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Message-ID: <CAK7LNASo6dDrgt=cyLDBqSuZKdb=+SpJCnigBXWN8Y5ricECKQ@mail.gmail.com>
Date: Sun, 31 Dec 2023 14:35:11 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: "Alessandro Carminati (Red Hat)" <alessandro.carminati@...il.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Steven Rostedt <rostedt@...dmis.org>,
Daniel Bristot de Oliveira <bristot@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
Luis Chamberlain <mcgrof@...nel.org>, Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>, Nicolas Schier <nicolas@...sle.eu>,
Alexander Lobakin <aleksander.lobakin@...el.com>, Nick Alcock <nick.alcock@...cle.com>,
Kris Van Hees <kris.van.hees@...cle.com>, Eugene Loh <eugene.loh@...cle.com>,
Francis Laniel <flaniel@...ux.microsoft.com>, Viktor Malik <vmalik@...hat.com>,
Petr Mladek <pmladek@...e.com>, Tom Rix <trix@...hat.com>, linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
llvm@...ts.linux.dev
Subject: Re: [PATCH v7] scripts/link-vmlinux.sh: Add alias to duplicate
symbols for kallsyms
On Tue, Dec 5, 2023 at 6:48 AM Alessandro Carminati (Red Hat)
<alessandro.carminati@...il.com> wrote:
>
> In the kernel environment, situations frequently arise where identical
> names are shared among symbols within both the core image and modules.
> While this doesn't pose issues for the kernel's binary itself, it
> complicates trace or probe operations using tools like kprobe.
>
> This patch introduces "kas_alias" to address this challenge.
>
> During the kernel's build process, just before linking the vmlinux
> image in the "scripts/link-vmlinux.sh", symbol name frequencies are
> collected.
> This collection includes both the core kernel components and modules.
> Subsequently, within the same action, the nm data relative to vmlinux
> is modified by adding aliases based on the comprehensive symbol
> information gathered.
>
> The collection process occurs in two phases:
>
> 1. First phase: Executed during the linking of vmlinux, "kas_alias" scans
> all symbols provided by the 'nm' data against the vmlinux core image
> and all objects used for module linkage. This phase requires all
> modules objects to be produced at this stage, thereby adding a vmlinux
> dependency for linking modules in 'scripts/Makefile.modfinal'.
>
> 2. Second phase: In a subsequent run in the same build, "kas_alias"
> processes module objects and injects aliases into the objects' symbol
> tables where necessary. This operation is done by modifying
> 'scripts/Makefile.modfinal' to include an action for each processed
> module.
>
> Example:
>
> Consider the symbol "device_show", you can expect an output like the
> following:
>
> ~ # cat /proc/kallsyms | grep " name_show"
> ffffcaa2bb4f01c8 t name_show
> ffffcaa2bb4f01c8 t name_show@...nel_irq_irqdesc_c_264
> ffffcaa2bb9c1a30 t name_show
> ffffcaa2bb9c1a30 t name_show@...vers_pnp_card_c_186
> ffffcaa2bbac4754 t name_show
> ffffcaa2bbac4754 t name_show@...vers_regulator_core_c_678
> ffffcaa2bbba4900 t name_show
> ffffcaa2bbba4900 t name_show@...vers_base_power_wakeup_stats_c_93
> ffffcaa2bbec4038 t name_show
> ffffcaa2bbec4038 t name_show@...vers_rtc_sysfs_c_26
> ffffcaa2bbecc920 t name_show
> ffffcaa2bbecc920 t name_show@...vers_i2c_i2c_core_base_c_660
> ffffcaa2bbed3840 t name_show
> ffffcaa2bbed3840 t name_show@...vers_i2c_i2c_dev_c_100
> ffffcaa2bbef7210 t name_show
> ffffcaa2bbef7210 t name_show@...vers_pps_sysfs_c_66
> ffffcaa2bbf03328 t name_show
> ffffcaa2bbf03328 t name_show@...vers_hwmon_hwmon_c_72
> ffffcaa2bbff6f3c t name_show
> ffffcaa2bbff6f3c t name_show@...vers_remoteproc_remoteproc_sysfs_c_215
> ffffcaa2bbff8d78 t name_show
> ffffcaa2bbff8d78 t name_show@...vers_rpmsg_rpmsg_core_c_455
> ffffcaa2bbfff7a4 t name_show
> ffffcaa2bbfff7a4 t name_show@...vers_devfreq_devfreq_c_1395
> ffffcaa2bc001f60 t name_show
> ffffcaa2bc001f60 t name_show@...vers_extcon_extcon_c_389
> ffffcaa2bc009890 t name_show
> ffffcaa2bc009890 t name_show@...vers_iio_industrialio_core_c_1396
> ffffcaa2bc01212c t name_show
> ffffcaa2bc01212c t name_show@...vers_iio_industrialio_trigger_c_51
> ffffcaa2bc025e2c t name_show
> ffffcaa2bc025e2c t name_show@...vers_fpga_fpga_mgr_c_618
> ffffcaa2a052102c t name_show [hello]
> ffffcaa2a052102c t name_show@...lo_hello_c_8 [hello]
> ffffcaa2a051955c t name_show [rpmsg_char]
> ffffcaa2a051955c t name_show@...vers_rpmsg_rpmsg_char_c_365 [rpmsg_char]
>
> where hello, is a plain helloworld module built OOT.
>
> Tested-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@...il.com>
>
> ---
>
> NOTE1:
> About the symbols name duplication that happens as consequence of the
> inclusion compat_binfmt_elf.c does, it is evident that this corner is
> inherently challenging the addr2line approach.
> Attempting to conceal this limitation would be counterproductive.
>
> compat_binfmt_elf.c includes directly binfmt_elf.c, addr2line can't help
> but report all functions and data declared by that file, coming from
> binfmt_elf.c.
>
> My position is that, rather than producing a more complicated pipeline
> to handle this corner case, it is better to fix the compat_binfmt_elf.c
> anomaly.
