[tip:x86/asm] x86/unwind: Add new unwind interface and implementations

[tip-bot for Josh Poimboeuf]

Commit-ID:  7c7900f89770d7fba96100d8a9e18043a1af3973
Gitweb: http://git.kernel.org/tip/7c7900f89770d7fba96100d8a9e18043a1af3973
Author: Josh Poimboeuf 
AuthorDate: Fri, 16 Sep 2016 14:18:12 -0500
Committer:  Ingo Molnar 
CommitDate: Tue, 20 Sep 2016 08:29:33 +0200

x86/unwind: Add new unwind interface and implementations

The x86 stack dump code is a bit of a mess.  dump_trace() uses
callbacks, and each user of it seems to have slightly different
requirements, so there are several slightly different callbacks floating
around.

Also there are some upcoming features which will need more changes to
the stack dump code, including the printing of stack pt_regs, reliable
stack detection for live patching, and a DWARF unwinder.  Each of those
features would at least need more callbacks and/or callback interfaces,
resulting in a much bigger mess than what we have today.

Before doing all that, we should try to clean things up and replace
dump_trace() with something cleaner and more flexible.

The new unwinder is a simple state machine which was heavily inspired by
a suggestion from Andy Lutomirski:

  
https://lkml.kernel.org/r/CALCETrUbNTqaM2LRyXGRx=kVLRPeY5A3Pc6k4TtQxF320rUT=w...@mail.gmail.com

It's also similar to the libunwind API:

  http://www.nongnu.org/libunwind/man/libunwind(3).html

Some if its advantages:

- Simplicity: no more callback sprawl and less code duplication.

- Flexibility: it allows the caller to stop and inspect the stack state
  at each step in the unwinding process.

- Modularity: the unwinder code, console stack dump code, and stack
  metadata analysis code are all better separated so that changing one
  of them shouldn't have much of an impact on any of the others.

Two implementations are added which conform to the new unwind interface:

- The frame pointer unwinder which is used for CONFIG_FRAME_POINTER=y.

- The "guess" unwinder which is used for CONFIG_FRAME_POINTER=n.  This
  isn't an "unwinder" per se.  All it does is scan the stack for kernel
  text addresses.  But with no frame pointers, guesses are better than
  nothing in most cases.

Suggested-by: Andy Lutomirski 
Signed-off-by: Josh Poimboeuf 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Byungchul Park 
Cc: Denys Vlasenko 
Cc: Frederic Weisbecker 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Nilay Vaish 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Link: 
http://lkml.kernel.org/r/6dc2f909c47533d213d0505f0a113e64585bec82.1474045023.git.jpoim...@redhat.com
Signed-off-by: Ingo Molnar 
---
 arch/x86/include/asm/unwind.h  | 73 +
 arch/x86/kernel/Makefile   |  6 +++
 arch/x86/kernel/unwind_frame.c | 93 ++
 arch/x86/kernel/unwind_guess.c | 43 +++
 4 files changed, 215 insertions(+)

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
new file mode 100644
index 000..c4b6d1c
--- /dev/null
+++ b/arch/x86/include/asm/unwind.h
@@ -0,0 +1,73 @@
+#ifndef _ASM_X86_UNWIND_H
+#define _ASM_X86_UNWIND_H
+
+#include 
+#include 
+#include 
+#include 
+
+struct unwind_state {
+   struct stack_info stack_info;
+   unsigned long stack_mask;
+   struct task_struct *task;
+   int graph_idx;
+#ifdef CONFIG_FRAME_POINTER
+   unsigned long *bp;
+#else
+   unsigned long *sp;
+#endif
+};
+
+void __unwind_start(struct unwind_state *state, struct task_struct *task,
+   struct pt_regs *regs, unsigned long *first_frame);
+
+bool unwind_next_frame(struct unwind_state *state);
+
+static inline bool unwind_done(struct unwind_state *state)
+{
+   return state->stack_info.type == STACK_TYPE_UNKNOWN;
+}
+
+static inline
+void unwind_start(struct unwind_state *state, struct task_struct *task,
+ struct pt_regs *regs, unsigned long *first_frame)
+{
+   first_frame = first_frame ? : get_stack_pointer(task, regs);
+
+   __unwind_start(state, task, regs, first_frame);
+}
+
+#ifdef CONFIG_FRAME_POINTER
+
+static inline
+unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
+{
+   if (unwind_done(state))
+   return NULL;
+
+   return state->bp + 1;
+}
+
+unsigned long unwind_get_return_address(struct unwind_state *state);
+
+#else /* !CONFIG_FRAME_POINTER */
+
+static inline
+unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
+{
+   return NULL;
+}
+
+static inline
+unsigned long unwind_get_return_address(struct unwind_state *state)
+{
+   if (unwind_done(state))
+   return 0;
+
+   

[tip:x86/asm] x86/unwind: Add new unwind interface and implementations

[tip-bot for Josh Poimboeuf]

Commit-ID:  7c7900f89770d7fba96100d8a9e18043a1af3973
Gitweb: http://git.kernel.org/tip/7c7900f89770d7fba96100d8a9e18043a1af3973
Author: Josh Poimboeuf 
AuthorDate: Fri, 16 Sep 2016 14:18:12 -0500
Committer:  Ingo Molnar 
CommitDate: Tue, 20 Sep 2016 08:29:33 +0200

x86/unwind: Add new unwind interface and implementations

The x86 stack dump code is a bit of a mess.  dump_trace() uses
callbacks, and each user of it seems to have slightly different
requirements, so there are several slightly different callbacks floating
around.

