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https://github.com/RGBCube/serenity
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91 lines
4.2 KiB
Markdown
91 lines
4.2 KiB
Markdown
## Name
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sys - SerenityOS SysFS
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## Description
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The kernel can expose system (kernel, firmware and hardware) related information in /sys.
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### `bus` directory
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This directory include a subdirectory for each discovered and registered bus in the system.
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Possible busses to be exposed in this directory are:
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1. The `pci` subdirectory that includes all discovered PCI devices as subdirectories.
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The subdirectories of the PCI devices include files with basic information on the devices.
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2. The `usb` subdirectory that includes all discovered USB devices as files.
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The files of the USB devices export basic information on the devices.
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### `dev` directory
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This directory include two subdirectories - `block` and `char`, each for block
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and character devices respectively. The files in these subdirectories are not
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device files, but merely a file with filename layout of "major:minor", to aid
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userspace in generating the appropriate device files.
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### `firmware` directory
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This directory include two subdirectories - `acpi` and `bios`.
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The `bios` subdirectory maintains files of the exposed SMBIOS blobs, if present
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by the firmware.
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The `acpi` subdirectory maintains files of the exposed ACPI tables, if present
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by the firmware.
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A file called `power_state` is responsible for power state switching.
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### `kernel` directory
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This directory includes two subdirectories - `net` and `variables`.
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All other files in the directory are global data nodes which provide statistics
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and other kernel-related data to userspace.
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#### `kernel` directory entries
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* **`processes`** - This node exports a list of all processes that currently exist.
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* **`cmdline`** - This node exports the kernel boot commandline that was passed from the bootloader.
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* **`cpuinfo`** - This node exports information on the CPU.
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* **`df`** - This node exports information on mounted filesystems and basic statistics on
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them.
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* **`dmesg`** - This node exports information from the kernel log.
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* **`interrupts`** - This node exports information on all IRQ handlers and basic statistics on
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them.
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* **`load_base`** - This node reveals the loading address of the kernel.
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* **`keymap`** - This node exports information on the currently used keymap.
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* **`memstat`** - This node exports statistics on memory allocation in the kernel.
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* **`profile`** - This node exports statistics on profiling data.
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* **`stats`** - This node exports statistics on scheduler timing data.
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* **`system_mode`** - This node exports the chosen system mode as it was decided based on the kernel commandline or a default value.
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* **`uptime`** - This node exports the uptime data.
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* **`jails`** - This node exports information about existing jails (only if the current process is not in jail).
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* **`power_state`** - This node only responds to write requests on it. A written value of `1` results
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in system reboot. A written value of `2` results in system shutdown.
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#### `net` directory
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* **`adapters`** - This node exports information on all currently-discovered network adapters.
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* **`arp`** - This node exports information on the kernel ARP table.
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* **`local`** - This node exports information on local (Unix) sockets.
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* **`tcp`** - This node exports information on TCP sockets.
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* **`udp`** - This node exports information on UDP sockets.
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#### `variables` directory
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This subdirectory includes global settings of the kernel.
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* **`caps_lock_to_ctrl`** - This node controls remapping of of caps lock to the Ctrl key.
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* **`kmalloc_stacks`** - This node controls whether to send information about kmalloc to debug log.
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* **`ubsan_is_deadly`** - This node controls the deadliness of the kernel undefined behavior
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sanitizer errors.
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### Consistency and stability of data across multiple read operations
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When opening a data node, the kernel generates the required data so it's prepared
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for read operation when requested to. However, in order to ensure that multiple reads
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will not create a corrupted data from that data node, a read operation alone will
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not inquire the kernel to refresh the data.
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To keep data output being refreshed, the userland has to re-open the data node with a
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new file descriptor, or to perform the `lseek` syscall on the open file descriptor to
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reset the offset to 0.
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## See also
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* [`mount`(2))](help://man/2/mount).
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