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clone.2: Document raw syscall interfaces on various other architectures 

Reported-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2016-09-25 21:00:14 +02:00
parent fda554706b
commit 2a15a76bba
1 changed files with 50 additions and 16 deletions
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66
man2/clone.2
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@ -54,11 +54,7 @@ clone, __clone2 \- create a child process
.BI " /* pid_t *" ptid ", void *" newtls \
", pid_t *" ctid " */ );"
/* Prototype for the raw system call */
.BI "long clone(unsigned long " flags ", void *" child_stack ,
.BI " int *" ptid ", int *" ctid ,
.BI " unsigned long " newtls );
/* For the prototype of the raw system call, see NOTES */
.fi
.SH DESCRIPTION
.BR clone ()
@ -821,16 +817,58 @@ arguments of the
.BR clone ()
wrapper function are omitted.
Furthermore, the argument order changes.
The raw system call interface on x86 and many other architectures is roughly:
In addition, there are variations across architectures.
The raw system call interface on x86-64 and some other architectures
(including sh, tile, and alpha) is roughly:
.in +4
.nf
.BI "long clone(unsigned long " flags ", void *" child_stack ,
.BI " int *" ptid ", int *" ctid ,
.BI " unsigned long " newtls );
.fi
.in
On x86-32, and several other common architectures
(including score, ARM, ARM 64, PA-RISC, arc, Power PC, xtensa,
and MIPS),
.\" CONFIG_CLONE_BACKWARDS
the order of the last two arguments is reversed:
.in +4
.nf
.BI "long clone(unsigned long " flags ", void *" child_stack ,
.BI " int *" ptid ", unsigned long " newtls ,
.BI " int *" ctid );
.fi
.in
On the cris and s390 architectures,
.\" CONFIG_CLONE_BACKWARDS2
the order of the first two arguments is reversed:
.in +4
.nf
.BI "long clone(void *" child_stack ", unsigned long " flags ,
.BI " int *" ptid ", int *" ctid ,
.BI " unsigned long " newtls );
.fi
.in
On the microblaze architecture,
.\" CONFIG_CLONE_BACKWARDS3
an additional argument is supplied:
.in +4
.nf
.BI "long clone(unsigned long " flags ", void *" child_stack ,
.BI " int " stack_size , "\fR /* Size of stack */"
.BI " int *" ptid ", int *" ctid ,
.BI " unsigned long " newtls );
.fi
.in
Another difference for the raw system call is that the
.I child_stack
argument may be zero, in which case copy-on-write semantics ensure that the
@ -839,15 +877,11 @@ the stack.
In this case, for correct operation, the
.B CLONE_VM
option should not be specified.
For some architectures, the order of the arguments for the system call
differs from that shown above.
On the score, microblaze, ARM, ARM 64, PA-RISC, arc, Power PC, xtensa,
and MIPS architectures,
the order of the fourth and fifth arguments is reversed.
On the cris and s390 architectures,
the order of the first and second arguments is reversed.
.\"
.SS blackfin, m68k, and sparc
.\" Mike Frysinger noted in a 2013 mail:
.\" these arches don't define __ARCH_WANT_SYS_CLONE:
.\" blackfin ia64 m68k sparc
The argument-passing conventions on
blackfin, m68k, and sparc are different from the descriptions above.
For details, see the kernel (and glibc) source.