+From 906230051aedc4af1dce033db79e56eb61af2b73 Mon Sep 17 00:00:00 2001
+From: Josh Poimboeuf <jpoimboe@redhat.com>
+Date: Mon, 24 Jul 2017 18:36:57 -0500
+Subject: [PATCH 035/231] x86/unwind: Add the ORC unwinder
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+CVE-2017-5754
+
+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 <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/0a6cbfb40f8da99b7a45a1a8302dc6aef16ec812.1500938583.git.jpoimboe@redhat.com
+[ Extended the changelog. ]
+Signed-off-by: Ingo Molnar <mingo@kernel.org>
+(cherry picked from commit ee9f8fce99640811b2b8e79d0d1dbe8bab69ba67)
+Signed-off-by: Andy Whitcroft <apw@canonical.com>
+Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
+(cherry picked from commit dccbf63d7a6cc431af23a86e28275a74904545cd)
+Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
+---
+ Documentation/x86/orc-unwinder.txt | 179 ++++++++++++
+ arch/x86/kernel/Makefile | 8 +-
+ scripts/Makefile.build | 14 +-
+ arch/um/include/asm/unwind.h | 8 +
+ arch/x86/include/asm/module.h | 9 +
+ arch/x86/include/asm/orc_lookup.h | 46 +++
+ arch/x86/include/asm/orc_types.h | 2 +-
+ arch/x86/include/asm/unwind.h | 76 +++--
+ include/asm-generic/vmlinux.lds.h | 27 +-
+ arch/x86/kernel/module.c | 11 +-
+ arch/x86/kernel/setup.c | 3 +
+ arch/x86/kernel/unwind_frame.c | 39 +--
+ arch/x86/kernel/unwind_guess.c | 5 +
+ arch/x86/kernel/unwind_orc.c | 582 +++++++++++++++++++++++++++++++++++++
+ arch/x86/Kconfig | 1 +
+ arch/x86/Kconfig.debug | 25 ++
+ arch/x86/kernel/vmlinux.lds.S | 3 +
+ lib/Kconfig.debug | 3 +
+ 18 files changed, 977 insertions(+), 64 deletions(-)
+ create mode 100644 Documentation/x86/orc-unwinder.txt
+ create mode 100644 arch/um/include/asm/unwind.h
+ create mode 100644 arch/x86/include/asm/orc_lookup.h
+ create mode 100644 arch/x86/kernel/unwind_orc.c
+
+diff --git a/Documentation/x86/orc-unwinder.txt b/Documentation/x86/orc-unwinder.txt
+new file mode 100644
+index 000000000000..af0c9a4c65a6
+--- /dev/null
++++ b/Documentation/x86/orc-unwinder.txt
+@@ -0,0 +1,179 @@
++ORC unwinder
++============
++
++Overview
++--------
++
++The kernel CONFIG_ORC_UNWINDER option enables the ORC unwinder, which is
++similar in concept to a DWARF unwinder. The difference is that the
++format of the ORC data is much simpler than DWARF, which in turn allows
++the ORC unwinder to be much simpler and faster.
++
++The ORC data consists of unwind tables which are generated by objtool.
++They contain out-of-band data which is used by the in-kernel ORC
++unwinder. Objtool generates the ORC data by first doing compile-time
++stack metadata validation (CONFIG_STACK_VALIDATION). After analyzing
++all the code paths of a .o file, it determines information about the
++stack state at each instruction address in the file and outputs that
++information to the .orc_unwind and .orc_unwind_ip sections.
++
++The per-object ORC sections are combined at link time and are sorted and
++post-processed at boot time. The unwinder uses the resulting data to
++correlate instruction addresses with their stack states at run time.
++
++
++ORC vs frame pointers
++---------------------
++
++With frame pointers enabled, GCC adds instrumentation code to every
++function in the kernel. The kernel's .text size increases by about
++3.2%, resulting in a broad kernel-wide slowdown. Measurements by Mel
++Gorman [1] have shown a slowdown of 5-10% for some workloads.
++
++In contrast, the ORC unwinder has no effect on text size or runtime
++performance, because the debuginfo is out of band. So if you disable
++frame pointers and enable the ORC unwinder, you get a nice performance
++improvement across the board, and still have reliable stack traces.
++
++Ingo Molnar says:
++
++ "Note that it's not just a performance improvement, but also an
++ instruction cache locality improvement: 3.2% .text savings almost
++ directly transform into a similarly sized reduction in cache
++ footprint. That can transform to even higher speedups for workloads
++ whose cache locality is borderline."
++
++Another benefit of ORC compared to frame pointers is that it can
++reliably unwind across interrupts and exceptions. Frame pointer based
++unwinds can sometimes skip the caller of the interrupted function, if it
++was a leaf function or if the interrupt hit before the frame pointer was
++saved.
++
++The main disadvantage of the ORC unwinder compared to frame pointers is
++that it needs more memory to store the ORC unwind tables: roughly 2-4MB
++depending on the kernel config.
++
++
++ORC vs DWARF
++------------
++
++ORC debuginfo's advantage over DWARF itself is that it's much simpler.
++It gets rid of the complex DWARF CFI state machine and also gets rid of
++the tracking of unnecessary registers. This allows the unwinder to be
++much simpler, meaning fewer bugs, which is especially important for
++mission critical oops code.
++
++The simpler debuginfo format also enables the unwinder to be much faster
++than DWARF, which is important for perf and lockdep. In a basic
++performance test by Jiri Slaby [2], the ORC unwinder was about 20x
++faster than an out-of-tree DWARF unwinder. (Note: That measurement was
++taken before some performance tweaks were added, which doubled
++performance, so the speedup over DWARF may be closer to 40x.)
++
++The ORC data format does have a few downsides compared to DWARF. ORC
++unwind tables take up ~50% more RAM (+1.3MB on an x86 defconfig kernel)
++than DWARF-based eh_frame tables.
