linux-kernel - [PATCH 3/3] module: Ignore L0 and rename is_arm_mapping

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Message-Id: <1680254153-14582-4-git-send-email-yangtiezhu@loongson.cn>
Date:   Fri, 31 Mar 2023 17:15:53 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn
Subject: [PATCH 3/3] module: Ignore L0 and rename is_arm_mapping_symbol()

The L0 symbol is generated when build module on LoongArch, ignore it in
modpost and when looking at module symbols, otherwise we can not see the
expected call trace.

Now is_arm_mapping_symbol() is not only for ARM, in order to reflect the
reality, rename is_arm_mapping_symbol() to is_mapping_symbol().

This is related with commit c17a2538704f ("mksysmap: Fix the mismatch of
'L0' symbols in System.map").

(1) Simple test case

  [loongson@...ux hello]$ cat hello.c
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/printk.h>

  static void test_func(void)
  {
  	  pr_info("This is a test\n");
	  dump_stack();
  }

  static int __init hello_init(void)
  {
	  pr_warn("Hello, world\n");
	  test_func();

	  return 0;
  }

  static void __exit hello_exit(void)
  {
	  pr_warn("Goodbye\n");
  }

  module_init(hello_init);
  module_exit(hello_exit);
  MODULE_LICENSE("GPL");
  [loongson@...ux hello]$ cat Makefile
  obj-m:=hello.o

  ccflags-y += -g -Og

  all:
	  make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) modules
  clean:
	  make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) clean

(2) Test environment

system: LoongArch CLFS 5.5
https://github.com/sunhaiyong1978/CLFS-for-LoongArch/releases/tag/5.0
It needs to update grub to avoid booting error "invalid magic number".

kernel: 6.3-rc1 with loongson3_defconfig + CONFIG_DYNAMIC_FTRACE=y

(3) Test result

Without this patch:

  [root@...ux hello]# insmod hello.ko
  [root@...ux hello]# dmesg
  ...
  Hello, world
  This is a test
  ...
  Call Trace:
  [<9000000000223728>] show_stack+0x68/0x18c
  [<90000000013374cc>] dump_stack_lvl+0x60/0x88
  [<ffff800002050028>] L0\x01+0x20/0x2c [hello]
  [<ffff800002058028>] L0\x01+0x20/0x30 [hello]
  [<900000000022097c>] do_one_initcall+0x88/0x288
  [<90000000002df890>] do_init_module+0x54/0x200
  [<90000000002e1e18>] __do_sys_finit_module+0xc4/0x114
  [<90000000013382e8>] do_syscall+0x7c/0x94
  [<9000000000221e3c>] handle_syscall+0xbc/0x158

With this patch:

  [root@...ux hello]# insmod hello.ko
  [root@...ux hello]# dmesg
  ...
  Hello, world
  This is a test
  ...
  Call Trace:
  [<9000000000223728>] show_stack+0x68/0x18c
  [<90000000013374cc>] dump_stack_lvl+0x60/0x88
  [<ffff800002050028>] test_func+0x28/0x34 [hello]
  [<ffff800002058028>] hello_init+0x28/0x38 [hello]
  [<900000000022097c>] do_one_initcall+0x88/0x288
  [<90000000002df890>] do_init_module+0x54/0x200
  [<90000000002e1e18>] __do_sys_finit_module+0xc4/0x114
  [<90000000013382e8>] do_syscall+0x7c/0x94
  [<9000000000221e3c>] handle_syscall+0xbc/0x158

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 include/linux/module_symbol.h | 4 +++-
 kernel/module/kallsyms.c      | 2 +-
 scripts/mod/modpost.c         | 4 ++--
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/module_symbol.h b/include/linux/module_symbol.h
index 9fa4173..7ace7ba 100644
--- a/include/linux/module_symbol.h
+++ b/include/linux/module_symbol.h
@@ -3,10 +3,12 @@
 #define _LINUX_MODULE_SYMBOL_H
 
 /* This ignores the intensely annoying "mapping symbols" found in ELF files. */
-static inline int is_arm_mapping_symbol(const char *str)
+static inline int is_mapping_symbol(const char *str)
 {
 	if (str[0] == '.' && str[1] == 'L')
 		return true;
+	if (str[0] == 'L' && str[1] == '0')
+		return true;
 	return str[0] == '$' &&
 	       (str[1] == 'a' || str[1] == 'd' || str[1] == 't' || str[1] == 'x')
 	       && (str[2] == '\0' || str[2] == '.');
diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index 5de3207..d8e426a 100644
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -289,7 +289,7 @@ static const char *find_kallsyms_symbol(struct module *mod,
 		 * and inserted at a whim.
 		 */
 		if (*kallsyms_symbol_name(kallsyms, i) == '\0' ||
-		    is_arm_mapping_symbol(kallsyms_symbol_name(kallsyms, i)))
+		    is_mapping_symbol(kallsyms_symbol_name(kallsyms, i)))
 			continue;
 
 		if (thisval <= addr && thisval > bestval) {
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 7241db8..5cddf76 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1115,7 +1115,7 @@ static int secref_whitelist(const struct sectioncheck *mismatch,
 
 /*
  * If there's no name there, ignore it; likewise, ignore it if it's
- * one of the magic symbols emitted used by current ARM tools.
+ * one of the magic symbols emitted used by current tools.
  *
  * Otherwise if find_symbols_between() returns those symbols, they'll
  * fail the whitelist tests and cause lots of false alarms ... fixable
@@ -1128,7 +1128,7 @@ static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym)
 
 	if (!name || !strlen(name))
 		return 0;
-	return !is_arm_mapping_symbol(name);
+	return !is_mapping_symbol(name);
 }
 
 /**
-- 
2.1.0