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References: <20230714150326.1152359-1-alessandro.carminati@gmail.com> <20230717105240.3d986331@gandalf.local.home>
In-Reply-To: <20230717105240.3d986331@gandalf.local.home>
From:   Alessandro Carminati <alessandro.carminati@gmail.com>
Date:   Tue, 18 Jul 2023 18:06:36 +0200
Message-ID: <CAPp5cGQVFU4FvVLAJhZTeAtcB1Lo=DXE+moEh-Ri1XDbjF2N6Q@mail.gmail.com>
Subject: Re: [PATCH v2] scripts/link-vmlinux.sh: Add alias to duplicate
 symbols for kallsyms
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Daniel Bristot de Oliveira <bristot@kernel.org>,
        Viktor Malik <vmalik@redhat.com>, linux-kernel@vger.kernel.org,
        linux-kbuild@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
        Nick Alcock <nick.alcock@oracle.com>, eugene.loh@oracle.com,
        kris.van.hees@oracle.com, mcgrof@kernel.org,
        live-patching@vger.kernel.org, bpf@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Steven,

Il giorno lun 17 lug 2023 alle ore 16:52 Steven Rostedt
<rostedt@goodmis.org> ha scritto:
>
> On Fri, 14 Jul 2023 15:03:26 +0000
> Alessandro Carminati <alessandro.carminati@gmail.com> wrote:
>
> > 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.
> >
> > The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> > symbol information from the kernel's ELF binary. However, when multiple
> > symbols share the same name, the standard nm output does not differentiate
> > between them. This can lead to confusion and difficulty when trying to
> > probe the intended symbol.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff8c4f76d0 t name_show
> >  ffffffff8c9cccb0 t name_show
> >  ffffffff8cb0ac20 t name_show
> >  ffffffff8cc728c0 t name_show
> >  ffffffff8ce0efd0 t name_show
> >  ffffffff8ce126c0 t name_show
> >  ffffffff8ce1dd20 t name_show
> >  ffffffff8ce24e70 t name_show
> >  ffffffff8d1104c0 t name_show
> >  ffffffff8d1fe480 t name_show
> >
> > **kas_alias** addresses this challenge by extending the symbol names with
> > unique suffixes during the kernel build process.
> > The newly created aliases for these duplicated symbols are unique names
> > that can be fed to the ftracefs interface. By doing so, it enables
> > previously unreachable symbols to be probed.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff974f76d0 t name_show
> >  ffffffff974f76d0 t name_show__alias__6340
> >  ffffffff979cccb0 t name_show
> >  ffffffff979cccb0 t name_show__alias__6341
> >  ffffffff97b0ac20 t name_show
> >  ffffffff97b0ac20 t name_show__alias__6342
> >  ffffffff97c728c0 t name_show
> >  ffffffff97c728c0 t name_show__alias__6343
> >  ffffffff97e0efd0 t name_show
> >  ffffffff97e0efd0 t name_show__alias__6344
> >  ffffffff97e126c0 t name_show
> >  ffffffff97e126c0 t name_show__alias__6345
> >  ffffffff97e1dd20 t name_show
> >  ffffffff97e1dd20 t name_show__alias__6346
> >  ffffffff97e24e70 t name_show
> >  ffffffff97e24e70 t name_show__alias__6347
> >  ffffffff981104c0 t name_show
> >  ffffffff981104c0 t name_show__alias__6348
> >  ffffffff981fe480 t name_show
> >  ffffffff981fe480 t name_show__alias__6349
> >  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
> >  > >/sys/kernel/tracing/kprobe_events
> >  ~ # cat /sys/kernel/tracing/kprobe_events
> >  p:kprobes/evnt1 name_show__alias__6349
> >
>
> Honestly, I think the "_alias_<some-random-number>" is useless. It doesn't
> give you any clue to what function you are actually attaching to. There's
> been other approaches that show module and/or file names. I know there's
> still some issues with getting those accepted, but I much rather have them
> than this!
>
> See: https://lore.kernel.org/all/20221205163157.269335-1-nick.alcock@oracle.com/
>

Thanks for sharing your thoughts on the current symbol naming convention and
Nick Alcock's approach.
I see your point about "alias<some-random-number>" not providing much context
about the attached function.
However, my intention was only to create a means to probe all functions.

While other approaches, such as including module and file names, are more
informative, it appears that these proposals are encountering certain
challenges in gaining acceptance. Also, they do not fully address the
specific problem I wanted to tackle.