>
> This patch does not deal with the two potentially problematic symbols
> defined by compat_binfmt_elf.c
>
> Changes from v1:
> * Integrated changes requested by Masami to exclude symbols with prefixes
> "_cfi" and "_pfx".
> * Introduced a small framework to handle patterns that need to be excluded
> from the alias production.
> * Excluded other symbols using the framework.
> * Introduced the ability to discriminate between text and data symbols.
> * Added two new config symbols in this version:
> CONFIG_KALLSYMS_ALIAS_DATA, which allows data for data, and
> CONFIG_KALLSYMS_ALIAS_DATA_ALL, which excludes all filters and provides
> an alias for each duplicated symbol.
>
> https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/
>
> Changes from v2:
> * Alias tags are created by querying DWARF information from the vmlinux.
> * The filename + line number is normalized and appended to the original
> name.
> * The tag begins with '@' to indicate the symbol source.
> * Not a change, but worth mentioning, since the alias is added to the
> existing list, the old duplicated name is preserved, and the livepatch
> way of dealing with duplicates is maintained.
> * Acknowledging the existence of scenarios where inlined functions
> declared in header files may result in multiple copies due to compiler
> behavior, though it is not actionable as it does not pose an operational
> issue.
> * Highlighting a single exception where the same name refers to different
> functions: the case of "compat_binfmt_elf.c," which directly includes
> "binfmt_elf.c" producing identical function copies in two separate
> modules.
>
> https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
>
> Changes from v3:
> * kas_alias was rewritten in Python to create a more concise and
> maintainable codebase.
> * The previous automation process used by kas_alias to locate the vmlinux
> and the addr2line has been replaced with an explicit command-line switch
> for specifying these requirements.
> * addr2line has been added into the main Makefile.
> * A new command-line switch has been introduced, enabling users to extend
> the alias to global data names.
>
> https://lore.kernel.org/all/20230828080423.3539686-1-alessandro.carminati@gmail.com/
>
> Changes from v4:
> * Fixed the O=<build dir> build issue
> * The tool halts execution upon encountering major issues, thereby ensuring
> the pipeline is interrupted.
> * A cmdline option to specify the source directory added.
> * Minor code adjusments.
> * Tested on mips32 and i386
>
> https://lore.kernel.org/all/20230919193948.465340-1-alessandro.carminati@gmail.com/
>
> Changes from v5:
> * Regex filter extended to all symbols
> * Alias creation extended to module objects
> * Code cleaned and commented
> * kas_alias verbose execution via KAS_ALIAS_DEBUG env variable
> * CONFIG_KALLSYMS_ALIAS_SRCLINE selects KBUILD_BUILTIN to ensure no races
> during modules build
> * Tested on x86_64, aarch64 and i386
>
> https://lore.kernel.org/all/20230927173516.1456594-1-alessandro.carminati@gmail.com/
>
> Changes from v6:
> * Generate a file to facilitate the construction of custom OOT modules using aliases.
> In this context, it is needed to export the modules.symbfreq file, a product of
> the build.
> * Previously, kas_alias was intended to run once, executing all tasks within the same
> session. In this version, two targets have been introduced to split the work into
> distinct phases: one for creating aliases for the core image and another for
> generating aliases for modules.
> * The module aliases production statement has been inserted in the
> scripts/Makefile.modfinal. Instead of being executed individually for each module,
> it now runs once for all modules.
> * The approach for excluding symbols in .init and .exit ELF sections has undergone a
> rewrite.
> * kas_alias is now capable of applying aliases to OOT modules. However, for this to
> occur, the 'modules.symbfreq' file needs to be accessible during the build.
> If it is not found, aliases won't be added.
>
> https://lore.kernel.org/all/20231024201157.748254-1-alessandro.carminati@gmail.com/
I am concerned with your code.
At least, I'd like you to understand the Makefile principle.
<output>: <input>
<command>
The <command> reads <input> and generates <output>.
The <command> must not modify <input>.
If you deviate from this principle,
we will never know where build artifacts are updated.
Your code looks like this:
%.ko: %.o %.mod.o
Your script inserts aliases to %.o
Link %.o and %.mod.o into %.ko
Your script updates the input file, %.o.
This is never acceptable.
Anyway, @FILENAME_LINE seems a cheesy workaround after all,
and I do not see a good reason to grow the ugliness.
> ---
> Makefile | 14 +-
> init/Kconfig | 22 ++
> scripts/Makefile.modfinal | 30 +-
> scripts/kas_alias.py | 600 ++++++++++++++++++++++++++++++++++++++
> scripts/link-vmlinux.sh | 27 +-
> 5 files changed, 688 insertions(+), 5 deletions(-)
> create mode 100755 scripts/kas_alias.py
>
> diff --git a/Makefile b/Makefile
> index 99db546fbb45..810a0cd21d20 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -479,6 +479,7 @@ OBJCOPY = $(LLVM_PREFIX)llvm-objcopy$(LLVM_SUFFIX)
> OBJDUMP = $(LLVM_PREFIX)llvm-objdump$(LLVM_SUFFIX)
> READELF = $(LLVM_PREFIX)llvm-readelf$(LLVM_SUFFIX)
> STRIP = $(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX)
> +ADDR2LINE = $(LLVM_PREFIX)llvm-addr2line$(LLVM_SUFFIX)
> else
> CC = $(CROSS_COMPILE)gcc
> LD = $(CROSS_COMPILE)ld
> @@ -488,6 +489,7 @@ OBJCOPY = $(CROSS_COMPILE)objcopy
> OBJDUMP = $(CROSS_COMPILE)objdump
> READELF = $(CROSS_COMPILE)readelf
> STRIP = $(CROSS_COMPILE)strip
> +ADDR2LINE = $(CROSS_COMPILE)addr2line
> endif
> RUSTC = rustc
> RUSTDOC = rustdoc
> @@ -591,7 +593,7 @@ export RUSTC_BOOTSTRAP := 1
> export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC HOSTPKG_CONFIG
> export RUSTC RUSTDOC RUSTFMT RUSTC_OR_CLIPPY_QUIET RUSTC_OR_CLIPPY BINDGEN CARGO
> export HOSTRUSTC KBUILD_HOSTRUSTFLAGS
> -export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AWK INSTALLKERNEL
> +export CPP AR NM STRIP OBJCOPY OBJDUMP READELF ADDR2LINE PAHOLE RESOLVE_BTFIDS LEX YACC AWK INSTALLKERNEL
> export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
> export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD
> export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
> @@ -1453,6 +1455,16 @@ KBUILD_BUILTIN := 1
> modules: vmlinux
> endif
>
> +# *.ko are usually independent of vmlinux, but CONFIG_KALLSYMS_ALIAS_SRCLINE
> +# is another exception.
