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Message-ID: <CAPp5cGSNqTHd2OsakGS=uGq-BFpk+ODusDzOE2miMZym=rnhaA@mail.gmail.com>
Date: Sat, 2 Sep 2023 09:27:11 +0200
From: Alessandro Carminati <alessandro.carminati@...il.com>
To: Masahiro Yamada <masahiroy@...nel.org>
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>, linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
live-patching@...r.kernel.org
Subject: Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate
symbols for kallsyms
Hello Masahiro,
This review is outstanding. Thanks for the time you used to write me this.
Il giorno ven 1 set 2023 alle ore 07:32 Masahiro Yamada
<masahiroy@...nel.org> ha scritto:
>
> On Mon, Aug 28, 2023 at 8:45 PM Alessandro Carminati (Red Hat)
> <alessandro.carminati@...il.com> wrote:
> >
> > From: Alessandro Carminati <alessandro.carminati@...il.com>
> >
> > 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
> >
> > 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.
> >
> > sample from new v3
> >
> > ~ # cat /proc/kallsyms | grep gic_mask_irq
> > ffffd0b03c04dae4 t gic_mask_irq
> > ffffd0b03c04dae4 t gic_mask_irq@...ivers_irqchip_irq-gic_c_167
> > ffffd0b03c050960 t gic_mask_irq
> > ffffd0b03c050960 t gic_mask_irq@...ivers_irqchip_irq-gic-v3_c_404
> > ~ #
> >
> > https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
> >
> > Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@...il.com>
> > ---
> > init/Kconfig | 36 ++++
> > scripts/Makefile | 4 +
> > scripts/kas_alias/Makefile | 4 +
> > scripts/kas_alias/a2l.c | 268 ++++++++++++++++++++++++++++
> > scripts/kas_alias/a2l.h | 32 ++++
> > 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 | 217 ++++++++++++++++++++++
> > scripts/link-vmlinux.sh | 11 +-
> > 11 files changed, 910 insertions(+), 3 deletions(-)
> > create mode 100644 scripts/kas_alias/Makefile
> > create mode 100644 scripts/kas_alias/a2l.c
> > create mode 100644 scripts/kas_alias/a2l.h
> > 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..bc69fcd9cbc8 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 && (DEBUG_INFO_DWARF4 || DEBUG_INFO_DWARF5)
>
>
> You can simplify this to
>
>
> depends on KALLSYMS && DEBUG_INFO
>
> I re-checked the commit log of
> a66049e2cf0ef166dba5bafdbb3062287fc965ad
>
> It says "GCC since ~4.8 has defaulted to DWARF v4
> implicitly, and GCC 11 has bumped this to v5"
>
>
> When DEBUG_INFO is enabled, the dwarf version is 4 or 5.
>
>
> Presumably, your code does not work with DEBUG_INFO_SPLIT
>
>
> depends on KALLSYMS && DEBUG_INFO && !DEBUG_INFO_SPLIT
>
>
>
>
I will make the necessary updates to v4 based on your analysis.
> > diff --git a/scripts/kas_alias/a2l.c b/scripts/kas_alias/a2l.c
> > new file mode 100644
> > index 000000000000..a9692ac30180
> > --- /dev/null
> > +++ b/scripts/kas_alias/a2l.c
> > @@ -0,0 +1,268 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +#include <sys/types.h>
> > +#include <sys/wait.h>
> > +#include <string.h>
>
>
> <string.h> is included twice.
>
> I always sort include directives alphabetically
> to avoid such a mistake.
