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Message-ID: <ab9a570f5c3098237a82f6e0dca61d284eb2d072.camel@physik.fu-berlin.de>
Date: Fri, 16 Jan 2026 18:19:31 +0100
From: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To: Ludwig Rydberg <ludwig.rydberg@...sler.com>, davem@...emloft.net,
andreas@...sler.com, brauner@...nel.org, shuah@...nel.org
Cc: sparclinux@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-kernel@...r.kernel.org, arnd@...db.de, geert@...ux-m68k.org,
schuster.simon@...mens-energy.com
Subject: Re: [PATCH 2/3] sparc: Add architecture support for clone3
Hi Ludwig,
On Fri, 2026-01-16 at 16:30 +0100, Ludwig Rydberg wrote:
> Add support for the clone3 system call to the SPARC architectures.
>
> The implementation follows the pattern of the original clone syscall.
> However, instead of explicitly calling kernel_clone, the clone3
> handler calls the generic sys_clone3 handler in kernel/fork.
> In case no stack is provided, the parents stack is reused.
>
> The return call conventions for clone on SPARC are kept for clone3:
> Parent --> %o0 == child's pid, %o1 == 0
> Child --> %o0 == parent's pid, %o1 == 1
>
> Closes: https://github.com/sparclinux/issues/issues/10
> Signed-off-by: Ludwig Rydberg <ludwig.rydberg@...sler.com>
> ---
> arch/sparc/include/asm/syscalls.h | 1 +
> arch/sparc/include/asm/unistd.h | 2 --
> arch/sparc/kernel/entry.S | 15 +++++++++++++++
> arch/sparc/kernel/kernel.h | 1 +
> arch/sparc/kernel/process.c | 25 +++++++++++++++++++++++++
> arch/sparc/kernel/process_32.c | 2 +-
> arch/sparc/kernel/process_64.c | 2 +-
> arch/sparc/kernel/syscalls.S | 6 ++++++
> arch/sparc/kernel/syscalls/syscall.tbl | 2 +-
> 9 files changed, 51 insertions(+), 5 deletions(-)
>
> diff --git a/arch/sparc/include/asm/syscalls.h b/arch/sparc/include/asm/syscalls.h
> index 35575fbfb9dc..282e62b66518 100644
> --- a/arch/sparc/include/asm/syscalls.h
> +++ b/arch/sparc/include/asm/syscalls.h
> @@ -7,5 +7,6 @@ struct pt_regs;
> asmlinkage long sparc_fork(struct pt_regs *regs);
> asmlinkage long sparc_vfork(struct pt_regs *regs);
> asmlinkage long sparc_clone(struct pt_regs *regs);
> +asmlinkage long sparc_clone3(struct pt_regs *regs);
>
> #endif /* _SPARC64_SYSCALLS_H */
> diff --git a/arch/sparc/include/asm/unistd.h b/arch/sparc/include/asm/unistd.h
> index 3380411a4537..d6bc76706a7a 100644
> --- a/arch/sparc/include/asm/unistd.h
> +++ b/arch/sparc/include/asm/unistd.h
> @@ -49,8 +49,6 @@
> #define __ARCH_WANT_COMPAT_STAT
> #endif
>
> -#define __ARCH_BROKEN_SYS_CLONE3
> -
> #ifdef __32bit_syscall_numbers__
> /* Sparc 32-bit only has the "setresuid32", "getresuid32" variants,
> * it never had the plain ones and there is no value to adding those
> diff --git a/arch/sparc/kernel/entry.S b/arch/sparc/kernel/entry.S
> index a3fdee4cd6fa..ea51ef52c952 100644
> --- a/arch/sparc/kernel/entry.S
> +++ b/arch/sparc/kernel/entry.S
> @@ -907,6 +907,21 @@ flush_patch_four:
> jmpl %l1 + %lo(sparc_vfork), %g0
> add %sp, STACKFRAME_SZ, %o0
>
> + .globl __sys_clone3, flush_patch_five
> +__sys_clone3:
> + mov %o7, %l5
> +flush_patch_five:
> + FLUSH_ALL_KERNEL_WINDOWS;
> + ld [%curptr + TI_TASK], %o4
> + rd %psr, %g4
> + WRITE_PAUSE
> + rd %wim, %g5
> + WRITE_PAUSE
> + std %g4, [%o4 + AOFF_task_thread + AOFF_thread_fork_kpsr]
