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, 76 insertions, 0 deletions

diff --git a/sound/soc/sof/sof-utils.c b/sound/soc/sof/sof-utils.c
new file mode 100644
index 000000000..f70089317
--- /dev/null
+++ b/sound/soc/sof/sof-utils.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+//
+// This file is provided under a dual BSD/GPLv2 license.  When using or
+// redistributing this file, you may do so under either license.
+//
+// Copyright(c) 2018-2022 Intel Corporation
+//
+// Author: Keyon Jie <yang.jie@linux.intel.com>
+//
+
+#include <linux/unaligned.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/device.h>
+#include <sound/memalloc.h>
+#include <linux/module.h>
+#include "sof-utils.h"
+
+/*
+ * Generic buffer page table creation.
+ * Take the each physical page address and drop the least significant unused
+ * bits from each (based on PAGE_SIZE). Then pack valid page address bits
+ * into compressed page table.
+ */
+
+int snd_sof_create_page_table(struct device *dev,
+			      struct snd_dma_buffer *dmab,
+			      unsigned char *page_table, size_t size)
+{
+	int i, pages;
+
+	pages = snd_sgbuf_aligned_pages(size);
+
+	dev_dbg(dev, "generating page table for %p size 0x%zx pages %d\n",
+		dmab->area, size, pages);
+
+	for (i = 0; i < pages; i++) {
+		/*
+		 * The number of valid address bits for each page is 20.
+		 * idx determines the byte position within page_table
+		 * where the current page's address is stored
+		 * in the compressed page_table.
+		 * This can be calculated by multiplying the page number by 2.5.
+		 */
+		u32 idx = (5 * i) >> 1;
+		u32 pfn = snd_sgbuf_get_addr(dmab, i * PAGE_SIZE) >> PAGE_SHIFT;
+		u8 *pg_table;
+
+		pg_table = (u8 *)(page_table + idx);
+
+		/*
+		 * pagetable compression:
+		 * byte 0     byte 1     byte 2     byte 3     byte 4     byte 5
+		 * ___________pfn 0__________ __________pfn 1___________  _pfn 2...
+		 * .... ....  .... ....  .... ....  .... ....  .... ....  ....
+		 * It is created by:
+		 * 1. set current location to 0, PFN index i to 0
+		 * 2. put pfn[i] at current location in Little Endian byte order
+		 * 3. calculate an intermediate value as
+		 *    x = (pfn[i+1] << 4) | (pfn[i] & 0xf)
+		 * 4. put x at offset (current location + 2) in LE byte order
+		 * 5. increment current location by 5 bytes, increment i by 2
+		 * 6. continue to (2)
+		 */
+		if (i & 1)
+			put_unaligned_le32((pg_table[0] & 0xf) | pfn << 4,
+					   pg_table);
+		else
+			put_unaligned_le32(pfn, pg_table);
+	}
+
+	return pages;
+}
+EXPORT_SYMBOL(snd_sof_create_page_table);
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_DESCRIPTION("SOF utils");