https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115937
Bug ID: 115937
Summary: duplicate .plt in module's elf header
Product: gcc
Version: 10.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: ellery1016 at 163 dot com
Target Milestone: ---
My system: aarch64
Kernel version: linux-4.19
GCC version: 10.3.1 & 7.3.0
I changed my gcc from 7.3.0 to 10.3.1 and recompiled kernel code.
After new kernel installed and rebooted, some call trace printed in dmesg as
below:
```
Jul 10 15:39:59 localhost kernel: sysfs: cannot create duplicate filename
'/module/virtio/sections/.plt'
Jul 10 15:39:59 localhost kernel: CPU: 94 PID: 831 Comm: systemd-udevd Not
tainted 4.19.90.rc1.aarch64 #1
Jul 10 15:39:59 localhost kernel: Hardware name: QEMU KVM Virtual Machine, BIOS
0.0.0 02/06/2015
Jul 10 15:39:59 localhost kernel: Call trace:
Jul 10 15:39:59 localhost kernel: dump_backtrace+0x0/0x190
Jul 10 15:39:59 localhost kernel: show_stack+0x28/0x34
Jul 10 15:39:59 localhost kernel: dump_stack+0xa4/0xe8
Jul 10 15:39:59 localhost kernel: sysfs_warn_dup+0x70/0x90
Jul 10 15:39:59 localhost kernel: sysfs_add_file_mode_ns+0x19c/0x1d0
Jul 10 15:39:59 localhost kernel: create_files+0xa8/0x200
Jul 10 15:39:59 localhost kernel: internal_create_group+0x178/0x210
Jul 10 15:39:59 localhost kernel: sysfs_create_group+0x30/0x40
Jul 10 15:39:59 localhost kernel: add_sect_attrs+0x174/0x200
Jul 10 15:39:59 localhost kernel: mod_sysfs_setup+0x1e8/0x210
Jul 10 15:39:59 localhost kernel: load_module+0x46c/0x820
Jul 10 15:39:59 localhost kernel: __se_sys_finit_module+0xb8/0x120
Jul 10 15:39:59 localhost kernel: __arm64_sys_finit_module+0x28/0x34
Jul 10 15:39:59 localhost kernel: el0_svc_common+0x7c/0x134
Jul 10 15:39:59 localhost kernel: el0_svc_handler+0x3c/0x7c
Jul 10 15:39:59 localhost kernel: el0_svc+0x8/0x1f8
```
In fact, it seemed that all kernel modules met the problem "cannot create
duplicate filename .plt"，which causes directory "sections" doesn't exist any
more under /sys/modules/.Meanwhile all the modules installed successfully,and
the system works fine so far.
As a test, I wrote a simple module like:
```
#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
MODULE_LICENSE("GPL");
MODULE_VERSION("1.0");
MODULE_AUTHOR("qink");
MODULE_DESCRIPTION("Test elf plt");
static __init int test_plt_init(void)
{
printk("Inset a new test module.\n");
return 0;
}
static __exit void test_plt_exit(void)
{
printk("New test module exits.\n");
}
module_init(test_plt_init);
module_exit(test_plt_exit);
```
My makefile is like:
```
obj-m :=test_plt.o
KDIR := /lib/modules/$(shell uname -r)/build
PWD :=$(shell pwd)
modules :
$(MAKE) -C $(KDIR) M=$(PWD) modules
clean :
rm -f *.o .*.cmd *.symvers
```
And I compiled with gcc 10.3.1 and insmod it, the same message showed again,
while I did the same thing on a gcc 7.3.0 system and there was no such message.
Since it seemed like a problem with somthing called ".plt", I used readelf -S
to see what is is.