In my upcoming proposal, I would like to maintain the conservative approach I
have followed so far while still achieving my original objective of making all
functions reachable from kprobe.

To date, I have been working on addressing all the necessary aspects from
outside the kernel source code. Essentially, I take the output of 'nm' and
refine it to provide more meaningful information.

I am working in a V3, I am considering using `addr2line` to
determine the origin of each symbol. Initially, I avoided it because the
configuration dependency it introduces, specifically requiring DWARF
information such as CONFIG_DEBUG_INFO_DWARF4 or
CONFIG_DEBUG_INFO_DWARF5.

However, after reading Luis' comment suggesting the use of
'filename + line number', I realized that relying on DWARF information might
be the only way to achieve a satisfying result.
I will try that and see if it works... unless you know it will not already :-)

Actually, I did a fast try using DWARF and addr2line, the strategy I'd like to
use in the v3, and the output looks like this: what do you guys think?

 $ ../kas_alias/main .tmp_vmlinux.kallsyms2.syms | grep name_show
 ffffffff8100e5e0 t __pfx_pmu_name_show
 ffffffff8100e5f0 t pmu_name_show
 ffffffff810ed8e0 t __pfx_name_show
 ffffffff810ed8f0 t name_show
 ffffffff810ed8f0 t name_show@_kernel_irq_irqdesc_c_232
 ffffffff810ed950 t __pfx_chip_name_show
 ffffffff810ed960 t chip_name_show
 ffffffff810ed960 t chip_name_show@_kernel_irq_irqdesc_c_168
 ffffffff814cae80 t __pfx_name_show
 ffffffff814cae90 t name_show
 ffffffff814cae90 t name_show@_drivers_pnp_card_c_186
 ffffffff816006d0 t __pfx_name_show
 ffffffff816006e0 t name_show
 ffffffff816006e0 t name_show@_drivers_gpu_drm_i915_gt_sysfs_engines_c_26
 ffffffff81765460 t __pfx_name_show
 ffffffff81765470 t name_show
 ffffffff81765470 t name_show@_drivers_base_power_wakeup_stats_c_93
 ffffffff8189b340 t __pfx_name_show
 [...]

I want to emphasize that my goal is to find a solution that satisfies everyone
involved and addresses the concerns raised.

Bests
Alessandro

> -- Steve
>
>
> > 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/
> >
> > Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> > ---
> >  init/Kconfig                        |  36 +++++
> >  scripts/Makefile                    |   4 +
> >  scripts/kas_alias/Makefile          |   4 +
> >  scripts/kas_alias/duplicates_list.c |  70 +++++++++
> >  scripts/kas_alias/duplicates_list.h |  15 ++
> >  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++++++
> >  scripts/kas_alias/item_list.h       |  26 ++++
> >  scripts/kas_alias/kas_alias.c       | 186 ++++++++++++++++++++++
> >  scripts/link-vmlinux.sh             |   6 +-
> >  9 files changed, 576 insertions(+), 1 deletion(-)
> >  create mode 100644 scripts/kas_alias/Makefile
> >  create mode 100644 scripts/kas_alias/duplicates_list.c
> >  create mode 100644 scripts/kas_alias/duplicates_list.h
> >  create mode 100644 scripts/kas_alias/item_list.c
> >  create mode 100644 scripts/kas_alias/item_list.h
> >  create mode 100644 scripts/kas_alias/kas_alias.c
> >
> > diff --git a/init/Kconfig b/init/Kconfig
> > index f7f65af4ee12..5ae7c613cdc4 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1737,6 +1737,42 @@ 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
> > +     bool "Produces alias for duplicated symbols" if EXPERT
> > +     depends on KALLSYMS
> > +     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 by extending the symbol names
> > +       with unique suffixes during the kernel build process.
> > +       The newly created aliases for these duplicated symbols are unique
> > +       names that can be fed to the ftrace sysfs interface. By doing so, it
> > +       enables previously unreachable symbols to be probed.
> > +
> > +config CONFIG_KALLSYMS_ALIAS_DATA
> > +     bool "Produces alias also for data"
> > +     depends on KALLSYMS_ALIAS
> > +     help
> > +       Sometimes it can be useful to refer to data. In live patch scenarios,
> > +       you may find yourself needing to use symbols that are shared with
> > +       other functions. Since symbols face the same issue as functions, this
> > +       option allows you to create aliases for data as well.
