mirror of
https://github.com/torvalds/linux
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26660a4046
Pull 'objtool' stack frame validation from Ingo Molnar:
"This tree adds a new kernel build-time object file validation feature
(ONFIG_STACK_VALIDATION=y): kernel stack frame correctness validation.
It was written by and is maintained by Josh Poimboeuf.
The motivation: there's a category of hard to find kernel bugs, most
of them in assembly code (but also occasionally in C code), that
degrades the quality of kernel stack dumps/backtraces. These bugs are
hard to detect at the source code level. Such bugs result in
incorrect/incomplete backtraces most of time - but can also in some
rare cases result in crashes or other undefined behavior.
The build time correctness checking is done via the new 'objtool'
user-space utility that was written for this purpose and which is
hosted in the kernel repository in tools/objtool/. The tool's (very
simple) UI and source code design is shaped after Git and perf and
shares quite a bit of infrastructure with tools/perf (which tooling
infrastructure sharing effort got merged via perf and is already
upstream). Objtool follows the well-known kernel coding style.
Objtool does not try to check .c or .S files, it instead analyzes the
resulting .o generated machine code from first principles: it decodes
the instruction stream and interprets it. (Right now objtool supports
the x86-64 architecture.)
From tools/objtool/Documentation/stack-validation.txt:
"The kernel CONFIG_STACK_VALIDATION option enables a host tool named
objtool which runs at compile time. It has a "check" subcommand
which analyzes every .o file and ensures the validity of its stack
metadata. It enforces a set of rules on asm code and C inline
assembly code so that stack traces can be reliable.
Currently it only checks frame pointer usage, but there are plans to
add CFI validation for C files and CFI generation for asm files.
For each function, it recursively follows all possible code paths
and validates the correct frame pointer state at each instruction.
It also follows code paths involving special sections, like
.altinstructions, __jump_table, and __ex_table, which can add
alternative execution paths to a given instruction (or set of
instructions). Similarly, it knows how to follow switch statements,
for which gcc sometimes uses jump tables."
When this new kernel option is enabled (it's disabled by default), the
tool, if it finds any suspicious assembly code pattern, outputs
warnings in compiler warning format:
warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
warning: objtool: cik_tiling_mode_table_init()+0x6ce: call without frame pointer save/setup
warning: objtool:__schedule()+0x3c0: duplicate frame pointer save
warning: objtool:__schedule()+0x3fd: sibling call from callable instruction with changed frame pointer
... so that scripts that pick up compiler warnings will notice them.
All known warnings triggered by the tool are fixed by the tree, most
of the commits in fact prepare the kernel to be warning-free. Most of
them are bugfixes or cleanups that stand on their own, but there are
also some annotations of 'special' stack frames for justified cases
such entries to JIT-ed code (BPF) or really special boot time code.
There are two other long-term motivations behind this tool as well:
- To improve the quality and reliability of kernel stack frames, so
that they can be used for optimized live patching.
- To create independent infrastructure to check the correctness of
CFI stack frames at build time. CFI debuginfo is notoriously
unreliable and we cannot use it in the kernel as-is without extra
checking done both on the kernel side and on the build side.
The quality of kernel stack frames matters to debuggability as well,
so IMO we can merge this without having to consider the live patching
or CFI debuginfo angle"
* 'core-objtool-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits)
objtool: Only print one warning per function
objtool: Add several performance improvements
tools: Copy hashtable.h into tools directory
objtool: Fix false positive warnings for functions with multiple switch statements
objtool: Rename some variables and functions
objtool: Remove superflous INIT_LIST_HEAD
objtool: Add helper macros for traversing instructions
objtool: Fix false positive warnings related to sibling calls
objtool: Compile with debugging symbols
objtool: Detect infinite recursion
objtool: Prevent infinite recursion in noreturn detection
objtool: Detect and warn if libelf is missing and don't break the build
tools: Support relative directory path for 'O='
objtool: Support CROSS_COMPILE
x86/asm/decoder: Use explicitly signed chars
objtool: Enable stack metadata validation on 64-bit x86
objtool: Add CONFIG_STACK_VALIDATION option
objtool: Add tool to perform compile-time stack metadata validation
x86/kprobes: Mark kretprobe_trampoline() stack frame as non-standard
sched: Always inline context_switch()
...
163 lines
4.8 KiB
Makefile
163 lines
4.8 KiB
Makefile
# Some of the tools (perf) use same make variables
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# as in kernel build.
