Merge tag 'clone3-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull clone3 system call from Christian Brauner:
 "This adds the clone3 syscall which is an extensible successor to clone
  after we snagged the last flag with CLONE_PIDFD during the 5.2 merge
  window for clone(). It cleanly supports all of the flags from clone()
  and thus all legacy workloads.

  There are few user visible differences between clone3 and clone.
  First, CLONE_DETACHED will cause EINVAL with clone3 so we can reuse
  this flag. Second, the CSIGNAL flag is deprecated and will cause
  EINVAL to be reported. It is superseeded by a dedicated "exit_signal"
  argument in struct clone_args thus freeing up even more flags. And
  third, clone3 gives CLONE_PIDFD a dedicated return argument in struct
  clone_args instead of abusing CLONE_PARENT_SETTID's parent_tidptr
  argument.

  The clone3 uapi is designed to be easy to handle on 32- and 64 bit:

    /* uapi */
    struct clone_args {
            __aligned_u64 flags;
            __aligned_u64 pidfd;
            __aligned_u64 child_tid;
            __aligned_u64 parent_tid;
            __aligned_u64 exit_signal;
            __aligned_u64 stack;
            __aligned_u64 stack_size;
            __aligned_u64 tls;
    };

  and a separate kernel struct is used that uses proper kernel typing:

    /* kernel internal */
    struct kernel_clone_args {
            u64 flags;
            int __user *pidfd;
            int __user *child_tid;
            int __user *parent_tid;
            int exit_signal;
            unsigned long stack;
            unsigned long stack_size;
            unsigned long tls;
    };

  The system call comes with a size argument which enables the kernel to
  detect what version of clone_args userspace is passing in. clone3
  validates that any additional bytes a given kernel does not know about
  are set to zero and that the size never exceeds a page.

  A nice feature is that this patchset allowed us to cleanup and
  simplify various core kernel codepaths in kernel/fork.c by making the
  internal _do_fork() function take struct kernel_clone_args even for
  legacy clone().

  This patch also unblocks the time namespace patchset which wants to
  introduce a new CLONE_TIMENS flag.

  Note, that clone3 has only been wired up for x86{_32,64}, arm{64}, and
  xtensa. These were the architectures that did not require special
  massaging.

  Other architectures treat fork-like system calls individually and
  after some back and forth neither Arnd nor I felt confident that we
  dared to add clone3 unconditionally to all architectures. We agreed to
  leave this up to individual architecture maintainers. This is why
  there's an additional patch that introduces __ARCH_WANT_SYS_CLONE3
  which any architecture can set once it has implemented support for
  clone3. The patch also adds a cond_syscall(clone3) for architectures
  such as nios2 or h8300 that generate their syscall table by simply
  including asm-generic/unistd.h. The hope is to get rid of
  __ARCH_WANT_SYS_CLONE3 and cond_syscall() rather soon"

* tag 'clone3-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  arch: handle arches who do not yet define clone3
  arch: wire-up clone3() syscall
  fork: add clone3

11 files changed, 22 insertions, 3 deletions

diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index 9fb00973c608..3676e82cf95c 100644
--- a/arch/arm/include/asm/unistd.h
+++ b/arch/arm/include/asm/unistd.h
@@ -37,6 +37,7 @@
 #define __ARCH_WANT_SYS_FORK
 #define __ARCH_WANT_SYS_VFORK
 #define __ARCH_WANT_SYS_CLONE
+#define __ARCH_WANT_SYS_CLONE3
 
 /*
  * Unimplemented (or alternatively implemented) syscalls
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index 81e6e1817c45..6da7dc4d79cc 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -448,3 +448,4 @@
 432	common	fsmount				sys_fsmount
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
+435	common	clone3				sys_clone3
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index ede7b88d4f15..2629a68b8724 100644
--- a/arch/arm64/include/asm/unistd.h
+++ b/arch/arm64/include/asm/unistd.h
@@ -38,10 +38,11 @@
 #define __ARM_NR_compat_set_tls		(__ARM_NR_COMPAT_BASE + 5)
 #define __ARM_NR_COMPAT_END		(__ARM_NR_COMPAT_BASE + 0x800)
 