> + add %sp, STACKFRAME_SZ, %o0
> + call sparc_clone3
> + mov %l5, %o7
> +
> .align 4
> linux_sparc_ni_syscall:
> sethi %hi(sys_ni_syscall), %l7
> diff --git a/arch/sparc/kernel/kernel.h b/arch/sparc/kernel/kernel.h
> index 8328a3b78a44..4ee85051521a 100644
> --- a/arch/sparc/kernel/kernel.h
> +++ b/arch/sparc/kernel/kernel.h
> @@ -18,6 +18,7 @@ extern int ncpus_probed;
> asmlinkage long sparc_clone(struct pt_regs *regs);
> asmlinkage long sparc_fork(struct pt_regs *regs);
> asmlinkage long sparc_vfork(struct pt_regs *regs);
> +asmlinkage long sparc_clone3(struct pt_regs *regs);
>
> #ifdef CONFIG_SPARC64
> /* setup_64.c */
> diff --git a/arch/sparc/kernel/process.c b/arch/sparc/kernel/process.c
> index 7d69877511fa..b8e23295db69 100644
> --- a/arch/sparc/kernel/process.c
> +++ b/arch/sparc/kernel/process.c
> @@ -12,6 +12,7 @@
> #include <linux/sched/task.h>
> #include <linux/sched/task_stack.h>
> #include <linux/signal.h>
> +#include <linux/syscalls.h>
>
> #include "kernel.h"
>
> @@ -118,3 +119,27 @@ asmlinkage long sparc_clone(struct pt_regs *regs)
>
> return ret;
> }
> +
> +asmlinkage long sparc_clone3(struct pt_regs *regs)
> +{
> + unsigned long sz;
> + long ret;
> + struct clone_args __user *cl_args;
> +
> + synchronize_user_stack();
> +
> + cl_args = (struct clone_args __user *)regs->u_regs[UREG_I0];
> + sz = regs->u_regs[UREG_I1];
> +
> + ret = sys_clone3(cl_args, sz);
> +
> + /* If we get an error and potentially restart the system
> + * call, we're screwed because copy_thread() clobbered
> + * the parent's %o1. So detect that case and restore it
> + * here.
> + */
> + if ((unsigned long)ret >= -ERESTART_RESTARTBLOCK)
> + regs->u_regs[UREG_I1] = sz;
> +
> + return ret;
> +}
> diff --git a/arch/sparc/kernel/process_32.c b/arch/sparc/kernel/process_32.c
> index 5a28c0e91bf1..216c07971c81 100644
> --- a/arch/sparc/kernel/process_32.c
> +++ b/arch/sparc/kernel/process_32.c
> @@ -261,11 +261,11 @@ extern void ret_from_kernel_thread(void);
> int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
> {
> u64 clone_flags = args->flags;
> - unsigned long sp = args->stack;
> unsigned long tls = args->tls;
> struct thread_info *ti = task_thread_info(p);
> struct pt_regs *childregs, *regs = current_pt_regs();
> char *new_stack;
> + unsigned long sp = args->stack ? args->stack : regs->u_regs[UREG_FP];
>
> #ifndef CONFIG_SMP
> if(last_task_used_math == current) {
> diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
> index 25781923788a..885d617ba29d 100644
> --- a/arch/sparc/kernel/process_64.c
> +++ b/arch/sparc/kernel/process_64.c
> @@ -568,13 +568,13 @@ void fault_in_user_windows(struct pt_regs *regs)
> int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
> {
> u64 clone_flags = args->flags;
> - unsigned long sp = args->stack;
> unsigned long tls = args->tls;
> struct thread_info *t = task_thread_info(p);
> struct pt_regs *regs = current_pt_regs();
> struct sparc_stackf *parent_sf;
> unsigned long child_stack_sz;
> char *child_trap_frame;
> + unsigned long sp = args->stack ? args->stack : regs->u_regs[UREG_FP];
>
> /* Calculate offset to stack_frame & pt_regs */
> child_stack_sz = (STACKFRAME_SZ + TRACEREG_SZ);
> diff --git a/arch/sparc/kernel/syscalls.S b/arch/sparc/kernel/syscalls.S
