[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). Thanks, Michael 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. > --- > man2/clone.2 | 26 ++++++++++++++++++++------ > 1 file changed, 20 insertions(+), 6 deletions(-) > > diff --git a/man2/clone.2 b/man2/clone.2 > index b867961..7c80e63 100644 > --- a/man2/clone.2 > +++ b/man2/clone.2 > @@ -51,14 +51,14 @@ clone, __clone2 \- create a child process > > .BI "int clone(int (*" "fn" ")(void *), void *" child_stack , > .BI " int " flags ", void *" "arg" ", ... " > -.BI " /* pid_t *" ptid ", struct user_desc *" tls \ > +.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 " void *" ptid ", void *" ctid , > -.BI " struct pt_regs *" regs ); > +.BI " unsigned long " newtls ); > .fi > .SH DESCRIPTION > .BR clone () > @@ -544,11 +544,25 @@ then trace the child also (see > .BR ptrace (2)). > .TP > .BR CLONE_SETTLS " (since Linux 2.5.32)" > -The > +The TLS (Thread Local Storage) descriptor is set to > +.I newtls. > + > +The interpretation of > +.I newtls > +and the resulting effect is architecture dependent. > +On x86, > .I newtls > -argument is the new TLS (Thread Local Storage) descriptor. > +is interpreted as a > +.IR "struct user_desc *" > (See > -.BR set_thread_area (2).) > +.BR set_thread_area (2)). > +On x86_64 it is the new value to be set for the %fs base register > +(See the > +.I ARCH_SET_FS > +argument to > +.BR arch_prctl (2)). > +On architectures with a dedicated TLS register, it is the new value > +of that register. > .TP > .BR CLONE_SIGHAND " (since Linux 2.0)" > If > @@ -813,7 +827,7 @@ The raw system call interface on x86 and many other architectures is roughly: > > .BI "long clone(unsigned long " flags ", void *" child_stack , > .BI " void *" ptid ", void *" ctid , > -.BI " struct pt_regs *" regs ); > +.BI " unsigned long " newtls ); > > .fi > .in > -- 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
