Receiving "Illegal Instruction" when executing glibc's ld-2.6.1.so
Background
"OS": Stripped down Linux, very customized, no internet access (no yum, apt-get, etc)
Kernel: 2.6.19.1
Target: 32-bit, armv5te
Current LibC: 2.3.6
Target LibC: 2.6.1
Issue
Received an .ipk from a 3rd party vendor containing an updated version of glibc. Started by investigating the compatibility of the shared objects contained within the .ipk package by placing them on the target platform and attempting to run the ld-2.6.1.so directly (chose this library because my understanding is that it has no dynamic linking to other objects).
Running this shared object library directly results in "Illegal Instruction". My initial thought was that ld was built for the wrong architecture, however, review of the readelf output appears to indicate it was set up correctly:
[root@blg_g34_z2_03 lib]# readelf -a ld-2.6.1.so
ELF Header:
Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: DYN (Shared object file)
Machine: ARM
Version: 0x1
Entry point address: 0x800
Start of program headers: 52 (bytes into file)
Start of section headers: 116488 (bytes into file)
Flags: 0x4000002, has entry point, Version4 EABI
Size of this header: 52 (bytes)
Size of program headers: 32 (bytes)
Number of program headers: 6
Size of section headers: 40 (bytes)
Number of section headers: 26
Section header string table index: 25
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] .hash HASH 000000f4 0000f4 0000c4 04 A 3 0 4
[ 2] .gnu.hash GNU_HASH 000001b8 0001b8 0000e0 04 A 3 0 4
[ 3] .dynsym DYNSYM 00000298 000298 0001e0 10 A 4 3 4
[ 4] .dynstr STRTAB 00000478 000478 0001ac 00 A 0 0 1
[ 5] .gnu.version VERSYM 00000624 000624 00003c 02 A 3 0 2
[ 6] .gnu.version_d VERDEF 00000660 000660 00005c 00 A 4 3 4
[ 7] .rel.dyn REL 000006bc 0006bc 0000b8 08 A 3 0 4
[ 8] .rel.plt REL 00000774 000774 000030 08 A 3 9 4
[ 9] .plt PROGBITS 000007a4 0007a4 00005c 04 AX 0 0 4
[10] .text PROGBITS 00000800 000800 017324 00 AX 0 0 16
[11] __libc_freeres_fn PROGBITS 00017b24 017b24 000148 00 AX 0 0 4
[12] .rodata PROGBITS 00017c6c 017c6c 003828 00 A 0 0 4
[13] .ARM.extab PROGBITS 0001b494 01b494 000048 00 A 0 0 4
[14] .ARM.exidx ARM_EXIDX 0001b4dc 01b4dc 000078 00 AL 10 0 4
[15] .eh_frame_hdr PROGBITS 0001b554 01b554 00001c 00 A 0 0 4
[16] .eh_frame PROGBITS 0001b570 01b570 00007c 00 A 0 0 4
[17] .data.rel.ro PROGBITS 00023db0 01bdb0 000194 00 WA 0 0 8
[18] .dynamic DYNAMIC 00023f44 01bf44 0000b8 08 WA 4 0 4
[19] .got PROGBITS 00024000 01c000 00005c 04 WA 0 0 4
[20] .data PROGBITS 00024060 01c060 000580 00 WA 0 0 8
[21] __libc_subfreeres PROGBITS 000245e0 01c5e0 000004 00 WA 0 0 4
[22] .bss NOBITS 000245e4 01c5e4 0000e4 00 WA 0 0 4
[23] .ARM.attributes ARM_ATTRIBUTES 00000000 01c5e4 000019 00 0 0 1
[24] .gnu_debuglink PROGBITS 00000000 01c5fd 000010 00 0 0 1
[25] .shstrtab STRTAB 00000000 01c60d 0000f8 00 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings)
I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
O (extra OS processing required) o (OS specific), p (processor specific)
There are no section groups in this file.