>
>
>
>
>
>
> > +#include <stdint.h>
> > +#include <stdbool.h>
> > +
> > +#include "a2l.h"
> > +
> > +int addr2line_pid = -1;
> > +int a2l_in[2];
> > +int a2l_out[2];
> > +char line[MAX_BUF];
> > +char vmlinux_path[MAX_BUF];
> > +char addr2line_cmd[MAX_CMD_LEN];
> > +FILE *a2l_stdin, *a2l_stdout;
> > +
> > +static char *normalize_path(const char *input_path, char *output_path)
> > +{
> > + char *prev_token = NULL;
> > + char *delimiter = "/";
> > + char inbuf[MAX_BUF];
> > + char *token;
> > + char *pos;
> > +
> > + memset(inbuf, 0, MAX_BUF);
> > + *output_path = '\0';
> > + strncpy(inbuf, input_path, MAX_BUF);
> > + if (!input_path || !output_path || strlen(input_path) == 0)
> > + return NULL;
> > +
> > + token = strtok(inbuf, delimiter);
> > + while (token) {
> > + if (strcmp(token, "..") == 0 && prev_token) {
> > + pos = strrchr(output_path, '/');
> > + if (pos)
> > + *pos = '\0';
> > +
> > + } else if (strcmp(token, ".") != 0) {
> > + strcat(output_path, "/");
> > + strcat(output_path, token);
> > + }
> > +
> > + prev_token = token;
> > + token = strtok(NULL, delimiter);
> > + }
> > +
> > + return output_path;
> > +}
> > +
> > +static void path_of(const char *full_path, char *path)
> > +{
> > + const char *last_slash = strrchr(full_path, '/');
> > + size_t path_length;
> > + char cwd[MAX_BUF];
> > +
> > + if (!last_slash) {
> > + if (getcwd(cwd, sizeof(cwd)))
> > + strcpy(path, cwd);
> > + else
> > + strcpy(path, ".");
> > + } else {
> > + path_length = last_slash - full_path;
> > + strncpy(path, full_path, path_length);
> > + path[path_length] = '\0';
> > + }
> > +}
> > +
> > +static bool file_exists(const char *file_path)
> > +{
> > + FILE *file;
> > +
> > + file = fopen(file_path, "r");
> > + if (file) {
> > + fclose(file);
> > + return true;
> > + }
> > + return false;
> > +}
> > +
> > +int addr2line_init(const char *cmd, const char *vmlinux)
> > +{
> > + if ((!file_exists(cmd)) || (!file_exists(vmlinux))) {
> > + printf("file not found\n");
> > + return 0;
> > + }
> > +
> > + path_of(vmlinux, vmlinux_path);
> > + if (pipe(a2l_in) == -1) {
> > + printf("Failed to create pipe\n");
> > + return 0;
> > + }
> > +
> > + if (pipe(a2l_out) == -1) {
> > + printf("Failed to create pipe\n");
> > + return 0;
> > + }
> > +
> > + addr2line_pid = fork();
> > + if (addr2line_pid == -1) {
> > + printf("Failed to fork process\n");
> > + close(a2l_in[P_READ]);
> > + close(a2l_in[P_WRITE]);
> > + close(a2l_out[P_READ]);
> > + close(a2l_out[P_WRITE]);
> > + return 0;
> > + }
> > +
> > + if (addr2line_pid == 0) {
> > + dup2(a2l_in[P_READ], 0);
> > + dup2(a2l_out[P_WRITE], 1);
> > + close(a2l_in[P_WRITE]);
> > + close(a2l_out[P_READ]);
> > +
> > + execlp(cmd, cmd, ADDR2LINE_ARGS, vmlinux, NULL);
> > +
> > + printf("Failed to execute addr2line command\n");
> > + exit(1);
> > + } else {
> > + close(a2l_in[P_READ]);
> > + close(a2l_out[P_WRITE]);
> > + }
> > +
> > + a2l_stdin = fdopen(a2l_in[P_WRITE], "w");
> > + if (!a2l_stdin) {
> > + printf("Failed to open pipe a2l_in\n");
> > + return 0;
> > + }
> > +
> > + a2l_stdout = fdopen(a2l_out[P_READ], "r");
> > + if (!a2l_stdout) {
> > + printf("Failed to open pipe a2l_out\n");
> > + fclose(a2l_stdin);
> > + return 0;
> > + }
> > +
> > + return 1;
> > +}
> > +
> > +const char *remove_subdir(const char *home, const char *f_path)
