1 files changed, 31 insertions, 69 deletions

diff --git a/arch/hexagon/kernel/process.c b/arch/hexagon/kernel/process.c
index 9f6d7411b574..06ae9ffcabd5 100644
--- a/arch/hexagon/kernel/process.c
+++ b/arch/hexagon/kernel/process.c
@@ -26,33 +26,6 @@
 #include <linux/slab.h>
 
 /*
- * Kernel thread creation.  The desired kernel function is "wrapped"
- * in the kernel_thread_helper function, which does cleanup
- * afterwards.
- */
-static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
-{
-        do_exit(fn(arg));
-}
-
-int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
-{
-        struct pt_regs regs;
-
-        memset(&regs, 0, sizeof(regs));
-        /*
-         * Yes, we're exploting illicit knowledge of the ABI here.
-         */
-        regs.r00 = (unsigned long) arg;
-        regs.r01 = (unsigned long) fn;
-        pt_set_elr(&regs, (unsigned long)kernel_thread_helper);
-        pt_set_kmode(&regs);
-
-        return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
-}
-EXPORT_SYMBOL(kernel_thread);
-
-/*
  * Program thread launch.  Often defined as a macro in processor.h,
  * but we're shooting for a small footprint and it's not an inner-loop
  * performance-critical operation.
@@ -114,8 +87,7 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
  * Copy architecture-specific thread state
  */
 int copy_thread(unsigned long clone_flags, unsigned long usp,
-                unsigned long unused, struct task_struct *p,
-                struct pt_regs *regs)
+                unsigned long arg, struct task_struct *p)
 {
         struct thread_info *ti = task_thread_info(p);
         struct hexagon_switch_stack *ss;
@@ -125,61 +97,51 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
         childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
                                         sizeof(*childregs));
 
-        memcpy(childregs, regs, sizeof(*childregs));
         ti->regs = childregs;
 
         /*
          * Establish kernel stack pointer and initial PC for new thread
+         * Note that unlike the usual situation, we do not copy the
+         * parent's callee-saved here; those are in pt_regs and whatever
+         * we leave here will be overridden on return to userland.
          */
         ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
                                                     sizeof(*ss));
         ss->lr = (unsigned long)ret_from_fork;
         p->thread.switch_sp = ss;
+        if (unlikely(p->flags & PF_KTHREAD)) {
+                memset(childregs, 0, sizeof(struct pt_regs));
+                /* r24 <- fn, r25 <- arg */
+                ss->r2524 = usp | ((u64)arg << 32);
+                pt_set_kmode(childregs);
+                return 0;
+        }
+        memcpy(childregs, current_pt_regs(), sizeof(*childregs));
+        ss->r2524 = 0;
 
-        /* If User mode thread, set pt_reg stack pointer as per parameter */
-        if (user_mode(childregs)) {
+        if (usp)
                 pt_set_rte_sp(childregs, usp);
 
-                /* Child sees zero return value */
-                childregs->r00 = 0;
-
-                /*
-                 * The clone syscall has the C signature:
-                 * int [r0] clone(int flags [r0],
-                 *           void *child_frame [r1],
-                 *           void *parent_tid [r2],
-                 *           void *child_tid [r3],
-                 *           void *thread_control_block [r4]);
-                 * ugp is used to provide TLS support.
-                 */
-                if (clone_flags & CLONE_SETTLS)
-                        childregs->ugp = childregs->r04;
-
-                /*
-                 * Parent sees new pid -- not necessary, not even possible at
-                 * this point in the fork process
-                 * Might also want to set things like ti->addr_limit
-                 */
-        } else {
-                /*
-                 * If kernel thread, resume stack is kernel stack base.
-                 * Note that this is pointer arithmetic on pt_regs *
-                 */
-                pt_set_rte_sp(childregs, (unsigned long)(childregs + 1));
-                /*
-                 * We need the current thread_info fast path pointer
-                 * set up in pt_regs.  The register to be used is
-                 * parametric for assembler code, but the mechanism
-                 * doesn't drop neatly into C.  Needs to be fixed.
-                 */
-                childregs->THREADINFO_REG = (unsigned long) ti;
-        }
+        /* Child sees zero return value */
+        childregs->r00 = 0;
+
+        /*
+         * The clone syscall has the C signature:
+         * int [r0] clone(int flags [r0],
+         *           void *child_frame [r1],
+         *           void *parent_tid [r2],
+         *           void *child_tid [r3],
+         *           void *thread_control_block [r4]);
+         * ugp is used to provide TLS support.
+         */
+        if (clone_flags & CLONE_SETTLS)
+                childregs->ugp = childregs->r04;
 
         /*
-         * thread_info pointer is pulled out of task_struct "stack"
-         * field on switch_to.
+         * Parent sees new pid -- not necessary, not even possible at
+         * this point in the fork process
+         * Might also want to set things like ti->addr_limit
          */
-        p->stack = (void *)ti;
 
         return 0;
 }