++
++Another potential downside is that, as GCC evolves, it's conceivable
++that the ORC data may end up being *too* simple to describe the state of
++the stack for certain optimizations. But IMO this is unlikely because
++GCC saves the frame pointer for any unusual stack adjustments it does,
++so I suspect we'll really only ever need to keep track of the stack
++pointer and the frame pointer between call frames. But even if we do
++end up having to track all the registers DWARF tracks, at least we will
++still be able to control the format, e.g. no complex state machines.
++
++
++ORC unwind table generation
++---------------------------
++
++The ORC data is generated by objtool. With the existing compile-time
++stack metadata validation feature, objtool already follows all code
++paths, and so it already has all the information it needs to be able to
++generate ORC data from scratch. So it's an easy step to go from stack
++validation to ORC data generation.
++
++It should be possible to instead generate the ORC data with a simple
++tool which converts DWARF to ORC data. However, such a solution would
++be incomplete due to the kernel's extensive use of asm, inline asm, and
++special sections like exception tables.
++
++That could be rectified by manually annotating those special code paths
++using GNU assembler .cfi annotations in .S files, and homegrown
++annotations for inline asm in .c files. But asm annotations were tried
++in the past and were found to be unmaintainable. They were often
++incorrect/incomplete and made the code harder to read and keep updated.
++And based on looking at glibc code, annotating inline asm in .c files
++might be even worse.
++
++Objtool still needs a few annotations, but only in code which does
++unusual things to the stack like entry code. And even then, far fewer
++annotations are needed than what DWARF would need, so they're much more
++maintainable than DWARF CFI annotations.
++
++So the advantages of using objtool to generate ORC data are that it
++gives more accurate debuginfo, with very few annotations. It also
++insulates the kernel from toolchain bugs which can be very painful to
++deal with in the kernel since we often have to workaround issues in
++older versions of the toolchain for years.
++
++The downside is that the unwinder now becomes dependent on objtool's
++ability to reverse engineer GCC code flow. If GCC optimizations become
++too complicated for objtool to follow, the ORC data generation might
++stop working or become incomplete. (It's worth noting that livepatch
++already has such a dependency on objtool's ability to follow GCC code
++flow.)
++
++If newer versions of GCC come up with some optimizations which break
++objtool, we may need to revisit the current implementation. Some
++possible solutions would be asking GCC to make the optimizations more
++palatable, or having objtool use DWARF as an additional input, or
++creating a GCC plugin to assist objtool with its analysis. But for now,
++objtool follows GCC code quite well.
++
++
++Unwinder implementation details
++-------------------------------
++
++Objtool generates the ORC data by integrating with the compile-time
++stack metadata validation feature, which is described in detail in
++tools/objtool/Documentation/stack-validation.txt. After analyzing all
++the code paths of a .o file, it creates an array of orc_entry structs,
++and a parallel array of instruction addresses associated with those
++structs, and writes them to the .orc_unwind and .orc_unwind_ip sections
++respectively.
++
++The ORC data is split into the two arrays for performance reasons, to
++make the searchable part of the data (.orc_unwind_ip) more compact. The
++arrays are sorted in parallel at boot time.
++
++Performance is further improved by the use of a fast lookup table which
++is created at runtime. The fast lookup table associates a given address
++with a range of indices for the .orc_unwind table, so that only a small
++subset of the table needs to be searched.
++
++
++Etymology
++---------
++
++Orcs, fearsome creatures of medieval folklore, are the Dwarves' natural
++enemies. Similarly, the ORC unwinder was created in opposition to the
++complexity and slowness of DWARF.
++
++"Although Orcs rarely consider multiple solutions to a problem, they do
++excel at getting things done because they are creatures of action, not
++thought." [3] Similarly, unlike the esoteric DWARF unwinder, the
++veracious ORC unwinder wastes no time or siloconic effort decoding
++variable-length zero-extended unsigned-integer byte-coded
++state-machine-based debug information entries.
++
++Similar to how Orcs frequently unravel the well-intentioned plans of
++their adversaries, the ORC unwinder frequently unravels stacks with
++brutal, unyielding efficiency.
++
++ORC stands for Oops Rewind Capability.
++
++
++[1] https://lkml.kernel.org/r/20170602104048.jkkzssljsompjdwy@suse.de
++[2] https://lkml.kernel.org/r/d2ca5435-6386-29b8-db87-7f227c2b713a@suse.cz
++[3] http://dustin.wikidot.com/half-orcs-and-orcs
+diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
+index a01892bdd61a..287eac7d207f 100644
+--- a/arch/x86/kernel/Makefile
++++ b/arch/x86/kernel/Makefile
+@@ -126,11 +126,9 @@ obj-$(CONFIG_PERF_EVENTS) += perf_regs.o
+ obj-$(CONFIG_TRACING) += tracepoint.o
+ obj-$(CONFIG_SCHED_MC_PRIO) += itmt.o
+
+-ifdef CONFIG_FRAME_POINTER
+-obj-y += unwind_frame.o
+-else
+-obj-y += unwind_guess.o
+-endif
++obj-$(CONFIG_ORC_UNWINDER) += unwind_orc.o
++obj-$(CONFIG_FRAME_POINTER_UNWINDER) += unwind_frame.o
++obj-$(CONFIG_GUESS_UNWINDER) += unwind_guess.o
+
+ ###
+ # 64 bit specific files
+diff --git a/scripts/Makefile.build b/scripts/Makefile.build
+index 273bc2228307..ab2c8ef43cdb 100644
+--- a/scripts/Makefile.build
++++ b/scripts/Makefile.build
+@@ -258,7 +258,8 @@ ifneq ($(SKIP_STACK_VALIDATION),1)
+
+ __objtool_obj := $(objtree)/tools/objtool/objtool
+
+-objtool_args = check
++objtool_args = $(if $(CONFIG_ORC_UNWINDER),orc generate,check)
++
+ ifndef CONFIG_FRAME_POINTER
+ objtool_args += --no-fp
+ endif
+@@ -276,6 +277,11 @@ objtool_obj = $(if $(patsubst y%,, \
+ endif # SKIP_STACK_VALIDATION
+ endif # CONFIG_STACK_VALIDATION
+
++# Rebuild all objects when objtool changes, or is enabled/disabled.
