8 files changed, 46 insertions, 116 deletions

diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
index 0744f7d7b1fd..e418803b6c8e 100644
--- a/arch/hexagon/Kconfig
+++ b/arch/hexagon/Kconfig
@@ -31,6 +31,8 @@ config HEXAGON
         select GENERIC_CLOCKEVENTS
         select GENERIC_CLOCKEVENTS_BROADCAST
         select MODULES_USE_ELF_RELA
+        select GENERIC_KERNEL_THREAD
+        select GENERIC_KERNEL_EXECVE
         ---help---
           Qualcomm Hexagon is a processor architecture designed for high
           performance and low power across a wide variety of applications.
diff --git a/arch/hexagon/include/asm/processor.h b/arch/hexagon/include/asm/processor.h
index e8ea459002a4..8483b49de036 100644
--- a/arch/hexagon/include/asm/processor.h
+++ b/arch/hexagon/include/asm/processor.h
@@ -34,7 +34,6 @@
 struct task_struct;
 
 /*  this is defined in arch/process.c  */
-extern pid_t kernel_thread(int (*fn)(void *), void * arg, unsigned long flags);
 extern unsigned long thread_saved_pc(struct task_struct *tsk);
 
 extern void start_thread(struct pt_regs *, unsigned long, unsigned long);
diff --git a/arch/hexagon/include/asm/ptrace.h b/arch/hexagon/include/asm/ptrace.h
index 3d2f607cd63c..7e1e3745cb8a 100644
--- a/arch/hexagon/include/asm/ptrace.h
+++ b/arch/hexagon/include/asm/ptrace.h
@@ -32,4 +32,8 @@
 extern int regs_query_register_offset(const char *name);
 extern const char *regs_query_register_name(unsigned int offset);
 
+#define current_pt_regs() \
+        ((struct pt_regs *) \
+         ((unsigned long)current_thread_info() + THREAD_SIZE) - 1)
+
 #endif
diff --git a/arch/hexagon/include/asm/unistd.h b/arch/hexagon/include/asm/unistd.h
index c0d5565030ae..acbd5adc9814 100644
--- a/arch/hexagon/include/asm/unistd.h
+++ b/arch/hexagon/include/asm/unistd.h
@@ -27,5 +27,6 @@
  */
 
 #define sys_mmap2 sys_mmap_pgoff
+#define __ARCH_WANT_SYS_EXECVE
 
 #include <asm-generic/unistd.h>
diff --git a/arch/hexagon/kernel/process.c b/arch/hexagon/kernel/process.c
index af51de63b835..8a016f7e3949 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.
@@ -114,7 +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;
 }
diff --git a/arch/hexagon/kernel/signal.c b/arch/hexagon/kernel/signal.c
index 1ea16bec7b91..28b9e2617769 100644
--- a/arch/hexagon/kernel/signal.c
+++ b/arch/hexagon/kernel/signal.c
@@ -249,14 +249,14 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
  */
 asmlinkage int sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
 {
-        struct pt_regs *regs = current_thread_info()->regs;
+        struct pt_regs *regs = current_pt_regs();
 
         return do_sigaltstack(uss, uoss, regs->r29);
 }
 
 asmlinkage int sys_rt_sigreturn(void)
 {
-        struct pt_regs *regs = current_thread_info()->regs;
+        struct pt_regs *regs = current_pt_regs();
         struct rt_sigframe __user *frame;
         sigset_t blocked;
 
diff --git a/arch/hexagon/kernel/syscall.c b/arch/hexagon/kernel/syscall.c
index 25a9bfe3445d..e28f4e5a6a7a 100644
--- a/arch/hexagon/kernel/syscall.c
+++ b/arch/hexagon/kernel/syscall.c
@@ -35,55 +35,13 @@
  * See signal.c for signal-related system call wrappers.
  */
 
-asmlinkage int sys_execve(char __user *ufilename,
-                          const char __user *const __user *argv,
-                          const char __user *const __user *envp)
-{
-        struct pt_regs *pregs = current_thread_info()->regs;
-        struct filename *filename;
-        int retval;
-
-        filename = getname(ufilename);
-        retval = PTR_ERR(filename);
-        if (IS_ERR(filename))
-                return retval;
-
-        retval = do_execve(filename->name, argv, envp, pregs);
-        putname(filename);
-
-        return retval;
-}
-
 asmlinkage int sys_clone(unsigned long clone_flags, unsigned long newsp,
                          unsigned long parent_tidp, unsigned long child_tidp)
 {
-        struct pt_regs *pregs = current_thread_info()->regs;
+        struct pt_regs *pregs = current_pt_regs();
 
         if (!newsp)
                 newsp = pregs->SP;
         return do_fork(clone_flags, newsp, pregs, 0, (int __user *)parent_tidp,
                        (int __user *)child_tidp);
 }
-
-/*
- * Do a system call from the kernel, so as to have a proper pt_regs
- * and recycle the sys_execvpe infrustructure.
- */
-int kernel_execve(const char *filename,
-                  const char *const argv[], const char *const envp[])
-{
-        register unsigned long __a0 asm("r0") = (unsigned long) filename;
-        register unsigned long __a1 asm("r1") = (unsigned long) argv;
-        register unsigned long __a2 asm("r2") = (unsigned long) envp;
-        int retval;
-
-        __asm__ volatile(
-                "       R6 = #%4;\n"
-                "       trap0(#1);\n"
-                "       %0 = R0;\n"
-                : "=r" (retval)
-                : "r" (__a0), "r" (__a1), "r" (__a2), "i" (__NR_execve)
-        );
-
-        return retval;
-}
diff --git a/arch/hexagon/kernel/vm_entry.S b/arch/hexagon/kernel/vm_entry.S
index 5b99066cbc8d..1a7fcf502093 100644
--- a/arch/hexagon/kernel/vm_entry.S
+++ b/arch/hexagon/kernel/vm_entry.S
@@ -266,4 +266,8 @@ _K_enter_machcheck:
         .globl ret_from_fork
 ret_from_fork:
         call schedule_tail
+        P0 = cmp.eq(R24, #0);
+        if P0 jump return_from_syscall
+        R0 = R25;
+        callr R24
         jump return_from_syscall