[PATCH v6 0/3] riscv: Add remaining module relocations and tests

[Charlie Jenkins]

A handful of module relocations were missing, this patch includes the
remaining ones. I also wrote some test cases to ensure that module
loading works properly. Some relocations cannot be supported in the
kernel, these include the ones that rely on thread local storage and
dynamic linking.

ULEB128 handling is a bit special because SET and SUB relocations must
happen together, and SET must happen before SUB. A psABI proposal [1]
mandates that the first SET_ULEB128 that appears before a SUB_ULEB128
is the associated SET_ULEB128.

This can be tested by enabling KUNIT, RUNTIME_KERNEL_TESTING_MENU, and
RISCV_MODULE_LINKING_KUNIT.

[1] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/403

Signed-off-by: Charlie Jenkins <charlie at rivosinc.com>
---
Changes in v6:
- Use (void *) instead of (u32 *) for handler type
- Constrain ULEB128 to be consecutive relocations
- Link to v5: https://lore.kernel.org/r/20231018-module_relocations-v5-0-dfee32d4dfc3@rivosinc.com

Changes in v5:
- Brought in patch by Emil and fixed it up to force little endian
- Fixed up issues with apply_r_riscv_32_pcrel_rela and
  apply_r_riscv_plt32_rela (Samuel)
- Added u8 cast in apply_r_riscv_sub6_rela (Andreas) 
- Link to v4: https://lore.kernel.org/r/20231017-module_relocations-v4-0-937f5ef316f0@rivosinc.com

Changes in v4:
- Complete removal of R_RISCV_RVC_LUI
- Fix bug in R_RISCV_SUB6 linking
- Only build ULEB128 tests if supported by toolchain
- Link to v3: https://lore.kernel.org/r/20231016-module_relocations-v3-0-a667fd6071e9@rivosinc.com

Changes in v3:
- Add prototypes to test_module_linking_main as recommended by intel
  zero day bot
- Improve efficiency of ULEB128 pair matching
- Link to v2: https://lore.kernel.org/r/20231006-module_relocations-v2-0-47566453fedc@rivosinc.com

Changes in v2:
- Added ULEB128 relocations
- Link to v1: https://lore.kernel.org/r/20230913-module_relocations-v1-0-bb3d8467e793@rivosinc.com

---
Charlie Jenkins (2):
      riscv: Add remaining module relocations
      riscv: Add tests for riscv module loading

Emil Renner Berthing (1):
      riscv: Avoid unaligned access when relocating modules

 arch/riscv/Kconfig.debug                           |   1 +
 arch/riscv/include/uapi/asm/elf.h                  |   5 +-
 arch/riscv/kernel/Makefile                         |   1 +
 arch/riscv/kernel/module.c                         | 368 +++++++++++++++------
 arch/riscv/kernel/tests/Kconfig.debug              |  35 ++
 arch/riscv/kernel/tests/Makefile                   |   1 +
 arch/riscv/kernel/tests/module_test/Makefile       |  15 +
 .../tests/module_test/test_module_linking_main.c   |  85 +++++
 arch/riscv/kernel/tests/module_test/test_set16.S   |  23 ++
 arch/riscv/kernel/tests/module_test/test_set32.S   |  20 ++
 arch/riscv/kernel/tests/module_test/test_set6.S    |  23 ++
 arch/riscv/kernel/tests/module_test/test_set8.S    |  23 ++
 arch/riscv/kernel/tests/module_test/test_sub16.S   |  22 ++
 arch/riscv/kernel/tests/module_test/test_sub32.S   |  22 ++
 arch/riscv/kernel/tests/module_test/test_sub6.S    |  22 ++
 arch/riscv/kernel/tests/module_test/test_sub64.S   |  27 ++
 arch/riscv/kernel/tests/module_test/test_sub8.S    |  22 ++
 arch/riscv/kernel/tests/module_test/test_uleb128.S |  20 ++
 18 files changed, 633 insertions(+), 102 deletions(-)
---
base-commit: 4d320c2d9a2b22f53523a1b012cda17a50220965
change-id: 20230908-module_relocations-f63ced651bd7
-- 
- Charlie