Also there are some upcoming features which will need more changes to
the stack dump code, including the printing of stack pt_regs, reliable
stack detection for live patching, and a DWARF unwinder.  Each of those
features would at least need more callbacks and/or callback interfaces,
resulting in a much bigger mess than what we have today.

Before doing all that, we should try to clean things up and replace
dump_trace() with something cleaner and more flexible.

The new unwinder is a simple state machine which was heavily inspired by
a suggestion from Andy Lutomirski:

  
https://lkml.kernel.org/r/CALCETrUbNTqaM2LRyXGRx=kVLRPeY5A3Pc6k4TtQxF320rUT=w...@mail.gmail.com

It's also similar to the libunwind API:

  http://www.nongnu.org/libunwind/man/libunwind(3).html

Some if its advantages:

- Simplicity: no more callback sprawl and less code duplication.

- Flexibility: it allows the caller to stop and inspect the stack state
  at each step in the unwinding process.

- Modularity: the unwinder code, console stack dump code, and stack
  metadata analysis code are all better separated so that changing one
  of them shouldn't have much of an impact on any of the others.

Two implementations are added which conform to the new unwind interface:

- The frame pointer unwinder which is used for CONFIG_FRAME_POINTER=y.

- The "guess" unwinder which is used for CONFIG_FRAME_POINTER=n.  This
  isn't an "unwinder" per se.  All it does is scan the stack for kernel
  text addresses.  But with no frame pointers, guesses are better than
  nothing in most cases.

Suggested-by: Andy Lutomirski 
Signed-off-by: Josh Poimboeuf 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Byungchul Park 
Cc: Denys Vlasenko 
Cc: Frederic Weisbecker 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Nilay Vaish 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Link: 
http://lkml.kernel.org/r/6dc2f909c47533d213d0505f0a113e64585bec82.1474045023.git.jpoim...@redhat.com
Signed-off-by: Ingo Molnar 
---
 arch/x86/include/asm/unwind.h  | 73 +
 arch/x86/kernel/Makefile   |  6 +++
 arch/x86/kernel/unwind_frame.c | 93 ++
 arch/x86/kernel/unwind_guess.c | 43 +++
 4 files changed, 215 insertions(+)

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
new file mode 100644
index 000..c4b6d1c
--- /dev/null
+++ b/arch/x86/include/asm/unwind.h
@@ -0,0 +1,73 @@
+#ifndef _ASM_X86_UNWIND_H
+#define _ASM_X86_UNWIND_H
+
+#include 
+#include 
+#include 
+#include 
+
+struct unwind_state {
+   struct stack_info stack_info;
+   unsigned long stack_mask;
+   struct task_struct *task;
+   int graph_idx;
+#ifdef CONFIG_FRAME_POINTER
+   unsigned long *bp;
+#else
+   unsigned long *sp;
+#endif
+};
+
+void __unwind_start(struct unwind_state *state, struct task_struct *task,
+   struct pt_regs *regs, unsigned long *first_frame);
+
+bool unwind_next_frame(struct unwind_state *state);
+
+static inline bool unwind_done(struct unwind_state *state)
+{
+   return state->stack_info.type == STACK_TYPE_UNKNOWN;
+}
+
+static inline
+void unwind_start(struct unwind_state *state, struct task_struct *task,
+ struct pt_regs *regs, unsigned long *first_frame)
+{
+   first_frame = first_frame ? : get_stack_pointer(task, regs);
+
+   __unwind_start(state, task, regs, first_frame);
+}
+
+#ifdef CONFIG_FRAME_POINTER
+
+static inline
+unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
+{
+   if (unwind_done(state))
+   return NULL;
+
+   return state->bp + 1;
+}
+
+unsigned long unwind_get_return_address(struct unwind_state *state);
+
+#else /* !CONFIG_FRAME_POINTER */
+
+static inline
+unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
+{
+   return NULL;
+}
+
+static inline
+unsigned long unwind_get_return_address(struct unwind_state *state)
+{
+   if (unwind_done(state))
+   return 0;
+
+   return ftrace_graph_ret_addr(state->task, >graph_idx,
+*state->sp, state->sp);
+}
+
+#endif /* CONFIG_FRAME_POINTER */
+
+#endif /* _ASM_X86_UNWIND_H */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 0503f5b..45257cf 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -125,6 +125,12 @@