> > +
> > +config CONFIG_KALLSYMS_ALIAS_DATA_ALL
> > +     bool "Removes all filter when producing data alias"
> > +     depends on CONFIG_KALLSYMS_ALIAS_DATA
> > +     help
> > +       When selecting data aliases, not all symbols are included in the set
> > +       This is because many symbols are unlikely to be used. If you choose
> > +       to have an alias for all data symbols, be aware that it will
> > +       significantly increase the size.
> > +
> > +       If unsure, say N.
> > +
> >  # end of the "standard kernel features (expert users)" menu
> >
> >  # syscall, maps, verifier
> > diff --git a/scripts/Makefile b/scripts/Makefile
> > index 32b6ba722728..65fafe17cfe5 100644
> > --- a/scripts/Makefile
> > +++ b/scripts/Makefile
> > @@ -49,3 +49,7 @@ subdir-$(CONFIG_SECURITY_SELINUX) += selinux
> >
> >  # Let clean descend into subdirs
> >  subdir-      += basic dtc gdb kconfig mod
> > +
> > +# KALLSyms alias
> > +subdir-$(CONFIG_KALLSYMS_ALIAS) += kas_alias
> > +
> > diff --git a/scripts/kas_alias/Makefile b/scripts/kas_alias/Makefile
> > new file mode 100644
> > index 000000000000..523fa3441013
> > --- /dev/null
> > +++ b/scripts/kas_alias/Makefile
> > @@ -0,0 +1,4 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +hostprogs-always-$(CONFIG_KALLSYMS_ALIAS)    += kas_alias
> > +
> > +kas_alias-objs        := duplicates_list.o item_list.o kas_alias.o
> > diff --git a/scripts/kas_alias/duplicates_list.c b/scripts/kas_alias/duplicates_list.c
> > new file mode 100644
> > index 000000000000..e7a3d2917937
> > --- /dev/null
> > +++ b/scripts/kas_alias/duplicates_list.c
> > @@ -0,0 +1,70 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdint.h>
> > +#include <stdio.h>
> > +#include <string.h>
> > +#include <stdlib.h>
> > +#include <stdbool.h>
> > +
> > +#include "item_list.h"
> > +#include "duplicates_list.h"
> > +
> > +struct duplicate_item *find_duplicates(struct item *list)
> > +{
> > +     struct duplicate_item *current_duplicate = NULL;
> > +     struct duplicate_item *duplicates = NULL;
> > +     struct duplicate_item *new_duplicate;
> > +     struct item *current_item = list;
> > +     bool prev_was_duplicate = false;
> > +     struct item *prev_item = NULL;
> > +
> > +     while (current_item) {
> > +             if ((prev_item && (strcmp(current_item->symb_name, prev_item->symb_name) == 0)) ||
> > +                 prev_was_duplicate) {
> > +                     if (!duplicates) {
> > +                             duplicates = malloc(sizeof(struct duplicate_item));
> > +                             if (!duplicates)
> > +                                     return NULL;
> > +
> > +                             duplicates->original_item = prev_item;
> > +                             duplicates->next = NULL;
> > +                             current_duplicate = duplicates;
> > +                     } else {
> > +                             new_duplicate = malloc(sizeof(struct duplicate_item));
> > +                             if (!new_duplicate) {
> > +                                     free_duplicates(&duplicates);
> > +                                     return NULL;
> > +                             }
> > +
> > +                             new_duplicate->original_item = prev_item;
> > +                             new_duplicate->next = NULL;
> > +                             current_duplicate->next = new_duplicate;
> > +                             current_duplicate = new_duplicate;
> > +
> > +                             if ((strcmp(current_item->symb_name, prev_item->symb_name) != 0) &&
> > +                                 (prev_was_duplicate))
> > +                                     prev_was_duplicate = false;
> > +                             else
> > +                                     prev_was_duplicate = true;
> > +                     }
> > +             }
> > +
> > +             prev_item = current_item;
> > +             current_item = current_item->next;
> > +     }
> > +
