readlinkat
Implemented in Antinomie 0.7.0 · Syscall list
Synopsis
Section titled “Synopsis”long readlinkat(int dfd, const char *path, char *buf, int bufsiz);| Number (x86-64) | 267 |
| ABI | common |
| Kernel entry point | sys_readlinkat |
This is the raw kernel prototype from the pinned Linux 6.12.94 schema, not the libc wrapper.
Description
Section titled “Description”Reads the target of a symbolic link relative to a directory descriptor and returns its length.
Arguments
Section titled “Arguments”| Name | Type | Meaning |
|---|---|---|
dfd (arg0) |
int |
Directory file descriptor that a relative path is resolved against, or AT_FDCWD (-100) for the current directory. |
path (arg1) |
const char * |
Path, as a NUL-terminated string in user memory. |
buf (arg2) |
char * |
Pointer to a data buffer. |
bufsiz (arg3) |
int |
Size of the buffer in bytes. |
Return value
Section titled “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
Section titled “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
Section titled “Man page”Captured by Antinomie
Section titled “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
Section titled “Arguments”| Argument | When | How | Recorded field key | Condition |
|---|---|---|---|---|
dfd (arg0) |
Entry | raw scalar word | args.0, args.dfd |
|
path (arg1) |
Entry | the pointer itself, as a raw word | args.1, args.raw[1] |
|
| ↳ pointee | Entry | NUL-terminated string, up to 4,096 bytes (PATH_MAX) | arg1.path |
always |
buf (arg2) |
Entry | the pointer itself, as a raw word | args.2, args.raw[2] |
|
| ↳ pointee | Exit | buffer, length min(bufsiz (arg3), result), limit 2 GiB - 1 bytes |
arg2.data |
result is 0 or greater |
bufsiz (arg3) |
Entry | raw scalar word | args.3, args.bufsiz |
Filter fields
Section titled “Filter fields”- Result:
ret,syscall.errno,syscall.success,syscall.duration_ns. - Argument words:
args.dfd(arg0),args.path(arg1),args.buf(arg2),args.bufsiz(arg3);args.0toargs.5by position. - Captured strings: the
args.<name>field of a path argument, andargs.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.