From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops 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 --- drivers/misc/eeprom/max6875.c | 204 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 204 insertions(+) create mode 100644 drivers/misc/eeprom/max6875.c (limited to 'drivers/misc/eeprom/max6875.c') diff --git a/drivers/misc/eeprom/max6875.c b/drivers/misc/eeprom/max6875.c new file mode 100644 index 000000000..be5e6d19b --- /dev/null +++ b/drivers/misc/eeprom/max6875.c @@ -0,0 +1,204 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * max6875.c - driver for MAX6874/MAX6875 + * + * Copyright (C) 2005 Ben Gardner + * + * Based on eeprom.c + * + * The MAX6875 has a bank of registers and two banks of EEPROM. + * Address ranges are defined as follows: + * * 0x0000 - 0x0046 = configuration registers + * * 0x8000 - 0x8046 = configuration EEPROM + * * 0x8100 - 0x82FF = user EEPROM + * + * This driver makes the user EEPROM available for read. + * + * The registers & config EEPROM should be accessed via i2c-dev. + * + * The MAX6875 ignores the lowest address bit, so each chip responds to + * two addresses - 0x50/0x51 and 0x52/0x53. + * + * Note that the MAX6875 uses i2c_smbus_write_byte_data() to set the read + * address, so this driver is destructive if loaded for the wrong EEPROM chip. + */ + +#include +#include +#include +#include +#include + +/* The MAX6875 can only read/write 16 bytes at a time */ +#define SLICE_SIZE 16 +#define SLICE_BITS 4 + +/* USER EEPROM is at addresses 0x8100 - 0x82FF */ +#define USER_EEPROM_BASE 0x8100 +#define USER_EEPROM_SIZE 0x0200 +#define USER_EEPROM_SLICES 32 + +/* MAX6875 commands */ +#define MAX6875_CMD_BLK_READ 0x84 + +/* Each client has this additional data */ +struct max6875_data { + struct i2c_client *fake_client; + struct mutex update_lock; + + u32 valid; + u8 data[USER_EEPROM_SIZE]; + unsigned long last_updated[USER_EEPROM_SLICES]; +}; + +static void max6875_update_slice(struct i2c_client *client, int slice) +{ + struct max6875_data *data = i2c_get_clientdata(client); + int i, j, addr; + u8 *buf; + + if (slice >= USER_EEPROM_SLICES) + return; + + mutex_lock(&data->update_lock); + + buf = &data->data[slice << SLICE_BITS]; + + if (!(data->valid & (1 << slice)) || + time_after(jiffies, data->last_updated[slice])) { + + dev_dbg(&client->dev, "Starting update of slice %u\n", slice); + + data->valid &= ~(1 << slice); + + addr = USER_EEPROM_BASE + (slice << SLICE_BITS); + + /* select the eeprom address */ + if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) { + dev_err(&client->dev, "address set failed\n"); + goto exit_up; + } + + if (i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_READ_I2C_BLOCK)) { + if (i2c_smbus_read_i2c_block_data(client, + MAX6875_CMD_BLK_READ, + SLICE_SIZE, + buf) != SLICE_SIZE) { + goto exit_up; + } + } else { + for (i = 0; i < SLICE_SIZE; i++) { + j = i2c_smbus_read_byte(client); + if (j < 0) { + goto exit_up; + } + buf[i] = j; + } + } + data->last_updated[slice] = jiffies; + data->valid |= (1 << slice); + } +exit_up: + mutex_unlock(&data->update_lock); +} + +static ssize_t max6875_read(struct file *filp, struct kobject *kobj, + const struct bin_attribute *bin_attr, + char *buf, loff_t off, size_t count) +{ + struct i2c_client *client = kobj_to_i2c_client(kobj); + struct max6875_data *data = i2c_get_clientdata(client); + int slice, max_slice; + + /* refresh slices which contain requested bytes */ + max_slice = (off + count - 1) >> SLICE_BITS; + for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++) + max6875_update_slice(client, slice); + + memcpy(buf, &data->data[off], count); + + return count; +} + +static const struct bin_attribute user_eeprom_attr = { + .attr = { + .name = "eeprom", + .mode = S_IRUGO, + }, + .size = USER_EEPROM_SIZE, + .read = max6875_read, +}; + +static int max6875_probe(struct i2c_client *client) +{ + struct i2c_adapter *adapter = client->adapter; + struct max6875_data *data; + int err; + + if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA + | I2C_FUNC_SMBUS_READ_BYTE)) + return -ENODEV; + + /* Only bind to even addresses */ + if (client->addr & 1) + return -ENODEV; + + data = kzalloc_obj(struct max6875_data); + if (!data) + return -ENOMEM; + + /* A fake client is created on the odd address */ + data->fake_client = i2c_new_dummy_device(client->adapter, client->addr + 1); + if (IS_ERR(data->fake_client)) { + err = PTR_ERR(data->fake_client); + goto exit_kfree; + } + + /* Init real i2c_client */ + i2c_set_clientdata(client, data); + mutex_init(&data->update_lock); + + err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr); + if (err) + goto exit_remove_fake; + + return 0; + +exit_remove_fake: + i2c_unregister_device(data->fake_client); +exit_kfree: + kfree(data); + return err; +} + +static void max6875_remove(struct i2c_client *client) +{ + struct max6875_data *data = i2c_get_clientdata(client); + + i2c_unregister_device(data->fake_client); + + sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr); + kfree(data); +} + +static const struct i2c_device_id max6875_id[] = { + { .name = "max6875" }, + { } +}; +MODULE_DEVICE_TABLE(i2c, max6875_id); + +static struct i2c_driver max6875_driver = { + .driver = { + .name = "max6875", + }, + .probe = max6875_probe, + .remove = max6875_remove, + .id_table = max6875_id, +}; + +module_i2c_driver(max6875_driver); + +MODULE_AUTHOR("Ben Gardner "); +MODULE_DESCRIPTION("MAX6875 driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1