> > +{
> > + int i = 0;
> > +
> > + while (*(home + i) == *(f_path + i))
> > + i++;
> > +
> > + return (strlen(home) != i) ? NULL : f_path + i;
> > +}
> > +
> > +char *addr2line_get_lines(uint64_t address)
> > +{
> > + char buf[MAX_BUF];
> > +
> > + fprintf(a2l_stdin, "%08lx\n", address);
> > + fflush(a2l_stdin);
> > +
> > + if (!fgets(line, sizeof(line), a2l_stdout)) {
> > + printf("Failed to read lines from addr2line\n");
> > + return NULL;
> > + }
> > +
> > + if (!fgets(line, sizeof(line), a2l_stdout)) {
> > + printf("Failed to read lines from addr2line\n");
> > + return NULL;
> > + }
> > +
> > + line[strcspn(line, "\n")] = '\0';
> > + strncpy(buf, line, MAX_BUF);
> > + return normalize_path(buf, line);
> > +}
> > +
> > +int addr2line_cleanup(void)
> > +{
> > + int status;
> > +
> > + if (addr2line_pid != -1) {
> > + kill(addr2line_pid, SIGKILL);
> > + waitpid(addr2line_pid, &status, 0);
> > + fclose(a2l_stdin);
> > + fclose(a2l_stdout);
> > + addr2line_pid = -1;
> > + }
> > +
> > + return 1;
> > +}
> > +
> > +static char *find_executable(const char *command)
> > +{
> > + char *path_env = getenv("PATH");
> > + char *executable_path;
> > + char *path_copy;
> > + char *path;
> > + int n;
> > +
> > + if (!path_env)
> > + return NULL;
> > +
> > + path_copy = strdup(path_env);
> > + if (!path_copy)
> > + return NULL;
> > +
> > + path = strtok(path_copy, ":");
> > + while (path) {
> > + n = snprintf(0, 0, "%s/%s", path, command);
> > + executable_path = (char *)malloc(n + 1);
> > + snprintf(executable_path, n + 1, "%s/%s", path, command);
> > + if (access(executable_path, X_OK) == 0) {
> > + free(path_copy);
> > + return executable_path;
> > + }
> > +
> > + path = strtok(NULL, ":");
> > + free(executable_path);
> > + executable_path = NULL;
> > + }
> > +
> > + free(path_copy);
> > + if (executable_path)
> > + free(executable_path);
> > + return NULL;
> > +}
> > +
> > +const char *get_addr2line(int mode)
> > +{
> > + char *buf = "";
> > +
> > + switch (mode) {
> > + case A2L_CROSS:
> > + buf = getenv("CROSS_COMPILE");
> > + memcpy(addr2line_cmd, buf, strlen(buf));
>
> Dangerous code.
> It is easy to cause a buffer overrun by setting a long string to CROSS_COMPILE.
>
>
> I am fine with adding ADDR2LINE in the top Makefile.
>
>
>
>
>
Understood. In version 4, I will remove all of this and place a new
variable, ADDR2LINE, in the top Makefile.
I'll remove all this in favour of a ne
> > + case A2L_DEFAULT:
> > + memcpy(addr2line_cmd + strlen(buf), ADDR2LINE, strlen(ADDR2LINE));
> > + buf = find_executable(addr2line_cmd);
> > + if (buf) {
> > + memcpy(addr2line_cmd, buf, strlen(buf));
> > + free(buf);
> > + }
> > + return addr2line_cmd;
> > + case A2L_LLVM:
> > + default:
> > + return NULL;
> > + }
> > +}
> > +
> > +char *get_vmlinux(char *input)
> > +{
> > + const char *match_string1 = ".syms";
> > + const char *match_string2 = ".tmp_vmlinux.kallsyms";
> > + char *result = NULL;
> > + char *match_pos;
> > +
> > + match_pos = strstr(input, match_string1);
> > + if (!match_pos)
> > + return NULL;
> > +
> > + match_pos = strstr(input, match_string2);
> > + if (!match_pos)
> > + return NULL;
> > +
> > + result = strdup(input);
> > + match_pos = strstr(result, match_string1);
> > + *match_pos = '\0';
> > + return result;
> > +}
>
> Tedious code to compute the vmlinux name.