> > +     return duplicates;
> > +}
> > +
> > +void free_duplicates(struct duplicate_item **duplicates)
> > +{
> > +     struct duplicate_item *duplicates_iterator = *duplicates;
> > +     struct duplicate_item *app;
> > +
> > +     while (duplicates_iterator) {
> > +             app = duplicates_iterator;
> > +             duplicates_iterator = duplicates_iterator->next;
> > +             free(app);
> > +     }
> > +
> > +     *duplicates = NULL;
> > +}
> > diff --git a/scripts/kas_alias/duplicates_list.h b/scripts/kas_alias/duplicates_list.h
> > new file mode 100644
> > index 000000000000..76aa73e584bc
> > --- /dev/null
> > +++ b/scripts/kas_alias/duplicates_list.h
> > @@ -0,0 +1,15 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef DUPLICATES_LIST_H
> > +#define DUPLICATES_LIST_H
> > +
> > +#include "item_list.h"
> > +
> > +struct duplicate_item {
> > +     struct item *original_item;
> > +     struct duplicate_item *next;
> > +};
> > +
> > +struct duplicate_item *find_duplicates(struct item *list);
> > +void free_duplicates(struct duplicate_item **duplicates);
> > +
> > +#endif
> > diff --git a/scripts/kas_alias/item_list.c b/scripts/kas_alias/item_list.c
> > new file mode 100644
> > index 000000000000..7c9d5aecca9a
> > --- /dev/null
> > +++ b/scripts/kas_alias/item_list.c
> > @@ -0,0 +1,230 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <stdint.h>
> > +#include <string.h>
> > +#include <stdbool.h>
> > +#include <assert.h>
> > +#include "item_list.h"
> > +
> > +#define CHECK_ORDER_BY_ADDRESS(sort_by, current, temp, op) \
> > +     ((sort_by) == BY_ADDRESS && (current)->addr op (temp)->addr)
> > +#define CHECK_ORDER_BY_NAME(sort_by, current, temp, op) \
> > +     ((sort_by) == BY_NAME && strcmp((current)->symb_name, (temp)->symb_name) op 0)
> > +
> > +struct item *list_index[96] = {0};
> > +
> > +void build_index(struct item *list)
> > +{
> > +     char current_first_letter = ' ';
> > +     struct item *current = list;
> > +
> > +     while (current) {
> > +             if (current->symb_name[0] != current_first_letter) {
> > +                     current_first_letter = current->symb_name[0];
> > +                     list_index[current_first_letter - 32] = current;
> > +             }
> > +             current = current->next;
> > +     }
> > +}
> > +
> > +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr)
> > +{
> > +     struct item *new_item;
> > +     struct item *current;
> > +
> > +     new_item = malloc(sizeof(struct item));
> > +     if (!new_item)
> > +             return NULL;
> > +
> > +     strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> > +     new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> > +     new_item->addr = addr;
> > +     new_item->stype = stype;
> > +     new_item->next = NULL;
> > +
> > +     if (!(*list)) {
> > +             *list = new_item;
> > +     } else {
> > +             current = *list;
> > +             while (current->next)
> > +                     current = current->next;
> > +
> > +             current->next = new_item;
> > +     }
> > +     return new_item;
> > +}
> > +
> > +void sort_list(struct item **list, int sort_by)
> > +{
> > +     struct item *current = *list;
> > +     struct item *sorted = NULL;
> > +     struct item *next_item;
> > +     struct item *temp;
> > +
> > +     if (!(*list) || !((*list)->next))
> > +             return;
> > +
> > +     while (current) {
> > +             next_item = current->next;
> > +             if (!sorted ||
> > +                (CHECK_ORDER_BY_ADDRESS(sort_by, current, sorted, <) ||
> > +                 CHECK_ORDER_BY_NAME(sort_by, current, sorted, >=))) {
> > +                     current->next = sorted;
> > +                     sorted = current;
> > +             } else {
> > +                     temp = sorted;
> > +                     while (temp->next &&
> > +                           (CHECK_ORDER_BY_ADDRESS(sort_by, current, temp->next, >=) ||
> > +                            CHECK_ORDER_BY_NAME(sort_by, current, temp->next, >=)))