++objtool_dep = $(objtool_obj) \
++ $(wildcard include/config/orc/unwinder.h \
++ include/config/stack/validation.h)
++
+ define rule_cc_o_c
+ $(call echo-cmd,checksrc) $(cmd_checksrc) \
+ $(call cmd_and_fixdep,cc_o_c) \
+@@ -298,14 +304,14 @@ cmd_undef_syms = echo
+ endif
+
+ # Built-in and composite module parts
+-$(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
++$(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
+ $(call cmd,force_checksrc)
+ $(call cmd,force_check_kmsg)
+ $(call if_changed_rule,cc_o_c)
+
+ # Single-part modules are special since we need to mark them in $(MODVERDIR)
+
+-$(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
++$(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
+ $(call cmd,force_checksrc)
+ $(call cmd,force_check_kmsg)
+ $(call if_changed_rule,cc_o_c)
+@@ -401,7 +407,7 @@ cmd_modversions_S = \
+ endif
+ endif
+
+-$(obj)/%.o: $(src)/%.S $(objtool_obj) FORCE
++$(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
+ $(call if_changed_rule,as_o_S)
+
+ targets += $(real-objs-y) $(real-objs-m) $(lib-y)
+diff --git a/arch/um/include/asm/unwind.h b/arch/um/include/asm/unwind.h
+new file mode 100644
+index 000000000000..7ffa5437b761
+--- /dev/null
++++ b/arch/um/include/asm/unwind.h
+@@ -0,0 +1,8 @@
++#ifndef _ASM_UML_UNWIND_H
++#define _ASM_UML_UNWIND_H
++
++static inline void
++unwind_module_init(struct module *mod, void *orc_ip, size_t orc_ip_size,
++ void *orc, size_t orc_size) {}
++
++#endif /* _ASM_UML_UNWIND_H */
+diff --git a/arch/x86/include/asm/module.h b/arch/x86/include/asm/module.h
+index e3b7819caeef..9eb7c718aaf8 100644
+--- a/arch/x86/include/asm/module.h
++++ b/arch/x86/include/asm/module.h
+@@ -2,6 +2,15 @@
+ #define _ASM_X86_MODULE_H
+
+ #include <asm-generic/module.h>
++#include <asm/orc_types.h>
++
++struct mod_arch_specific {
++#ifdef CONFIG_ORC_UNWINDER
++ unsigned int num_orcs;
++ int *orc_unwind_ip;
++ struct orc_entry *orc_unwind;
++#endif
++};
+
+ #ifdef CONFIG_X86_64
+ /* X86_64 does not define MODULE_PROC_FAMILY */
+diff --git a/arch/x86/include/asm/orc_lookup.h b/arch/x86/include/asm/orc_lookup.h
+new file mode 100644
+index 000000000000..91c8d868424d
+--- /dev/null
++++ b/arch/x86/include/asm/orc_lookup.h
+@@ -0,0 +1,46 @@
++/*
++ * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
++ *
++ * This program is free software; you can redistribute it and/or
++ * modify it under the terms of the GNU General Public License
++ * as published by the Free Software Foundation; either version 2
++ * of the License, or (at your option) any later version.
++ *
++ * This program is distributed in the hope that it will be useful,
++ * but WITHOUT ANY WARRANTY; without even the implied warranty of
++ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
++ * GNU General Public License for more details.
++ *
++ * You should have received a copy of the GNU General Public License
++ * along with this program; if not, see <http://www.gnu.org/licenses/>.
++ */
++#ifndef _ORC_LOOKUP_H
++#define _ORC_LOOKUP_H
++
++/*
++ * This is a lookup table for speeding up access to the .orc_unwind table.
++ * Given an input address offset, the corresponding lookup table entry
++ * specifies a subset of the .orc_unwind table to search.
++ *
++ * Each block represents the end of the previous range and the start of the
++ * next range. An extra block is added to give the last range an end.
++ *
++ * The block size should be a power of 2 to avoid a costly 'div' instruction.
++ *
++ * A block size of 256 was chosen because it roughly doubles unwinder
++ * performance while only adding ~5% to the ORC data footprint.
