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s390: trim ancient junk from copy_thread() 

Setting and ->psw.addr in childregs of kernel thread is a rudiment of
the old kernel_thread()/kernel_execve() implementation.  Mainline hadn't
been using them since 2012.

And clarify the assignments to frame->sf.gprs - the array stores
grp6..gpr15 values to be set by __switch_to(), so frame->sf.gprs[5]
actually affects grp11, etc.

Better spell that as frame->sf.gprs[11 - 6]...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/ZAU6BYFisE8evmYf@ZenIV
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Al Viro 2023-03-06 00:55:33 +00:00 committed by Vasily Gorbik
parent 72c2112ce9
commit fb77914a69
1 changed files with 4 additions and 6 deletions
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10
arch/s390/kernel/process.c
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@ -136,12 +136,12 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
p->thread.last_break = 1;
frame->sf.back_chain = 0;
frame->sf.gprs[5] = (unsigned long)frame + sizeof(struct stack_frame);
frame->sf.gprs[6] = (unsigned long)p;
frame->sf.gprs[11 - 6] = (unsigned long)&frame->childregs;
frame->sf.gprs[12 - 6] = (unsigned long)p;
/* new return point is ret_from_fork */
frame->sf.gprs[8] = (unsigned long)ret_from_fork;
frame->sf.gprs[14 - 6] = (unsigned long)ret_from_fork;
/* fake return stack for resume(), don't go back to schedule */
frame->sf.gprs[9] = (unsigned long)frame;
frame->sf.gprs[15 - 6] = (unsigned long)frame;
/* Store access registers to kernel stack of new process. */
if (unlikely(args->fn)) {
@ -149,8 +149,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
memset(&frame->childregs, 0, sizeof(struct pt_regs));
frame->childregs.psw.mask = PSW_KERNEL_BITS | PSW_MASK_IO |
PSW_MASK_EXT | PSW_MASK_MCHECK;
frame->childregs.psw.addr =
(unsigned long)__ret_from_fork;
frame->childregs.gprs[9] = (unsigned long)args->fn;
frame->childregs.gprs[10] = (unsigned long)args->fn_arg;
frame->childregs.orig_gpr2 = -1;