Hi Jack, On 12/2/22 23:44, Jack Pearson wrote:
Document that Linux will report EINVAL when exit_signal is specified and either CLONE_THREAD or CLONE_PARENT is specified. From clone3_args_valid in Linux: ``` if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) && kargs->exit_signal) return false; ``` I have verified that this happens on my kernel with a small program, and that this doesn't happen with normal `clone` through the glibc helper.
Could you please also send a test program with the glibc wrapper?BTW, glibc has a clone3(2) wrapper since last year. It would be interesting to document it instead of the raw syscall.
Cheers, Alex
The program:
```
#include <stdio.h>
#include <linux/sched.h>
#include <signal.h>
#include <sys/syscall.h>
#include <unistd.h>
int main() {
struct clone_args ca = {
.flags = CLONE_THREAD | CLONE_SIGHAND | CLONE_VM,
.exit_signal = SIGCHLD, // comment me out to fix error
.set_tid_size = 0,
};
syscall(SYS_clone3, &ca, sizeof(struct clone_args));
perror("");
}
```
Signed-off-by: Jack Pearson <jack@xxxxxxxxxxx>
---
man2/clone.2 | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/man2/clone.2 b/man2/clone.2
index 093630859..a0fa50d83 100644
--- a/man2/clone.2
+++ b/man2/clone.2
@@ -1433,6 +1433,16 @@ One of the PIDs specified in
.I set_tid
was an invalid.
.TP
+.BR EINVAL " (" clone3 "() only)"
+.\" commit 7f192e3cd316ba58c88dfa26796cf77789dd9872
+.B CLONE_THREAD
+or
+.B CLONE_PARENT
+was specified in the
+.I flags
+mask, but a signal was specified in
+.I exit_signal.
+.TP
.BR EINVAL " (AArch64 only, Linux 4.6 and earlier)"
.I stack
was not aligned to a 128-bit boundary.
--
2.35.1
-- <http://www.alejandro-colomar.es/>
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