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, 183 insertions, 0 deletions

diff --git a/drivers/block/n64cart.c b/drivers/block/n64cart.c
new file mode 100644
index 000000000..328da73b6
--- /dev/null
+++ b/drivers/block/n64cart.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for the N64 cart.
+ *
+ * Copyright (c) 2021 Lauri Kasanen
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/bitops.h>
+#include <linux/blkdev.h>
+#include <linux/dma-mapping.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/string.h>
+
+enum {
+	PI_DRAM_REG = 0,
+	PI_CART_REG,
+	PI_READ_REG,
+	PI_WRITE_REG,
+	PI_STATUS_REG,
+};
+
+#define PI_STATUS_DMA_BUSY	(1 << 0)
+#define PI_STATUS_IO_BUSY	(1 << 1)
+
+#define CART_DOMAIN		0x10000000
+#define CART_MAX		0x1FFFFFFF
+
+#define MIN_ALIGNMENT		8
+
+static u32 __iomem *reg_base;
+
+static unsigned int start;
+module_param(start, uint, 0);
+MODULE_PARM_DESC(start, "Start address of the cart block data");
+
+static unsigned int size;
+module_param(size, uint, 0);
+MODULE_PARM_DESC(size, "Size of the cart block data, in bytes");
+
+static void n64cart_write_reg(const u8 reg, const u32 value)
+{
+	writel(value, reg_base + reg);
+}
+
+static u32 n64cart_read_reg(const u8 reg)
+{
+	return readl(reg_base + reg);
+}
+
+static void n64cart_wait_dma(void)
+{
+	while (n64cart_read_reg(PI_STATUS_REG) &
+		(PI_STATUS_DMA_BUSY | PI_STATUS_IO_BUSY))
+		cpu_relax();
+}
+
+/*
+ * Process a single bvec of a bio.
+ */
+static bool n64cart_do_bvec(struct device *dev, struct bio_vec *bv, u32 pos)
+{
+	dma_addr_t dma_addr;
+	const u32 bstart = pos + start;
+
+	/* Alignment check */
+	WARN_ON_ONCE((bv->bv_offset & (MIN_ALIGNMENT - 1)) ||
+		     (bv->bv_len & (MIN_ALIGNMENT - 1)));
+
+	dma_addr = dma_map_bvec(dev, bv, DMA_FROM_DEVICE, 0);
+	if (dma_mapping_error(dev, dma_addr))
+		return false;
+
+	n64cart_wait_dma();
+
+	n64cart_write_reg(PI_DRAM_REG, dma_addr);
+	n64cart_write_reg(PI_CART_REG, (bstart | CART_DOMAIN) & CART_MAX);
+	n64cart_write_reg(PI_WRITE_REG, bv->bv_len - 1);
+
+	n64cart_wait_dma();
+
+	dma_unmap_page(dev, dma_addr, bv->bv_len, DMA_FROM_DEVICE);
+	return true;
+}
+
+static void n64cart_submit_bio(struct bio *bio)
+{
+	struct bio_vec bvec;
+	struct bvec_iter iter;
+	struct device *dev = bio->bi_bdev->bd_disk->private_data;
+	u32 pos = bio->bi_iter.bi_sector << SECTOR_SHIFT;
+
+	bio_for_each_segment(bvec, bio, iter) {
+		if (!n64cart_do_bvec(dev, &bvec, pos)) {
+			bio_io_error(bio);
+			return;
+		}
+		pos += bvec.bv_len;
+	}
+
+	bio_endio(bio);
+}
+
+static const struct block_device_operations n64cart_fops = {
+	.owner		= THIS_MODULE,
+	.submit_bio	= n64cart_submit_bio,
+};
+
+/*
+ * The target device is embedded and RAM-constrained. We save RAM
+ * by initializing in __init code that gets dropped late in boot.
+ * For the same reason there is no module or unloading support.
+ */
+static int __init n64cart_probe(struct platform_device *pdev)
+{
+	struct queue_limits lim = {
+		.physical_block_size	= 4096,
+		.logical_block_size	= 4096,
+	};
+	struct gendisk *disk;
+	int err = -ENOMEM;
+
+	if (!start || !size) {
+		pr_err("start or size not specified\n");
+		return -ENODEV;
+	}
+
+	if (size & 4095) {
+		pr_err("size must be a multiple of 4K\n");
+		return -ENODEV;
+	}
+
+	reg_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(reg_base))
+		return PTR_ERR(reg_base);
+
+	disk = blk_alloc_disk(&lim, NUMA_NO_NODE);
+	if (IS_ERR(disk)) {
+		err = PTR_ERR(disk);
+		goto out;
+	}
+
+	disk->first_minor = 0;
+	disk->flags = GENHD_FL_NO_PART;
+	disk->fops = &n64cart_fops;
+	disk->private_data = &pdev->dev;
+	strscpy(disk->disk_name, "n64cart");
+
+	set_capacity(disk, size >> SECTOR_SHIFT);
+	set_disk_ro(disk, 1);
+
+	err = add_disk(disk);
+	if (err)
+		goto out_cleanup_disk;
+
+	pr_info("n64cart: %u kb disk\n", size / 1024);
+
+	return 0;
+
+out_cleanup_disk:
+	put_disk(disk);
+out:
+	return err;
+}
+
+static struct platform_driver n64cart_driver = {
+	.driver = {
+		.name = "n64cart",
+	},
+};
+
+static int __init n64cart_init(void)
+{
+	return platform_driver_probe(&n64cart_driver, n64cart_probe);
+}
+
+module_init(n64cart_init);
+
+MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>");
+MODULE_DESCRIPTION("Driver for the N64 cart");
+MODULE_LICENSE("GPL");