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 -- 2.8.1 -- 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
