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From:   "Alessandro Carminati (Red Hat)" <alessandro.carminati@gmail.com>
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     Masami Hiramatsu <mhiramat@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Daniel Bristot de Oliveira <bristot@kernel.org>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>,
        Alexander Lobakin <aleksander.lobakin@intel.com>,
        Nick Alcock <nick.alcock@oracle.com>,
        Kris Van Hees <kris.van.hees@oracle.com>,
        Eugene Loh <eugene.loh@oracle.com>,
        Francis Laniel <flaniel@linux.microsoft.com>,
        Viktor Malik <vmalik@redhat.com>,
        Petr Mladek <pmladek@suse.com>, Tom Rix <trix@redhat.com>,
        Alessandro Carminati <alessandro.carminati@gmail.com>,
        linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: [PATCH v7] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
Date:   Mon,  4 Dec 2023 21:46:35 +0000
Message-Id: <20231204214635.2916691-1-alessandro.carminati@gmail.com>
MIME-Version: 1.0
Content-type: text/plain
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Precedence: bulk

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@kernel_irq_irqdesc_c_264
ffffcaa2bb9c1a30 t name_show
ffffcaa2bb9c1a30 t name_show@drivers_pnp_card_c_186
ffffcaa2bbac4754 t name_show
ffffcaa2bbac4754 t name_show@drivers_regulator_core_c_678
ffffcaa2bbba4900 t name_show
ffffcaa2bbba4900 t name_show@drivers_base_power_wakeup_stats_c_93
ffffcaa2bbec4038 t name_show
ffffcaa2bbec4038 t name_show@drivers_rtc_sysfs_c_26
ffffcaa2bbecc920 t name_show
ffffcaa2bbecc920 t name_show@drivers_i2c_i2c_core_base_c_660
ffffcaa2bbed3840 t name_show
ffffcaa2bbed3840 t name_show@drivers_i2c_i2c_dev_c_100
ffffcaa2bbef7210 t name_show
ffffcaa2bbef7210 t name_show@drivers_pps_sysfs_c_66
ffffcaa2bbf03328 t name_show
ffffcaa2bbf03328 t name_show@drivers_hwmon_hwmon_c_72
ffffcaa2bbff6f3c t name_show
ffffcaa2bbff6f3c t name_show@drivers_remoteproc_remoteproc_sysfs_c_215
ffffcaa2bbff8d78 t name_show
ffffcaa2bbff8d78 t name_show@drivers_rpmsg_rpmsg_core_c_455
ffffcaa2bbfff7a4 t name_show
ffffcaa2bbfff7a4 t name_show@drivers_devfreq_devfreq_c_1395
ffffcaa2bc001f60 t name_show
ffffcaa2bc001f60 t name_show@drivers_extcon_extcon_c_389
ffffcaa2bc009890 t name_show
ffffcaa2bc009890 t name_show@drivers_iio_industrialio_core_c_1396
ffffcaa2bc01212c t name_show
ffffcaa2bc01212c t name_show@drivers_iio_industrialio_trigger_c_51
ffffcaa2bc025e2c t name_show
ffffcaa2bc025e2c t name_show@drivers_fpga_fpga_mgr_c_618
ffffcaa2a052102c t name_show	[hello]
ffffcaa2a052102c t name_show@hello_hello_c_8	[hello]
ffffcaa2a051955c t name_show	[rpmsg_char]
ffffcaa2a051955c t name_show@drivers_rpmsg_rpmsg_char_c_365	[rpmsg_char]

where hello, is a plain helloworld module built OOT.

Tested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.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/
---
 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 ?=
+
+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 $(if_changed{,_dep}). As an
 # optimization, we don't need to read them if the target does not
diff --git a/scripts/kas_alias.py b/scripts/kas_alias.py
new file mode 100755
index 000000000000..5b0517771389
--- /dev/null
+++ b/scripts/kas_alias.py
@@ -0,0 +1,600 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Copyright (C) 2023 Red Hat, Inc. Alessandro Carminati <alessandro.carminati@gmail.com>
+#
+# kas_alias: Adds alias to duplicate symbols for the kallsyms output.
+
+import os
+import re
+import sys
+import inspect
+import argparse
+import subprocess
+from enum import Enum
+from collections import namedtuple
+
+# Regex representing symbols that need no alias
+regex_filter = [
+        "^__compound_literal\\.[0-9]+$",
+        "^__[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
+
+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)
+
+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.")
+    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" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
+			ldflags="${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}
 }
 
 # 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 {} \;
 }
 
 # Use "make V=1" to debug this script
-- 
2.34.1