[PATCH 00/19] x86/dumpstack: rewrite x86 stack dump code

From: Josh Poimboeuf
Date: Thu Jul 21 2016 - 17:22:14 EST

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

Also there are some upcoming features which will require more changes to
the stack dump code: reliable stack detection for live patching,
hardened user copy, and the 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:


It's also similar to the libunwind API:


Some if its advantages:

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

- flexibility: 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.

Josh Poimboeuf (19):
x86/dumpstack: remove show_trace()
x86/dumpstack: add get_stack_pointer() and get_frame_pointer()
x86/dumpstack: remove unnecessary stack pointer arguments
x86/dumpstack: make printk_stack_address() more generally useful
x86/dumpstack: fix function graph tracing stack dump reliability
x86/dumpstack: remove extra brackets around "EOE"
x86/dumpstack: add IRQ_USABLE_STACK_SIZE define
x86/dumpstack: don't disable preemption in show_stack_log_lvl() and
x86/dumpstack: simplify in_exception_stack()
x86/dumpstack: add get_stack_info() interface
x86/dumptrace: add new unwind interface and implementations
perf/x86: convert perf_callchain_kernel() to the new unwinder
x86/stacktrace: convert save_stack_trace_*() to the new unwinder
oprofile/x86: convert x86_backtrace() to the new unwinder
x86/dumpstack: convert show_trace_log_lvl() to the new unwinder
x86/dumpstack: remove dump_trace()
x86/entry/dumpstack: encode pt_regs pointer in frame pointer
x86/dumpstack: print stack identifier on its own line
x86/dumpstack: print any pt_regs found on the stack

arch/x86/entry/calling.h | 21 +++
arch/x86/entry/entry_64.S | 7 +-
arch/x86/events/core.c | 32 +---
arch/x86/include/asm/kdebug.h | 2 -
arch/x86/include/asm/page_64_types.h | 19 ++-
arch/x86/include/asm/stacktrace.h | 127 +++++++-------
arch/x86/include/asm/unwind.h | 91 ++++++++++
arch/x86/kernel/Makefile | 6 +
arch/x86/kernel/cpu/common.c | 2 +-
arch/x86/kernel/dumpstack.c | 269 +++++++++++++++---------------
arch/x86/kernel/dumpstack_32.c | 120 +++++++-------
arch/x86/kernel/dumpstack_64.c | 310 ++++++++++-------------------------
arch/x86/kernel/setup_percpu.c | 2 +-
arch/x86/kernel/stacktrace.c | 74 ++++-----
arch/x86/kernel/unwind_frame.c | 133 +++++++++++++++
arch/x86/kernel/unwind_guess.c | 40 +++++
arch/x86/oprofile/backtrace.c | 44 +++--
17 files changed, 713 insertions(+), 586 deletions(-)
create mode 100644 arch/x86/include/asm/unwind.h
create mode 100644 arch/x86/kernel/unwind_frame.c
create mode 100644 arch/x86/kernel/unwind_guess.c