> +# At the time when vmlinux is being linked, kas_alias operates on both vmlinux
> +# and modules. To prevent races with modules, kas_alias needs to pause operations
> +# while it is executed.
> +ifdef CONFIG_KALLSYMS_ALIAS_SRCLINE
> +KBUILD_BUILTIN := 1
> +modules: vmlinux
> +endif
> +
> modules: modules_prepare
>
> # Target to prepare building external modules
> diff --git a/init/Kconfig b/init/Kconfig
> index 9ffb103fc927..f68341b29576 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1738,6 +1738,28 @@ config KALLSYMS_BASE_RELATIVE
> time constants, and no relocation pass is required at runtime to fix
> up the entries based on the runtime load address of the kernel.
>
> +config KALLSYMS_ALIAS_SRCLINE
> + bool "Produces alias for duplicated text symbols" if EXPERT
> + depends on KALLSYMS && DEBUG_INFO && !DEBUG_INFO_SPLIT
> + help
> + It is not uncommon for drivers or modules related to similar
> + peripherals to have symbols with the exact same name.
> + While this is not a problem for the kernel's binary itself, it
> + becomes an issue when attempting to trace or probe specific
> + functions using infrastructure like ftrace or kprobe.
> +
> + This option addresses this challenge, producing alias for text
> + symbol names that include the file name and line where the symbols
> + are defined in the source code.
> +
> +config KALLSYMS_ALIAS_SRCLINE_DATA
> + bool "Produces alias also for global variables names"
> + depends on KALLSYMS_ALIAS_SRCLINE
> + help
> + Sometimes it can be useful to refer to global vars by name. Since
> + they suffer the same issue as text symbols, this config option
> + allows having aliases for global variables names too.
> +
> # end of the "standard kernel features (expert users)" menu
>
> # syscall, maps, verifier
> diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> index 8568d256d6fb..acde29a46c6b 100644
> --- a/scripts/Makefile.modfinal
> +++ b/scripts/Makefile.modfinal
> @@ -15,6 +15,32 @@ include $(srctree)/scripts/Makefile.lib
> # find all modules listed in modules.order
> modules := $(call read-file, $(MODORDER))
>
> +ifeq ($(KBUILD_BUILTIN),y)
> + ifeq ($(or $(CONFIG_DEBUG_INFO_BTF_MODULES),$(CONFIG_KALLSYMS_ALIAS_SRCLINE)),y)
> + VMLINUX_DEP := vmlinux
> + endif
> +endif
> +
> +VMLINUX_DEP ?=
This line seems meaningless to me.
> +
> +ifeq ($(CONFIG_KALLSYMS_ALIAS_SRCLINE),y)
> + ifeq ($(CONFIG_KALLSYMS_ALIAS_SRCLINE_DATA),y)
> + KAS_DATA := --process_data
> + endif
> +
> + ifdef KAS_ALIAS_DEBUG
> + DEBUG_FLAG := $(KAS_ALIAS_DEBUG)
> + else
> + DEBUG_FLAG := 0
> + endif
> +
> + KAS_ALIAS_MODULE_CMD := $(srctree)/scripts/kas_alias.py --symbol_frequency $(extmod_prefix)modules.symbfreq \
> + --debug $(DEBUG_FLAG) --nm $(NM) $(KAS_DATA) \
> + --addr2line $(ADDR2LINE) --basedir $(srctree) --separator @ \
> + single_module \
> + --objcopy $(OBJCOPY) --objdump $(OBJDUMP) --target-module
> +endif
> +
> __modfinal: $(modules:%.o=%.ko)
> @:
>
> @@ -30,6 +56,7 @@ quiet_cmd_cc_o_c = CC [M] $@
>
> quiet_cmd_ld_ko_o = LD [M] $@
> cmd_ld_ko_o += \
> + [ "$(KAS_ALIAS_MODULE_CMD)" != "" ] && $(KAS_ALIAS_MODULE_CMD) $<; \
> $(LD) -r $(KBUILD_LDFLAGS) \
> $(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
> -T scripts/module.lds -o $@ $(filter %.o, $^)
> @@ -52,7 +79,7 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \
> printf '%s\n' 'savedcmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
>
> # Re-generate module BTFs if either module's .ko or vmlinux changed
> -%.ko: %.o %.mod.o scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),vmlinux) FORCE
> +%.ko: %.o %.mod.o scripts/module.lds $(VMLINUX_DEP) FORCE
> +$(call if_changed_except,ld_ko_o,vmlinux)
> ifdef CONFIG_DEBUG_INFO_BTF_MODULES
> +$(if $(newer-prereqs),$(call cmd,btf_ko))
> @@ -65,7 +92,6 @@ targets += $(modules:%.o=%.ko) $(modules:%.o=%.mod.o)
>
> PHONY += FORCE
> FORCE:
> -
> # Read all saved command lines and dependencies for the $(targets) we
> # may be building above, using $(if_changed{,_dep}). As an
> # optimization, we don't need to read them if the target does not
> diff --git a/scripts/kas_alias.py b/scripts/kas_alias.py
> new file mode 100755
> index 000000000000..5b0517771389
> --- /dev/null
> +++ b/scripts/kas_alias.py
> @@ -0,0 +1,600 @@
> +#!/usr/bin/env python3
> +# SPDX-License-Identifier: GPL-2.0-only
> +#
> +# Copyright (C) 2023 Red Hat, Inc. Alessandro Carminati <alessandro.carminati@...il.com>
> +#
> +# kas_alias: Adds alias to duplicate symbols for the kallsyms output.
