Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull low-level x86 updates from Ingo Molnar:
 "In this cycle this topic tree has become one of those 'super topics'
  that accumulated a lot of changes:

   - Add CONFIG_VMAP_STACK=y support to the core kernel and enable it on
     x86 - preceded by an array of changes. v4.8 saw preparatory changes
     in this area already - this is the rest of the work. Includes the
     thread stack caching performance optimization. (Andy Lutomirski)

   - switch_to() cleanups and all around enhancements. (Brian Gerst)

   - A large number of dumpstack infrastructure enhancements and an
     unwinder abstraction. The secret long term plan is safe(r) live
     patching plus maybe another attempt at debuginfo based unwinding -
     but all these current bits are standalone enhancements in a frame
     pointer based debug environment as well. (Josh Poimboeuf)

   - More __ro_after_init and const annotations. (Kees Cook)

   - Enable KASLR for the vmemmap memory region. (Thomas Garnier)"

[ The virtually mapped stack changes are pretty fundamental, and not
  x86-specific per se, even if they are only used on x86 right now. ]

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  x86/asm: Get rid of __read_cr4_safe()
  thread_info: Use unsigned long for flags
  x86/alternatives: Add stack frame dependency to alternative_call_2()
  x86/dumpstack: Fix show_stack() task pointer regression
  x86/dumpstack: Remove dump_trace() and related callbacks
  x86/dumpstack: Convert show_trace_log_lvl() to use the new unwinder
  oprofile/x86: Convert x86_backtrace() to use the new unwinder
  x86/stacktrace: Convert save_stack_trace_*() to use the new unwinder
  perf/x86: Convert perf_callchain_kernel() to use the new unwinder
  x86/unwind: Add new unwind interface and implementations
  x86/dumpstack: Remove NULL task pointer convention
  fork: Optimize task creation by caching two thread stacks per CPU if CONFIG_VMAP_STACK=y
  sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK
  lib/syscall: Pin the task stack in collect_syscall()
  x86/process: Pin the target stack in get_wchan()
  x86/dumpstack: Pin the target stack when dumping it
  kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function
  sched/core: Add try_get_task_stack() and put_task_stack()
  x86/entry/64: Fix a minor comment rebase error
  iommu/amd: Don't put completion-wait semaphore on stack
  ...

1 files changed, 12 insertions, 13 deletions

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 63236d8f84bf..de9acaf2d371 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -50,8 +50,6 @@
 #include <asm/switch_to.h>
 #include <asm/xen/hypervisor.h>
 
-asmlinkage extern void ret_from_fork(void);
-
 __visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
 
 /* Prints also some state that isn't saved in the pt_regs */
@@ -141,12 +139,17 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 {
 	int err;
 	struct pt_regs *childregs;
+	struct fork_frame *fork_frame;
+	struct inactive_task_frame *frame;
 	struct task_struct *me = current;
 
 	p->thread.sp0 = (unsigned long)task_stack_page(p) + THREAD_SIZE;
 	childregs = task_pt_regs(p);
-	p->thread.sp = (unsigned long) childregs;
-	set_tsk_thread_flag(p, TIF_FORK);
+	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;
 
 	savesegment(gs, p->thread.gsindex);
@@ -160,15 +163,11 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 	if (unlikely(p->flags & PF_KTHREAD)) {
 		/* kernel thread */
 		memset(childregs, 0, sizeof(struct pt_regs));
-		childregs->sp = (unsigned long)childregs;
-		childregs->ss = __KERNEL_DS;
-		childregs->bx = sp; /* function */
-		childregs->bp = arg;
-		childregs->orig_ax = -1;
-		childregs->cs = __KERNEL_CS | get_kernel_rpl();
-		childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
+		frame->bx = sp;		/* function */
+		frame->r12 = arg;
 		return 0;
 	}
+	frame->bx = 0;
 	*childregs = *current_pt_regs();
 
 	childregs->ax = 0;
@@ -511,7 +510,7 @@ void set_personality_ia32(bool x32)
 		current->personality &= ~READ_IMPLIES_EXEC;
 		/* in_compat_syscall() uses the presence of the x32
 		   syscall bit flag to determine compat status */
-		current_thread_info()->status &= ~TS_COMPAT;
+		current->thread.status &= ~TS_COMPAT;
 	} else {
 		set_thread_flag(TIF_IA32);
 		clear_thread_flag(TIF_X32);
@@ -519,7 +518,7 @@ void set_personality_ia32(bool x32)
 			current->mm->context.ia32_compat = TIF_IA32;
 		current->personality |= force_personality32;
 		/* Prepare the first "return" to user space */
-		current_thread_info()->status |= TS_COMPAT;
+		current->thread.status |= TS_COMPAT;
 	}
 }
 EXPORT_SYMBOL_GPL(set_personality_ia32);