From ee9f8fce99640811b2b8e79d0d1dbe8bab69ba67 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 24 Jul 2017 18:36:57 -0500 Subject: x86/unwind: Add the ORC unwinder Add the new ORC unwinder which is enabled by CONFIG_ORC_UNWINDER=y. It plugs into the existing x86 unwinder framework. It relies on objtool to generate the needed .orc_unwind and .orc_unwind_ip sections. For more details on why ORC is used instead of DWARF, see Documentation/x86/orc-unwinder.txt - but the short version is that it's a simplified, fundamentally more robust debugninfo data structure, which also allows up to two orders of magnitude faster lookups than the DWARF unwinder - which matters to profiling workloads like perf. Thanks to Andy Lutomirski for the performance improvement ideas: splitting the ORC unwind table into two parallel arrays and creating a fast lookup table to search a subset of the unwind table. Signed-off-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jiri Slaby Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/0a6cbfb40f8da99b7a45a1a8302dc6aef16ec812.1500938583.git.jpoimboe@redhat.com [ Extended the changelog. ] Signed-off-by: Ingo Molnar --- lib/Kconfig.debug | 3 +++ 1 file changed, 3 insertions(+) (limited to 'lib') diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 98fe715522e8..0f0d019ffb99 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -374,6 +374,9 @@ config STACK_VALIDATION pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure that runtime stack traces are more reliable. + This is also a prerequisite for generation of ORC unwind data, which + is needed for CONFIG_ORC_UNWINDER. + For more information, see tools/objtool/Documentation/stack-validation.txt. -- cgit v1.2.3 From a34a766ff96d9e88572e35a45066279e40a85d84 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 24 Jul 2017 18:36:58 -0500 Subject: x86/kconfig: Make it easier to switch to the new ORC unwinder A couple of Kconfig changes which make it much easier to switch to the new CONFIG_ORC_UNWINDER: 1) Remove x86 dependencies on CONFIG_FRAME_POINTER for lockdep, latencytop, and fault injection. x86 has a 'guess' unwinder which just scans the stack for kernel text addresses. It's not 100% accurate but in many cases it's good enough. This allows those users who don't want the text overhead of the frame pointer or ORC unwinders to still use these features. More importantly, this also makes it much more straightforward to disable frame pointers. 2) Make CONFIG_ORC_UNWINDER depend on !CONFIG_FRAME_POINTER. While it would be possible to have both enabled, it doesn't really make sense to do so. So enforce a sane configuration to prevent the user from making a dumb mistake. With these changes, when you disable CONFIG_FRAME_POINTER, "make oldconfig" will ask if you want to enable CONFIG_ORC_UNWINDER. Signed-off-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jiri Slaby Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/9985fb91ce5005fe33ea5cc2a20f14bd33c61d03.1500938583.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/Kconfig.debug | 7 +++---- lib/Kconfig.debug | 6 +++--- 2 files changed, 6 insertions(+), 7 deletions(-) (limited to 'lib') diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index dc10ec6ead6e..268a318f9439 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -357,7 +357,7 @@ config PUNIT_ATOM_DEBUG config ORC_UNWINDER bool "ORC unwinder" - depends on X86_64 + depends on X86_64 && !FRAME_POINTER select STACK_VALIDATION ---help--- This option enables the ORC (Oops Rewind Capability) unwinder for @@ -365,9 +365,8 @@ config ORC_UNWINDER a simplified version of the DWARF Call Frame Information standard. This unwinder is more accurate across interrupt entry frames than the - frame pointer unwinder. It can also enable a 5-10% performance - improvement across the entire kernel if CONFIG_FRAME_POINTER is - disabled. + frame pointer unwinder. It also enables a 5-10% performance + improvement across the entire kernel compared to frame pointers. Enabling this option will increase the kernel's runtime memory usage by roughly 2-4MB, depending on your kernel config. diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 0f0d019ffb99..32a48e739e26 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1124,7 +1124,7 @@ config LOCKDEP bool depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT select STACKTRACE - select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE + select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE && !X86 select KALLSYMS select KALLSYMS_ALL @@ -1543,7 +1543,7 @@ config FAULT_INJECTION_STACKTRACE_FILTER depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT depends on !X86_64 select STACKTRACE - select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE + select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE && !X86 help Provide stacktrace filter for fault-injection capabilities @@ -1552,7 +1552,7 @@ config LATENCYTOP depends on DEBUG_KERNEL depends on STACKTRACE_SUPPORT depends on PROC_FS - select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC + select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86 select KALLSYMS select KALLSYMS_ALL select STACKTRACE -- cgit v1.2.3