> > +                             temp = temp->next;
> > +
> > +                     current->next = temp->next;
> > +                     temp->next = current;
> > +             }
> > +             current = next_item;
> > +     }
> > +
> > +     *list = sorted;
> > +}
> > +
> > +struct item *merge(struct item *left, struct item *right, int sort_by)
> > +{
> > +     struct item *current = NULL;
> > +     struct item *result = NULL;
> > +
> > +     if (!left)
> > +             return right;
> > +     if (!right)
> > +             return left;
> > +
> > +     if (sort_by == BY_NAME) {
> > +             if (strcmp(left->symb_name, right->symb_name) <= 0) {
> > +                     result = left;
> > +                     left = left->next;
> > +             } else {
> > +                     result = right;
> > +                     right = right->next;
> > +             }
> > +     } else {
> > +             if (sort_by == BY_ADDRESS) {
> > +                     if (left->addr <= right->addr) {
> > +                             result = left;
> > +                             left = left->next;
> > +                     } else {
> > +                             result = right;
> > +                             right = right->next;
> > +                     }
> > +             }
> > +     }
> > +
> > +     current = result;
> > +
> > +     while (left && right) {
> > +             if (sort_by == BY_NAME) {
> > +                     if (strcmp(left->symb_name, right->symb_name) <= 0) {
> > +                             current->next = left;
> > +                             left = left->next;
> > +                     } else {
> > +                             current->next = right;
> > +                             right = right->next;
> > +                     }
> > +             } else {
> > +                     if (sort_by == BY_ADDRESS) {
> > +                             if (left->addr <= right->addr) {
> > +                                     current->next = left;
> > +                                     left = left->next;
> > +                             } else {
> > +                                     current->next = right;
> > +                                     right = right->next;
> > +                             }
> > +                     }
> > +             }
> > +
> > +             current = current->next;
> > +     }
> > +
> > +     if (left) {
> > +             current->next = left;
> > +     } else {
> > +             if (right)
> > +                     current->next = right;
> > +     }
> > +
> > +     return result;
> > +}
> > +
> > +struct item *merge_sort(struct item *head, int sort_by)
> > +{
> > +     struct item *right;
> > +     struct item *slow;
> > +     struct item *fast;
> > +     struct item *left;
> > +
> > +     if (!head || !head->next)
> > +             return head;
> > +
> > +     slow = head;
> > +     fast = head->next;
> > +
> > +     while (fast && fast->next) {
> > +             slow = slow->next;
> > +             fast = fast->next->next;
> > +     }
> > +
> > +     left = head;
> > +     right = slow->next;
> > +     slow->next = NULL;
> > +
> > +     left = merge_sort(left, sort_by);
> > +     right = merge_sort(right, sort_by);
> > +
> > +     return merge(left, right, sort_by);
> > +}
> > +
> > +void sort_list_m(struct item **head, int sort_by)
> > +{
> > +     if (!(*head) || !((*head)->next))
> > +             return;
> > +
> > +     *head = merge_sort(*head, sort_by);
> > +}
> > +
> > +int insert_after(struct item *list, const uint64_t search_addr,
> > +              const char *name, uint64_t addr, char stype)
> > +{
> > +     struct item *new_item;
> > +     struct item *current;
> > +     int ret = 0;
> > +
> > +     current = (list_index[name[0] - 32]) ? list_index[name[0] - 32] : list;
> > +     while (current) {
> > +             if (current->addr == search_addr) {
> > +                     new_item = malloc(sizeof(struct item));