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export srctree=
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export objtree=
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include scripts/Makefile.include
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help:
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@echo 'Possible targets:'
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@echo ''
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@echo ' acpi - ACPI tools'
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@echo ' cgroup - cgroup tools'
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@echo ' cpupower - a tool for all things x86 CPU power'
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@echo ' firewire - the userspace part of nosy, an IEEE-1394 traffic sniffer'
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@echo ' freefall - laptop accelerometer program for disk protection'
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@echo ' gpio - GPIO tools'
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@echo ' hv - tools used when in Hyper-V clients'
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@echo ' iio - IIO tools'
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@echo ' lguest - a minimal 32-bit x86 hypervisor'
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@echo ' net - misc networking tools'
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@echo ' perf - Linux performance measurement and analysis tool'
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@echo ' selftests - various kernel selftests'
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@echo ' spi - spi tools'
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@echo ' objtool - an ELF object analysis tool'
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@echo ' tmon - thermal monitoring and tuning tool'
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@echo ' turbostat - Intel CPU idle stats and freq reporting tool'
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@echo ' usb - USB testing tools'
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@echo ' virtio - vhost test module'
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@echo ' vm - misc vm tools'
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@echo ' x86_energy_perf_policy - Intel energy policy tool'
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@echo ''
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@echo 'You can do:'
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@echo ' $$ make -C tools/ <tool>_install'
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@echo ''
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@echo ' from the kernel command line to build and install one of'
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@echo ' the tools above'
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@echo ''
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@echo ' $$ make tools/all'
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@echo ''
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@echo ' builds all tools.'
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@echo ''
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@echo ' $$ make tools/install'
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@echo ''
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@echo ' installs all tools.'
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@echo ''
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@echo 'Cleaning targets:'
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@echo ''
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@echo ' all of the above with the "_clean" string appended cleans'
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@echo ' the respective build directory.'
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@echo ' clean: a summary clean target to clean _all_ folders'
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acpi: FORCE
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$(call descend,power/$@)
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cpupower: FORCE
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$(call descend,power/$@)
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cgroup firewire hv guest spi usb virtio vm net iio gpio objtool: FORCE
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$(call descend,$@)
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liblockdep: FORCE
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$(call descend,lib/lockdep)
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libapi: FORCE
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$(call descend,lib/api)
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# The perf build does not follow the descend function setup,
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# invoking it via it's own make rule.
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PERF_O = $(if $(O),$(O)/tools/perf,)
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perf: FORCE
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$(Q)mkdir -p $(PERF_O) .
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$(Q)$(MAKE) --no-print-directory -C perf O=$(PERF_O) subdir=
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selftests: FORCE
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$(call descend,testing/$@)
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turbostat x86_energy_perf_policy: FORCE
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$(call descend,power/x86/$@)
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tmon: FORCE
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$(call descend,thermal/$@)
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freefall: FORCE
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$(call descend,laptop/$@)
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all: acpi cgroup cpupower hv firewire lguest \
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perf selftests turbostat usb \
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virtio vm net x86_energy_perf_policy \
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tmon freefall objtool
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acpi_install:
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$(call descend,power/$(@:_install=),install)
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cpupower_install:
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$(call descend,power/$(@:_install=),install)
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cgroup_install firewire_install hv_install lguest_install perf_install usb_install virtio_install vm_install net_install objtool_install:
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$(call descend,$(@:_install=),install)
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selftests_install:
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$(call descend,testing/$(@:_install=),install)
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turbostat_install x86_energy_perf_policy_install:
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$(call descend,power/x86/$(@:_install=),install)
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tmon_install:
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$(call descend,thermal/$(@:_install=),install)
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freefall_install:
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$(call descend,laptop/$(@:_install=),install)
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install: acpi_install cgroup_install cpupower_install hv_install firewire_install lguest_install \
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perf_install selftests_install turbostat_install usb_install \
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virtio_install vm_install net_install x86_energy_perf_policy_install \
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tmon_install freefall_install objtool_install
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acpi_clean:
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$(call descend,power/acpi,clean)
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cpupower_clean:
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$(call descend,power/cpupower,clean)
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cgroup_clean hv_clean firewire_clean lguest_clean spi_clean usb_clean virtio_clean vm_clean net_clean iio_clean gpio_clean objtool_clean:
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$(call descend,$(@:_clean=),clean)
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liblockdep_clean:
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$(call descend,lib/lockdep,clean)
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libapi_clean:
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$(call descend,lib/api,clean)
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libbpf_clean:
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$(call descend,lib/bpf,clean)
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libsubcmd_clean:
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$(call descend,lib/subcmd,clean)
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perf_clean:
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$(call descend,$(@:_clean=),clean)
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selftests_clean:
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$(call descend,testing/$(@:_clean=),clean)
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turbostat_clean x86_energy_perf_policy_clean:
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$(call descend,power/x86/$(@:_clean=),clean)
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tmon_clean:
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$(call descend,thermal/tmon,clean)
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freefall_clean:
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$(call descend,laptop/freefall,clean)
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build_clean:
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$(call descend,build,clean)
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clean: acpi_clean cgroup_clean cpupower_clean hv_clean firewire_clean lguest_clean \
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perf_clean selftests_clean turbostat_clean spi_clean usb_clean virtio_clean \
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vm_clean net_clean iio_clean x86_energy_perf_policy_clean tmon_clean \
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freefall_clean build_clean libbpf_clean libsubcmd_clean liblockdep_clean \
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gpio_clean objtool_clean
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.PHONY: FORCE
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