readlink

Implemented in Antinomie 0.7.0 · Syscall list

Synopsis

long readlink(const char *path, char *buf, int bufsiz);

Number (x86-64)	89
ABI	common
Kernel entry point	sys_readlink

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

Description

Reads the target of a symbolic link into a buffer and returns the number of bytes, without a terminating zero.

Arguments

Name	Type	Meaning
path (arg0)	const char *	Path, as a NUL-terminated string in user memory.
buf (arg1)	char *	Pointer to a data buffer.
bufsiz (arg2)	int	Size of the buffer in bytes.

Return value

On success: The number of bytes transferred (see the description for what 0 means).

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
-22	EINVAL	An argument is invalid.
-2	ENOENT	A path component or the named object does not exist.

Man page

readlink(2) on man7.org

Captured by Antinomie

Coverage mark: Implemented. Every pointer argument has a capture rule in the pinned kernel patch and none of them records a “no decoder”, “address only” or “not observed” gap on any code path. Individual values can still be incomplete on a particular call; see the capture statuses.

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
path (arg0)	Entry	the pointer itself, as a raw word	args.0, args.raw[0]
↳ pointee	Entry	NUL-terminated string, up to 4,096 bytes (PATH_MAX)	arg0.path	always
buf (arg1)	Entry	the pointer itself, as a raw word	args.1, args.raw[1]
↳ pointee	Exit	buffer, length min(bufsiz (arg2), result), limit 2 GiB - 1 bytes	arg1.data	result is 0 or greater
bufsiz (arg2)	Entry	raw scalar word	args.2, args.bufsiz

Filter fields

• Result: ret, syscall.errno, syscall.success, syscall.duration_ns.
• Argument words: args.path (arg0), args.buf (arg1), args.bufsiz (arg2); args.0 to args.5 by position.
• Captured strings: the args.<name> field of a path argument, and args.path, give the captured text instead of the pointer.

See Syscall Trace filter for the full syntax.

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