How to Solve Segfault on VCS Linux

VLSI synopsys vcs

Preamble

This is education project. It is made to allow studying computer science, computer architectures and debugging binary codes.

Problem

segfault in VCS R-2020.12-SP1

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Command line: ./simv

--- Stack trace follows:

Dumping VCS Annotated Stack:
#0  0xf7ffd430 in __kernel_vsyscall ()
#1  0x006d569b in waitpid () from /lib/libc.so.6
#2  0x0066ebe3 in do_system () from /lib/libc.so.6
#3  0x0066ef72 in system () from /lib/libc.so.6
#4  0x007db9ed in system () from /lib/libpthread.so.0
#5  0xee4a66ec in SNPSle_10ee25eff68cd8461c9146fa1d0b35e87067f3c8015b313e639d2928478c79b3f673f99203bcf8be64600612100082236bffb2007f1e0ef9 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/liberrorinf.so
#6  0xee4a795b in SNPSle_10ee25eff68cd8461c9146fa1d0b35e87067f3c8015b313efba706aab251478fa49e66610e453774633a6c152e7ef778f2202cda681f3d4e () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/liberrorinf.so
#7  0xee49fd5b in SNPSle_d35ca1ff70d465c2b9b1a72eee90a50630165806651fae9621672f4baea6f56e () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/liberrorinf.so
#8  0xea2beb40 in SNPSle_64133461705005bb725549e2e6fa1b3f () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#9  0xe9f6c74c in SNPSle_82244d58c54c18c70d63edc9becab634 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#11 0xee448195 in mem_free () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libsnpsmalloc.so
#12 0xee420bc4 in snpsFreeFunc () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libsnpsmalloc.so
#13 0xe9ce58ee in SNPSle_edfd0437dc1f3ca1 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#14 0xe9ce631d in SNPSle_e2e2cbb6d2283a4d () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#15 0xe9ce40ad in SNPSle_382d0af7df412362 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#16 0xe9ce4636 in SNPSle_59279f7c9b103b1e () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#17 0xe9ce4776 in SNPSle_207fb97ffa75eca3 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#18 0x007d3bc9 in start_thread () from /lib/libpthread.so.0
#19 0x0071711e in clone () from /lib/libc.so.6
#0  0xf7ffd430 in __kernel_vsyscall ()
#1  0x006d5b86 in nanosleep () from /lib/libc.so.6
#2  0x006d59b0 in sleep () from /lib/libc.so.6
#3  0xe9a93da9 in SNPSle_95ae9cc2e78cc668673c60b8d88c4908 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#4  0xe9a93f17 in SNPSle_92de4d0d4cf0d6931bc37e8d42a01d93 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#5  0xe9a921b7 in SNPSle_b76ef993ee82b3d58a5cadddbec8b67c () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#6  0xe9a92528 in SNPSle_f28f24b8c84ac8f6e02e0b03bcd33aa8 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#7  0xe9a7be98 in SNPSle_5e54eaa1df739f6ed4c1ff24a0986ee6 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#8  0xe9a7c0c3 in SNPSle_058778405d2a6c04ddd18247ba7f440f () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#9  0xe9a7dabd in SNPSle_e376be325e61b493d6bd988d8077bacc () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#10 0xe9a7e742 in SNPSle_a10369bdf7c5916ddd6866ce7e2e861c () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#11 0xe9a81cad in SNPSle_00b1acee80c770570cd75f9efbe24cca () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#12 0xe9a77e9d in SNPSle_ba11b1edbd04051f5bb81b1861cdf84a () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#13 0xe9a67573 in SNPSle_2e65c0794628fc5af60953149776c29b () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#14 0xe9a63b74 in SNPSle_541f757be362289a7c9e5618c0ff28327846f8d3cc02839f () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#15 0xe9a647e9 in SNPSle_541f757be362289a7c9e5618c0ff283244765933a2ab0071 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#16 0xe9a5dc62 in SNPSle_c0de1345d5ab80930e06dd2b68f214c3 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#17 0xe9a5de3e in SNPSle_25cd5712eacded5ff943afa9a81fcb09 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#18 0xe9a5e1bc in SNPSle_25cd5712eacded5feaee03dc3430943e () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#19 0xe9a5e8e9 in SNPSle_541f757be362289a7c9e5618c0ff28323e4fa62265ee8f28 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#20 0xea2e0042 in SNPSle_490598bfebcc8e8183ad3550288b1f82 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#21 0xea2ebac4 in SNPSle_490598bfebcc8e81 () from /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so
#22 0x0805cdd7 in main ()

Process VmPeak: 553656 kb, VmSize: 421564 kb
System Free Memory: 2006344 kb, System Free Swap: 16657512 kb

Solution

Let’s get objdump

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$ objdump -D /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so &> dump