++ */
++#define LOOKUP_BLOCK_ORDER 8
++#define LOOKUP_BLOCK_SIZE (1 << LOOKUP_BLOCK_ORDER)
++
++#ifndef LINKER_SCRIPT
++
++extern unsigned int orc_lookup[];
++extern unsigned int orc_lookup_end[];
++
++#define LOOKUP_START_IP (unsigned long)_stext
++#define LOOKUP_STOP_IP (unsigned long)_etext
++
++#endif /* LINKER_SCRIPT */
++
++#endif /* _ORC_LOOKUP_H */
+diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
+index 7dc777a6cb40..9c9dc579bd7d 100644
+--- a/arch/x86/include/asm/orc_types.h
++++ b/arch/x86/include/asm/orc_types.h
+@@ -88,7 +88,7 @@ struct orc_entry {
+ unsigned sp_reg:4;
+ unsigned bp_reg:4;
+ unsigned type:2;
+-};
++} __packed;
+
+ /*
+ * This struct is used by asm and inline asm code to manually annotate the
+diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
+index e6676495b125..25b8d31a007d 100644
+--- a/arch/x86/include/asm/unwind.h
++++ b/arch/x86/include/asm/unwind.h
+@@ -12,11 +12,14 @@ struct unwind_state {
+ struct task_struct *task;
+ int graph_idx;
+ bool error;
+-#ifdef CONFIG_FRAME_POINTER
++#if defined(CONFIG_ORC_UNWINDER)
++ bool signal, full_regs;
++ unsigned long sp, bp, ip;
++ struct pt_regs *regs;
++#elif defined(CONFIG_FRAME_POINTER)
+ bool got_irq;
+- unsigned long *bp, *orig_sp;
++ unsigned long *bp, *orig_sp, ip;
+ struct pt_regs *regs;
+- unsigned long ip;
+ #else
+ unsigned long *sp;
+ #endif
+@@ -24,41 +27,30 @@ struct unwind_state {
+
+ 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);
+-
+ unsigned long unwind_get_return_address(struct unwind_state *state);
++unsigned long *unwind_get_return_address_ptr(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);
+-}
+-
+ static inline bool unwind_error(struct unwind_state *state)
+ {
+ return state->error;
+ }
+
+-#ifdef CONFIG_FRAME_POINTER
+-
+ static inline
+-unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
++void unwind_start(struct unwind_state *state, struct task_struct *task,
++ struct pt_regs *regs, unsigned long *first_frame)
+ {
+- if (unwind_done(state))
+- return NULL;
++ first_frame = first_frame ? : get_stack_pointer(task, regs);
+
+- return state->regs ? &state->regs->ip : state->bp + 1;
++ __unwind_start(state, task, regs, first_frame);
+ }
+
++#if defined(CONFIG_ORC_UNWINDER) || defined(CONFIG_FRAME_POINTER)
+ static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
+ {
+ if (unwind_done(state))
+@@ -66,20 +58,46 @@ static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
+
+ return state->regs;
+ }
+-
+-#else /* !CONFIG_FRAME_POINTER */
+-
+-static inline
+-unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
++#else
++static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
+ {
+ return NULL;
+ }
++#endif
+
+-static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
++#ifdef CONFIG_ORC_UNWINDER
++void unwind_init(void);
++void unwind_module_init(struct module *mod, void *orc_ip, size_t orc_ip_size,
++ void *orc, size_t orc_size);
++#else
++static inline void unwind_init(void) {}
++static inline
++void unwind_module_init(struct module *mod, void *orc_ip, size_t orc_ip_size,
++ void *orc, size_t orc_size) {}
++#endif
++
++/*
++ * This disables KASAN checking when reading a value from another task's stack,
++ * since the other task could be running on another CPU and could have poisoned
++ * the stack in the meantime.
++ */
++#define READ_ONCE_TASK_STACK(task, x) \
++({ \
++ unsigned long val; \
++ if (task == current) \
++ val = READ_ONCE(x); \
++ else \
++ val = READ_ONCE_NOCHECK(x); \
++ val; \
++})
++
++static inline bool task_on_another_cpu(struct task_struct *task)
+ {
+- return NULL;
++#ifdef CONFIG_SMP
++ return task != current && task->on_cpu;
++#else
++ return false;
++#endif
+ }
+
+-#endif /* CONFIG_FRAME_POINTER */
+-
+ #endif /* _ASM_X86_UNWIND_H */
+diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
+index e7e955d4ab9e..9fdb54a95976 100644
+--- a/include/asm-generic/vmlinux.lds.h
++++ b/include/asm-generic/vmlinux.lds.h
+@@ -686,6 +686,31 @@
+ #define BUG_TABLE
+ #endif
+
++#ifdef CONFIG_ORC_UNWINDER
++#define ORC_UNWIND_TABLE \
++ . = ALIGN(4); \
++ .orc_unwind_ip : AT(ADDR(.orc_unwind_ip) - LOAD_OFFSET) { \
++ VMLINUX_SYMBOL(__start_orc_unwind_ip) = .; \
++ KEEP(*(.orc_unwind_ip)) \
++ VMLINUX_SYMBOL(__stop_orc_unwind_ip) = .; \
++ } \
++ . = ALIGN(6); \
++ .orc_unwind : AT(ADDR(.orc_unwind) - LOAD_OFFSET) { \
++ VMLINUX_SYMBOL(__start_orc_unwind) = .; \
++ KEEP(*(.orc_unwind)) \
++ VMLINUX_SYMBOL(__stop_orc_unwind) = .; \
++ } \
++ . = ALIGN(4); \
++ .orc_lookup : AT(ADDR(.orc_lookup) - LOAD_OFFSET) { \
++ VMLINUX_SYMBOL(orc_lookup) = .; \
++ . += (((SIZEOF(.text) + LOOKUP_BLOCK_SIZE - 1) / \
++ LOOKUP_BLOCK_SIZE) + 1) * 4; \
++ VMLINUX_SYMBOL(orc_lookup_end) = .; \
++ }
++#else
++#define ORC_UNWIND_TABLE
++#endif
++
+ #ifdef CONFIG_PM_TRACE
+ #define TRACEDATA \
+ . = ALIGN(4); \
+@@ -872,7 +897,7 @@
+ DATA_DATA \
+ CONSTRUCTORS \
+ } \
+- BUG_TABLE
++ BUG_TABLE \
+
+ #define INIT_TEXT_SECTION(inittext_align) \
+ . = ALIGN(inittext_align); \
+diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
+index f67bd3205df7..62e7d70aadd5 100644
+--- a/arch/x86/kernel/module.c
++++ b/arch/x86/kernel/module.c
+@@ -35,6 +35,7 @@
+ #include <asm/page.h>
+ #include <asm/pgtable.h>
+ #include <asm/setup.h>
++#include <asm/unwind.h>
+
+ #if 0
+ #define DEBUGP(fmt, ...) \
+@@ -213,7 +214,7 @@ int module_finalize(const Elf_Ehdr *hdr,
+ struct module *me)
+ {
+ const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
+- *para = NULL;
++ *para = NULL, *orc = NULL, *orc_ip = NULL;
+ char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
+
+ for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
+@@ -225,6 +226,10 @@ int module_finalize(const Elf_Ehdr *hdr,
+ locks = s;
+ if (!strcmp(".parainstructions", secstrings + s->sh_name))
+ para = s;
++ if (!strcmp(".orc_unwind", secstrings + s->sh_name))
++ orc = s;
++ if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name))
++ orc_ip = s;
+ }
+
+ if (alt) {
+@@ -248,6 +253,10 @@ int module_finalize(const Elf_Ehdr *hdr,
+ /* make jump label nops */
+ jump_label_apply_nops(me);
+
++ if (orc && orc_ip)
++ unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size,
++ (void *)orc->sh_addr, orc->sh_size);
++
+ return 0;
+ }
+
+diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
+index f964bfddfefd..dd6e8707e969 100644
+--- a/arch/x86/kernel/setup.c
++++ b/arch/x86/kernel/setup.c
+@@ -121,6 +121,7 @@
+ #include <asm/microcode.h>
+ #include <asm/mmu_context.h>
+ #include <asm/kaslr.h>
++#include <asm/unwind.h>
+
+ /*
+ * max_low_pfn_mapped: highest direct mapped pfn under 4GB
+@@ -1325,6 +1326,8 @@ void __init setup_arch(char **cmdline_p)
+ if (efi_enabled(EFI_BOOT))
+ efi_apply_memmap_quirks();
+ #endif
++
++ unwind_init();
+ }
+
+ #ifdef CONFIG_X86_32
+diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
+index c29e5bc7e9c9..d145a0b1f529 100644
+--- a/arch/x86/kernel/unwind_frame.c
++++ b/arch/x86/kernel/unwind_frame.c
+@@ -10,20 +10,22 @@
+
+ #define FRAME_HEADER_SIZE (sizeof(long) * 2)
+
+-/*
+- * This disables KASAN checking when reading a value from another task's stack,
+- * since the other task could be running on another CPU and could have poisoned
+- * the stack in the meantime.
