[Qemu-devel] AArch64 ELF File Loading

[Christopher Covington <cov@codeaurora.org>]

Hi,

I think the AArch64 port has a problem with a self-modifying code sequence
that appears to run fine on other simulators, but I can't get QEMU to run the
small bare metal test case I created to try to reproduce the issue. Any help
would be appreciated.

qemu-system-aarch64 -nodefaults -nographic -monitor none -M virt -semihosting
-d exec,in_asm /tmp/test-nooverwrite 2>&1 | less

qemu: fatal: Trying to execute code outside RAM or ROM at 0x0000000000000000

qemu-system-aarch64 -nodefaults -nographic -monitor none -M virt -semihosting
-d exec,in_asm -bios /tmp/test-nooverwrite 2>&1 | less

qemu: fatal: Trying to execute code outside RAM or ROM at 0x0000000000000000

qemu-system-aarch64 -nodefaults -nographic -monitor none -M virt -semihosting
-d exec,in_asm -kernel /tmp/test-nooverwrite 2>&1 | less

IN:
0x0000000040000000:  e3a00000      mov  r0, #0  ; 0x0
0x0000000040000004:  e59f1004      ldr  r1, [pc, #4]    ; 0x40000010
0x0000000040000008:  e59f2004      ldr  r2, [pc, #4]    ; 0x40000014
0x000000004000000c:  e59ff004      ldr  pc, [pc, #4]    ; 0x40000018

Trace 0x7f309f012000 [0000000040000000]

Note that the above are A32 instructions, but my ELF is A64 and this is not
the specified entry point.

aarch64-linux-gnu-readelf -h /tmp/test-nooverwrite
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           AArch64
  Version:                           0x1
  Entry point address:               0x80001140
  Start of program headers:          64 (bytes into file)
  Start of section headers:          186600 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         3
  Size of section headers:           64 (bytes)
  Number of section headers:         17
  Section header string table index: 14

To generate a test bare metal executable, you can download the
aarch64-none-elf toolchain from Linaro and:

echo '#include <stdio.h>

int main() {
  printf("Hello, world!\n");
  return 0;
}' > hello.c

aarch64-none-elf-gcc -specs=aem-ve.specs hello.c -o hello

Thanks,
Christopher

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