From 22098763a10d9c1340827fcf6edab66f153b27f0 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 13 Sep 2026 12:27:00 -0700 Subject: Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Don't destroy user event fields when removal fails User event fields are destroyed before the event is removed from visibility. But that can fail leaving the still visible event with no fields. Move the destroying of the fields to after the event is successfully removed from visibility. - Initialize function graph state is fork before calling copy_exec_state() For non-CLONE_VM forks, copy_exec_state() allocates a new task_exec_state. If that allocation fails, ftrace_graph_exit_task() will free the tasks ret_stack pointer. Since that pointer is still using the parent's ret_stack, it mistakenly frees the parent's pointer too. Call ftrace_graph_init() on the task first which will NULL out the new tasks's ret_stack and if the copy fails, it will not free anything. - Remove FGRAPH_MAX_INDEX The macro FGRAPH_MAX_INDEX was added but never used. Remove it. - Save ent_size in function graph printing of nested functions The function graph tracer needs to look at the next event to see if the next event is the return of the current function entry. If it is, it prints a single line: ktime_get(); Otherwise it prints it like a nested function: tick_nohz_irq_exit() { ktime_get(); kcpustat_irq_exit(); } In order to look at the next event, it must save the current event so that it has the information to print from it. It saves the event in the iterator descriptor called "ent". What it doesn't save is the ent_size of the event which is now used to know if the function graph arguments are to be printed. The peek doesn't save the size so the size used happens to be that of the size of the last event that was seen. Save the entry event size in the iterator descriptor so that the correct size is used. - Fix several errors with freeing data in the histogram code The histogram code had a lot of leaked or or incorrect accounting when failures happen. Correct them. - Fix histogram regression of .percent and .graph modifiers Up until 6.3 histogram values could have "percent" or "graph" modifiers that changed how they were printed. But a change that added restricting histograms values from being strings, stack traces and other modifiers inadvertently prevented them from using the percent and graph modifiers, which were legal use cases for values. Put back the percent and graph modifiers. - Fix various typos in the comments - Set the trace_clock before initializing a histogram with clock argument The histogram API allows the user to specific which trace clock to use via a "clock=" string. The histogram is set up first before the clock is checked. If the passed in clock is not valid, it exits without fully fixing up the histogram leaving it on the list and a use-after-free can trigger. Update the clock argument first and if it fails then exit gracefully before the histogram trigger is placed on any lists. - Restore :mod: trailer after parsing in ftrace_set_clr_event The function ftrace_set_clr_event() modifies the parse string and needs to put it back to what was passed in. It searches for ":mod:" via a strsep() but fails to put back the first ':' in the string. Add back the ':' in the passed in string. - Take trace_array reference when opening a tracer options file The options files are dynamically created and some tracers add their own options. When a tracer adds their own list of options, the trace_array holding them has an array to hold the list of options for each tracer. This array increases in size via a krealloc(), and the new entry gets a newly allocated array to hold the options of the new tracer being added. The element in each entry of the tracer's option array holds a pointer back to the trace_array, a pointer to the tracer it is associated to, a pointer to the flags of the option. The issue is that these arrays are freed when the trace_array is freed when its instance it represents is removed from the instances directory. There's a race that an open of one of these options files can happen when the instance is being removed. Add a new helper function to be called by the open function of the options file to iterate all existing trace_arrays under a lock and find the one that has the given option element in one of it's tracer arrays. If found, then update the associated trace_array's reference counter to keep it from being freed. If not found, have the open call return -ENODEV. - Disable interrupts when acquiring the lock in rb_wake_up_waiters() The function rb_wake_up_waiters() assumes it will be called in interrupt context and does not disable irqs when taking cpu_buffer->reader_lock, which can be called in hard interrupt context. The issue is in PREEMPT_RT, this function is called in thread context leaving this lock open to a deadlock. Take the lock with interrupts disabled. - Use rcu_assign_pointer() for tmp_ops filter hash The tmp_ops used in update_ftrace_direct_mod() assigns its filter_hash field directly, but that field is annotated as __rcu and sparse complains. Assign it with rcu_assign_pointer() - Fix use-after-free in enable_trigger_private_data_free() The trace_event_call is accessed