Re: [PATCH 1/2] arch: mark syscall number 435 reserved for clone3

On Fri, Jul 19, 2019 at 09:13:16PM +1000, Michael Ellerman wrote:

Christian Brauner [off-list ref] writes:

quoted

On Fri, Jul 19, 2019 at 08:18:02PM +1000, Michael Ellerman wrote:

quoted

Christian Brauner [off-list ref] writes:

quoted

On Mon, Jul 15, 2019 at 03:56:04PM +0200, Christian Borntraeger wrote:

quoted

I think Vasily already has a clone3 patch for s390x with 435. 

A quick follow-up on this. Helge and Michael have asked whether there
are any tests for clone3. Yes, there will be and I try to have them
ready by the end of the this or next week for review. In the meantime I
hope the following minimalistic test program that just verifies very
very basic functionality (It's not pretty.) will help you test:

Hi Christian,

Thanks for the test.

This actually oopses on powerpc, it hits the BUG_ON in CHECK_FULL_REGS
in process.c around line 1633:

	} else {
		/* user thread */
		struct pt_regs *regs = current_pt_regs();
		CHECK_FULL_REGS(regs);
		*childregs = *regs;
		if (usp)


So I'll have to dig into how we fix that before we wire up clone3.

Turns out testing is good! :)

Indeed. I have a test-suite for clone3 in mind and I hope to have it
ready by the end of next week. It's just always the finding the time
part that is annoying. :)

I know the feeling!

quoted

Thanks for digging into this, Michael!

No worries, happy to help where I can.

In the intervening five minutes I remembered how we handle this, we just
need a little wrapper to save the non-volatile regs:

_GLOBAL(ppc_clone3)
	bl	save_nvgprs
	bl	sys_clone3
	b	.Lsyscall_exit

Sounds good.

A while back I meant to make it generate those automatically based on a
flag in the syscall.tbl but of course haven't got around to it :)

So with the above it seems all good:

$ ./clone3 ; echo $?
Parent process received child's pid 4204 as return value
Parent process received child's pidfd 3
Parent process received child's pid 4204 as return argument
Child process with pid 4204
0

I'll send a patch to wire it up on Monday.

Excellent! Thank you!
Christian