[PATCH] RISC-V: Support more rigorous check for CSR, and update them to spec 1.12.

[Nelson Chu]

Dear binutils,

I do some modifications for the previous CSR checking patches.

There are four updated patches as follows:
0001-RISC-V-Update-the-CSR-to-privilege-spec-1.12
0002-RISC-V-Support-the-ISA-dependent-CSR-checking
0003-RISC-V-Support-read-only-CSR-checking
0004-RISC-V-Disable-the-CSR-checking-by-default

The first patch is the same as the previous version.  In the second
patch, the `csr_extra_hash` only record the extra information of CSR.
For now we just need to record the `csr_class` in the `csr_extra_hash`
to support the ISA-dependent CSR checking.  The CRS addresses are
stored in the `reg_names_hash` as before.  I also update some comments
and fix typo for the third and fourth patches.

Any comment or suggestion is appreciated :)

Thanks and regards
Nelson


On Wed, Nov 6, 2019 at 5:57 PM Nelson Chu <nelson.chu@sifive.com> wrote:
> After the discussion, we now promote a new implementation for the CSR
> checking.  Keep the original DECLARE_CSR and DECLARE_CSR_ALIAS in the
> include/opcode/riscv-opc.h, and then extend them to record the extra
> information for CSR.
>
> DECLARE_CSR(ustatus, CSR_USTATUS, CSR_CLASS_I)
> DECLARE_CSR(uie, CSR_UIE, CSR_CLASS_I)
> DECLARE_CSR(utvec, CSR_UTVEC, CSR_CLASS_I)
> DECLARE_CSR(uscratch, CSR_USCRATCH, CSR_CLASS_I)
> ...
>
> Then we can create and insert hash table with the key (CSR name) to
> store the CSR address and ISA class for the CSR.  As for GDB, I have
> regenerated the 32bit-csr.xml and 64bit-csr.xml files through the
> modified rebuild-csr-xml.sh.  The modified rebuild-csr-xml.sh can
> filter the rv32-only CSR for the 64bit-csr.xml.
>
> If we keep and extend the original DECLARE_SCR macro, then we still
> need a big switch statement in the opcodes/riscv-dis.c and
> gdb/riscv-tdep.c.  If we use the previous method that record the CSR
> information via table in opcodes/riscv-opc.c, then we probably need to
> parse the table in the rebuild-csr-xml.sh or other methods.  I'm not
> sure which one is better, either is OK for me, so I just implement the
> minimal changed method in this mail.
>
> The CSR version checking and privilege mode checking are more
> complicated.  Currently, I have no idea that GCC should choose what
> format and method to pass the CSR version and privilege mode to
> assembler, maybe use the .option, --mxxx options, or the ELF
> attribute, or all three are.  Therefore, I prefer to support these two
> CSR checking in the later patches after the full discussion :)
>
> There are four new patches to support the CSR checking as follows:
> 0001-RISC-V-Update-the-CSR-to-privilege-spec-1.12.patch
> 0002-RISC-V-Support-more-rigorous-check-for-CSR.patch
> 0003-RISC-V-Support-read-only-CSR-checking.patch
> 0004-RISC-V-Disable-the-CSR-checking-by-default.patch
>
> The first patch is used to update the CSR to the privilege spec 1.12,
> the two xml files are also regenerated.  The second patch is used to
> support the ISA-dependent CSR checking.  The third patch is used to
> support the Read-only CSR checking.  The CSR checking should be an
> opt-in feature for now.  Therefore, we support the new options
> "-mcsrcheck/-mno-csrcheck" and ".option csrcheck/nocsrcheck" to
> enable/disable the CSR checking, and disable the CSR checking by
> default in the fourth patch.
>
> If the first patch is accepted, then I will update the CSR to the
> privilege spec 1.12 for Qemu and OpenOCD later.
>
> Thanks
> Best Regards
> Nelson
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