through the event_trigger_data's trace_event_file pointer to put the trace_event_call on freeing. The issue is that the trace_event_file data may have been freed already causing a use-after-free. Add a field to the event_trigger_data that points directly to the trace_event_call so that it can decrement its reference directly without needing to go through the trace_event_file. - Fix accounting of buffer data remote headers trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount the number of pages is needed for the asked for size as it doesn't take into account the meta data on each page. Add a helper function to do the calculation properly and use that in these functions. - Catch nr_page_va overflow in ring_buffer_desc sizing The number of pages per remote ring buffer is capped by ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to overflow that field would silently allocate a descriptor smaller than what was asked for. - Do not resize the subbuf order if any per_cpu buffer is disabled The mmapping of ring buffers disables resizing the subbuffers, but it is done per-cpu whereas the subbuf size change is done for all the per_cpu buffers under the buffer->mutex. It could change the size of some while the mapping is happening on others. Have the resize of the subbuf order check all the per_cpu buffers under the lock to see if any of them is disabled before starting and causing an inconsistency between buffers that are being mapped. * tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits) ring-buffer: Check resize_disabled before publishing the new subbuf order tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing tracing/remotes: Account for ring buffer page header in size calculation tracing: Don't dereference trace_event_file in deferred trigger free ftrace: Use rcu_assign_pointer() for tmp_ops filter hash ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters() tracing: Take trace_array reference when opening a tracer options file tracing: Fix ring_buffer_read_page_size() kernel-doc tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event() tracing: Fix memory corruption from a "STACKTRACE" histogram key tracing: Fix memory corruption from the histogram stacktrace modifier tracing: Undo the registration when enabling the histogram trigger fails tracing: Take the reference before publishing the named histogram trigger tracing: Set the trace clock before registering the histogram trigger tracing: Fix typo "preceeded" in comment tracing: Fix typo "availabe" in comment tracing: Let histogram values keep the percent and graph modifiers tracing: Keep the entry count when the histogram stats allocation fails tracing: Free histogram the field rejected for a bad modifier tracing: Free histogram the var ref when its initialization fails ... --- Documentation/driver-api/serial/driver.rst | 105 ++++++++++++++++ Documentation/driver-api/serial/index.rst | 20 +++ Documentation/driver-api/serial/serial-iso7816.rst | 90 ++++++++++++++ Documentation/driver-api/serial/serial-rs485.rst | 135 +++++++++++++++++++++ 4 files changed, 350 insertions(+) create mode 100644 Documentation/driver-api/serial/driver.rst create mode 100644 Documentation/driver-api/serial/index.rst create mode 100644 Documentation/driver-api/serial/serial-iso7816.rst create mode 100644 Documentation/driver-api/serial/serial-rs485.rst (limited to 'Documentation/driver-api/serial') diff --git a/Documentation/driver-api/serial/driver.rst b/Documentation/driver-api/serial/driver.rst new file mode 100644 index 000000000..c1db6a1a6 --- /dev/null +++ b/Documentation/driver-api/serial/driver.rst @@ -0,0 +1,105 @@ +==================== +Low Level Serial API +==================== + + +This document is meant as a brief overview of some aspects of the new serial +driver. It is not complete, any questions you have should be directed to + + +The reference implementation is contained within amba-pl011.c. + + + +Low Level Serial Hardware Driver +-------------------------------- + +The low level serial hardware driver is responsible for supplying port +information (defined by uart_port) and a set of control methods (defined +by uart_ops) to the core serial driver. The low level driver is also +responsible for handling interrupts for the port, and providing any +console support. + + +Console Support +--------------- + +The serial core provides a few helper functions. This includes +decoding command line arguments (uart_parse_options()). + +There is also a helper function (uart_console_write()) which performs a +character by character write, translating newlines to CRLF sequences. +Driver writers are recommended to use this function rather than implementing +their own version. + + +Locking +------- + +It is the responsibility of the low level hardware driver to perform the +necessary locking using port->lock. There are some exceptions (which +are described in the struct uart_ops listing below.) + +There are two locks. A per-port spinlock, and an overall semaphore. + +From the core driver perspective, the port->lock locks the following +data:: + + port->mctrl + port->icount + port->state->xmit.head (circ_buf->head) + port->state->xmit.tail (circ_buf->tail) + +The low level driver is free to use this lock to provide