x86/process: Unify copy_thread_tls()

While looking at the TSS io bitmap it turned out that any change in that
area would require identical changes to copy_thread_tls(). The 32 and 64
bit variants share sufficient code to consolidate them into a common
function to avoid duplication of upcoming modifications.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>

1 files changed, 100 insertions, 0 deletions

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 5e94c4354d4e..7e07f0bb0def 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -132,6 +132,106 @@ void exit_thread(struct task_struct *tsk)
 	fpu__drop(fpu);
 }
 
+static int set_new_tls(struct task_struct *p, unsigned long tls)
+{
+	struct user_desc __user *utls = (struct user_desc __user *)tls;
+
+	if (in_ia32_syscall())
+		return do_set_thread_area(p, -1, utls, 0);
+	else
+		return do_set_thread_area_64(p, ARCH_SET_FS, tls);
+}
+
+static inline int copy_io_bitmap(struct task_struct *tsk)
+{
+	if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP)))
+		return 0;
+
+	tsk->thread.io_bitmap_ptr = kmemdup(current->thread.io_bitmap_ptr,
+					    IO_BITMAP_BYTES, GFP_KERNEL);
+	if (!tsk->thread.io_bitmap_ptr) {
+		tsk->thread.io_bitmap_max = 0;
+		return -ENOMEM;
+	}
+	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
+	return 0;
+}
+
+static inline void free_io_bitmap(struct task_struct *tsk)
+{
+	if (tsk->thread.io_bitmap_ptr) {
+		kfree(tsk->thread.io_bitmap_ptr);
+		tsk->thread.io_bitmap_ptr = NULL;
+		tsk->thread.io_bitmap_max = 0;
+	}
+}
+
+int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
+		    unsigned long arg, struct task_struct *p, unsigned long tls)
+{
+	struct inactive_task_frame *frame;
+	struct fork_frame *fork_frame;
+	struct pt_regs *childregs;
+	int ret;
+
+	childregs = task_pt_regs(p);
+	fork_frame = container_of(childregs, struct fork_frame, regs);
+	frame = &fork_frame->frame;
+
+	frame->bp = 0;
+	frame->ret_addr = (unsigned long) ret_from_fork;
+	p->thread.sp = (unsigned long) fork_frame;
+	p->thread.io_bitmap_ptr = NULL;
+	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
+
+#ifdef CONFIG_X86_64
+	savesegment(gs, p->thread.gsindex);
+	p->thread.gsbase = p->thread.gsindex ? 0 : current->thread.gsbase;
+	savesegment(fs, p->thread.fsindex);
+	p->thread.fsbase = p->thread.fsindex ? 0 : current->thread.fsbase;
+	savesegment(es, p->thread.es);
+	savesegment(ds, p->thread.ds);
+#else
+	p->thread.sp0 = (unsigned long) (childregs + 1);
+	/*
+	 * Clear all status flags including IF and set fixed bit. 64bit
+	 * does not have this initialization as the frame does not contain
+	 * flags. The flags consistency (especially vs. AC) is there
+	 * ensured via objtool, which lacks 32bit support.
+	 */
+	frame->flags = X86_EFLAGS_FIXED;
+#endif
+
+	/* Kernel thread ? */
+	if (unlikely(p->flags & PF_KTHREAD)) {
+		memset(childregs, 0, sizeof(struct pt_regs));
+		kthread_frame_init(frame, sp, arg);
+		return 0;
+	}
+
+	frame->bx = 0;
+	*childregs = *current_pt_regs();
+	childregs->ax = 0;
+	if (sp)
+		childregs->sp = sp;
+
+#ifdef CONFIG_X86_32
+	task_user_gs(p) = get_user_gs(current_pt_regs());
+#endif
+
+	ret = copy_io_bitmap(p);
+	if (ret)
+		return ret;
+
+	/* Set a new TLS for the child thread? */
+	if (clone_flags & CLONE_SETTLS) {
+		ret = set_new_tls(p, tls);
+		if (ret)
+			free_io_bitmap(p);
+	}
+	return ret;
+}
+
 void flush_thread(void)
 {
 	struct task_struct *tsk = current;