> +
> +import os
> +import re
> +import sys
> +import inspect
> +import argparse
> +import subprocess
> +from enum import Enum
> +from collections import namedtuple
> +
> +# Regex representing symbols that need no alias
> +regex_filter = [
> + "^__compound_literal\\.[0-9]+$",
> + "^__[wm]*key\\.[0-9]+$",
> + "^_*TRACE_SYSTEM.*$",
> + "^__already_done\\.[0-9]+$",
> + "^__msg\\.[0-9]+$",
> + "^__func__\\.[0-9]+$",
> + "^CSWTCH\\.[0-9]+$",
> + "^_rs\\.[0-9]+$",
> + "^___tp_str\\.[0-9]+$",
> + "^__flags\\.[0-9]+$",
> + "^___done\\.[0-9]+$",
> + "^__print_once\\.[0-9]+$",
> + "^___once_key\\.[0-9]+$",
> + "^__pfx_.*$",
> + "^__cfi_.*$",
> + "^\\.LC[0-9]+$",
> + "^\\.L[0-9]+.[0-9]+$",
> + "^__UNIQUE_ID_.*$",
> + "^symbols\\.[0-9]+$",
> + "^_note_[0-9]+$"
> + ]
> +
> +class DebugLevel(Enum):
> + PRODUCTION = 0
> + INFO = 1
> + DEBUG_BASIC = 2
> + DEBUG_MODULES = 3
> + DEBUG_ALL = 4
Re-inventing a wheel?
Python supports the "logging" module.
> +
> +class SeparatorType:
> + def __call__(self, separator):
> + if len(separator) != 1:
> + raise argparse.ArgumentTypeError("Separator must be a single character")
> + return separator
> +
> +Line = namedtuple('Line', ['address', 'type', 'name', 'addr_int'])
> +
> +def get_caller():
> + """
> + Used only to produce debug messages:
> + Gets the caller's caller name if any, "kas_alias" otherwise
> + Args:
> + None
> + Returns:
> + A string representing a name of a function.
> + """
> + stack = inspect.stack()
> + if len(stack) > 2:
> + caller = stack[2][0]
> + caller_name = caller.f_code.co_name
> + return caller_name
> + else:
> + return "kas_alias"
> +
> +def debug_print(config, print_debug_level, text):
> + """
> + Prints text if current debug level is greater or equal to print_debug_level.
> + Args:
> + current_debug_level: Application debug level specified by command line.
> + print_debug_level: Minimum debug level message should be printed.
> + text: string representing the message.
> + Returns:
> + Nothing.
> + """
> + if int(config.debug) >= print_debug_level:
> + print(f"{get_caller()}: " + text)
> +
> +def parse_nm_lines(config, lines, name_occurrences=None):
> + """
> + Parses a given nm output and returns the symbol list along with a hash of
> + symbol occurrences.
> + Args:
> + lines: List of tuples representing one nm line.
> + name_occurrences: Hash having the name as key, used to count names'
> + occurrences.
> + Returns:
> + Creates a new line list proper for the nm output it parsed and, updates
> + the occurrences hash.
> + """
> + debug_print(config, DebugLevel.DEBUG_BASIC.value, "parse_nm_lines: parse start")
> +
> + if name_occurrences is None:
> + name_occurrences = {}
> +
> + symbol_list = []
> +
> + for line in lines:
> + fields = line.strip().split()
> +
> + if len(fields) >= 3:
> + address, type, name = fields[0], fields[1], ' '.join(fields[2:])
> + symbol_list.append(Line(address, type, name, int(address, 16)))
> + name_occurrences[name] = name_occurrences.get(name, 0) + 1
> +
> + return symbol_list, name_occurrences
> +
> +def start_addr2line_process(binary_file, config):
> + """
> + Initializes an addr2line server process operating on the given ELF object.
> + Args:
> + binary_file: String representing the binary file name object of addr2line
> + queries.
> + addr2line_file: String representing the addr2line executable name.
> + Returns:
> + Returns addr2line process descriptor.
> + """
> + debug_print(config, DebugLevel.DEBUG_BASIC.value, f"Starting addr2line process on {binary_file}")
> +
> + try:
> + addr2line_process = subprocess.Popen([config.addr2line_file, '-fe',
> + binary_file],
> + stdin=subprocess.PIPE,
> + stdout=subprocess.PIPE,
> + stderr=subprocess.PIPE,
> + text=True)
> + return addr2line_process
> + except Exception as e:
> + debug_print(config, DebugLevel.PRODUCTION.value, f"Script terminated due to an error ({type(e).__name__}): {str(e)}")
> + sys.exit(-2)
> +
> +def addr2line_fetch_address(config, addr2line_process, address):
> + """
> + Queries a specific address using the active addr2line process.
> + Args:
> + addr2line_process: Descriptor of the addr2line process that is wanted to
> + handle the query.
> + address: The address of the symbol that needs to be resolved.
> + Returns:
> + Returns a string representing the file and line number where the symbol
> + at the specified address has been defined. The address is normalized
> + before being returned.
> + """
> + debug_print(config, DebugLevel.DEBUG_ALL.value, f"Resolving {address}")
> +
> + try:
> + addr2line_process.stdin.write(address + '\n')
> + addr2line_process.stdin.flush()
> + addr2line_process.stdout.readline().strip()
> + output = addr2line_process.stdout.readline().strip()
> +
> + return os.path.normpath(output)
> + except Exception as e:
> + debug_print(config, DebugLevel.PRODUCTION.value, f"Script terminated due to an error ({type(e).__name__}): {str(e)}")
> + sys.exit(-2)
> +
> +def process_line(line, config, section_map):
> + """
> + Determines whether a duplicate item requires an alias or not.