VIM allows to open big dump file. After opening find - SNPSle_207fb97ffa75eca3 

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019e273a <SNPSle_207fb97ffa75eca3>:
 19e273a:   55                      push   %ebp
 19e273b:   31 c0                   xor    %eax,%eax
 19e273d:   89 e5                   mov    %esp,%ebp
 19e273f:   56                      push   %esi
 19e2740:   8b 75 08                mov    0x8(%ebp),%esi
 19e2743:   53                      push   %ebx
 19e2744:   e8 c6 14 5c 02          call   3fa3c0f <SNPSle_715314d83d0f61da9168d7348e45a64b3af050ec97b0cd6b>
 19e2749:   81 c3 b7 58 28 04       add    $0x42858b7,%ebx
 19e274f:   85 f6                   test   %esi,%esi
 19e2751:   74 1a                   je     19e276d <SNPSle_207fb97ffa75eca3+0x33>
 19e2753:   8b 06                   mov    (%esi),%eax
 19e2755:   85 c0                   test   %eax,%eax
 19e2757:   74 63                   je     19e27bc <SNPSle_207fb97ffa75eca3+0x82>
 19e2759:   69 c0 40 42 0f 00       imul   $0xf4240,%eax,%eax
 19e275f:   83 ec 0c                sub    $0xc,%esp
 19e2762:   50                      push   %eax
 19e2763:   e8 28 03 55 ff          call   f32a90 <usleep@plt>
 19e2768:   83 c4 10                add    $0x10,%esp
 19e276b:   eb 4f                   jmp    19e27bc <SNPSle_207fb97ffa75eca3+0x82>
 19e276d:   83 ec 0c                sub    $0xc,%esp
 19e2770:   50                      push   %eax
 19e2771:   e8 b0 fd ff ff          call   19e2526 <SNPSle_59279f7c9b103b1e>
 19e2776:   83 c4 10                add    $0x10,%esp
 19e2779:   48                      dec    %eax
 19e277a:   8b 83 70 f6 ff ff       mov    -0x990(%ebx),%eax
 19e2780:   75 09                   jne    19e278b <SNPSle_207fb97ffa75eca3+0x51>
 19e2782:   c7 40 64 02 00 00 00    movl   $0x2,0x64(%eax)

We are interested in line - 19e2771: e8 b0 fd ff ff call 19e2526
It’s callq instruction which we can replace by some nop instructions.
Nop instruction is 0x90 in hex code.

First of all you must make backup of VCS tool!

Edit binary file via hexedit

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$ hexedit /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so

Find e8 b0 fd ff ff which is at 19e2771 address. And replace this bytes by 0x90! Save changes and close library.
So let’s check result via objdump: 

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$ objdump -D /eda/SYNOPSYS/vcs/R-2020.12-SP1/linux/lib/libvcsnew.so &> new_dump
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019e273a <SNPSle_207fb97ffa75eca3>:
 19e273a:   55                      push   %ebp
 19e273b:   31 c0                   xor    %eax,%eax
 19e273d:   89 e5                   mov    %esp,%ebp
 19e273f:   56                      push   %esi
 19e2740:   8b 75 08                mov    0x8(%ebp),%esi
 19e2743:   53                      push   %ebx
 19e2744:   e8 c6 14 5c 02          call   3fa3c0f <SNPSle_715314d83d0f61da9168d7348e45a64b3af050ec97b0cd6b>
 19e2749:   81 c3 b7 58 28 04       add    $0x42858b7,%ebx
 19e274f:   85 f6                   test   %esi,%esi
 19e2751:   74 1a                   je     19e276d <SNPSle_207fb97ffa75eca3+0x33>
 19e2753:   8b 06                   mov    (%esi),%eax
 19e2755:   85 c0                   test   %eax,%eax
 19e2757:   74 63                   je     19e27bc <SNPSle_207fb97ffa75eca3+0x82>
 19e2759:   69 c0 40 42 0f 00       imul   $0xf4240,%eax,%eax
 19e275f:   83 ec 0c                sub    $0xc,%esp
 19e2762:   50                      push   %eax
 19e2763:   e8 28 03 55 ff          call   f32a90 <usleep@plt>
 19e2768:   83 c4 10                add    $0x10,%esp
 19e276b:   eb 4f                   jmp    19e27bc <SNPSle_207fb97ffa75eca3+0x82>
 19e276d:   83 ec 0c                sub    $0xc,%esp
 19e2770:   50                      push   %eax
 19e2771:   90                      nop
 19e2772:   90                      nop
 19e2773:   90                      nop
 19e2774:   90                      nop
 19e2775:   90                      nop
 19e2776:   83 c4 10                add    $0x10,%esp
 19e2779:   48                      dec    %eax
 19e277a:   8b 83 70 f6 ff ff       mov    -0x990(%ebx),%eax
 19e2780:   75 09                   jne    19e278b <SNPSle_207fb97ffa75eca3+0x51>
 19e2782:   c7 40 64 02 00 00 00    movl   $0x2,0x64(%eax)
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