x86/kconfig: Consolidate unwinders into multiple choice selection

There are three mutually exclusive unwinders.  Make that more obvious by
combining them into a multiple-choice selection:

  CONFIG_FRAME_POINTER_UNWINDER
  CONFIG_ORC_UNWINDER
  CONFIG_GUESS_UNWINDER (if CONFIG_EXPERT=y)

Frame pointers are still the default (for now).

The old CONFIG_FRAME_POINTER option is still used in some
arch-independent places, so keep it around, but make it
invisible to the user on x86 - it's now selected by
CONFIG_FRAME_POINTER_UNWINDER=y.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/20170725135424.zukjmgpz3plf5pmt@treble
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7ccf26a427cb423bb3a1f1f62a9c7abe2754cb87..9b302121584d2125f67a9d3d4a35bbc9d3eea8f5 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -73,7 +73,6 @@ config X86
        select ARCH_USE_QUEUED_RWLOCKS
        select ARCH_USE_QUEUED_SPINLOCKS
        select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
-       select ARCH_WANT_FRAME_POINTERS
        select ARCH_WANTS_DYNAMIC_TASK_STRUCT
        select ARCH_WANTS_THP_SWAP              if X86_64
        select BUILDTIME_EXTABLE_SORT
@@ -168,7 +167,7 @@ config X86
        select HAVE_PERF_REGS
        select HAVE_PERF_USER_STACK_DUMP
        select HAVE_REGS_AND_STACK_ACCESS_API
-       select HAVE_RELIABLE_STACKTRACE         if X86_64 && FRAME_POINTER && STACK_VALIDATION
+       select HAVE_RELIABLE_STACKTRACE         if X86_64 && FRAME_POINTER_UNWINDER && STACK_VALIDATION
        select HAVE_STACK_VALIDATION            if X86_64
        select HAVE_SYSCALL_TRACEPOINTS
        select HAVE_UNSTABLE_SCHED_CLOCK

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 268a318f9439bffb15a13082c112fe90e29b32a3..93bbb31456fd38a88d19803aa44a9ed0317f1b08 100644 (file)
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -355,9 +355,32 @@ config PUNIT_ATOM_DEBUG
          The current power state can be read from
          /sys/kernel/debug/punit_atom/dev_power_state
 
+choice
+       prompt "Choose kernel unwinder"
+       default FRAME_POINTER_UNWINDER
+       ---help---
+         This determines which method will be used for unwinding kernel stack
+         traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
+         livepatch, lockdep, and more.
+
+config FRAME_POINTER_UNWINDER
+       bool "Frame pointer unwinder"
+       select FRAME_POINTER
+       ---help---
+         This option enables the frame pointer unwinder for unwinding kernel
+         stack traces.
+
+         The unwinder itself is fast and it uses less RAM than the ORC
+         unwinder, but the kernel text size will grow by ~3% and the kernel's
+         overall performance will degrade by roughly 5-10%.
+
+         This option is recommended if you want to use the livepatch
+         consistency model, as this is currently the only way to get a
+         reliable stack trace (CONFIG_HAVE_RELIABLE_STACKTRACE).
+
 config ORC_UNWINDER
        bool "ORC unwinder"
-       depends on X86_64 && !FRAME_POINTER
+       depends on X86_64
        select STACK_VALIDATION
        ---help---
          This option enables the ORC (Oops Rewind Capability) unwinder for
@@ -371,12 +394,22 @@ config ORC_UNWINDER
          Enabling this option will increase the kernel's runtime memory usage
          by roughly 2-4MB, depending on your kernel config.
 
-config FRAME_POINTER_UNWINDER
-       def_bool y
-       depends on !ORC_UNWINDER && FRAME_POINTER
-
 config GUESS_UNWINDER
-       def_bool y
-       depends on !ORC_UNWINDER && !FRAME_POINTER
+       bool "Guess unwinder"
+       depends on EXPERT
+       ---help---
+         This option enables the "guess" unwinder for unwinding kernel stack
+         traces.  It scans the stack and reports every kernel text address it
+         finds.  Some of the addresses it reports may be incorrect.
+
+         While this option often produces false positives, it can still be
+         useful in many cases.  Unlike the other unwinders, it has no runtime
+         overhead.
+
+endchoice
+
+config FRAME_POINTER
+       depends on !ORC_UNWINDER && !GUESS_UNWINDER
+       bool
 
 endmenu

diff --git a/arch/x86/configs/tiny.config b/arch/x86/configs/tiny.config
index 4b429df40d7a2fb9ee9fce2eb5315b592d1200e9..550cd5012b7354efd1d1eb3eaeebffd8cd7e30eb 100644 (file)
--- a/arch/x86/configs/tiny.config
+++ b/arch/x86/configs/tiny.config
@@ -1,3 +1,5 @@
 CONFIG_NOHIGHMEM=y
 # CONFIG_HIGHMEM4G is not set
 # CONFIG_HIGHMEM64G is not set
+CONFIG_GUESS_UNWINDER=y
+# CONFIG_FRAME_POINTER_UNWINDER is not set

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index 25b8d31a007d214b3a1d88e266feb067a8671e8f..e9f793e2df7a135f72a5dcbeee6a09a1d73fb383 100644 (file)
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -16,7 +16,7 @@ struct unwind_state {
        bool signal, full_regs;
        unsigned long sp, bp, ip;
        struct pt_regs *regs;
-#elif defined(CONFIG_FRAME_POINTER)
+#elif defined(CONFIG_FRAME_POINTER_UNWINDER)
        bool got_irq;
        unsigned long *bp, *orig_sp, ip;
        struct pt_regs *regs;
@@ -50,7 +50,7 @@ void unwind_start(struct unwind_state *state, struct task_struct *task,
        __unwind_start(state, task, regs, first_frame);
 }
 
-#if defined(CONFIG_ORC_UNWINDER) || defined(CONFIG_FRAME_POINTER)
+#if defined(CONFIG_ORC_UNWINDER) || defined(CONFIG_FRAME_POINTER_UNWINDER)
 static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
 {
        if (unwind_done(state))