+- */
+-#define READ_ONCE_TASK_STACK(task, x) \
+-({ \
+- unsigned long val; \
+- if (task == current) \
+- val = READ_ONCE(x); \
+- else \
+- val = READ_ONCE_NOCHECK(x); \
+- val; \
+-})
++unsigned long unwind_get_return_address(struct unwind_state *state)
++{
++ if (unwind_done(state))
++ return 0;
++
++ return __kernel_text_address(state->ip) ? state->ip : 0;
++}
++EXPORT_SYMBOL_GPL(unwind_get_return_address);
++
++unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
++{
++ if (unwind_done(state))
++ return NULL;
++
++ return state->regs ? &state->regs->ip : state->bp + 1;
++}
+
+ static void unwind_dump(struct unwind_state *state)
+ {
+@@ -66,15 +68,6 @@ static void unwind_dump(struct unwind_state *state)
+ }
+ }
+
+-unsigned long unwind_get_return_address(struct unwind_state *state)
+-{
+- if (unwind_done(state))
+- return 0;
+-
+- return __kernel_text_address(state->ip) ? state->ip : 0;
+-}
+-EXPORT_SYMBOL_GPL(unwind_get_return_address);
+-
+ static size_t regs_size(struct pt_regs *regs)
+ {
+ /* x86_32 regs from kernel mode are two words shorter: */
+diff --git a/arch/x86/kernel/unwind_guess.c b/arch/x86/kernel/unwind_guess.c
+index 039f36738e49..4f0e17b90463 100644
+--- a/arch/x86/kernel/unwind_guess.c
++++ b/arch/x86/kernel/unwind_guess.c
+@@ -19,6 +19,11 @@ unsigned long unwind_get_return_address(struct unwind_state *state)
+ }
+ EXPORT_SYMBOL_GPL(unwind_get_return_address);
+
++unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
++{
++ return NULL;
++}
++
+ bool unwind_next_frame(struct unwind_state *state)
+ {
+ struct stack_info *info = &state->stack_info;
+diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
+new file mode 100644
+index 000000000000..570b70d3f604
+--- /dev/null
++++ b/arch/x86/kernel/unwind_orc.c
+@@ -0,0 +1,582 @@
++#include <linux/module.h>
++#include <linux/sort.h>
++#include <asm/ptrace.h>
++#include <asm/stacktrace.h>
++#include <asm/unwind.h>
++#include <asm/orc_types.h>
++#include <asm/orc_lookup.h>
++#include <asm/sections.h>
++
++#define orc_warn(fmt, ...) \
++ printk_deferred_once(KERN_WARNING pr_fmt("WARNING: " fmt), ##__VA_ARGS__)
++
++extern int __start_orc_unwind_ip[];
++extern int __stop_orc_unwind_ip[];
++extern struct orc_entry __start_orc_unwind[];
++extern struct orc_entry __stop_orc_unwind[];
++
++static DEFINE_MUTEX(sort_mutex);
++int *cur_orc_ip_table = __start_orc_unwind_ip;
++struct orc_entry *cur_orc_table = __start_orc_unwind;
++
++unsigned int lookup_num_blocks;
++bool orc_init;
++
++static inline unsigned long orc_ip(const int *ip)
++{
++ return (unsigned long)ip + *ip;
++}
++
++static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
++ unsigned int num_entries, unsigned long ip)
++{
++ int *first = ip_table;
++ int *last = ip_table + num_entries - 1;
++ int *mid = first, *found = first;
++
++ if (!num_entries)
++ return NULL;
++
++ /*
++ * Do a binary range search to find the rightmost duplicate of a given
++ * starting address. Some entries are section terminators which are
++ * "weak" entries for ensuring there are no gaps. They should be
++ * ignored when they conflict with a real entry.
