arm: split ret_from_fork, simplify kernel_thread() [based on patch by rmk]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 2f88d8d..a949eec2 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -49,6 +49,7 @@
select GENERIC_STRNCPY_FROM_USER
select GENERIC_STRNLEN_USER
select DCACHE_WORD_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && !CPU_BIG_ENDIAN
+ select GENERIC_KERNEL_THREAD
help
The ARM series is a line of low-power-consumption RISC chip designs
licensed by ARM Ltd and targeted at embedded applications and
diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 99afa74..06e7d50 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -85,11 +85,6 @@
#define cpu_relax() barrier()
#endif
-/*
- * 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/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 978eac5..9a48b7a 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -91,6 +91,18 @@
b ret_slow_syscall
ENDPROC(ret_from_fork)
+ENTRY(ret_from_kernel_thread)
+ UNWIND(.fnstart)
+ UNWIND(.cantunwind)
+ bl schedule_tail
+ mov r0, r4
+ adr lr, BSYM(1f) @ kernel threads should not exit
+ mov pc, r5
+1: bl do_exit
+ nop
+ UNWIND(.fnend)
+ENDPROC(ret_from_kernel_thread)
+
.equ NR_syscalls,0
#define CALL(x) .equ NR_syscalls,NR_syscalls+1
#include "calls.S"
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 693b744..c10e439 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -373,6 +373,7 @@
}
asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
+asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");
int
copy_thread(unsigned long clone_flags, unsigned long stack_start,
@@ -381,13 +382,20 @@
struct thread_info *thread = task_thread_info(p);
struct pt_regs *childregs = task_pt_regs(p);
- *childregs = *regs;
- childregs->ARM_r0 = 0;
- childregs->ARM_sp = stack_start;
-
memset(&thread->cpu_context, 0, sizeof(struct cpu_context_save));
+
+ if (likely(regs)) {
+ *childregs = *regs;
+ childregs->ARM_r0 = 0;
+ childregs->ARM_sp = stack_start;
+ thread->cpu_context.pc = (unsigned long)ret_from_fork;
+ } else {
+ thread->cpu_context.r4 = stk_sz;
+ thread->cpu_context.r5 = stack_start;
+ thread->cpu_context.pc = (unsigned long)ret_from_kernel_thread;
+ childregs->ARM_cpsr = SVC_MODE;
+ }
thread->cpu_context.sp = (unsigned long)childregs;
- thread->cpu_context.pc = (unsigned long)ret_from_fork;
clear_ptrace_hw_breakpoint(p);
@@ -423,63 +431,6 @@
}
EXPORT_SYMBOL(dump_fpu);
-/*
- * Shuffle the argument into the correct register before calling the
- * thread function. r4 is the thread argument, r5 is the pointer to
- * the thread function, and r6 points to the exit function.
- */
-extern void kernel_thread_helper(void);
-asm( ".pushsection .text\n"
-" .align\n"
-" .type kernel_thread_helper, #function\n"
-"kernel_thread_helper:\n"
-#ifdef CONFIG_TRACE_IRQFLAGS
-" bl trace_hardirqs_on\n"
-#endif
-" msr cpsr_c, r7\n"
-" mov r0, r4\n"
-" mov lr, r6\n"
-" mov pc, r5\n"
-" .size kernel_thread_helper, . - kernel_thread_helper\n"
-" .popsection");
-
-#ifdef CONFIG_ARM_UNWIND
-extern void kernel_thread_exit(long code);
-asm( ".pushsection .text\n"
-" .align\n"
-" .type kernel_thread_exit, #function\n"
-"kernel_thread_exit:\n"
-" .fnstart\n"
-" .cantunwind\n"
-" bl do_exit\n"
-" nop\n"
-" .fnend\n"
-" .size kernel_thread_exit, . - kernel_thread_exit\n"
-" .popsection");
-#else
-#define kernel_thread_exit do_exit
-#endif
-
-/*
- * Create a kernel thread.
- */
-pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
-{
- struct pt_regs regs;
-
- memset(®s, 0, sizeof(regs));
-
- regs.ARM_r4 = (unsigned long)arg;
- regs.ARM_r5 = (unsigned long)fn;
- regs.ARM_r6 = (unsigned long)kernel_thread_exit;
- regs.ARM_r7 = SVC_MODE | PSR_ENDSTATE | PSR_ISETSTATE;
- regs.ARM_pc = (unsigned long)kernel_thread_helper;
- regs.ARM_cpsr = regs.ARM_r7 | PSR_I_BIT;
-
- return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, ®s, 0, NULL, NULL);
-}
-EXPORT_SYMBOL(kernel_thread);
-
unsigned long get_wchan(struct task_struct *p)
{
struct stackframe frame;