[Bug 1914021] Re: qemu: uncaught target signal 4 (Illegal instruction) but gdb remote-debug exited normally

[Peter Maydell]

For me, with current head-of-git QEMU, the program crashes with a
SIGSEGV very early in execution, because:

0x00008260:  e59f30f0  ldr      r3, [pc, #0xf0]

loads 0 into r3, and then

0x00008270:  e1a0d003  mov      sp, r3

sets sp to 0, and then

0x000087b0:  e92d4030  push     {r4, r5, lr}

tries to write to addres 0, which causes a SEGV.

This happens whether using the gdbstub or not.

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https://bugs.launchpad.net/bugs/1914021

Title:
  qemu: uncaught target signal 4 (Illegal instruction) but gdb remote-
  debug exited normally

Status in QEMU:
  New

Bug description:
  I'm getting Illegal instruction (core dumped) when running the
  attached a.out_err binary in qemu, but when using Gdb to remote-debug
  the program, it exited normally. will appreciate if you can help look
  into this qemu issue.

  readelf -h a.out_err
  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:                              EXEC (Executable file)
    Machine:                           ARM
    Version:                           0x1
    Entry point address:               0x8220
    Start of program headers:          52 (bytes into file)
    Start of section headers:          54228 (bytes into file)
    Flags:                             0x5000200, Version5 EABI, soft-float ABI
    Size of this header:               52 (bytes)
    Size of program headers:           32 (bytes)
    Number of program headers:         3
    Size of section headers:           40 (bytes)
    Number of section headers:         16
    Section header string table index: 15

  qemu-arm version 4.0.0

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