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x01b4dc 0x0001b4dc 0x0001b4dc 0x00078 0x00078 R 0x4
LOAD 0x000000 0x00000000 0x00000000 0x1b5ec 0x1b5ec R E 0x8000
LOAD 0x01bdb0 0x00023db0 0x00023db0 0x00834 0x00918 RW 0x8000
DYNAMIC 0x01bf44 0x00023f44 0x00023f44 0x000b8 0x000b8 RW 0x4
GNU_EH_FRAME 0x01b554 0x0001b554 0x0001b554 0x0001c 0x0001c R 0x4
GNU_RELRO 0x01bdb0 0x00023db0 0x00023db0 0x00250 0x00250 R 0x1
Section to Segment mapping:
Segment Sections...
00 .ARM.exidx
01 .hash .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_d .rel.dyn .rel.plt .plt .text __libc_freeres_fn .rodata .ARM.extab .ARM.exidx .eh_frame_hdr .eh_frame
02 .data.rel.ro .dynamic .got .data __libc_subfreeres .bss
03 .dynamic
04 .eh_frame_hdr
05 .data.rel.ro .dynamic
Dynamic section at offset 0x1bf44 contains 19 entries:
Tag Type Name/Value
0x0000000e (SONAME) Library soname: [ld-linux.so.3]
0x00000004 (HASH) 0xf4
0x6ffffef5 (GNU_HASH) 0x1b8
0x00000005 (STRTAB) 0x478
0x00000006 (SYMTAB) 0x298
0x0000000a (STRSZ) 428 (bytes)
0x0000000b (SYMENT) 16 (bytes)
0x00000003 (PLTGOT) 0x24000
0x00000002 (PLTRELSZ) 48 (bytes)
0x00000014 (PLTREL) REL
0x00000017 (JMPREL) 0x774
0x00000011 (REL) 0x6bc
0x00000012 (RELSZ) 184 (bytes)
0x00000013 (RELENT) 8 (bytes)
0x6ffffffc (VERDEF) 0x660
0x6ffffffd (VERDEFNUM) 3
0x6ffffff0 (VERSYM) 0x624
0x6ffffffa (RELCOUNT) 20
0x00000000 (NULL) 0x0
Relocation section '.rel.dyn' at offset 0x6bc contains 23 entries:
Offset Info Type Sym.Value Sym. Name
00023e8c 00000017 R_ARM_RELATIVE
00023e90 00000017 R_ARM_RELATIVE
00023e94 00000017 R_ARM_RELATIVE
00023e98 00000017 R_ARM_RELATIVE
00023e9c 00000017 R_ARM_RELATIVE
00023ea0 00000017 R_ARM_RELATIVE
00023ea4 00000017 R_ARM_RELATIVE
00023ea8 00000017 R_ARM_RELATIVE
00024024 00000017 R_ARM_RELATIVE
00024028 00000017 R_ARM_RELATIVE
00024030 00000017 R_ARM_RELATIVE
00024038 00000017 R_ARM_RELATIVE
0002403c 00000017 R_ARM_RELATIVE
00024040 00000017 R_ARM_RELATIVE
00024044 00000017 R_ARM_RELATIVE
00024048 00000017 R_ARM_RELATIVE
0002404c 00000017 R_ARM_RELATIVE
00024050 00000017 R_ARM_RELATIVE
00024054 00000017 R_ARM_RELATIVE
000245e0 00000017 R_ARM_RELATIVE
0002402c 00001b15 R_ARM_GLOB_DAT 00023f0c __stack_chk_guard
00024034 00001815 R_ARM_GLOB_DAT 00014c84 malloc
00024058 00000b15 R_ARM_GLOB_DAT 000246b4 _r_debug
Relocation section '.rel.plt' at offset 0x774 contains 6 entries:
Offset Info Type Sym.Value Sym. Name
0002400c 00000e16 R_ARM_JUMP_SLOT 00014b50 __libc_memalign
00024010 00001816 R_ARM_JUMP_SLOT 00014c84 malloc