> + Args:
> + line: nm line object that needs to be checked.
> + section_map: map correlating symbols and the ELF section they are from
> + Returns:
> + Returns true if the line needs to be processed, false otherwise.
> + """
> + debug_print(config, DebugLevel.DEBUG_ALL.value, f"Processing {line.address} {line.type} {line.name}")
> +
> + # The module contains symbols that were discarded after being loaded. Typically,
> + # these symbols belong to the initialization function. These symbols have their
> + # address in the init section addresses, so this check prevents these symbols
> + # from being assigned aliases.
> + if section_map != None:
> + if line.name in section_map:
> + if (".init" in section_map[line.name] or ".exit" in section_map[line.name]):
> + return False
> + else:
> + return False
> +
> + if config.process_data_sym:
> + return not (any(re.match(regex, line.name) for regex in regex_filter))
> + else:
> + return (line.type in {"T", "t"}) and (
> + not (any(re.match(regex, line.name) for regex in regex_filter)))
> +
> +def fetch_file_lines(config, filename):
> + """
> + Reads a text file and retrieves its content.
> + Args:
> + filename: String representing the name of the file that needs to be read.
> + Returns:
> + Returns a string list representing the lines read in the file.
> + """
> + debug_print(config, DebugLevel.DEBUG_BASIC.value, f"Fetch {filename}")
> +
> + try:
> + with open(filename, 'r') as file:
> + lines = [line.strip() for line in file.readlines()]
> + return lines
> + except FileNotFoundError:
> + debug_print(config, DebugLevel.PRODUCTION.value, f"Script terminated due to an error ({type(FileNotFoundError).__name__}): {str(FileNotFoundError)}")
> + sys.exit(-2)
> +
> +def do_nm(filename, config):
> + """
> + Runs the nm command on a specified file.
> + Args:
> + filename: String representing the name of the file on which nm should
> + run against.
> + nm_executable: String representing the nm executable filename.
> + Returns:
> + Returns a strings list representing the nm output.
> + """
> + debug_print(config, DebugLevel.DEBUG_BASIC.value, f"executing {config.nm_file} -n {filename}")
> +
> + try:
> + nm_output = subprocess.check_output([config.nm_file, '-n', filename],
> + universal_newlines=True, stderr=subprocess.STDOUT).splitlines()
> + return nm_output
> + except subprocess.CalledProcessError as e:
> + debug_print(config, DebugLevel.PRODUCTION.value, f"Script terminated due to an error ({type(e).__name__}): {str(e)}")
> + sys.exit(-2)
> +
> +def make_objcpy_arg(config, line, decoration, section_map):
> + """
> + Produces an objcopy argument statement for a single alias to be added in a
> + module.
> + Args:
> + line: nm line object target for this iteration.
> + decoration: String representing the decoration (normalized addr2line
> + output) to be added at the symbol name to have the alias.
> + section_map: map correlating symbols and the ELF section they are from
> + Returns:
> + Returns a string that directly maps the argument string objcopy should
> + use to add the alias.
> + """
> + try:
> + flag = "global" if line.type.isupper() else "local"
> + debug_print(config, DebugLevel.DEBUG_MODULES.value,
> + f"{line.name + decoration}={section_map[line.name]}:0x{line.address},{flag}")
> + return (
> + "--add-symbol "
> + f"{line.name + decoration}={section_map[line.name]}:0x{line.address},{flag} "
> + )
> + except Exception:
> + debug_print(config, DebugLevel.PRODUCTION.value,
> + f"make_objcpy_arg warning: Skip alias for {line.name}"
> + f" type {line.type} because no corresponding section found.")
> + return ""
> +
> +def execute_objcopy(config, objcopy_args, object_file):
> + """
> + Uses objcopy to add aliases to a given module object file.
> + Since objcopy can't operate in place, the original object file is renamed
> + before operating on it. At function end, a new object file having the old
> + object's name is carrying the aliases for the duplicate symbols.
> + Args:
> + objcopy_executable: String representing the object copy executable file.
> + objcopy_args: Arguments (aliases to add to the object file) to be used
> + in the objcopy execution command line.
> + object_file: Target object file (module object file) against which objcopy is executed.
> + Returns:
> + Nothing is returned, but as a side effect of this function execution,
> + the module's object file contains the aliases for duplicated symbols.
> + """
> + # Rename the original object file by adding a suffix
> + backup_file = object_file + '.orig'
> + debug_print(config, DebugLevel.DEBUG_MODULES.value, f"rename {object_file} to {backup_file}")
> + os.rename(object_file, backup_file)
> +
> + full_command = (
> + f"{config.objcopy_file} "
> + f"{objcopy_args} {backup_file} {object_file}"
> + )
> + debug_print(config, DebugLevel.DEBUG_MODULES.value, f"executing {full_command}")
> +
> + try:
> + subprocess.run(full_command, shell=True, check=True)
> + except subprocess.CalledProcessError as e:
> + debug_print(config, DebugLevel.PRODUCTION.value, f"Script terminated due to an error ({type(e).__name__}): {str(e)}")
> + sys.exit(-2)
> +
> +def generate_decoration(line, config, addr2line_process):
> + """
> + Generates symbol decoration to be used to make the alias name, by
> + querying addr2line.
> + Args:
> + line: nm line object that needs an alias.
> + config: Object containing command line configuration.
> + addr2line_process: Descriptor of the addr2line process that serves
> + the binary object where the symbol belongs.
> + Returns:
> + Returns a string representing the decoration for the given symbol,
> + or empty string if this can not be done. E.g., addr2line can't find
> + the point where the symbol is defined.
