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, 188 insertions, 0 deletions

diff --git a/arch/powerpc/xmon/nonstdio.c b/arch/powerpc/xmon/nonstdio.c
new file mode 100644
index 000000000..9b0d85bff
--- /dev/null
+++ b/arch/powerpc/xmon/nonstdio.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 1996-2005 Paul Mackerras.
+ */
+#include <linux/string.h>
+#include <asm/udbg.h>
+#include <asm/time.h>
+#include "nonstdio.h"
+
+static bool paginating, paginate_skipping;
+static unsigned long paginate_lpp; /* Lines Per Page */
+static unsigned long paginate_pos;
+
+void xmon_start_pagination(void)
+{
+	paginating = true;
+	paginate_skipping = false;
+	paginate_pos = 0;
+}
+
+void xmon_end_pagination(void)
+{
+	paginating = false;
+}
+
+void xmon_set_pagination_lpp(unsigned long lpp)
+{
+	paginate_lpp = lpp;
+}
+
+static int xmon_readchar(void)
+{
+	if (udbg_getc)
+		return udbg_getc();
+	return -1;
+}
+
+static int xmon_write(const char *ptr, int nb)
+{
+	int rv = 0;
+	const char *p = ptr, *q;
+	const char msg[] = "[Hit a key (a:all, q:truncate, any:next page)]";
+
+	if (nb <= 0)
+		return rv;
+
+	if (paginating && paginate_skipping)
+		return nb;
+
+	if (paginate_lpp) {
+		while (paginating && (q = strchr(p, '\n'))) {
+			rv += udbg_write(p, q - p + 1);
+			p = q + 1;
+			paginate_pos++;
+
+			if (paginate_pos >= paginate_lpp) {
+				udbg_write(msg, strlen(msg));
+
+				switch (xmon_readchar()) {
+				case 'a':
+					paginating = false;
+					break;
+				case 'q':
+					paginate_skipping = true;
+					break;
+				default:
+					/* nothing */
+					break;
+				}
+
+				paginate_pos = 0;
+				udbg_write("\r\n", 2);
+
+				if (paginate_skipping)
+					return nb;
+			}
+		}
+	}
+
+	return rv + udbg_write(p, nb - (p - ptr));
+}
+
+int xmon_putchar(int c)
+{
+	char ch = c;
+
+	if (c == '\n')
+		xmon_putchar('\r');
+	return xmon_write(&ch, 1) == 1? c: -1;
+}
+
+static char line[256];
+static char *lineptr;
+static int lineleft;
+
+static int xmon_getchar(void)
+{
+	int c;
+
+	if (lineleft == 0) {
+		lineptr = line;
+		for (;;) {
+			c = xmon_readchar();
+			if (c == -1 || c == 4)
+				break;
+			if (c == '\r' || c == '\n') {
+				*lineptr++ = '\n';
+				xmon_putchar('\n');
+				break;
+			}
+			switch (c) {
+			case 0177:
+			case '\b':
+				if (lineptr > line) {
+					xmon_putchar('\b');
+					xmon_putchar(' ');
+					xmon_putchar('\b');
+					--lineptr;
+				}
+				break;
+			case 'U' & 0x1F:
+				while (lineptr > line) {
+					xmon_putchar('\b');
+					xmon_putchar(' ');
+					xmon_putchar('\b');
+					--lineptr;
+				}
+				break;
+			default:
+				if (lineptr >= &line[sizeof(line) - 1])
+					xmon_putchar('\a');
+				else {
+					xmon_putchar(c);
+					*lineptr++ = c;
+				}
+			}
+		}
+		lineleft = lineptr - line;
+		lineptr = line;
+	}
+	if (lineleft == 0)
+		return -1;
+	--lineleft;
+	return *lineptr++;
+}
+
+char *xmon_gets(char *str, int nb)
+{
+	char *p;
+	int c;
+
+	for (p = str; p < str + nb - 1; ) {
+		c = xmon_getchar();
+		if (c == -1) {
+			if (p == str)
+				return NULL;
+			break;
+		}
+		*p++ = c;
+		if (c == '\n')
+			break;
+	}
+	*p = 0;
+	return str;
+}
+
+void xmon_printf(const char *format, ...)
+{
+	va_list args;
+	static char xmon_outbuf[1024];
+	int rc, n;
+
+	va_start(args, format);
+	n = vsnprintf(xmon_outbuf, sizeof(xmon_outbuf), format, args);
+	va_end(args);
+
+	rc = xmon_write(xmon_outbuf, n);
+
+	if (n && rc == 0) {
+		/* No udbg hooks, fallback to printk() - dangerous */
+		pr_cont("%s", xmon_outbuf);
+	}
+}
+
+void xmon_puts(const char *str)
+{
+	xmon_write(str, strlen(str));
+}