wait4
Implemented in Antinomie 0.7.0 · Syscall list
Synopsis
Section titled “Synopsis”long wait4(pid_t pid, int *stat_addr, int options, struct rusage *ru);| Number (x86-64) | 61 |
| ABI | common |
| Kernel entry point | sys_wait4 |
This is the raw kernel prototype from the pinned Linux 6.12.94 schema, not the libc wrapper.
Description
Section titled “Description”Waits for a child to change state and returns its pid, optionally storing the wait status and resource usage.
Arguments
Section titled “Arguments”| Name | Type | Meaning |
|---|---|---|
pid (arg0) |
pid_t |
Process or thread id. |
stat_addr (arg1) |
int * |
Pointer to store the wait status. |
options (arg2) |
int |
Option flags. |
ru (arg3) |
struct rusage * |
Pointer to a resource usage structure the kernel fills. |
Return value
Section titled “Return value”On success: The process id of the child that changed state.
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 |
|---|---|---|
-10 |
ECHILD |
There is no child to wait for. |
-4 |
EINTR |
The call was interrupted by a signal. |
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 |
|---|---|---|---|---|
pid (arg0) |
Entry | raw scalar word | args.0, args.pid |
|
stat_addr (arg1) |
Entry | the pointer itself, as a raw word | args.1, args.raw[1] |
|
| ↳ pointee | Exit | structure wait_status (fixed size) |
arg1.data |
result is greater than 0 |
options (arg2) |
Entry | raw scalar word; Syscall Trace also decodes it into flag names (wait4 group), listing unknown bits separately |
args.2, args.options |
|
ru (arg3) |
Entry | the pointer itself, as a raw word | args.3, args.raw[3] |
|
| ↳ pointee | Exit | structure rusage (fixed size) |
arg3.data |
result is greater than 0 |
Filter fields
Section titled “Filter fields”- Result:
ret,syscall.errno,syscall.success,syscall.duration_ns. - Argument words:
args.pid(arg0),args.stat_addr(arg1),args.options(arg2),args.ru(arg3);args.0toargs.5by position. - Structure
wait_statusbehindstat_addr(arg1):args.stat_addr.<member>forvalue. - Structure
rusagebehindru(arg3):args.ru.<member>forru_idrss,ru_inblock,ru_isrss,ru_ixrss,ru_majflt,ru_maxrss,ru_minflt,ru_msgrcv,ru_msgsnd,ru_nivcsw,ru_nsignals,ru_nswap,ru_nvcsw,ru_oublock,ru_stime.tv_sec,ru_stime.tv_usec,ru_utime.tv_sec,ru_utime.tv_usec.
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.