> + """
> + output = addr2line_fetch_address(config, addr2line_process, line.address)
> + base_dir = config.linux_base_dir + "/"
> + cwd = os.getcwd() + "/"
> + absolute_base_dir = os.path.abspath(os.path.join(cwd, base_dir))
> +
> + if output.startswith(base_dir):
> + output = output[len(base_dir):]
> +
> + if output.startswith(absolute_base_dir):
> + output = output[len(absolute_base_dir):]
> +
> + if output.startswith('/'):
> + output = output[1:]
> +
> + decoration = config.separator + "".join(
> + "_" if not c.isalnum() else c for c in output
> + )
> + # The addr2line can emit the special string "?:??" when addr2line can not find the
> + # specified address in the DWARF section that after normalization it becomes "____".
> + # In such cases, emitting an alias wouldn't make sense, so it is skipped.
> + if decoration != config.separator + "____":
> + return decoration
> + return ""
> +
> +def section_interesting(section):
> + """
> + checks if a section is of interest.
> + Args:
> + section: string representing the section needed to be tested.
> + Returns:
> + True if it is, False otherwise.
> + """
> + sections_regex = [r".text", r".data", r".bss", r".rodata"]
> +
> + for pattern in sections_regex:
> + if re.search(pattern, section):
> + return True
> + return False
> +
> +def get_symbol2section(config, file_to_operate):
> + """
> + This function aims to produce a map{symbol_name]=section_name for
> + any given object file.
> + Args:
> + objdump_executable: String representing the objdump executable.
> + file_to_operate: file whose section names are wanted.
> + Returns:
> + Returns a map, where the key is the symbol name and the value is
> + a section name.
> + """
> + try:
> + output = subprocess.check_output(
> + [config.objdump_file, '-h', file_to_operate],
> + universal_newlines=True)
> + section_pattern = re.compile(r'^ *[0-9]+ ([.a-z_]+) +([0-9a-f]+).*$', re.MULTILINE)
> + section_names = section_pattern.findall(output)
> + result = {}
> + for section, section_siza in section_names:
> + if int(section_siza, 16) != 0 and section_interesting(section):
> + debug_print(config, DebugLevel.DEBUG_ALL.value, f"CMD => {config.objdump_file} -tj {section} {file_to_operate}")
> + try:
> + output = subprocess.check_output(
> + [config.objdump_file, '-tj', section, file_to_operate],
> + universal_newlines=True)
> + except subprocess.CalledProcessError:
> + pass
> + func_names_pattern = re.compile(r'[0-9a-f]+.* ([.a-zA-Z_][.A-Za-z_0-9]+)$', re.MULTILINE)
> + matches = func_names_pattern.findall(output)
> + for func_name in matches:
> + result[func_name] = section
> +
> +
> + except Exception as e:
> + debug_print(config, DebugLevel.PRODUCTION.value, f"Script terminated due to an error ({type(e).__name__}): {str(e)}")
> + sys.exit(-2)
> + return result
> +
> +def produce_output_modules(config, symbol_list, name_occurrences,
> + module_file_name, addr2line_process):
> + """
> + Computes the alias addition on a given module object file.
> + Args:
> + config: Object containing command line configuration.
> + symbol_list: List of tuples representing nm lines for the given object
> + file.
> + name_occurrences: Hash that stores symbol occurrences for the build.
> + module_file_name: String representing the target moule object file.
> + addr2line_process: Descriptor of the addr2line process that is wanted to
> + handle the query.
> + Returns:
> + Nothing is returned, but as a side effect of this function execution,
> + the module's object file contains the aliases for duplicated symbols.
> + """
> + debug_print(config, DebugLevel.DEBUG_ALL.value, "produce_output_modules computation starts here ")
> + objcopy_args = "";
> + args_cnt = 0
> + section_map = get_symbol2section(config, module_file_name)
> + for module_symbol in symbol_list:
> + debug_print(config, DebugLevel.DEBUG_ALL.value, f"--> Processing {module_symbol}")
> + try:
> + if (name_occurrences[module_symbol.name] > 1) and process_line(module_symbol, config, section_map):
> + decoration = generate_decoration(module_symbol, config, addr2line_process)
> + debug_print(config, DebugLevel.DEBUG_ALL.value, f"--- {module_symbol} occurred multiple times and is a candidate for alias: decoration '{decoration}'")
> + if decoration != "":
> + objcopy_args = objcopy_args + make_objcpy_arg(config, module_symbol, decoration, section_map)
> + args_cnt = args_cnt + 1
> + if args_cnt > 50:
> + debug_print(config, DebugLevel.DEBUG_MODULES.value, "Number of arguments high, split objcopy"
> + " call into multiple statements.")
> + execute_objcopy(config, objcopy_args, module_file_name)
> + args_cnt = 0> + objcopy_args = ""
> + except KeyError:
> + pass
> + execute_objcopy(config, objcopy_args, module_file_name)
So, you call execute_objcopy() to do
"rename <mod> <mod>.orig" and "objcopy <mod>.orig <mod>"
even when no alias is inserted?
> +
> +def produce_output_vmlinux(config, symbol_list, name_occurrences, addr2line_process):
> + """
> + Computes the alias addition for the core Linux on image.
> + Args:
> + config: Object containing command line configuration.
> + symbol_list: List of tuples representing nm lines for the given object
> + file.
> + name_occurrences: Hash that stores symbol occurreces for the build.
> + addr2line_process: Descriptor of the addr2line process that is wanted to
> + handle the query.
> + Returns:
> + Nothing is returned, but as a side effect of this function execution,
> + the core kernel image contains the aliases for duplicated symbols.
> + """
> + with open(config.output_file, 'w') as output_file:
> + for obj in symbol_list:
> + output_file.write(f"{obj.address} {obj.type} {obj.name}\n")
> + if (name_occurrences[obj.name] > 1) and process_line(obj, config, None):
> + decoration = generate_decoration(obj, config, addr2line_process)
> + debug_print(config,DebugLevel.DEBUG_ALL.value, f"Symbol {obj.name} appears multiple times, and decoration is {decoration}")
> + if decoration != "":
> + debug_print(config, DebugLevel.DEBUG_ALL.value, f"Writing on {config.output_file} the additional '{obj.address} {obj.type} {obj.name + decoration}'")
> + output_file.write(f"{obj.address} {obj.type} {obj.name + decoration}\n")
> +
> +def read_name_occurrences(config):
> + """
> + Reads symbol frequencies from the file specified in the 'config' argument.