> index 0e8ab0602c36..c8d374a37f98 100644
> --- a/arch/sparc/kernel/syscalls.S
> +++ b/arch/sparc/kernel/syscalls.S
> @@ -103,6 +103,12 @@ sys_clone:
> ba,pt %xcc, sparc_clone
> add %sp, PTREGS_OFF, %o0
>
> + .align 32
> +__sys_clone3:
> + flushw
> + ba,pt %xcc, sparc_clone3
> + add %sp, PTREGS_OFF, %o0
> +
> .globl ret_from_fork
> ret_from_fork:
> /* Clear current_thread_info()->new_child. */
> diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
> index 39aa26b6a50b..c0307bb09892 100644
> --- a/arch/sparc/kernel/syscalls/syscall.tbl
> +++ b/arch/sparc/kernel/syscalls/syscall.tbl
> @@ -480,7 +480,7 @@
> 432 common fsmount sys_fsmount
> 433 common fspick sys_fspick
> 434 common pidfd_open sys_pidfd_open
> -# 435 reserved for clone3
> +435 common clone3 __sys_clone3
> 436 common close_range sys_close_range
> 437 common openat2 sys_openat2
> 438 common pidfd_getfd sys_pidfd_getfd
Applied on top of 6.19-rc5, tested on a Sun Netra 240 (UltraSPARC IIIi).
Running the kernel selftest for clone3 works fine:
root@...erin:/usr/src/linux/tools/testing/selftests/clone3# uname -a
Linux raverin 6.19.0-rc5+ #18 Fri Jan 16 16:02:10 UTC 2026 sparc64 GNU/Linux
root@...erin:/usr/src/linux/tools/testing/selftests/clone3# make
CC clone3
CC clone3_clear_sighand
CC clone3_set_tid
CC clone3_cap_checkpoint_restore
root@...erin:/usr/src/linux/tools/testing/selftests/clone3# ./clone3
TAP version 13
1..19
# clone3() syscall supported
# Running test 'simple clone3()'
# [1385] Trying clone3() with flags 0 (size 0)
# I am the parent (1385). My child's pid is 1386
# I am the child, my PID is 1386
# [1385] clone3() with flags says: 0 expected 0
ok 1 simple clone3()
# Running test 'clone3() in a new PID_NS'
# [1385] Trying clone3() with flags 0x20000000 (size 0)
# I am the child, my PID is 1
# I am the parent (1385). My child's pid is 1387
# [1385] clone3() with flags says: 0 expected 0
ok 2 clone3() in a new PID_NS
# Running test 'CLONE_ARGS_SIZE_VER0'
# [1385] Trying clone3() with flags 0 (size 64)
# I am the parent (1385). My child's pid is 1388
# I am the child, my PID is 1388
# [1385] clone3() with flags says: 0 expected 0
ok 3 CLONE_ARGS_SIZE_VER0
# Running test 'CLONE_ARGS_SIZE_VER0 - 8'
# [1385] Trying clone3() with flags 0 (size 56)
# Invalid argument - Failed to create new process
# [1385] clone3() with flags says: -22 expected -22
ok 4 CLONE_ARGS_SIZE_VER0 - 8
# Running test 'sizeof(struct clone_args) + 8'
# [1385] Trying clone3() with flags 0 (size 96)
# I am the parent (1385). My child's pid is 1389
# I am the child, my PID is 1389
# [1385] clone3() with flags says: 0 expected 0
ok 5 sizeof(struct clone_args) + 8
# Running test 'exit_signal with highest 32 bits non-zero'
# [1385] Trying clone3() with flags 0 (size 0)
# Invalid argument - Failed to create new process
# [1385] clone3() with flags says: -22 expected -22
ok 6 exit_signal with highest 32 bits non-zero
# Running test 'negative 32-bit exit_signal'
# [1385] Trying clone3() with flags 0 (size 0)
# Invalid argument - Failed to create new process
# [1385] clone3() with flags says: -22 expected -22
ok 7 negative 32-bit exit_signal