> > +                     if (!new_item)
> > +                             return ret;
> > +                     strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> > +                     new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> > +                     new_item->addr = addr;
> > +                     new_item->stype = stype;
> > +                     new_item->next = current->next;
> > +                     current->next = new_item;
> > +                     ret = 1;
> > +                     break;
> > +             }
> > +             current = current->next;
> > +     }
> > +     return ret;
> > +}
> > +
> > +void free_items(struct item **head)
> > +{
> > +     struct item *app, *item_iterator = *head;
> > +
> > +     while (item_iterator) {
> > +             app = item_iterator;
> > +             item_iterator = item_iterator->next;
> > +             free(app);
> > +     }
> > +     *head = NULL;
> > +}
> > diff --git a/scripts/kas_alias/item_list.h b/scripts/kas_alias/item_list.h
> > new file mode 100644
> > index 000000000000..b4891cb088ee
> > --- /dev/null
> > +++ b/scripts/kas_alias/item_list.h
> > @@ -0,0 +1,26 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef ITEM_LIST_H
> > +#define ITEM_LIST_H
> > +#include <stdint.h>
> > +
> > +#define MAX_NAME_SIZE 256
> > +#define BY_ADDRESS 1
> > +#define BY_NAME 2
> > +
> > +struct item {
> > +     char            symb_name[MAX_NAME_SIZE];
> > +     uint64_t        addr;
> > +     char            stype;
> > +     struct item     *next;
> > +};
> > +
> > +void build_index(struct item *list);
> > +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr);
> > +void sort_list(struct item **list, int sort_by);
> > +struct item *merge(struct item *left, struct item *right, int sort_by);
> > +struct item *merge_sort(struct item *head, int sort_by);
> > +void sort_list_m(struct item **head, int sort_by);
> > +int insert_after(struct item *list, const uint64_t search_addr,
> > +              const char *name, uint64_t addr, char stype);
> > +void free_items(struct item **head);
> > +#endif
> > diff --git a/scripts/kas_alias/kas_alias.c b/scripts/kas_alias/kas_alias.c
> > new file mode 100644
> > index 000000000000..eb873b368023
> > --- /dev/null
> > +++ b/scripts/kas_alias/kas_alias.c
> > @@ -0,0 +1,186 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <stdint.h>
> > +#include <string.h>
> > +#include <stdbool.h>
> > +#include <stdarg.h>
> > +#include <regex.h>
> > +
> > +#include "item_list.h"
> > +#include "duplicates_list.h"
> > +
> > +#define SYMB_IS_TEXT(s) ((((s)->stype) == 't') ||  (((s)->stype) == 'T'))
> > +#define SYMB_IS_DATA(s) ((((s)->stype) == 'b') ||  (((s)->stype) == 'B') || \
> > +                      (((s)->stype) == 'd') ||  (((s)->stype) == 'D') || \
> > +                      (((s)->stype) == 'r') ||  (((s)->stype) == 'R'))
> > +#ifdef CONFIG_KALLSYMS_ALIAS_DATA
> > +#define SYMB_NEEDS_ALIAS(s) (SYMB_IS_TEXT(s) || SYMB_IS_DATA(s))
> > +#else
> > +#define SYMB_NEEDS_ALIAS(s) SYMB_IS_TEXT(s)
> > +#endif
> > +#define FNOMATCH 0
> > +#define FMATCH 1
> > +#define EREGEX 2
> > +
> > +const char *ignore_regex[] = {
> > +     "^__cfi_.*$",                           // __cfi_ preamble
> > +#ifndef CONFIG_KALLSYMS_ALIAS_DATA_ALL
> > +     "^_*TRACE_SYSTEM.*$",
> > +     "^__already_done\\.[0-9]+$",            // Call a function once data
> > +     "^___tp_str\\.[0-9]+$",
> > +     "^___done\\.[0-9]+$",
> > +     "^__print_once\\.[0-9]+$",
> > +     "^_rs\\.[0-9]+$",
> > +     "^__compound_literal\\.[0-9]+$",
> > +     "^___once_key\\.[0-9]+$",
> > +     "^__func__\\.[0-9]+$",
> > +     "^__msg\\.[0-9]+$",
> > +     "^CSWTCH\\.[0-9]+$",
> > +     "^__flags\\.[0-9]+$",
> > +     "^__wkey.*$",
> > +     "^__mkey.*$",
> > +     "^__key.*$",
> > +#endif
> > +     "^__pfx_.*$"                            // NOP-padding
> > +};
> > +
> > +int suffix_serial;
> > +
> > +static inline void verbose_msg(bool verbose, const char *fmt, ...)