> +
> + If the file is not found, it gracefully returns an empty map.
> +
> + Args:
> + config: A configuration object or dictionary containing necessary information
> + to locate the file.
> +
> + Returns:
> + A map where keys represent symbol names and values represent their frequencies.
> + """
> + name_occurrences = {}
> + # This code reads occurrences of symbol names from a file containing both the core image
> + # and modules frequencies resulted from the computation of the "core_image" action.
> + # It reads from the file specified by command-line arguments; if the file doesn't exist
> + # or the filename isn't specified, it returns an empty map.
> + # The code relies on accessing and reading config.symbol_frequency_file containing
> + # symbol name frequencies.
> + # In a complete build, this file is generated during the "core image" action earlier
> + # in the build process.
> + # However, when building a custom OOT module, it is needed to ensure that this file
> + # is accessible in the current directory where the module source code is being built.
> + # Not having this file result in a module that have no aliases even if they are needed
> + if config.symbol_frequency_file is not None:
> + try:
> + with open(config.symbol_frequency_file, 'r') as file:
> + for line in file:
> + key, value = line.strip().split(':')
> + name_occurrences[key]=int(value)
> + except FileNotFoundError:
> + pass
> +
> + return name_occurrences
> +
> +def check_aliases(config, module_nm_lines):
> + """
> + Flags modules that already have aliases based on the given 'module_nm_lines'.
> +
> + This function takes in configuration details and a list of strings representing
> + the 'nm' command output for a specific module. It detects instances where a module
> + already possesses an alias, which might occur after a build interruption and restart.
> +
> + The detection logic is straightforward: it examines if the separator character is
> + present in the symbol name. If found, it uses this separator to check if the
> + previous symbol shares the same name. This detection assumes 'nm' is invoked with
> + the '-n' flag, ensuring symbol sorting.
> +
> + Args:
> + config: A configuration object or dictionary containing necessary information.
> + module_nm_lines: A list of strings representing the 'nm' command output for a module.
> +
> + Returns:
> + True if the module_nm_lines contains aliases, False otherwise.
> + """
> + prev = None
> + for line in module_nm_lines:
> + if ('@' in line.name and line.name.split(config.separator)[0] == prev):
> + return False
> + prev = line.name
> + return True
> +
> +def main():
> + # Handles command-line arguments and generates a config object
> + parser = argparse.ArgumentParser(description='Add alias to multiple occurring symbols name in kallsyms')
> + subparsers = parser.add_subparsers(title='Subcommands', dest='action')
> + core_image_parser = subparsers.add_parser('core_image', help='Operates for in tree computation.')
> + core_image_parser.add_argument('-n', "--nmdata", dest="nm_data_file", required=True, help="Set vmlinux nm output file to use for core image.")
> + core_image_parser.add_argument('-o', "--outfile", dest="output_file", required=True, help="Set the vmlinux nm output file containing aliases.")
> + core_image_parser.add_argument('-v', "--vmlinux", dest="vmlinux_file", required=True, help="Set the vmlinux core image file.")
> + core_image_parser.add_argument('-m', "--modules_list", dest="module_list", required=True, help="Set the file containing the list of the modules object files.")
> +
> + single_module_parser = subparsers.add_parser('single_module', help='Operates for out of tree computation.')
> + single_module_parser.add_argument('-c', "--objcopy", dest="objcopy_file", required=True, help="Set the objcopy executable to be used.")
> + single_module_parser.add_argument('-u', "--objdump", dest="objdump_file", required=True, help="Set objdump executable to be used.")
Usually dest= should be omitted.
You can access config.objcopy, config.objdumpm,
instead of config.objcopy_file, config_objdump_file.
> + single_module_parser.add_argument('-q', "--target-module", dest="target_module", required=False, help="Sets a tharget module to operate.")
> +
> + parser.add_argument('-j', "--symbol_frequency", dest="symbol_frequency_file", required=True, help="Specify the symbol frequency needed to use for producing aliases")
> + parser.add_argument('-z', "--debug", dest="debug", required=False, help="Set the debug level.", choices=[f"{level.value}" for level in DebugLevel], default="1" )
> + parser.add_argument('-a', "--addr2line", dest="addr2line_file", required=True, help="Set the addr2line executable to be used.")
> + parser.add_argument('-b', "--basedir", dest="linux_base_dir", required=True, help="Set base directory of the source kernel code.")
> + parser.add_argument('-s', "--separator", dest="separator", required=False, help="Set separator, character that separates original name from the addr2line data in alias symbols.", default="@", type=SeparatorType())
> + parser.add_argument('-d', "--process_data", dest="process_data_sym", required=False, help="Requires the tool to process data symbols along with text symbols.", action='store_true')
> + parser.add_argument('-e', "--nm", dest="nm_file", required=True, help="Set the nm executable to be used.")