++ */
++ while (first <= last) {
++ mid = first + ((last - first) / 2);
++
++ if (orc_ip(mid) <= ip) {
++ found = mid;
++ first = mid + 1;
++ } else
++ last = mid - 1;
++ }
++
++ return u_table + (found - ip_table);
++}
++
++#ifdef CONFIG_MODULES
++static struct orc_entry *orc_module_find(unsigned long ip)
++{
++ struct module *mod;
++
++ mod = __module_address(ip);
++ if (!mod || !mod->arch.orc_unwind || !mod->arch.orc_unwind_ip)
++ return NULL;
++ return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind,
++ mod->arch.num_orcs, ip);
++}
++#else
++static struct orc_entry *orc_module_find(unsigned long ip)
++{
++ return NULL;
++}
++#endif
++
++static struct orc_entry *orc_find(unsigned long ip)
++{
++ if (!orc_init)
++ return NULL;
++
++ /* For non-init vmlinux addresses, use the fast lookup table: */
++ if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) {
++ unsigned int idx, start, stop;
++
++ idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE;
++
++ if (unlikely((idx >= lookup_num_blocks-1))) {
++ orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%lx\n",
++ idx, lookup_num_blocks, ip);
++ return NULL;
++ }
++
++ start = orc_lookup[idx];
++ stop = orc_lookup[idx + 1] + 1;
++
++ if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) ||
++ (__start_orc_unwind + stop > __stop_orc_unwind))) {
++ orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%lx\n",
++ idx, lookup_num_blocks, start, stop, ip);
++ return NULL;
++ }
++
++ return __orc_find(__start_orc_unwind_ip + start,
++ __start_orc_unwind + start, stop - start, ip);
++ }
++
++ /* vmlinux .init slow lookup: */
++ if (ip >= (unsigned long)_sinittext && ip < (unsigned long)_einittext)
++ return __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
++ __stop_orc_unwind_ip - __start_orc_unwind_ip, ip);
++
++ /* Module lookup: */
++ return orc_module_find(ip);
++}
++
++static void orc_sort_swap(void *_a, void *_b, int size)
++{
++ struct orc_entry *orc_a, *orc_b;
++ struct orc_entry orc_tmp;
++ int *a = _a, *b = _b, tmp;
++ int delta = _b - _a;
++
++ /* Swap the .orc_unwind_ip entries: */
++ tmp = *a;
++ *a = *b + delta;
++ *b = tmp - delta;
++
++ /* Swap the corresponding .orc_unwind entries: */
++ orc_a = cur_orc_table + (a - cur_orc_ip_table);
++ orc_b = cur_orc_table + (b - cur_orc_ip_table);
++ orc_tmp = *orc_a;
++ *orc_a = *orc_b;
++ *orc_b = orc_tmp;
++}
++
++static int orc_sort_cmp(const void *_a, const void *_b)
++{
++ struct orc_entry *orc_a;
++ const int *a = _a, *b = _b;
++ unsigned long a_val = orc_ip(a);
++ unsigned long b_val = orc_ip(b);
++
++ if (a_val > b_val)
++ return 1;
++ if (a_val < b_val)
++ return -1;
++
++ /*
++ * The "weak" section terminator entries need to always be on the left
++ * to ensure the lookup code skips them in favor of real entries.
++ * These terminator entries exist to handle any gaps created by
++ * whitelisted .o files which didn't get objtool generation.
++ */
++ orc_a = cur_orc_table + (a - cur_orc_ip_table);
++ return orc_a->sp_reg == ORC_REG_UNDEFINED ? -1 : 1;
++}
++
++#ifdef CONFIG_MODULES
++void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,
++ void *_orc, size_t orc_size)
++{
++ int *orc_ip = _orc_ip;
++ struct orc_entry *orc = _orc;
++ unsigned int num_entries = orc_ip_size / sizeof(int);
++
++ WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 ||
++ orc_size % sizeof(*orc) != 0 ||
++ num_entries != orc_size / sizeof(*orc));
++
++ /*
++ * The 'cur_orc_*' globals allow the orc_sort_swap() callback to
++ * associate an .orc_unwind_ip table entry with its corresponding
++ * .orc_unwind entry so they can both be swapped.
++ */
++ mutex_lock(&sort_mutex);
++ cur_orc_ip_table = orc_ip;
++ cur_orc_table = orc;
++ sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap);
++ mutex_unlock(&sort_mutex);
++
++ mod->arch.orc_unwind_ip = orc_ip;
++ mod->arch.orc_unwind = orc;
++ mod->arch.num_orcs = num_entries;
++}
++#endif
++
++void __init unwind_init(void)
++{
++ size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip;
++ size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind;
++ size_t num_entries = orc_ip_size / sizeof(int);
++ struct orc_entry *orc;
++ int i;
++
++ if (!num_entries || orc_ip_size % sizeof(int) != 0 ||
++ orc_size % sizeof(struct orc_entry) != 0 ||
++ num_entries != orc_size / sizeof(struct orc_entry)) {
++ orc_warn("WARNING: Bad or missing .orc_unwind table. Disabling unwinder.\n");
++ return;
++ }
++
++ /* Sort the .orc_unwind and .orc_unwind_ip tables: */
++ sort(__start_orc_unwind_ip, num_entries, sizeof(int), orc_sort_cmp,
++ orc_sort_swap);
++
++ /* Initialize the fast lookup table: */
++ lookup_num_blocks = orc_lookup_end - orc_lookup;
++ for (i = 0; i < lookup_num_blocks-1; i++) {
++ orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
++ num_entries,
++ LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i));
++ if (!orc) {
++ orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
++ return;
++ }
++
++ orc_lookup[i] = orc - __start_orc_unwind;
++ }
++
++ /* Initialize the ending block: */
++ orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries,
++ LOOKUP_STOP_IP);
++ if (!orc) {
++ orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
++ return;
++ }
++ orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind;
++
++ orc_init = true;
++}
++
++unsigned long unwind_get_return_address(struct unwind_state *state)
++{
++ if (unwind_done(state))
++ return 0;
++
++ return __kernel_text_address(state->ip) ? state->ip : 0;
++}
++EXPORT_SYMBOL_GPL(unwind_get_return_address);
++
++unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
++{
++ if (unwind_done(state))
++ return NULL;
++
++ if (state->regs)
++ return &state->regs->ip;
++
++ if (state->sp)
++ return (unsigned long *)state->sp - 1;
++
++ return NULL;
++}
++
++static bool stack_access_ok(struct unwind_state *state, unsigned long addr,
++ size_t len)
++{
++ struct stack_info *info = &state->stack_info;
++
++ /*
++ * If the address isn't on the current stack, switch to the next one.