> You can pass vmlinux from command line.
>
>
>
>
> > diff --git a/scripts/kas_alias/item_list.c b/scripts/kas_alias/item_list.c
> > new file mode 100644
> > index 000000000000..48f2e525592a
> > --- /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;
>
>
> What is the purpose of the ->next traverse in while() loop?
>
> If you remember the last item,
> you know where the new item should be connected, don't you?
>
>
>
>
>
Yes, I can keep the last item I added and avoid the seek.
I will make this on the v4.
> > +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)
>
>
>
> Any reason why you did not use qsort() in the C library?
>
>
> One disadvantage of quick sort is that it is not "stable sort".
>
> But, your algorithm (sort by name and sort by address)
> does not keep the order anyway.
>
>
>
>
> > 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..532aeb39f851
> > --- /dev/null
> > +++ b/scripts/kas_alias/kas_alias.c
> > @@ -0,0 +1,217 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <stdint.h>
> > +#include <unistd.h>
> > +#include <string.h>
> > +#include <stdbool.h>
> > +#include <stdarg.h>
> > +#include <regex.h>
> > +
> > +#include "item_list.h"
> > +#include "duplicates_list.h"
> > +#include "a2l.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
>
>
>
> Please do not use #ifdef CONFIG_ in host programs.
>
> Also, please note include/linux/kconfig.h is not included
> for host programs, so this #ifdef is always false.
>
> You never tested this CONFIG_KALLSYMS_ALIAS_DATA
>
>
>
>
>
>
>
I initiated a conversation with Masami to inquire about the practical
utility of these two items. I personally find them useful, but it's
possible they may not serve a significant purpose.
Therefore, before proceeding with any modifications, I'd like to
receive feedback regarding their usefulness.
In essence, these two configuration items enable the creation of unique
variable names. Since I couldn't identify any other method to ensure
their uniqueness except by adding the "__alias__<seqnum>" as seen in my
v1 patch, it's important to note that the resulting names may be less
meaningful than those for function names.
> > +#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, ...)
>
> Meaningless 'inline'. Only 'static' is enough.
>
>
> > +{
> > + va_list args;
> > +
> > + va_start(args, fmt);
> > + if (verbose)
> > + printf(fmt, args);
>
>
>
> You cannot pass va_list to printf().
>
> The correct code is:
>
> vprintf(fmt, args);
>
>
>
>
>
>
>
>
> > +
> > + va_end(args);
> > +}
>
>
> verbose_msg() prints the message to stdout.
>
> If verbose_msge is enabled, the output file breaks
> because you redirect both real data and debug messages
> in this way:
> scripts/kas_alias/kas_alias <input> > <output>
>
>
> If you implement debug logging, I recommend this:
>
> scripts/kas_alias/kas_alias <input> <output>
>
>
>
>
>
> > +
> > +static void create_suffix(const char *name, char *output_suffix)
> > +{
> > + sprintf(output_suffix, "%s__alias__%d", name, suffix_serial++);
> > +}
> > +
> > +static void create_file_suffix(const char *name, uint64_t address, char *output_suffix, char *cwd)
> > +{
> > + const char *f_path;
> > + char *buf;
> > + int i = 0;
> > +
> > + buf = addr2line_get_lines(address);
> > + f_path = remove_subdir(cwd, buf);
> > + if (f_path) {
> > + sprintf(output_suffix, "%s@%s", name, f_path);
> > + while (*(output_suffix + i) != '\0') {
> > + switch (*(output_suffix + i)) {
> > + case '/':
> > + case ':':
> > + case '.':
> > + *(output_suffix + i) = '_';
> > + break;
> > + default:
> > + }
> > + i++;
> > + }
> > + } else {
> > + create_suffix(name, output_suffix);
> > + }
> > +}
> > +
> > +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(®ex, ignore_list[i], REG_EXTENDED);
> > + if (res)
> > + return -EREGEX;
> > +
> > + res = regexec(®ex, symbol, 0, NULL, 0);
> > + regfree(®ex);
> > + 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};
>
>
>
> This might be something new I should learn.