> +
> + config = parser.parse_args()
> +
> + try:
> + # The core_image target is utilized for gathering symbol statistics from the core image and modules,
> + # generating aliases for the core image. This target is designed to be invoked from scripts/link-vmlinux.sh
> + if config.action == 'core_image':
> + debug_print(config, DebugLevel.INFO.value,"Start core_image processing")
> +
> + # Determine kernel source code base directory
> + if not config.linux_base_dir.startswith('/'):
> + config.linux_base_dir = os.path.normpath(os.getcwd() + "/" + config.linux_base_dir) + "/"
> + debug_print(config, DebugLevel.DEBUG_BASIC.value, f"Configuration: {config}")
> +
> + debug_print(config, DebugLevel.INFO.value, "Process nm data from vmlinux")
> + # Process nm data from vmlinux
> + debug_print(config, DebugLevel.DEBUG_BASIC.value, f"fetch_file_lines({config.nm_data_file})")
> + vmlinux_nm_lines = fetch_file_lines(config, config.nm_data_file)
> + vmlinux_symbol_list, name_occurrences = parse_nm_lines(config, vmlinux_nm_lines)
> +
> + debug_print(config, DebugLevel.INFO.value,"Process nm data for modules")
> + # Process nm data for modules
> + debug_print(config, DebugLevel.DEBUG_BASIC.value, f"fetch_file_lines({config.nm_data_file})")
> + module_list = fetch_file_lines(config, config.module_list)
> + module_symbol_list = {}
> + for module in module_list:
> + module_nm_lines = do_nm(module, config)
> + module_symbol_list[module], name_occurrences = parse_nm_lines(config, module_nm_lines, name_occurrences)
> +
> + debug_print(config, DebugLevel.INFO.value, f"Save name_occurrences data: {config.symbol_frequency_file}")
> + with open(config.symbol_frequency_file, 'w') as file:
> + for key, value in name_occurrences.items():
> + file.write(f"{key}:{value}\n")
> +
> + debug_print(config, DebugLevel.INFO.value, "Produce file for vmlinux")
> + # Produce file for vmlinux
> + debug_print(config, DebugLevel.DEBUG_BASIC.value, f"addr2line_process({config.vmlinux_file}, {config.addr2line_file})")
> + addr2line_process = start_addr2line_process(config.vmlinux_file, config)
> + produce_output_vmlinux(config, vmlinux_symbol_list, name_occurrences, addr2line_process)
> + addr2line_process.stdin.close()
> + addr2line_process.stdout.close()
> + addr2line_process.stderr.close()
> + addr2line_process.wait()
> +
> + # Expects to be called from scripts/Makefile.modfinal
> + elif config.action == 'single_module':
> + debug_print(config, DebugLevel.INFO.value,"Start single_module processing")
> + # read simbol name frequency file
> + name_occurrences = read_name_occurrences(config)
> + # scan current module
> + module_nm_lines = do_nm(config.target_module, config)
> + mudule_nm_data, _ = parse_nm_lines(config, module_nm_lines)
> + if check_aliases(config, mudule_nm_data,):
> + debug_print(config, DebugLevel.DEBUG_BASIC.value, f"addr2line_process({config.target_module}, {config.addr2line_file})")
> + addr2line_process = start_addr2line_process(config.target_module, config)
> + debug_print(config, DebugLevel.DEBUG_BASIC.value,"adding aliases to module")
> + produce_output_modules(config, mudule_nm_data, name_occurrences, config.target_module, addr2line_process)
> + addr2line_process.stdin.close()
> + addr2line_process.stdout.close()
> + addr2line_process.stderr.close()
> + addr2line_process.wait()
> + else:
> + debug_print(config, DebugLevel.INFO.value,"module is already aliased, skipping")
> +
> + else:
> + raise SystemExit("Script terminated: unknown action")
> +
> + except Exception as e:
> + debug_print(config, DebugLevel.PRODUCTION.value, f"Script terminated due to an error ({type(e).__name__}): {str(e)}")
> + sys.exit(-2)
> +
> +if __name__ == "__main__":
> + main()
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index a432b171be82..31afac64d7ed 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -91,7 +91,12 @@ vmlinux_link()
>
> # The kallsyms linking does not need debug symbols included.
> if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> - ldflags="${ldflags} ${wl}--strip-debug"
> + # The kallsyms linking does not need debug symbols included,
> + # unless the KALLSYMS_ALIAS_SRCLINE.
> + if ! is_enabled CONFIG_KALLSYMS_ALIAS_SRCLINE && \
> + [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
This is the same condition as checked 5 lines above, isn't it?
> + ldflags="${ldflags} ${wl}--strip-debug"
> + fi
> fi
>
> if is_enabled CONFIG_VMLINUX_MAP; then
> @@ -161,7 +166,24 @@ kallsyms()
> fi
>
> info KSYMS ${2}
> - scripts/kallsyms ${kallsymopt} ${1} > ${2}
> + ALIAS=""
> + KAS_DATA=""
> + if is_enabled CONFIG_KALLSYMS_ALIAS_SRCLINE_DATA; then
> + KAS_DATA="--process_data"
> + fi
> + if is_enabled CONFIG_KALLSYMS_ALIAS_SRCLINE; then
> + ALIAS=".alias"
> + # You can use KAS_ALIAS_DEBUG=<debug level> in the make statements to enable
> + # verbose execution for kas_alias.
> + ${srctree}/scripts/kas_alias.py --symbol_frequency modules.symbfreq \
> + --debug ${KAS_ALIAS_DEBUG:-0} \
> + --addr2line ${ADDR2LINE} --basedir ${srctree} --nm ${NM} \
> + --separator @ ${KAS_DATA} \
> + core_image \
> + --modules_list ${MODORDER} --vmlinux ${kallsyms_vmlinux} \
> + --nmdata ${1} --outfile ${1}${ALIAS}
> + fi
> + scripts/kallsyms ${kallsymopt} ${1}${ALIAS} > ${2}
I do not understand your quoting policy.
In shell, there is no need to quote literals,
need to quote variables.
You are doing the opposite.
KAS_DATA="--process_data"
--> KAS_DATA=--process_data
${ADDR2LINE} --> "${ADDR2LINE}"
> }
>
> # Perform one step in kallsyms generation, including temporary linking of
> @@ -203,6 +225,7 @@ cleanup()
> rm -f System.map
> rm -f vmlinux
> rm -f vmlinux.map
> + find . -type f -name "*.orig" -exec rm {} \;
I am upset with deleting files with a well known suffix like this.
When the 'patch' command fails, *.orig and *.rej will be created.
> }
>
> # Use "make V=1" to debug this script
> --
> 2.34.1
>
--
Best Regards
Masahiro Yamada
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