00024014 00001016 R_ARM_JUMP_SLOT 00014d38 calloc
00024018 00000916 R_ARM_JUMP_SLOT 00014c90 realloc
0002401c 00000716 R_ARM_JUMP_SLOT 000086d4 _dl_cache_libcmp
00024020 00000816 R_ARM_JUMP_SLOT 00014b08 free
Unwind table index '.ARM.exidx' at offset 0x1b4dc contains 15 entries:
0x8ed4: 0x80b0b0b0
Compact model index: 0
0xb0 finish
0xb0 finish
0xb0 finish
0x8f0c: 0x8000abb0
Compact model index: 0
0x00 vsp = vsp + 4
0xab pop {r4, r5, r6, r7, r14}
0xb0 finish
0x8ff0: 0x8000abb0
Compact model index: 0
0x00 vsp = vsp + 4
0xab pop {r4, r5, r6, r7, r14}
0xb0 finish
0x91b0: 0x800eafb0
Compact model index: 0
0x0e vsp = vsp + 60
0xaf pop {r4, r5, r6, r7, r8, r9, r10, r11, r14}
0xb0 finish
0x9574: @0x1b494
Compact model index: 1
0x9b vsp = r11
0x49 vsp = vsp - 40
0x86 0xff pop {r4, r5, r6, r7, r8, r9, r10, r11, r13, r14}
0xb0 finish
0xb0 finish
0xcf44: 0x800aafb0
Compact model index: 0
0x0a vsp = vsp + 44
0xaf pop {r4, r5, r6, r7, r8, r9, r10, r11, r14}
0xb0 finish
0xd060: 0x8014afb0
Compact model index: 0
0x14 vsp = vsp + 84
0xaf pop {r4, r5, r6, r7, r8, r9, r10, r11, r14}
0xb0 finish
0xd5c0: 0x8006afb0
Compact model index: 0
0x06 vsp = vsp + 28
0xaf pop {r4, r5, r6, r7, r8, r9, r10, r11, r14}
0xb0 finish
0x15380: @0x1b4a0
Compact model index: 1
0x01 vsp = vsp + 8
0x80 0x08 pop {r7}
0xb1 0x0e pop {r1, r2, r3}
0xb0 finish
0x158c0: @0x1b4ac
Compact model index: 1
0x02 vsp = vsp + 12
0xb1 0x0f pop {r0, r1, r2, r3}
0x8f 0xff pop {r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15}
0xb0 finish
0x158d8: @0x1b4b8
Compact model index: 1
0x07 vsp = vsp + 32
0xb1 0x0f pop {r0, r1, r2, r3}
0x8f 0xff pop {r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15}
0xb0 finish
0x158e8: @0x1b4c4
Compact model index: 1
0x29 vsp = vsp + 168
0xb1 0x0f pop {r0, r1, r2, r3}
0x8f 0xff pop {r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15}
0xb0 finish
0x158f8: @0x1b4d0
Compact model index: 1
0x27 vsp = vsp + 160
0xb1 0x0f pop {r0, r1, r2, r3}
0x8f 0xff pop {r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15}
0xb0 finish
0x1704c: 0x8004afb0
Compact model index: 0
0x04 vsp = vsp + 20
0xaf pop {r4, r5, r6, r7, r8, r9, r10, r11, r14}
0xb0 finish
0x17580: 0x8002afb0
Compact model index: 0
0x02 vsp = vsp + 12
0xaf pop {r4, r5, r6, r7, r8, r9, r10, r11, r14}
0xb0 finish
Symbol table '.dynsym' contains 30 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 00000000 0 NOTYPE LOCAL DEFAULT UND
1: 00000800 0 SECTION LOCAL DEFAULT 10
2: 00023db0 0 SECTION LOCAL DEFAULT 17
