[PATCH v2 0/8] Fixes for load/store misaligned and access faults

[Bo Gan]

Re-visit the load/store misaligned and access fault handlers to fix
issues related to coding patterns, floating-point state, and instruction
decoding:

 a. Vector misaligned load/store emulator is invoked improperly
 b. vsstatus.FS is not set dirty when V=1
 c. No checking of previous XLEN, resulting in wrong insn decoding
 d. Load/Store base address is wrongly assumed to be trap address
 e. High 32-bits of tinst needs to be checked against 0

The pathset is validated on a modified QEMU[1] that exposed misaligned
faults, and QEMU[2], which further disabled the insn transformation.
[2] covers more insn decoding branches, including the particular ones
which can trigger the wrong decoding (c)

The patchset is also validated on Sifive P550 core (ESWIN EIC7700),
which is RV64-only in M/(V)S/(V)U, no HW misaligned support, no vector,
and mtinst always 0. Refer to [3] for the git repo/branch that has all
6 patches applied along with the test case that exercises all integer
and floating-point load/store instructions.

Test case used is available in PATCH 8.

There's no change to the behavior of the vector misaligned load/store
handler. However, I've found additional issues with them:

 - `uint8_t mask[VLEN_MAX / 8]` in sbi_trap_v_ldst.c is 8KB, which
   can overflow the default 4KB stack.
 - tinst should be zero'ed out to not confuse previous mode when
   redirecting faults, otherwise the vector insn can be mistaken
   as a regular load/store.
 - VS in previous mode must be set dirty for loads.

These will be addressed in follow-up patches.

[1] https://github.com/ganboing/qemu/tree/ganboing-misalign
[2] https://github.com/ganboing/qemu/tree/ganboing-misalign-no-tinst
[3] https://github.com/ganboing/opensbi/tree/fix-ldst-v2
---
Changes in v2:
 - Addressed Anup's comment for PATCH 5 in v1
 - Validate load/store offset is 0 in misaligned faults w/ DEBUG build

---
Bo Gan (8):
  include: sbi: Add more mstatus and instruction encoding
  include: sbi: Add sbi_regs_prev_xlen
  include: sbi: Add GET_RDS_NUM/SET(_FP32/_FP64)_RDS macros
  include: sbi: set FS dirty in vsstatus when V=1
  lib: sbi: Do not override emulator callback for vector load/store
  Makefile: define OPENSBI_DEBUG if DEBUG builds
  lib: sbi: Rework load/store emulator instruction decoding
  [NOT-FOR-UPSTREAM] Test program for misaligned load/store

 Makefile                     |   1 +
 include/sbi/riscv_encoding.h |  21 +-
 include/sbi/riscv_fp.h       |  30 ++-
 include/sbi/sbi_platform.h   |  92 +++++--
 include/sbi/sbi_trap.h       |  59 ++++
 include/sbi/sbi_trap_ldst.h  |   4 +-
 lib/sbi/sbi_trap_ldst.c      | 510 ++++++++++++++++++++++++-----------
 lib/sbi/sbi_trap_v_ldst.c    |  25 +-
 tests/ldst.S                 | 134 +++++++++
 tests/ldst.h                 | 170 ++++++++++++
 tests/test-misaligned-ldst.c | 154 +++++++++++
 11 files changed, 994 insertions(+), 206 deletions(-)
 create mode 100644 tests/ldst.S
 create mode 100644 tests/ldst.h
 create mode 100644 tests/test-misaligned-ldst.c

-- 
2.34.1