> > +{
> > +     va_list args;
> > +
> > +     va_start(args, fmt);
> > +     if (verbose)
> > +             printf(fmt, args);
> > +
> > +     va_end(args);
> > +}
> > +
> > +static void create_suffix(const char *name, char *output_suffix)
> > +{
> > +     sprintf(output_suffix, "%s__alias__%d", name, suffix_serial++);
> > +}
> > +
> > +static int filter_symbols(char *symbol, const char **ignore_list, int regex_no)
> > +{
> > +     regex_t regex;
> > +     int res, i;
> > +
> > +     for (i = 0; i < regex_no; i++) {
> > +             res = regcomp(&regex, ignore_list[i], REG_EXTENDED);
> > +             if (res)
> > +                     return -EREGEX;
> > +
> > +             res = regexec(&regex, symbol, 0, NULL, 0);
> > +             regfree(&regex);
> > +             switch (res) {
> > +             case 0:
> > +                     return FMATCH;
> > +             case REG_NOMATCH:
> > +                     break;
> > +             default:
> > +                     return -EREGEX;
> > +             }
> > +
> > +     }
> > +
> > +     return FNOMATCH;
> > +}
> > +
> > +int main(int argc, char *argv[])
> > +{
> > +     char t, sym_name[MAX_NAME_SIZE], new_name[MAX_NAME_SIZE + 15];
> > +     struct duplicate_item  *duplicate_iterator;
> > +     struct duplicate_item *duplicate;
> > +     struct item *head = {NULL};
> > +     bool need_2_process = true;
> > +     struct item *last = {NULL};
> > +     struct item  *current;
> > +     int verbose_mode = 0;
> > +     uint64_t address;
> > +     FILE *fp;
> > +     int res;
> > +
> > +     if (argc < 2 || argc > 3) {
> > +             printf("Usage: %s <nmfile> [-verbose]\n", argv[0]);
> > +             return 1;
> > +     }
> > +
> > +     if (argc == 3 && strcmp(argv[2], "-verbose") == 0)
> > +             verbose_mode = 1;
> > +
> > +     verbose_msg(verbose_mode, "Scanning nm data(%s)\n", argv[1]);
> > +
> > +     fp = fopen(argv[1], "r");
> > +     if (!fp) {
> > +             printf("Can't open input file.\n");
> > +             return 1;
> > +     }
> > +
> > +     while (fscanf(fp, "%lx %c %99s\n", &address, &t, sym_name) == 3) {
> > +             if (strstr(sym_name, "__alias__1") != NULL) {
> > +                     if (verbose_mode && need_2_process)
> > +                             printf("Already processed\n");
> > +                     need_2_process = false;
> > +                     }
> > +             last = add_item(&last, sym_name, t, address);
> > +             if (!last) {
> > +                     printf("Error in allocate memory\n");
> > +                     free_items(&head);
> > +                     return 1;
> > +             }
> > +
> > +             if (!head)
> > +                     head = last;
> > +     }
> > +
> > +     fclose(fp);
> > +
> > +     if (need_2_process) {
> > +             verbose_msg(verbose_mode, "Sorting nm data\n");
> > +             sort_list_m(&head, BY_NAME);
> > +             verbose_msg(verbose_mode, "Scanning nm data for duplicates\n");
> > +             duplicate = find_duplicates(head);
> > +             if (!duplicate) {
> > +                     printf("Error in duplicates list\n");
> > +                     return 1;
> > +             }
> > +
> > +             verbose_msg(verbose_mode, "Applying suffixes\n");
> > +             build_index(head);
> > +             duplicate_iterator = duplicate;
> > +             while (duplicate_iterator) {
> > +                     res = filter_symbols(duplicate_iterator->original_item->symb_name,
> > +                                          ignore_regex, sizeof(ignore_regex) /
> > +                                          sizeof(ignore_regex[0]));
> > +                     if ((res != FMATCH) &&
> > +                        SYMB_NEEDS_ALIAS(duplicate_iterator->original_item)) {
> > +                             if (res < 0)
> > +                                     return 1;
> > +
> > +                             create_suffix(duplicate_iterator->original_item->symb_name,
> > +                                           new_name);
> > +                             if (!insert_after(head, duplicate_iterator->original_item->addr,
> > +                                               new_name, duplicate_iterator->original_item->addr,
> > +                                               duplicate_iterator->original_item->stype))
> > +                                     return 1;
> > +                     }
> > +
> > +                     duplicate_iterator = duplicate_iterator->next;
> > +             }
> > +
> > +             sort_list_m(&head, BY_ADDRESS);
> > +     }
> > +     current = head;
> > +     while (current) {
> > +             printf("%08lx %c %s\n", current->addr, current->stype, current->symb_name);
> > +             current = current->next;
> > +     }
> > +
> > +     free_items(&head);
> > +     free_duplicates(&duplicate);
> > +
> > +     return 0;
> > +}
> > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > index a432b171be82..4e3dea3ac2df 100755
> > --- a/scripts/link-vmlinux.sh
> > +++ b/scripts/link-vmlinux.sh
> > @@ -161,7 +161,11 @@ kallsyms()
> >       fi
> >
> >       info KSYMS ${2}
> > -     scripts/kallsyms ${kallsymopt} ${1} > ${2}
> > +     if is_enabled CONFIG_KALLSYMS_ALIAS; then
> > +             ALIAS=".alias"
> > +             scripts/kas_alias/kas_alias ${1} >${1}${ALIAS}
> > +             fi
> > +     scripts/kallsyms ${kallsymopt} ${1}${ALIAS} > ${2}
> >  }
> >
> >  # Perform one step in kallsyms generation, including temporary linking of
>