3: 000103d4 44 FUNC GLOBAL DEFAULT 10 _dl_get_tls_static_info@@GLIBC_PRIVATE
4: 00023f10 4 OBJECT GLOBAL DEFAULT 17 __pointer_chk_guard@@GLIBC_PRIVATE
5: 00000000 0 OBJECT GLOBAL DEFAULT ABS GLIBC_PRIVATE
6: 00000000 0 OBJECT GLOBAL DEFAULT ABS GLIBC_2.4
7: 000086d4 260 FUNC GLOBAL DEFAULT 10 _dl_cache_libcmp@@GLIBC_PRIVATE
8: 00014b08 72 FUNC WEAK DEFAULT 10 free@@GLIBC_2.4
9: 00014c90 168 FUNC WEAK DEFAULT 10 realloc@@GLIBC_2.4
10: 00010ed8 40 FUNC GLOBAL DEFAULT 10 _dl_allocate_tls@@GLIBC_PRIVATE
11: 000246b4 20 OBJECT GLOBAL DEFAULT 22 _r_debug@@GLIBC_2.4
12: 00023f3c 4 OBJECT GLOBAL DEFAULT 17 __libc_stack_end@@GLIBC_2.4
13: 0001063c 160 FUNC GLOBAL DEFAULT 10 _dl_tls_get_addr_soft@@GLIBC_PRIVATE
14: 00014b50 308 FUNC WEAK DEFAULT 10 __libc_memalign@@GLIBC_2.4
15: 00010920 192 FUNC GLOBAL DEFAULT 10 _dl_deallocate_tls@@GLIBC_PRIVATE
16: 00014d38 92 FUNC WEAK DEFAULT 10 calloc@@GLIBC_2.4
17: 000245e4 4 OBJECT GLOBAL DEFAULT 22 _dl_argv@@GLIBC_PRIVATE
18: 0000f474 1384 FUNC GLOBAL DEFAULT 10 _dl_mcount@@GLIBC_2.4
19: 0001117c 204 FUNC GLOBAL DEFAULT 10 _dl_tls_setup@@GLIBC_PRIVATE
20: 0000e598 4 FUNC GLOBAL DEFAULT 10 _dl_debug_state@@GLIBC_PRIVATE
21: 00024060 1408 OBJECT GLOBAL DEFAULT 20 _rtld_global@@GLIBC_PRIVATE
22: 00010ce4 272 FUNC GLOBAL DEFAULT 10 __tls_get_addr@@GLIBC_2.4
23: 00011404 188 FUNC GLOBAL DEFAULT 10 _dl_make_stack_executable@@GLIBC_PRIVATE
24: 00014c84 12 FUNC WEAK DEFAULT 10 malloc@@GLIBC_2.4
25: 000106dc 540 FUNC GLOBAL DEFAULT 10 _dl_allocate_tls_init@@GLIBC_PRIVATE
26: 00023db0 264 OBJECT GLOBAL DEFAULT 17 _rtld_global_ro@@GLIBC_PRIVATE
27: 00023f0c 4 OBJECT GLOBAL DEFAULT 17 __stack_chk_guard@@GLIBC_2.4
28: 00023f38 4 OBJECT GLOBAL DEFAULT 17 __libc_enable_secure@@GLIBC_PRIVATE
29: 00007bc0 456 FUNC GLOBAL DEFAULT 10 _dl_rtld_di_serinfo@@GLIBC_PRIVATE
Histogram for bucket list length (total of 17 buckets):
Length Number % of total Coverage
0 2 ( 11.8%)
1 6 ( 35.3%) 22.2%
2 6 ( 35.3%) 66.7%
3 3 ( 17.6%) 100.0%
Histogram for `.gnu.hash' bucket list length (total of 17 buckets):
Length Number % of total Coverage
0 2 ( 11.8%)
1 8 ( 47.1%) 29.6%
2 3 ( 17.6%) 51.9%
3 3 ( 17.6%) 85.2%
4 1 ( 5.9%) 100.0%
Version symbols section '.gnu.version' contains 30 entries:
Addr: 0000000000000624 Offset: 0x000624 Link: 3 (.dynsym)
000: 0 (*local*) 0 (*local*) 0 (*local*) 3 (GLIBC_PRIVATE)
004: 3 (GLIBC_PRIVATE) 3 (GLIBC_PRIVATE) 2 (GLIBC_2.4) 3 (GLIBC_PRIVATE)
008: 2 (GLIBC_2.4) 2 (GLIBC_2.4) 3 (GLIBC_PRIVATE) 2 (GLIBC_2.4)
00c: 2 (GLIBC_2.4) 3 (GLIBC_PRIVATE) 2 (GLIBC_2.4) 3 (GLIBC_PRIVATE)