any additional +locking. + +The port_sem semaphore is used to protect against ports being added/ +removed or reconfigured at inappropriate times. Since v2.6.27, this +semaphore has been the 'mutex' member of the tty_port struct, and +commonly referred to as the port mutex. + + +uart_ops +-------- + +.. kernel-doc:: include/linux/serial_core.h + :identifiers: uart_ops + +Other functions +--------------- + +.. kernel-doc:: drivers/tty/serial/serial_core.c + :identifiers: uart_update_timeout uart_get_baud_rate uart_get_divisor + uart_match_port uart_write_wakeup uart_register_driver + uart_unregister_driver uart_suspend_port uart_resume_port + uart_add_one_port uart_remove_one_port uart_console_write + uart_parse_earlycon uart_parse_options uart_set_options + uart_get_lsr_info uart_handle_dcd_change uart_handle_cts_change + uart_try_toggle_sysrq + +.. kernel-doc:: include/linux/serial_core.h + :identifiers: uart_port_tx_limited uart_port_tx + +Other notes +----------- + +It is intended some day to drop the 'unused' entries from uart_port, and +allow low level drivers to register their own individual uart_port's with +the core. This will allow drivers to use uart_port as a pointer to a +structure containing both the uart_port entry with their own extensions, +thus:: + + struct my_port { + struct uart_port port; + int my_stuff; + }; + +Modem control lines via GPIO +---------------------------- + +Some helpers are provided in order to set/get modem control lines via GPIO. + +.. kernel-doc:: drivers/tty/serial/serial_mctrl_gpio.c + :identifiers: mctrl_gpio_init mctrl_gpio_to_gpiod + mctrl_gpio_set mctrl_gpio_get mctrl_gpio_enable_ms + mctrl_gpio_disable_ms_sync mctrl_gpio_disable_ms_no_sync diff --git a/Documentation/driver-api/serial/index.rst b/Documentation/driver-api/serial/index.rst new file mode 100644 index 000000000..610744df5 --- /dev/null +++ b/Documentation/driver-api/serial/index.rst @@ -0,0 +1,20 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================== +Support for Serial devices +========================== + +.. toctree:: + :maxdepth: 1 + + + driver + +Serial drivers +============== + +.. toctree:: + :maxdepth: 1 + + serial-iso7816 + serial-rs485 diff --git a/Documentation/driver-api/serial/serial-iso7816.rst b/Documentation/driver-api/serial/serial-iso7816.rst new file mode 100644 index 000000000..d990143de --- /dev/null +++ b/Documentation/driver-api/serial/serial-iso7816.rst @@ -0,0 +1,90 @@ +============================= +ISO7816 Serial Communications +============================= + +1. Introduction +=============== + + ISO/IEC7816 is a series of standards specifying integrated circuit cards (ICC) + also known as smart cards. + +2. Hardware-related considerations +================================== + + Some CPUs/UARTs (e.g., Microchip AT91) contain a built-in mode capable of + handling communication with a smart card. + + For these microcontrollers, the Linux driver should be made capable of + working in both modes, and proper ioctls (see later) should be made + available at user-level to allow switching from one mode to the other, and + vice versa. + +3. Data Structures Already Available in the Kernel +================================================== + + The Linux kernel provides the serial_iso7816 structure (see [1]) to handle + ISO7816 communications. This data structure is used to set and configure + ISO7816 parameters in ioctls. + + Any driver for devices capable of working both as RS232 and ISO7816 should + implement the iso7816_config callback in the uart_port structure. The + serial_core calls iso7816_config to do the device specific part in response + to TIOCGISO7816 and TIOCSISO7816 ioctls (see below). The iso7816_config + callback receives a pointer to struct serial_iso7816. + +4. Usage from user-level +======================== + + From user-level, ISO7816 configuration can be get/set using the previous + ioctls. For instance, to set ISO7816 you can use the following code:: + + #include + + /* Include definition for ISO7816 ioctls: TIOCSISO7816 and TIOCGISO7816 */ + #include + + /* Open your specific device (e.g., /dev/mydevice): */ + int fd = open ("/dev/mydevice", O_RDWR); + if (fd < 0) { + /* Error handling. See errno. */ + } + + struct serial_iso7816 iso7816conf; + + /* Reserved fields as to be zeroed */ + memset(&iso7816conf, 0, sizeof(iso7816conf)); + + /* Enable ISO7816 mode: */ + iso7816conf.flags |= SER_ISO7816_ENABLED; + + /* Select the protocol: */ + /* T=0 */ + iso7816conf.flags |= SER_ISO7816_T(0); + /* or T=1 */ + iso7816conf.flags |= SER_ISO7816_T(1); + + /* Set the guard time: */ + iso7816conf.tg = 2; + + /* Set the clock frequency*/ + iso7816conf.clk = 3571200; + + /* Set transmission factors: */ + iso7816conf.sc_fi = 372; + iso7816conf.sc_di = 1; + + if (ioctl(fd_usart, TIOCSISO7816, &iso7816conf) < 0) { + /* Error handling. See errno. */ + } + + /* Use read() and write() syscalls here... */ + + /* Close the device when finished: */ + if (close (fd) < 0) { + /* Error handling. See errno. */ + } + +5. References +============= + + [1] include/uapi/linux/serial.h diff --git a/Documentation/driver-api/serial/serial-rs485.rst b/Documentation/driver-api/serial/serial-rs485.rst new file mode 100644 index 