ioctl

Partial in Antinomie 0.7.0 · Syscall list

Synopsis

long ioctl(unsigned int fd, unsigned int cmd, unsigned long arg);

Number (x86-64)	16
ABI	64
Kernel entry point	sys_ioctl

This is the raw kernel prototype from the pinned Linux 6.12.94 schema, not the libc wrapper.

Description

Sends a device or file specific control request to a file descriptor. The meaning of the third argument depends on the request.

Arguments

Name	Type	Meaning
fd (arg0)	unsigned int	File descriptor to operate on.
cmd (arg1)	unsigned int	ioctl request code; its bits encode direction, size and a driver-specific number.
arg (arg2)	unsigned long	Request-specific value or pointer.

Return value

On success: a request-specific value, usually 0.

In an Antinomie trace the Return column and the ret filter field show the raw kernel return value. On failure that is the negative errno, for example -2 for ENOENT, not the -1 plus errno that the libc wrapper gives. syscall.errno holds the positive errno and syscall.success is false.

Common errors

Raw return	Name	Meaning
-9	EBADF	A file descriptor is not valid for this operation.
-14	EFAULT	A pointer argument points outside the accessible address space.
-22	EINVAL	An argument is invalid.
-25	ENOTTY	The request does not apply to this kind of file.

Man page

ioctl(2) on man7.org

Captured by Antinomie

Coverage mark: Partial. Only terminal requests (TCGETS, TCSETS*, TIOCGWINSZ, TIOCSWINSZ, FIONREAD on a tty device) have their arg pointee decoded. For every other request the recorder logs the pointer with a “no decoder” gap at entry.

Every call is recorded as an Entry record (the six argument words and the pointees copied at entry) and an Exit record (the return value and the pointees copied at exit).

Arguments

Argument	When	How	Recorded field key	Condition
fd (arg0)	Entry	raw scalar word	args.0, args.fd
cmd (arg1)	Entry	raw scalar word	args.1, args.cmd
arg (arg2)	Entry	raw scalar word	args.2, args.arg

Family notes

• The pointee of arg is decoded only for terminal requests on a tty device; see the capture rules above.

Filter fields

• Result: ret, syscall.errno, syscall.success, syscall.duration_ns.
• Argument words: args.fd (arg0), args.cmd (arg1), args.arg (arg2); args.0 to args.5 by position.

See Syscall Trace filter for the full syntax.

Known gaps

• Any other request records arg2.ioctl with the “no decoder” status at entry.
• See the coverage mark above for the code paths that record a gap.

For what the capture statuses mean, see Capture statuses. For what is never recorded, see Known gaps.