[CC += Mike Frysinger, since he also commented on this in the past] On 09/04/2016 07:11 AM, Josh Triplett wrote: > On Sun, Sep 04, 2016 at 04:30:44PM +1200, Michael Kerrisk (man-pages) wrote: >> [CC += Josh] >> >> Josh, I know you were submitting patches relate to the clone() TLS argument a >> while back. Could you comment on this patch proposal below (also >> https://bugzilla.kernel.org/show_bug.cgi?id=118241 is relevant). > > Sure. > >> On 08/24/2016 03:06 PM, Keno Fischer wrote: >>> The prototype for the system call was added in 81f10dad, but looking at the >>> kernel's fork.c, I believe the relevant definition is >>> >>> SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, >>> int __user *, parent_tidptr, >>> int __user *, child_tidptr, >>> unsigned long, tls) >>> >>> so the last argument is the tls argument, not a pt_regs argument. >>> I stumbled upon this while trying to understand CLONE_SETTLS, so I expanded >>> that description a little to cover other architectures. > > This description and patch looks correct to me. > Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Thanks, Josh. > Ideally, I'd suggest a follow-up patch to improve the prototypes for the > various architectures. Rather than saying "x86 looks roughly this way, > on these architectures swap these arguments, on these architectures > ...", I'd suggest explicitly giving each of the four prototypes (normal, > CONFIG_CLONE_BACKWARDS, CONFIG_CLONE_BACKWARDS2, > CONFIG_CLONE_BACKWARDS3) and the corresponding architectures. I applied the patch below. Okay? Cheers, Michael diff --git a/man2/clone.2 b/man2/clone.2 index 5c1e301..26c6b30 100644 --- a/man2/clone.2 +++ b/man2/clone.2 @@ -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, microblaze, 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. -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