# Running test 'exit_signal not fitting into CSIGNAL mask'
# [1385] Trying clone3() with flags 0 (size 0)
# Invalid argument - Failed to create new process
# [1385] clone3() with flags says: -22 expected -22
ok 8 exit_signal not fitting into CSIGNAL mask
# Running test 'NSIG < exit_signal < CSIG'
# [1385] Trying clone3() with flags 0 (size 0)
# Invalid argument - Failed to create new process
# [1385] clone3() with flags says: -22 expected -22
ok 9 NSIG < exit_signal < CSIG
# Running test 'Arguments sizeof(struct clone_args) + 8'
# [1385] Trying clone3() with flags 0 (size 96)
# I am the parent (1385). My child's pid is 1390
# I am the child, my PID is 1390
# [1385] clone3() with flags says: 0 expected 0
ok 10 Arguments sizeof(struct clone_args) + 8
# Running test 'Arguments sizeof(struct clone_args) + 16'
# [1385] Trying clone3() with flags 0 (size 104)
# Argument list too long - Failed to create new process
# [1385] clone3() with flags says: -7 expected -7
ok 11 Arguments sizeof(struct clone_args) + 16
# Running test 'Arguments sizeof(struct clone_arg) * 2'
# [1385] Trying clone3() with flags 0 (size 104)
# Argument list too long - Failed to create new process
# [1385] clone3() with flags says: -7 expected -7
ok 12 Arguments sizeof(struct clone_arg) * 2
# Running test 'Arguments > page size'
# [1385] Trying clone3() with flags 0 (size 8200)
# Argument list too long - Failed to create new process
# [1385] clone3() with flags says: -7 expected -7
ok 13 Arguments > page size
# Running test 'CLONE_ARGS_SIZE_VER0 in a new PID NS'
# [1385] Trying clone3() with flags 0x20000000 (size 64)
# I am the parent (1385). My child's pid is 1391
# I am the child, my PID is 1
# [1385] clone3() with flags says: 0 expected 0
ok 14 CLONE_ARGS_SIZE_VER0 in a new PID NS
# Running test 'CLONE_ARGS_SIZE_VER0 - 8 in a new PID NS'
# [1385] Trying clone3() with flags 0x20000000 (size 56)
# Invalid argument - Failed to create new process
# [1385] clone3() with flags says: -22 expected -22
ok 15 CLONE_ARGS_SIZE_VER0 - 8 in a new PID NS
# Running test 'sizeof(struct clone_args) + 8 in a new PID NS'
# [1385] Trying clone3() with flags 0x20000000 (size 96)
# I am the parent (1385). My child's pid is 1392
# I am the child, my PID is 1
# [1385] clone3() with flags says: 0 expected 0
ok 16 sizeof(struct clone_args) + 8 in a new PID NS
# Running test 'Arguments > page size in a new PID NS'
# [1385] Trying clone3() with flags 0x20000000 (size 8200)
# Argument list too long - Failed to create new process
# [1385] clone3() with flags says: -7 expected -7
ok 17 Arguments > page size in a new PID NS
# Time namespaces are not supported
ok 18 # SKIP New time NS
# Running test 'exit signal (SIGCHLD) in flags'
# [1385] Trying clone3() with flags 0x14 (size 0)
# Invalid argument - Failed to create new process
# [1385] clone3() with flags says: -22 expected -22
ok 19 exit signal (SIGCHLD) in flags
# 1 skipped test(s) detected. Consider enabling relevant config options to improve coverage.
# Totals: pass:18 fail:0 xfail:0 xpass:0 skip:1 error:0
root@...erin:/usr/src/linux/tools/testing/selftests/clone3#
Tested-by: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Thanks,
Adrian
--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer
`. `' Physicist
`- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
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