>
> When I initialize a pointer, I always write like this:
> struct item *head = NULL;
>
>
> I have never seen this style before:
> struct item *head = {NULL};
>
> But, the compiler does not warn about it.
> Could you educate me how it works?
>
>
>
>
>
You might be giving me too much credit, or perhaps I didn't catch onto
your humor.
To clarify, what you're witnessing is an error that arose during the
debugging process. During my debugging phase, I had a habit of
initializing variables. However, when it came time to reset them to
NULL, I inadvertently made the wrong adjustment.
>From a compiler's perspective, these mistakes yield the same outcome
and no error as setting the pointer to NULL, which is why the error
went unnoticed.
Moving forward, I plan to be more attentive to ensure I produce
higher-quality code for my upcoming contributions.
> > + 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)
>
>
> "-v" or "--verbose" is better
> (although there is no way to enable it.)
>
>
> Anyway, I only see super-boring messages
> even with -verbose given.
>
> Scanning nm data()
> Sorting nm data
> Scanning nm data for duplicates
> Applying suffixes
>
>
>
> > + 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;
> > + }
> > +
> > + if (!addr2line_init(get_addr2line(A2L_DEFAULT), get_vmlinux(argv[1])))
> > + return 1;
> > +
> > + while (fscanf(fp, "%lx %c %99s\n", &address, &t, sym_name) == 3) {
> > + if (strstr(sym_name, "@_")) {
> > + 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_file_suffix(duplicate_iterator->original_item->symb_name,
> > + duplicate_iterator->original_item->addr,
> > + new_name, vmlinux_path);
> > + 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);
>
>
>
> Do you sort just for finding duplicates?
>
>
> Since you sort the list by name, and then sort by address.
>
> It can potentially change the order.
>
>
> [input]
> 00000000 D foo
> 00000000 D bar
> 00000010 D baz
>
> [merge sort by name]
> 00000000 D bar
> 00000010 D baz
> 00000000 D foo
>
> [merge sort by address = final result]
> 00000000 D bar
> 00000000 D foo
> 00000010 D baz
>
>
> It may not be a big deal, but such a destructive algorithm is frowned.
>
>
>
> You do not need to sort the list to find duplicates.
>
>
> Another choice is a hashtable of { name : count }.
> Traversing the list, you can count the number of occurrences.
> If count >= 2, it is duplicated.
>
> The average look-up of a hashtable is O(1).
> So, the hashtable (or set) algorithm is O(N).
>
>
> Sorting is O(N log N).
>
>
>
>
>
> > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > index a432b171be82..cacf60b597ce 100755
> > --- a/scripts/link-vmlinux.sh
> > +++ b/scripts/link-vmlinux.sh
> > @@ -89,8 +89,9 @@ vmlinux_link()
> >
> > ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
> >
> > - # The kallsyms linking does not need debug symbols included.
> > - if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> > + # The kallsyms linking does not need debug symbols included, unless the KALLSYMS_ALIAS.
> > + if [ ! is_enabled CONFIG_KALLSYMS_ALIAS ] && \
>
>
> I observed this error message:
>
>
> scripts/link-vmlinux.sh: 93: [: is_enabled: unexpected operator
>
>
> The correct code is this:
>
>
> if ! is_enabled CONFIG_KALLSYMS_ALIAS && \
>
>
>
>
>
>
>
>
>
>
> > + [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> > ldflags="${ldflags} ${wl}--strip-debug"
> > fi
> >
> > @@ -161,7 +162,11 @@ 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
> > --
> > 2.34.1
> >
>
>
> --
> Best Regards
>
>
>
> Masahiro Yamada
thank you
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