frv: split ret_from_fork, simplify kernel_thread() a lot

Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

5 files changed, 32 insertions, 100 deletions

diff --git a/arch/frv/kernel/Makefile b/arch/frv/kernel/Makefile
index ad4087b6996..7b10bc19106 100644
--- a/arch/frv/kernel/Makefile
+++ b/arch/frv/kernel/Makefile
@@ -7,7 +7,7 @@ heads-$(CONFIG_MMU)		:= head-mmu-fr451.o
 
 extra-y:= head.o vmlinux.lds
 
-obj-y := $(heads-y) entry.o entry-table.o break.o switch_to.o kernel_thread.o \
+obj-y := $(heads-y) entry.o entry-table.o break.o switch_to.o \
          kernel_execve.o process.o traps.o ptrace.o signal.o dma.o \
          sys_frv.o time.o setup.o frv_ksyms.o \
          debug-stub.o irq.o sleep.o uaccess.o
diff --git a/arch/frv/kernel/entry.S b/arch/frv/kernel/entry.S
index 7d5e000fd32..7a886130ca1 100644
--- a/arch/frv/kernel/entry.S
+++ b/arch/frv/kernel/entry.S
@@ -863,6 +863,14 @@ ret_from_fork:
         setlos.p        #0,gr8
         bra             __syscall_exit
 
+        .globl          ret_from_kernel_thread
+ret_from_kernel_thread:
+        lddi.p          @(gr28,#REG_GR(8)),gr20
+        call            schedule_tail
+        or.p            gr20,gr20,gr8
+        calll           @(gr21,gr0)
+        bra             sys_exit
+
 ###################################################################################################
 #
 # Return to user mode is not as complex as all this looks,
diff --git a/arch/frv/kernel/frv_ksyms.c b/arch/frv/kernel/frv_ksyms.c
index a89803b58b9..86c516d96dc 100644
--- a/arch/frv/kernel/frv_ksyms.c
+++ b/arch/frv/kernel/frv_ksyms.c
@@ -30,7 +30,6 @@ EXPORT_SYMBOL(ip_fast_csum);
 EXPORT_SYMBOL(local_irq_count);
 EXPORT_SYMBOL(local_bh_count);
 #endif
-EXPORT_SYMBOL(kernel_thread);
 
 EXPORT_SYMBOL(__res_bus_clock_speed_HZ);
 EXPORT_SYMBOL(__page_offset);
diff --git a/arch/frv/kernel/kernel_thread.S b/arch/frv/kernel/kernel_thread.S
deleted file mode 100644
index f0e52943f92..00000000000
--- a/arch/frv/kernel/kernel_thread.S
+++ /dev/null
@@ -1,77 +0,0 @@
-/* kernel_thread.S: kernel thread creation
- *
- * Copyright (C) 2003 Red Hat, Inc. All Rights Reserved.
- * Written by David Howells (dhowells@redhat.com)
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version
- * 2 of the License, or (at your option) any later version.
- */
-
-#include <linux/linkage.h>
-#include <linux/kern_levels.h>
-#include <asm/unistd.h>
-
-#define CLONE_VM        0x00000100      /* set if VM shared between processes */
-
-        .section .rodata
-kernel_thread_emsg:
-        .asciz  KERN_ERR "failed to create kernel thread: error=%d\n"
-
-        .text
-        .balign         4
-
-###############################################################################
-#
-# Create a kernel thread
-#
-# int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
-#
-###############################################################################
-        .globl          kernel_thread
-        .type           kernel_thread,@function
-kernel_thread:
-        or.p            gr8,gr0,gr4
-        or              gr9,gr0,gr5
-
-        # start by forking the current process, but with shared VM
-        setlos.p        #__NR_clone,gr7         ; syscall number
-        ori             gr10,#CLONE_VM,gr8      ; first syscall arg     [clone_flags]
-        sethi.p         #0xe4e4,gr9             ; second syscall arg    [newsp]
-        setlo           #0xe4e4,gr9
-        setlos.p        #0,gr10                 ; third syscall arg     [parent_tidptr]
-        setlos          #0,gr11                 ; fourth syscall arg    [child_tidptr]
-        tira            gr0,#0
-        setlos.p        #4095,gr7
-        andcc           gr8,gr8,gr0,icc0
-        addcc.p         gr8,gr7,gr0,icc1
-        bnelr           icc0,#2
-        bc              icc1,#0,kernel_thread_error
-
-        # now invoke the work function
-        or              gr5,gr0,gr8
-        calll           @(gr4,gr0)
-
-        # and finally exit the thread
-        setlos          #__NR_exit,gr7          ; syscall number
-        tira            gr0,#0
-
-kernel_thread_error:
-        subi            sp,#8,sp
-        movsg           lr,gr4
-        sti             gr8,@(sp,#0)
-        sti.p           gr4,@(sp,#4)
-
-        or              gr8,gr0,gr9
-        sethi.p         %hi(kernel_thread_emsg),gr8
-        setlo           %lo(kernel_thread_emsg),gr8
-
-        call            printk
-
-        ldi             @(sp,#4),gr4
-        ldi             @(sp,#0),gr8
-        subi            sp,#8,sp
-        jmpl            @(gr4,gr0)
-
-        .size           kernel_thread,.-kernel_thread
diff --git a/arch/frv/kernel/process.c b/arch/frv/kernel/process.c
index ff95f50efea..0f02dee25e2 100644
--- a/arch/frv/kernel/process.c
+++ b/arch/frv/kernel/process.c
@@ -37,6 +37,7 @@
 #include "local.h"
 
