hexagon: kernel_thread()/kernel_execve() conversion

[firefly-linux-kernel-4.4.55.git] / arch / hexagon / kernel / process.c

diff --git a/arch/hexagon/kernel/process.c b/arch/hexagon/kernel/process.c
index af51de63b8359fface711d6b89424afc7f2d937d..8a016f7e39496aaa69ea4285283569adfd59b228 100644 (file)
--- a/arch/hexagon/kernel/process.c
+++ b/arch/hexagon/kernel/process.c
@@ -25,33 +25,6 @@
 #include <linux/uaccess.h>
 #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
@@ -114,7 +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,
+               unsigned long arg, struct task_struct *p,
                struct pt_regs *regs)
 {
        struct thread_info *ti = task_thread_info(p);
@@ -125,61 +98,50 @@ 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 User mode thread, set pt_reg stack pointer as per parameter */
-       if (user_mode(childregs)) {
-               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;
+       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, regs, sizeof(*childregs));
+       ss->r2524 = 0;
+
+       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;
 
        /*
-        * 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;
 }