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Subject[PATCH 1/5] x86, 64-bit: Move kernel_thread to C
Date
Prepare for merging with 32-bit.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
---
arch/x86/kernel/entry_64.S | 49 ++-----------------------------------
arch/x86/kernel/process_64.c | 31 ++++++++++++++++++++++-
arch/x86/kernel/x8664_ksyms_64.c | 2 -
3 files changed, 32 insertions(+), 50 deletions(-)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 63bca79..73d9b2c 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1166,63 +1166,20 @@ bad_gs:
jmp 2b
.previous

-/*
- * Create a kernel thread.
- *
- * C extern interface:
- * extern long kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
- *
- * asm input arguments:
- * rdi: fn, rsi: arg, rdx: flags
- */
-ENTRY(kernel_thread)
- CFI_STARTPROC
- FAKE_STACK_FRAME $child_rip
- SAVE_ALL
-
- # rdi: flags, rsi: usp, rdx: will be &pt_regs
- movq %rdx,%rdi
- orq kernel_thread_flags(%rip),%rdi
- movq $-1, %rsi
- movq %rsp, %rdx
-
- xorl %r8d,%r8d
- xorl %r9d,%r9d
-
- # clone now
- call do_fork
- movq %rax,RAX(%rsp)
- xorl %edi,%edi
-
- /*
- * It isn't worth to check for reschedule here,
- * so internally to the x86_64 port you can rely on kernel_thread()
- * not to reschedule the child before returning, this avoids the need
- * of hacks for example to fork off the per-CPU idle tasks.
- * [Hopefully no generic code relies on the reschedule -AK]
- */
- RESTORE_ALL
- UNFAKE_STACK_FRAME
- ret
- CFI_ENDPROC
-END(kernel_thread)
-
-ENTRY(child_rip)
+ENTRY(kernel_thread_helper)
pushq $0 # fake return address
CFI_STARTPROC
/*
* Here we are in the child and the registers are set as they were
* at kernel_thread() invocation in the parent.
*/
- movq %rdi, %rax
- movq %rsi, %rdi
- call *%rax
+ call *%rsi
# exit
mov %eax, %edi
call do_exit
ud2 # padding for call trace
CFI_ENDPROC
-END(child_rip)
+END(kernel_thread_helper)

/*
* execve(). This function needs to use IRET, not SYSRET, to set up all state properly.
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index c95c8f4..866b4b4 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -59,8 +59,6 @@ asmlinkage extern void ret_from_fork(void);
DEFINE_PER_CPU(unsigned long, old_rsp);
static DEFINE_PER_CPU(unsigned char, is_idle);

-unsigned long kernel_thread_flags = CLONE_VM | CLONE_UNTRACED;
-
static ATOMIC_NOTIFIER_HEAD(idle_notifier);

void idle_notifier_register(struct notifier_block *n)
@@ -231,6 +229,35 @@ void show_regs(struct pt_regs *regs)
show_trace(NULL, regs, (void *)(regs + 1), regs->bp);
}

+/*
+ * This gets run with %si containing the
+ * function to call, and %di containing
+ * the "args".
+ */
+extern void kernel_thread_helper(void);
+
+/*
+ * Create a kernel thread
+ */
+int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
+{
+ struct pt_regs regs;
+
+ memset(&regs, 0, sizeof(regs));
+
+ regs.si = (unsigned long) fn;
+ regs.di = (unsigned long) arg;
+
+ regs.orig_ax = -1;
+ regs.ip = (unsigned long) kernel_thread_helper;
+ regs.cs = __KERNEL_CS;
+ regs.flags = X86_EFLAGS_IF;
+
+ /* Ok, create the new process.. */
+ return do_fork(flags | CLONE_VM | CLONE_UNTRACED, ~0UL, &regs, 0, NULL, NULL);
+}
+EXPORT_SYMBOL(kernel_thread);
+
void release_thread(struct task_struct *dead_task)
{
if (dead_task->mm) {
diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c
index a102976..9fafaf8 100644
--- a/arch/x86/kernel/x8664_ksyms_64.c
+++ b/arch/x86/kernel/x8664_ksyms_64.c
@@ -17,8 +17,6 @@
EXPORT_SYMBOL(mcount);
#endif

-EXPORT_SYMBOL(kernel_thread);
-
EXPORT_SYMBOL(__get_user_1);
EXPORT_SYMBOL(__get_user_2);
EXPORT_SYMBOL(__get_user_4);
--
1.6.5.2


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