Hi Jack,
On 3/1/23 00:42, 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:
>
> ```
> #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("");
> }
> ```
>
> And I have verified that this doesn't happen with normal `clone` through
> the glibc helper:
>
> ```
> #define _GNU_SOURCE
>
> #include <sched.h>
> #include <signal.h>
> #include <stdio.h>
> #include <sys/mman.h>
>
> int do_nothing(void *_) { return 0; }
>
> int main() {
> void *map = mmap(NULL, 0x10000, PROT_READ | PROT_WRITE,
> MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
> void *stack_top = map + 0x10000 - 1;
> clone(do_nothing, stack_top,
> CLONE_THREAD | CLONE_VM | CLONE_SIGHAND | SIGCHLD, NULL);
> perror("");
> }
> ```
>
> Signed-off-by: Jack Pearson <jack@xxxxxxxxxxx>
> ---
> man2/clone.2 | 10 ++++++++++
> 1 file changed, 10 insertions(+)
Patch applied. Thanks!
Alex
>
> diff --git a/man2/clone.2 b/man2/clone.2
> index d63895189..be802a280 100644
> --- a/man2/clone.2
> +++ b/man2/clone.2
> @@ -1436,6 +1436,16 @@ 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.
--
<http://www.alejandro-colomar.es/>
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