arm64: Use generic kernel_thread() implementation

This patch enables CONFIG_GENERIC_KERNEL_THREAD on arm64, changes
copy_threads to cope with kernel threads creation and adapts
ret_from_fork accordingly. The arm64-specific kernel_thread
implementation is no longer needed.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7ff68c9..4077b71 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -6,6 +6,7 @@ config ARM64
        select GENERIC_IOMAP
        select GENERIC_IRQ_PROBE
        select GENERIC_IRQ_SHOW
+       select GENERIC_KERNEL_THREAD
        select GENERIC_SMP_IDLE_THREAD
        select GENERIC_TIME_VSYSCALL
        select HARDIRQS_SW_RESEND

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 39a208a..d6331ac 100644 (file)
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -136,11 +136,6 @@ unsigned long get_wchan(struct task_struct *p);
 extern struct task_struct *cpu_switch_to(struct task_struct *prev,
                                         struct task_struct *next);
 
-/*
- * Create a new kernel thread
- */
-extern int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
-
 #define task_pt_regs(p) \
        ((struct pt_regs *)(THREAD_START_SP + task_stack_page(p)) - 1)
 

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index a6f3f7d..08db897 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -611,7 +611,10 @@ ENDPROC(ret_to_user)
  */
 ENTRY(ret_from_fork)
        bl      schedule_tail
-       get_thread_info tsk
+       cbz     x19, 1f                         // not a kernel thread
+       mov     x0, x20
+       blr     x19
+1:     get_thread_info tsk
        b       ret_to_user
 ENDPROC(ret_from_fork)
 

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index f22965e..bf615e2 100644 (file)
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -240,27 +240,35 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
        struct pt_regs *childregs = task_pt_regs(p);
        unsigned long tls = p->thread.tp_value;
 
-       *childregs = *regs;
-       childregs->regs[0] = 0;
+       memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));
 
-       if (is_compat_thread(task_thread_info(p)))
-               childregs->compat_sp = stack_start;
-       else {
+       if (likely(regs)) {
+               *childregs = *regs;
+               childregs->regs[0] = 0;
+               if (is_compat_thread(task_thread_info(p))) {
+                       childregs->compat_sp = stack_start;
+               } else {
+                       /*
+                        * Read the current TLS pointer from tpidr_el0 as it may be
+                        * out-of-sync with the saved value.
+                        */
+                       asm("mrs %0, tpidr_el0" : "=r" (tls));
+                       childregs->sp = stack_start;
+               }
                /*
-                * Read the current TLS pointer from tpidr_el0 as it may be
-                * out-of-sync with the saved value.
+                * If a TLS pointer was passed to clone (4th argument), use it
+                * for the new thread.
                 */
-               asm("mrs %0, tpidr_el0" : "=r" (tls));
-               childregs->sp = stack_start;
+               if (clone_flags & CLONE_SETTLS)
+                       tls = regs->regs[3];
+       } else {
+               memset(childregs, 0, sizeof(struct pt_regs));
+               childregs->pstate = PSR_MODE_EL1h;
+               p->thread.cpu_context.x19 = stack_start;
+               p->thread.cpu_context.x20 = stk_sz;
        }
-
-       memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));
-       p->thread.cpu_context.sp = (unsigned long)childregs;
        p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
-
-       /* If a TLS pointer was passed to clone, use that for the new thread. */
-       if (clone_flags & CLONE_SETTLS)
-               tls = regs->regs[3];
+       p->thread.cpu_context.sp = (unsigned long)childregs;
        p->thread.tp_value = tls;
 
        ptrace_hw_copy_thread(p);
@@ -327,43 +335,6 @@ int dump_fpu (struct pt_regs *regs, struct user_fp *fp)
 }
 EXPORT_SYMBOL(dump_fpu);
 
-/*
- * Shuffle the argument into the correct register before calling the
- * thread function.  x1 is the thread argument, x2 is the pointer to
- * the thread function, and x3 points to the exit function.
- */
-extern void kernel_thread_helper(void);
-asm(   ".section .text\n"
-"      .align\n"
-"      .type   kernel_thread_helper, #function\n"
-"kernel_thread_helper:\n"
-"      mov     x0, x1\n"
-"      mov     x30, x3\n"
-"      br      x2\n"
-"      .size   kernel_thread_helper, . - kernel_thread_helper\n"
-"      .previous");
-
-#define kernel_thread_exit     do_exit
-
-/*
- * Create a kernel thread.
- */
-pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
-{
-       struct pt_regs regs;
-
-       memset(&regs, 0, sizeof(regs));
-
-       regs.regs[1] = (unsigned long)arg;
-       regs.regs[2] = (unsigned long)fn;
-       regs.regs[3] = (unsigned long)kernel_thread_exit;
-       regs.pc = (unsigned long)kernel_thread_helper;
-       regs.pstate = PSR_MODE_EL1h;
-
-       return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
-}
-EXPORT_SYMBOL(kernel_thread);
-
 unsigned long get_wchan(struct task_struct *p)
 {
        struct stackframe frame;