The result with module test_plt.ko compiled with gcc 7.3.0:
```
There are 37 section headers, starting at offset 0x2a910:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .note.gnu.build-i NOTE 0000000000000000 00000040
0000000000000024 0000000000000000 A 0 0 4
[ 2] .text PROGBITS 0000000000000000 00000064
0000000000000000 0000000000000000 AX 0 0 1
[ 3] .init.text PROGBITS 0000000000000000 00000064
0000000000000028 0000000000000000 AX 0 0 4
[ 4] .rela.init.text RELA 0000000000000000 00017278
0000000000000060 0000000000000018 I 34 3 8
[ 5] .exit.text PROGBITS 0000000000000000 0000008c
000000000000001c 0000000000000000 AX 0 0 4
[ 6] .rela.exit.text RELA 0000000000000000 000172d8
0000000000000048 0000000000000018 I 34 5 8
[ 7] .modinfo PROGBITS 0000000000000000 000000a8
00000000000000ce 0000000000000000 A 0 0 8
[ 8] .rodata.str1.8 PROGBITS 0000000000000000 00000178
0000000000000038 0000000000000001 AMS 0 0 8
[ 9] .eh_frame PROGBITS 0000000000000000 000001b0
000000000000005c 0000000000000000 A 0 0 8
[10] .rela.eh_frame RELA 0000000000000000 00017320
0000000000000030 0000000000000018 I 34 9 8
[11] __mcount_loc PROGBITS 0000000000000000 00000210
0000000000000008 0000000000000000 A 0 0 8
[12] .rela__mcount_loc RELA 0000000000000000 00017350
0000000000000018 0000000000000018 I 34 11 8
[13] .note.Linux PROGBITS 0000000000000000 00000218
0000000000000018 0000000000000000 A 0 0 4
[14] __versions PROGBITS 0000000000000000 00000230
00000000000000c0 0000000000000000 A 0 0 8
[15] .data PROGBITS 0000000000000000 000002f0
0000000000000000 0000000000000000 WA 0 0 1
[16] .gnu.linkonce.thi PROGBITS 0000000000000000 00000300
0000000000000380 0000000000000000 WA 0 0 64
[17] .rela.gnu.linkonc RELA 0000000000000000 00017368
0000000000000030 0000000000000018 I 34 16 8
[18] .plt NOBITS 0000000000000380 00000680
0000000000000001 0000000000000000 WA 0 0 1
[19] .init.plt NOBITS 0000000000000381 00000680
0000000000000001 0000000000000000 WA 0 0 1
[20] .text.ftrace_tram NOBITS 0000000000000382 00000680
0000000000000001 0000000000000000 WA 0 0 1
[21] .bss NOBITS 0000000000000000 00000680
0000000000000000 0000000000000000 WA 0 0 1
[22] .debug_info PROGBITS 0000000000000000 00000680
000000000000bb4a 0000000000000000 0 0 1
[23] .rela.debug_info RELA 0000000000000000 00017398
0000000000013320 0000000000000018 I 34 22 8
[24] .debug_abbrev PROGBITS 0000000000000000 0000c1ca
0000000000000900 0000000000000000 0 0 1
[25] .debug_aranges PROGBITS 0000000000000000 0000caca
0000000000000060 0000000000000000 0 0 1
[26] .rela.debug_arang RELA 0000000000000000 0002a6b8
0000000000000060 0000000000000018 I 34 25 8
[27] .debug_ranges PROGBITS 0000000000000000 0000cb2a
0000000000000030 0000000000000000 0 0 1
[28] .rela.debug_range RELA 0000000000000000 0002a718
0000000000000060 0000000000000018 I 34 27 8
[29] .debug_line PROGBITS 0000000000000000 0000cb5a
0000000000000c5f 0000000000000000 0 0 1
[30] .rela.debug_line RELA 0000000000000000 0002a778
0000000000000030 0000000000000018 I 34 29 8
[31] .debug_str PROGBITS 0000000000000000 0000d7b9
0000000000009478 0000000000000001 MS 0 0 1
[32] .comment PROGBITS 0000000000000000 00016c31
0000000000000024 0000000000000001 MS 0 0 1
[33] .note.GNU-stack PROGBITS 0000000000000000 00016c55
0000000000000000 0000000000000000 0 0 1
[34] .symtab SYMTAB 0000000000000000 00016c58
00000000000004e0 0000000000000018 35 47 8
[35] .strtab STRTAB 0000000000000000 00017138
0000000000000139 0000000000000000 0 0 1
[36] .shstrtab STRTAB 0000000000000000 0002a7a8
0000000000000165 0000000000000000 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
p (processor specific)
```
The result with module test_plt.ko compiled with gcc 10.3.1:
```
There are 39 section headers, starting at offset 0xb8f0:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .note.gnu.bu[...] NOTE 0000000000000000 00000040
0000000000000024 0000000000000000 A 0 0 4
[ 2] .note.Linux NOTE 0000000000000000 00000064
0000000000000018 0000000000000000 A 0 0 4
[ 3] .text PROGBITS 0000000000000000 0000007c
0000000000000000 0000000000000000 AX 0 0 1
[ 4] .init.text PROGBITS 0000000000000000 0000007c
000000000000002c 0000000000000000 AX 0 0 4
[ 5] .rela.init.text RELA 0000000000000000 00006b48
0000000000000060 0000000000000018 I 36 4 8
[ 6] .exit.text PROGBITS 0000000000000000 000000a8
000000000000001c 0000000000000000 AX 0 0 4
[ 7] .rela.exit.text RELA 0000000000000000 00006ba8
0000000000000048 0000000000000018 I 36 6 8
[ 8] .plt PROGBITS 0000000000000000 000000c4
