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

[Nelson Chu <nelson dot chu at sifive dot com>]

Dear binutils,

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

Attachment: 0001-RISC-V-Update-the-CSR-to-privilege-spec-1.12.patch
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Attachment: 0002-RISC-V-Support-more-rigorous-check-for-CSR.patch
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Attachment: 0003-RISC-V-Support-read-only-CSR-checking.patch
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Attachment: 0004-RISC-V-Disable-the-CSR-checking-by-default.patch
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