Generate new riscv-64 objects from source code

[thixotropist]

The first set of Ghidra import test cases relied on external packages. Add new import test cases compiled (or assembled) from source code with an imported cross-platform toolchain.

Initially, the test cases will use a riscv-64, gcc 12 linux toolchain with C, C++, and possibly assembly sources. The build options should try to model a mix of normal user process, user sharable library, and loadable kernel module elements.

The first tests are limited to exercise features involving riscv-64 relocation and concurrency controls.

Example:

Compile the following with a riscv-64 toolchain with PIE enabled and PIC disabled.

char bssString[4096];
#include <stdio.h>
int
main (void)
{
  // exercise store into .bss with small offset
  bssString[8] = 0;
  // exercise store into .bss with 12 bit offset
  bssString[2049] = 0;
  // reference bssString to prevent optimization erasure and pass a bss address as a parameter
  printf(bssString);
  return 0;
}

Readelf shows that this generates an object file with multiple relocation types - more relocations than lines of actual code!

0000000000000004  0000000e00000017 R_RISCV_PCREL_HI20     0000000000000000 bssString + 0
0000000000000004  0000000000000033 R_RISCV_RELAX                             0
0000000000000008  0000000900000018 R_RISCV_PCREL_LO12_I   0000000000000004 .L0  + 0
0000000000000008  0000000000000033 R_RISCV_RELAX                             0
0000000000000010  0000000e00000017 R_RISCV_PCREL_HI20     0000000000000000 bssString + 801
0000000000000010  0000000000000033 R_RISCV_RELAX                             801
0000000000000014  0000000a00000019 R_RISCV_PCREL_LO12_S   0000000000000010 .L0  + 0
0000000000000014  0000000000000033 R_RISCV_RELAX                             0
0000000000000018  0000000f00000013 R_RISCV_CALL_PLT       0000000000000000 printf + 0
0000000000000018  0000000000000033 R_RISCV_RELAX                             0

A successful test case will bundle:

• the C source code
• the toolchain configuration used to compile that source code into an object file and a linked executable
• readelf or other analyses of the generated output
• a Ghidra decompiler export from the object file that should essentially match the input source code
• optionally include other data, such as the Gnu assembler source code emitted by the gcc compiler

RISCV has a lot of different relocation codes. To get started, we will ignore any RISCV relocation codes that aren't known to the binutils-2_40 assembler. So we will care about relocations to GOT and BSS, but ignore relocations into things like task-local storage. Debugging relocations and frame tables are similarly out of scope.

[thixotropist]

closed with b06f08b