++ *
++ * We may have to traverse multiple stacks to deal with the possibility
++ * that info->next_sp could point to an empty stack and the address
++ * could be on a subsequent stack.
++ */
++ while (!on_stack(info, (void *)addr, len))
++ if (get_stack_info(info->next_sp, state->task, info,
++ &state->stack_mask))
++ return false;
++
++ return true;
++}
++
++static bool deref_stack_reg(struct unwind_state *state, unsigned long addr,
++ unsigned long *val)
++{
++ if (!stack_access_ok(state, addr, sizeof(long)))
++ return false;
++
++ *val = READ_ONCE_TASK_STACK(state->task, *(unsigned long *)addr);
++ return true;
++}
++
++#define REGS_SIZE (sizeof(struct pt_regs))
++#define SP_OFFSET (offsetof(struct pt_regs, sp))
++#define IRET_REGS_SIZE (REGS_SIZE - offsetof(struct pt_regs, ip))
++#define IRET_SP_OFFSET (SP_OFFSET - offsetof(struct pt_regs, ip))
++
++static bool deref_stack_regs(struct unwind_state *state, unsigned long addr,
++ unsigned long *ip, unsigned long *sp, bool full)
++{
++ size_t regs_size = full ? REGS_SIZE : IRET_REGS_SIZE;
++ size_t sp_offset = full ? SP_OFFSET : IRET_SP_OFFSET;
++ struct pt_regs *regs = (struct pt_regs *)(addr + regs_size - REGS_SIZE);
++
++ if (IS_ENABLED(CONFIG_X86_64)) {
++ if (!stack_access_ok(state, addr, regs_size))
++ return false;
++
++ *ip = regs->ip;
++ *sp = regs->sp;
++
++ return true;
++ }
++
++ if (!stack_access_ok(state, addr, sp_offset))
++ return false;
++
++ *ip = regs->ip;
++
++ if (user_mode(regs)) {
++ if (!stack_access_ok(state, addr + sp_offset,
++ REGS_SIZE - SP_OFFSET))
++ return false;
++
++ *sp = regs->sp;
++ } else
++ *sp = (unsigned long)®s->sp;
++
++ return true;
++}
++
++bool unwind_next_frame(struct unwind_state *state)
++{
++ unsigned long ip_p, sp, orig_ip, prev_sp = state->sp;
++ enum stack_type prev_type = state->stack_info.type;
++ struct orc_entry *orc;
++ struct pt_regs *ptregs;
++ bool indirect = false;
++
++ if (unwind_done(state))
++ return false;
++
++ /* Don't let modules unload while we're reading their ORC data. */
++ preempt_disable();
++
++ /* Have we reached the end? */
++ if (state->regs && user_mode(state->regs))
++ goto done;
++
++ /*
++ * Find the orc_entry associated with the text address.
++ *
++ * Decrement call return addresses by one so they work for sibling
++ * calls and calls to noreturn functions.
++ */
++ orc = orc_find(state->signal ? state->ip : state->ip - 1);
++ if (!orc || orc->sp_reg == ORC_REG_UNDEFINED)
++ goto done;
++ orig_ip = state->ip;
++
++ /* Find the previous frame's stack: */
++ switch (orc->sp_reg) {
++ case ORC_REG_SP:
++ sp = state->sp + orc->sp_offset;
++ break;
++
++ case ORC_REG_BP:
++ sp = state->bp + orc->sp_offset;
++ break;
++
++ case ORC_REG_SP_INDIRECT:
++ sp = state->sp + orc->sp_offset;
++ indirect = true;
++ break;
++
++ case ORC_REG_BP_INDIRECT:
++ sp = state->bp + orc->sp_offset;
++ indirect = true;
++ break;
++
++ case ORC_REG_R10:
++ if (!state->regs || !state->full_regs) {
++ orc_warn("missing regs for base reg R10 at ip %p\n",
++ (void *)state->ip);
++ goto done;
++ }
++ sp = state->regs->r10;
++ break;
++
++ case ORC_REG_R13:
++ if (!state->regs || !state->full_regs) {
++ orc_warn("missing regs for base reg R13 at ip %p\n",
++ (void *)state->ip);
++ goto done;
++ }
++ sp = state->regs->r13;
++ break;
++
++ case ORC_REG_DI:
++ if (!state->regs || !state->full_regs) {
++ orc_warn("missing regs for base reg DI at ip %p\n",
++ (void *)state->ip);
++ goto done;
++ }
++ sp = state->regs->di;
++ break;
++
++ case ORC_REG_DX:
++ if (!state->regs || !state->full_regs) {
++ orc_warn("missing regs for base reg DX at ip %p\n",
++ (void *)state->ip);
++ goto done;
++ }
++ sp = state->regs->dx;
++ break;
++
++ default:
++ orc_warn("unknown SP base reg %d for ip %p\n",
++ orc->sp_reg, (void *)state->ip);
++ goto done;
++ }
++
++ if (indirect) {
++ if (!deref_stack_reg(state, sp, &sp))
++ goto done;
++ }
++
++ /* Find IP, SP and possibly regs: */
++ switch (orc->type) {
++ case ORC_TYPE_CALL:
++ ip_p = sp - sizeof(long);
++
++ if (!deref_stack_reg(state, ip_p, &state->ip))
++ goto done;
++
++ state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
++ state->ip, (void *)ip_p);
++
++ state->sp = sp;
++ state->regs = NULL;
++ state->signal = false;
++ break;
++
++ case ORC_TYPE_REGS:
++ if (!deref_stack_regs(state, sp, &state->ip, &state->sp, true)) {
++ orc_warn("can't dereference registers at %p for ip %p\n",
++ (void *)sp, (void *)orig_ip);
++ goto done;
++ }
++
++ state->regs = (struct pt_regs *)sp;
++ state->full_regs = true;
++ state->signal = true;
++ break;
++
++ case ORC_TYPE_REGS_IRET:
++ if (!deref_stack_regs(state, sp, &state->ip, &state->sp, false)) {
++ orc_warn("can't dereference iret registers at %p for ip %p\n",
++ (void *)sp, (void *)orig_ip);
++ goto done;
++ }
++
++ ptregs = container_of((void *)sp, struct pt_regs, ip);
