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, 34 insertions, 45 deletions

diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 4738f5e0f2ab..0653788026e2 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -8,80 +8,69 @@
 #include <linux/export.h>
 #include <linux/uaccess.h>
 #include <asm/stacktrace.h>
+#include <asm/unwind.h>
 
-static int save_stack_stack(void *data, char *name)
+static int save_stack_address(struct stack_trace *trace, unsigned long addr,
+                              bool nosched)
 {
-        return 0;
-}
-
-static int
-__save_stack_address(void *data, unsigned long addr, bool reliable, bool nosched)
-{
-        struct stack_trace *trace = data;
-#ifdef CONFIG_FRAME_POINTER
-        if (!reliable)
-                return 0;
-#endif
         if (nosched && in_sched_functions(addr))
                 return 0;
+
         if (trace->skip > 0) {
                 trace->skip--;
                 return 0;
         }
-        if (trace->nr_entries < trace->max_entries) {
-                trace->entries[trace->nr_entries++] = addr;
-                return 0;
-        } else {
-                return -1; /* no more room, stop walking the stack */
-        }
-}
 
-static int save_stack_address(void *data, unsigned long addr, int reliable)
-{
-        return __save_stack_address(data, addr, reliable, false);
+        if (trace->nr_entries >= trace->max_entries)
+                return -1;
+
+        trace->entries[trace->nr_entries++] = addr;
+        return 0;
 }
 
-static int
-save_stack_address_nosched(void *data, unsigned long addr, int reliable)
+static void __save_stack_trace(struct stack_trace *trace,
+                               struct task_struct *task, struct pt_regs *regs,
+                               bool nosched)
 {
-        return __save_stack_address(data, addr, reliable, true);
-}
+        struct unwind_state state;
+        unsigned long addr;
 
-static const struct stacktrace_ops save_stack_ops = {
-        .stack          = save_stack_stack,
-        .address        = save_stack_address,
-        .walk_stack     = print_context_stack,
-};
+        if (regs)
+                save_stack_address(trace, regs->ip, nosched);
 
-static const struct stacktrace_ops save_stack_ops_nosched = {
-        .stack          = save_stack_stack,
-        .address        = save_stack_address_nosched,
-        .walk_stack     = print_context_stack,
-};
+        for (unwind_start(&state, task, regs, NULL); !unwind_done(&state);
+             unwind_next_frame(&state)) {
+                addr = unwind_get_return_address(&state);
+                if (!addr || save_stack_address(trace, addr, nosched))
+                        break;
+        }
+
+        if (trace->nr_entries < trace->max_entries)
+                trace->entries[trace->nr_entries++] = ULONG_MAX;
+}
 
 /*
  * Save stack-backtrace addresses into a stack_trace buffer.
  */
 void save_stack_trace(struct stack_trace *trace)
 {
-        dump_trace(current, NULL, NULL, 0, &save_stack_ops, trace);
-        if (trace->nr_entries < trace->max_entries)
-                trace->entries[trace->nr_entries++] = ULONG_MAX;
+        __save_stack_trace(trace, current, NULL, false);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace);
 
 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 {
-        dump_trace(current, regs, NULL, 0, &save_stack_ops, trace);
-        if (trace->nr_entries < trace->max_entries)
-                trace->entries[trace->nr_entries++] = ULONG_MAX;
+        __save_stack_trace(trace, current, regs, false);
 }
 
 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 {
-        dump_trace(tsk, NULL, NULL, 0, &save_stack_ops_nosched, trace);
-        if (trace->nr_entries < trace->max_entries)
-                trace->entries[trace->nr_entries++] = ULONG_MAX;
+        if (!try_get_task_stack(tsk))
+                return;
+
+        __save_stack_trace(trace, tsk, NULL, true);
+
+        put_task_stack(tsk);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);