, 0, ctor(shift));
+	if (!new)
+		panic("Could not allocate pgtable cache for order %d", shift);
+
+	kfree(name);
+	pgtable_cache[shift] = new;
+
+	pr_debug("Allocated pgtable cache for order %d\n", shift);
+}
+EXPORT_SYMBOL_GPL(pgtable_cache_add);	/* used by kvm_hv module */
+
+void pgtable_cache_init(void)
+{
+	pgtable_cache_add(PGD_INDEX_SIZE);
+
+	if (PMD_CACHE_INDEX)
+		pgtable_cache_add(PMD_CACHE_INDEX);
+	/*
+	 * In all current configs, when the PUD index exists it's the
+	 * same size as either the pgd or pmd index except with THP enabled
+	 * on book3s 64
+	 */
+	if (PUD_CACHE_INDEX)
+		pgtable_cache_add(PUD_CACHE_INDEX);
+}