010: 2 (GLIBC_2.4) 3 (GLIBC_PRIVATE) 2 (GLIBC_2.4) 3 (GLIBC_PRIVATE)
014: 3 (GLIBC_PRIVATE) 3 (GLIBC_PRIVATE) 2 (GLIBC_2.4) 3 (GLIBC_PRIVATE)
018: 2 (GLIBC_2.4) 3 (GLIBC_PRIVATE) 3 (GLIBC_PRIVATE) 2 (GLIBC_2.4)
01c: 3 (GLIBC_PRIVATE) 3 (GLIBC_PRIVATE)
Version definition section '.gnu.version_d' contains 3 entries:
Addr: 0x0000000000000660 Offset: 0x000660 Link: 4 (.dynstr)
000000: Rev: 1 Flags: BASE Index: 1 Cnt: 1 Name: ld-linux.so.3
0x001c: Rev: 1 Flags: none Index: 2 Cnt: 1 Name: GLIBC_2.4
0x0038: Rev: 1 Flags: none Index: 3 Cnt: 2 Name: GLIBC_PRIVATE
0x0054: Parent 1: GLIBC_2.4
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "5TE"
Tag_CPU_arch: v5TE
Tag_ARM_ISA_use: Yes
My next thought was that I know glibc provides an interface to the kernel, so perhaps it was expecting a kernel version different from 2.6.19.1. However I am not sure how to determine what version of the kernel ld is targeting.
I can post more information as its requested, open to any and all ideas. Thanks in advance.
asked on Stack Overflow Jan 20, 2017 by 
BackDoorNoBaby
BackDoorNoBaby1 Answer
My next thought was that I know glibc provides an interface to the kernel, so perhaps it was expecting a kernel version different from 2.6.19.1. However I am not sure how to determine what version of the kernel ld is targeting.
You can find out what kernel this build requires with readelf -n libc.so.6, which will produce something like:
Notes at offset 0x00000254 with length 0x00000020:
Owner Data size Description
GNU 0x00000010 NT_GNU_ABI_TAG (ABI version tag)
OS: Linux, ABI: 2.6.15 <--- this is the minimal kernel version
That said, the ld-linux should not crash with SIGILL when running on a too-old kernel. It actually tried to execute illegal instruction, and your next step should be to try to figure out which instruction that is.
gdb ./ld-2.6.1.so
(gdb) run
... wait for SIGILL
(gdb) x/i $pc <--- this will show the instruction causing SIGILL
(gdb) where <--- this will show how you got to that instruction.
Running this shared object library directly
Does any other dynamically linked binary work on this system when using this build of GLIBC?
While running ld-linux directly should work, it's not how it normally runs, so if everything else works fine, maybe you don't actually have a problem.
answered on Stack Overflow Jan 21, 2017 by 
Employed Russian • edited Jan 21, 2017 by Employed Russian
Employed Russian • edited Jan 21, 2017 by Employed RussianUser contributions licensed under CC BY-SA 3.0