++ if ((unsigned long)ptregs >= prev_sp &&
++ on_stack(&state->stack_info, ptregs, REGS_SIZE)) {
++ state->regs = ptregs;
++ state->full_regs = false;
++ } else
++ state->regs = NULL;
++
++ state->signal = true;
++ break;
++
++ default:
++ orc_warn("unknown .orc_unwind entry type %d\n", orc->type);
++ break;
++ }
++
++ /* Find BP: */
++ switch (orc->bp_reg) {
++ case ORC_REG_UNDEFINED:
++ if (state->regs && state->full_regs)
++ state->bp = state->regs->bp;
++ break;
++
++ case ORC_REG_PREV_SP:
++ if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp))
++ goto done;
++ break;
++
++ case ORC_REG_BP:
++ if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp))
++ goto done;
++ break;
++
++ default:
++ orc_warn("unknown BP base reg %d for ip %p\n",
++ orc->bp_reg, (void *)orig_ip);
++ goto done;
++ }
++
++ /* Prevent a recursive loop due to bad ORC data: */
++ if (state->stack_info.type == prev_type &&
++ on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) &&
++ state->sp <= prev_sp) {
++ orc_warn("stack going in the wrong direction? ip=%p\n",
++ (void *)orig_ip);
++ goto done;
++ }
++
++ preempt_enable();
++ return true;
++
++done:
++ preempt_enable();
++ state->stack_info.type = STACK_TYPE_UNKNOWN;
++ return false;
++}
++EXPORT_SYMBOL_GPL(unwind_next_frame);
++
++void __unwind_start(struct unwind_state *state, struct task_struct *task,
++ struct pt_regs *regs, unsigned long *first_frame)
++{
++ memset(state, 0, sizeof(*state));
++ state->task = task;
++
++ /*
++ * Refuse to unwind the stack of a task while it's executing on another
++ * CPU. This check is racy, but that's ok: the unwinder has other
++ * checks to prevent it from going off the rails.
++ */
++ if (task_on_another_cpu(task))
++ goto done;
++
++ if (regs) {
++ if (user_mode(regs))
++ goto done;
++
++ state->ip = regs->ip;
++ state->sp = kernel_stack_pointer(regs);
++ state->bp = regs->bp;
++ state->regs = regs;
++ state->full_regs = true;
++ state->signal = true;
++
++ } else if (task == current) {
++ asm volatile("lea (%%rip), %0\n\t"
++ "mov %%rsp, %1\n\t"
++ "mov %%rbp, %2\n\t"
++ : "=r" (state->ip), "=r" (state->sp),
++ "=r" (state->bp));
++
++ } else {
++ struct inactive_task_frame *frame = (void *)task->thread.sp;
++
++ state->sp = task->thread.sp;
++ state->bp = READ_ONCE_NOCHECK(frame->bp);
++ state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
++ }
++
++ if (get_stack_info((unsigned long *)state->sp, state->task,
++ &state->stack_info, &state->stack_mask))
++ return;
++
++ /*
++ * The caller can provide the address of the first frame directly
++ * (first_frame) or indirectly (regs->sp) to indicate which stack frame
++ * to start unwinding at. Skip ahead until we reach it.
++ */
++
++ /* When starting from regs, skip the regs frame: */
++ if (regs) {
++ unwind_next_frame(state);
++ return;
++ }
++
++ /* Otherwise, skip ahead to the user-specified starting frame: */
++ while (!unwind_done(state) &&
++ (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
++ state->sp <= (unsigned long)first_frame))
++ unwind_next_frame(state);
++
++ return;
++
++done:
++ state->stack_info.type = STACK_TYPE_UNKNOWN;
++ return;
++}
++EXPORT_SYMBOL_GPL(__unwind_start);
+diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
+index 658fcf67862c..d6f45f6d1054 100644
+--- a/arch/x86/Kconfig
++++ b/arch/x86/Kconfig
+@@ -158,6 +158,7 @@ config X86
+ select HAVE_MEMBLOCK
+ select HAVE_MEMBLOCK_NODE_MAP
+ select HAVE_MIXED_BREAKPOINTS_REGS
++ select HAVE_MOD_ARCH_SPECIFIC
+ select HAVE_NMI
+ select HAVE_OPROFILE
+ select HAVE_OPTPROBES
+diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
+index 1fc519f3c49e..d5bca2ec8a74 100644
+--- a/arch/x86/Kconfig.debug
++++ b/arch/x86/Kconfig.debug
+@@ -356,4 +356,29 @@ config PUNIT_ATOM_DEBUG
+ The current power state can be read from
+ /sys/kernel/debug/punit_atom/dev_power_state
+
++config ORC_UNWINDER
++ bool "ORC unwinder"
++ depends on X86_64
++ select STACK_VALIDATION
++ ---help---
++ This option enables the ORC (Oops Rewind Capability) unwinder for
++ unwinding kernel stack traces. It uses a custom data format which is
++ 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.
++
++ 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
++
+ endmenu
+diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
+index c8a3b61be0aa..f05f00acac89 100644
+--- a/arch/x86/kernel/vmlinux.lds.S
++++ b/arch/x86/kernel/vmlinux.lds.S
+@@ -24,6 +24,7 @@
+ #include <asm/asm-offsets.h>
+ #include <asm/thread_info.h>
+ #include <asm/page_types.h>
++#include <asm/orc_lookup.h>
+ #include <asm/cache.h>
+ #include <asm/boot.h>
+
+@@ -148,6 +149,8 @@ SECTIONS
+
+ BUG_TABLE
+
++ ORC_UNWIND_TABLE
++
+ . = ALIGN(PAGE_SIZE);
+ __vvar_page = .;
+
+diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
+index c617b9d1d6cb..0b4d1b3880b0 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.
+
+--
+2.14.2
+