0000000000000001 0000000000000000 AX 0 0 1
[ 9] .rodata.str1.8 PROGBITS 0000000000000000 000000c8
0000000000000038 0000000000000001 AMS 0 0 8
[10] .modinfo PROGBITS 0000000000000000 00000100
00000000000000d2 0000000000000000 A 0 0 8
[11] .eh_frame PROGBITS 0000000000000000 000001d8
0000000000000054 0000000000000000 A 0 0 8
[12] .rela.eh_frame RELA 0000000000000000 00006bf0
0000000000000030 0000000000000018 I 36 11 8
[13] __mcount_loc PROGBITS 0000000000000000 00000230
0000000000000008 0000000000000000 A 0 0 8
[14] .rela__mcount_loc RELA 0000000000000000 00006c20
0000000000000018 0000000000000018 I 36 13 8
[15] __versions PROGBITS 0000000000000000 00000238
00000000000000c0 0000000000000000 A 0 0 8
[16] .data PROGBITS 0000000000000000 000002f8
0000000000000000 0000000000000000 WA 0 0 1
[17] .gnu.linkonc[...] PROGBITS 0000000000000000 00000300
0000000000000380 0000000000000000 WA 0 0 64
[18] .rela.gnu.li[...] RELA 0000000000000000 00006c38
0000000000000030 0000000000000018 I 36 17 8
[19] .plt.idx PROGBITS 0000000000000380 00000680
0000000000000001 0000000000000000 A 0 0 1
[20] .plt PROGBITS 0000000000000381 00000681
0000000000000001 0000000000000000 AX 0 0 1
[21] .init.plt NOBITS 0000000000000382 00000682
0000000000000001 0000000000000000 A 0 0 1
[22] .text.ftrace[...] PROGBITS 0000000000000383 00000682
0000000000000001 0000000000000000 AX 0 0 1
[23] .bss NOBITS 0000000000000000 00000683
0000000000000000 0000000000000000 WA 0 0 1
[24] .debug_info PROGBITS 0000000000000000 00000683
0000000000002bbb 0000000000000000 0 0 1
[25] .rela.debug_info RELA 0000000000000000 00006c68
0000000000004a28 0000000000000018 I 36 24 8
[26] .debug_abbrev PROGBITS 0000000000000000 0000323e
0000000000000511 0000000000000000 0 0 1
[27] .debug_aranges PROGBITS 0000000000000000 0000374f
0000000000000060 0000000000000000 0 0 1
[28] .rela.debug_[...] RELA 0000000000000000 0000b690
0000000000000060 0000000000000018 I 36 27 8
[29] .debug_ranges PROGBITS 0000000000000000 000037af
0000000000000030 0000000000000000 0 0 1
[30] .rela.debug_[...] RELA 0000000000000000 0000b6f0
0000000000000060 0000000000000018 I 36 29 8
[31] .debug_line PROGBITS 0000000000000000 000037df
0000000000000448 0000000000000000 0 0 1
[32] .rela.debug_line RELA 0000000000000000 0000b750
0000000000000030 0000000000000018 I 36 31 8
[33] .debug_str PROGBITS 0000000000000000 00003c27
00000000000028a9 0000000000000001 MS 0 0 1
[34] .comment PROGBITS 0000000000000000 000064d0
0000000000000026 0000000000000001 MS 0 0 1
[35] .note.GNU-stack PROGBITS 0000000000000000 000064f6
0000000000000000 0000000000000000 0 0 1
[36] .symtab SYMTAB 0000000000000000 000064f8
0000000000000510 0000000000000018 37 49 8
[37] .strtab STRTAB 0000000000000000 00006a08
0000000000000139 0000000000000000 0 0 1
[38] .shstrtab STRTAB 0000000000000000 0000b780
000000000000016e 0000000000000000 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
D (mbind), p (processor specific)
```
It does show that .plt becomes two, I suppose this is the reason why kernel
detect multi .plt in load_module and remove directory "sections".
My gcc version for 7.3.0:
```
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/aarch64-linux-gnu/7.3.0/lto-wrapper
Target: aarch64-linux-gnu
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-linker-build-id --with-linker-hash-style=gnu
--enable-languages=c,c++,objc,obj-c++,fortran,lto --enable-plugin
--enable-initfini-array --disable-libgcj --without-isl --without-cloog
--enable-gnu-indirect-function --build=aarch64-linux-gnu
--with-stage1-ldflags=' -Wl,-z,relro,-z,now' --with-boot-ldflags='
-Wl,-z,relro,-z,now' --with-multilib-list=lp64
Thread model: posix
gcc version 7.3.0 (GCC)
```
gcc version for 10.3.1:
```
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/aarch64-linux-gnu/10.3.1/lto-wrapper
Target: aarch64-linux-gnu
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-linker-build-id --with-linker-hash-style=gnu
--enable-languages=c,c++,objc,obj-c++,fortran,lto --enable-plugin
--enable-initfini-array --disable-libgcj --with-isl --without-cloog
--enable-gnu-indirect-function --build=aarch64-linux-gnu
--with-stage1-ldflags=' -Wl,-z,relro,-z,now' --with-boot-ldflags='
-Wl,-z,relro,-z,now' --disable-bootstrap --with-multilib-list=lp64
--enable-bolt
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.3.1 (GCC)
```
Now I wonder that does this matter with gcc? Is there any gcc option I can use
to avoid it? What are the effects if "sections" doesn't exist under
/sys/modules?