 asmlinkage void ret_from_fork(void);
+asmlinkage void ret_from_kernel_thread(void);
 
 #include <asm/pgalloc.h>
 
@@ -172,29 +173,21 @@ int copy_thread(unsigned long clone_flags,
                 unsigned long usp, unsigned long topstk,
                 struct task_struct *p, struct pt_regs *regs)
 {
-        struct pt_regs *childregs0, *childregs, *regs0;
+        struct pt_regs *childregs;
 
-        regs0 = __kernel_frame0_ptr;
-        childregs0 = (struct pt_regs *)
+        childregs = (struct pt_regs *)
                 (task_stack_page(p) + THREAD_SIZE - FRV_FRAME0_SIZE);
-        childregs = childregs0;
 
         /* set up the userspace frame (the only place that the USP is stored) */
-        *childregs0 = *regs0;
-
-        childregs0->gr8         = 0;
-        childregs0->sp          = usp;
-        childregs0->next_frame  = NULL;
-
-        /* set up the return kernel frame if called from kernel_thread() */
-        if (regs != regs0) {
-                childregs--;
-                *childregs = *regs;
-                childregs->sp = (unsigned long) childregs0;
-                childregs->next_frame = childregs0;
-                childregs->gr15 = (unsigned long) task_thread_info(p);
-                childregs->gr29 = (unsigned long) p;
-        }
+        *childregs = *regs;
+
+        childregs->sp           = usp;
+        childregs->next_frame   = NULL;
+
+        if (unlikely(!user_mode(regs)))
+                p->thread.pc = (unsigned long) ret_from_kernel_thread;
+        else
+                p->thread.pc = (unsigned long) ret_from_fork;
 
         p->set_child_tid = p->clear_child_tid = NULL;
 
@@ -203,8 +196,7 @@ int copy_thread(unsigned long clone_flags,
         p->thread.sp     = (unsigned long) childregs;
         p->thread.fp     = 0;
         p->thread.lr     = 0;
-        p->thread.pc     = (unsigned long) ret_from_fork;
-        p->thread.frame0 = childregs0;
+        p->thread.frame0 = childregs;
 
         /* the new TLS pointer is passed in as arg #5 to sys_clone() */
         if (clone_flags & CLONE_SETTLS)
@@ -347,3 +339,13 @@ int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpregs)
                sizeof(current->thread.user->f));
         return 1;
 }
+
+int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
+{
+        struct pt_regs regs = {
+                .gr8 = (unsigned long)arg;
+                .gr9 = (unsigned long)fn;
+                .psr = PSR_S;
+        };
+        return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
+}