000000000..f53043d21 --- /dev/null +++ b/Documentation/driver-api/serial/serial-rs485.rst @@ -0,0 +1,135 @@ +=========================== +RS485 Serial Communications +=========================== + +1. Introduction +=============== + + EIA-485, also known as TIA/EIA-485 or RS-485, is a standard defining the + electrical characteristics of drivers and receivers for use in balanced + digital multipoint systems. + This standard is widely used for communications in industrial automation + because it can be used effectively over long distances and in electrically + noisy environments. + +2. Hardware-related Considerations +================================== + + Some CPUs/UARTs (e.g., Atmel AT91 or 16C950 UART) contain a built-in + half-duplex mode capable of automatically controlling line direction by + toggling RTS or DTR signals. That can be used to control external + half-duplex hardware like an RS485 transceiver or any RS232-connected + half-duplex devices like some modems. + + For these microcontrollers, the Linux driver should be made capable of + working in both modes, and proper ioctls (see later) should be made + available at user-level to allow switching from one mode to the other, and + vice versa. + +3. Data Structures Already Available in the Kernel +================================================== + + The Linux kernel provides the struct serial_rs485 to handle RS485 + communications. This data structure is used to set and configure RS485 + parameters in the platform data and in ioctls. + + The device tree can also provide RS485 boot time parameters + [#DT-bindings]_. The serial core fills the struct serial_rs485 from the + values given by the device tree when the driver calls + uart_get_rs485_mode(). + + Any driver for devices capable of working both as RS232 and RS485 should + implement the ``rs485_config`` callback and provide ``rs485_supported`` + in the ``struct uart_port``. The serial core calls ``rs485_config`` to do + the device specific part in response to TIOCSRS485 ioctl (see below). The + ``rs485_config`` callback receives a pointer to a sanitizated struct + serial_rs485. The struct serial_rs485 userspace provides is sanitized + before calling ``rs485_config`` using ``rs485_supported`` that indicates + what RS485 features the driver supports for the ``struct uart_port``. + TIOCGRS485 ioctl can be used to read back the struct serial_rs485 + matching to the current configuration. + +.. kernel-doc:: include/uapi/linux/serial.h + :identifiers: serial_rs485 uart_get_rs485_mode + +4. Usage from user-level +======================== + + From user-level, RS485 configuration can be get/set using the previous + ioctls. For instance, to set RS485 you can use the following code:: + + #include + + /* Include definition for RS485 ioctls: TIOCGRS485 and TIOCSRS485 */ + #include + + /* Open your specific device (e.g., /dev/mydevice): */ + int fd = open ("/dev/mydevice", O_RDWR); + if (fd < 0) { + /* Error handling. See errno. */ + } + + struct serial_rs485 rs485conf; + + /* Enable RS485 mode: */ + rs485conf.flags |= SER_RS485_ENABLED; + + /* Set logical level for RTS pin equal to 1 when sending: */ + rs485conf.flags |= SER_RS485_RTS_ON_SEND; + /* or, set logical level for RTS pin equal to 0 when sending: */ + rs485conf.flags &= ~(SER_RS485_RTS_ON_SEND); + + /* Set logical level for RTS pin equal to 1 after sending: */ + rs485conf.flags |= SER_RS485_RTS_AFTER_SEND; + /* or, set logical level for RTS pin equal to 0 after sending: */ + rs485conf.flags &= ~(SER_RS485_RTS_AFTER_SEND); + + /* Set rts delay before send, if needed: */ + rs485conf.delay_rts_before_send = ...; + + /* Set rts delay after send, if needed: */ + rs485conf.delay_rts_after_send = ...; + + /* Set this flag if you want to receive data even while sending data */ + rs485conf.flags |= SER_RS485_RX_DURING_TX; + + if (ioctl (fd, TIOCSRS485, &rs485conf) < 0) { + /* Error handling. See errno. */ + } + + /* Use read() and write() syscalls here... */ + + /* Close the device when finished: */ + if (close (fd) < 0) { + /* Error handling. See errno. */ + } + +5. Multipoint Addressing +======================== + + The Linux kernel provides addressing mode for multipoint RS-485 serial + communications line. The addressing mode is enabled with + ``SER_RS485_ADDRB`` flag in struct serial_rs485. The struct serial_rs485 + has two additional flags and fields for enabling receive and destination + addresses. + + Address mode flags: + - ``SER_RS485_ADDRB``: Enabled addressing mode (sets also ADDRB in termios). + - ``SER_RS485_ADDR_RECV``: Receive (filter) address enabled. + - ``SER_RS485_ADDR_DEST``: Set destination address. + + Address fields (enabled with corresponding ``SER_RS485_ADDR_*`` flag): + - ``addr_recv``: Receive address. + - ``addr_dest``: Destination address. + + Once a receive address is set, the communication can occur only with the + particular device and other peers are filtered out. It is left up to the + receiver side to enforce the filtering. Receive address will be cleared + if ``SER_RS485_ADDR_RECV`` is not set. + + Note: not all devices supporting RS485 support multipoint addressing. + +6. References +============= + +.. [#DT-bindings] Documentation/devicetree/bindings/serial/rs485.yaml -- cgit v1.3.1