[PATCH v3 1/2] RISC-V: PR27916, Support mapping symbols.

[Jim Wilson]

On Tue, Aug 24, 2021 at 6:36 PM Nelson Chu <nelson.chu@sifive.com> wrote:

> ping :)
>
> Thanks
> Nelson
>
> On Tue, Jul 13, 2021 at 6:09 PM Nelson Chu <nelson.chu@sifive.com> wrote:
> >
> > Similar to ARM/AARCH64, we add mapping symbols in the symbol table,
> > to mark the start addresses of data and instructions.  The $d means
> > data, and the $x means instruction.  Then the disassembler uses these
> > symbols to decide whether we should dump data or instruction.


Looks OK to me.  I guess you want an approval because of the readelf.c
change?  That is just a minor comment change though.

I did notice one typo in a comment in gas/config/tc-riscv.c in
riscv_check_mapping_symbols where you have fragmnet which should be
fragment.

Same file in riscv_mapping_state you have
+  /* The mapping symbol should be emitted.  */

+  if (from_state == to_state)

+    return;
which looks a little funny.  Maybe you meant that we should emit it now
that we know that it is a text section.  But then you have code to not emit
it if we are already in the right mapping state which is a little
confusing.  Could be something like "should be emitted if not in the right
mapping state."

I saw the comment about -D in the disassembler.  -D really is supposed to
disassemble data.  The arm/aarch64 ports get this right.  -D is useful in
rare cases where you have instruction templates in the data section, and
you want to disassemble them to verify that they are correct.  Maybe you
are disassembling a compiler so it has instructions in data.  Or maybe this
is some self modifying code.  Anyways, -D should disassemble data same as
arm/aarch64.

Mapping symbols are still a proposal for the psABI, but I think this is
OK.  There was only disagreement on the more complicated stuff that this
patch doesn't attempt to implement.

Jim