-#define __NR_compat_syscalls		435
+#define __NR_compat_syscalls		436
 #endif
 
 #define __ARCH_WANT_SYS_CLONE
+#define __ARCH_WANT_SYS_CLONE3
 
 #ifndef __COMPAT_SYSCALL_NR
 #include <uapi/asm/unistd.h>
diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index 52415923e08f..94ab29cf4f00 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -877,6 +877,8 @@ __SYSCALL(__NR_fsmount, sys_fsmount)
 __SYSCALL(__NR_fspick, sys_fspick)
 #define __NR_pidfd_open 434
 __SYSCALL(__NR_pidfd_open, sys_pidfd_open)
+#define __NR_clone3 435
+__SYSCALL(__NR_clone3, sys_clone3)
 
 /*
  * Please add new compat syscalls above this comment and update
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index ad706f83c755..09b0cd7dab0a 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -440,3 +440,4 @@
 432	common	fsmount				sys_fsmount
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
+435	common	clone3				sys_clone3
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 43e4429a5272..c00019abd076 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -439,3 +439,4 @@
 432	i386	fsmount			sys_fsmount			__ia32_sys_fsmount
 433	i386	fspick			sys_fspick			__ia32_sys_fspick
 434	i386	pidfd_open		sys_pidfd_open			__ia32_sys_pidfd_open
+435	i386	clone3			sys_clone3			__ia32_sys_clone3
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 1bee0a77fdd3..c29976eca4a8 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -356,6 +356,7 @@
 432	common	fsmount			__x64_sys_fsmount
 433	common	fspick			__x64_sys_fspick
 434	common	pidfd_open		__x64_sys_pidfd_open
+435	common	clone3			__x64_sys_clone3/ptregs
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/arch/x86/ia32/sys_ia32.c b/arch/x86/ia32/sys_ia32.c
index a43212036257..64a6c952091e 100644
--- a/arch/x86/ia32/sys_ia32.c
+++ b/arch/x86/ia32/sys_ia32.c
@@ -237,6 +237,14 @@ COMPAT_SYSCALL_DEFINE5(x86_clone, unsigned long, clone_flags,
 		       unsigned long, newsp, int __user *, parent_tidptr,
 		       unsigned long, tls_val, int __user *, child_tidptr)
 {
-	return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr,
-			tls_val);
+	struct kernel_clone_args args = {
+		.flags		= (clone_flags & ~CSIGNAL),
+		.child_tid	= child_tidptr,
+		.parent_tid	= parent_tidptr,
+		.exit_signal	= (clone_flags & CSIGNAL),
+		.stack		= newsp,
+		.tls		= tls_val,
+	};
+
+	return _do_fork(&args);
 }
diff --git a/arch/x86/include/asm/unistd.h b/arch/x86/include/asm/unistd.h
index 146859efd83c..097589753fec 100644
--- a/arch/x86/include/asm/unistd.h
+++ b/arch/x86/include/asm/unistd.h
@@ -54,5 +54,6 @@
 # define __ARCH_WANT_SYS_FORK
 # define __ARCH_WANT_SYS_VFORK
 # define __ARCH_WANT_SYS_CLONE
+# define __ARCH_WANT_SYS_CLONE3
 
 #endif /* _ASM_X86_UNISTD_H */
diff --git a/arch/xtensa/include/asm/unistd.h b/arch/xtensa/include/asm/unistd.h
index 30af4dc3ce7b..b52236245e51 100644
--- a/arch/xtensa/include/asm/unistd.h
+++ b/arch/xtensa/include/asm/unistd.h
@@ -3,6 +3,7 @@
 #define _XTENSA_UNISTD_H
 
 #define __ARCH_WANT_SYS_CLONE
+#define __ARCH_WANT_SYS_CLONE3
 #include <uapi/asm/unistd.h>
 
 #define __ARCH_WANT_NEW_STAT
diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl
index 782b81945ccc..25f4de729a6d 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -405,3 +405,4 @@
 432	common	fsmount				sys_fsmount
 433	common	fspick				sys_fspick
 434	common	pidfd_open			sys_pidfd_open
+435	common	clone3				sys_clone3