[PATCH 0/3] RISC-V: Fix address printer on the disassembler

[Tsukasa OI]

Hello,

This patchset contains a fix to PR29342.

Tracker on GitHub:
<https://github.com/a4lg/binutils-gdb/wiki/riscv_dis_fix_addr>

Original Issue as reported by H. Peter Anvin:
<https://sourceware.org/bugzilla/show_bug.cgi?id=29342>

First of all, this bug is caused by address computation of maybe_print_address
on disassembling RV32 programs.

Let me show the pseudocode of `maybe_print_address':

    if (high part of the register [for address sequence] is set)
    {
        pd->print_addr = (high part) + offset;        // (1)
        unset high part (as used);
    }
    else if (base register == `gp' && __global_pointer$ is available)
        pd->print_addr = __global_pointer$ + offset;  // (2)
    else if (base register == `tp' || base register == `zero')
        pd->print_addr = offset;                      // (3)
    // Sign-extend a 32-bit value to 64-bit
    if (instruction is ADDIW or C.ADDIW)
        pd->print_addr = (bfd_vma)(int32_t)pd->print_addr;

In here, it implicitly sign-extends an `int'-typed variable `offset' to generate
an address.  (3) is the direct cause of PR29342 but other locations have
similar issue.

On an example provided by Peter, IOREG_FOO has an address value of 0xffffff00.
However, due to incorrect sign-extension, the disassembler considers that the
`sw' instruction operates on an incorrect address 0xffffffff_ffffff00 EVEN ON
RV32.  This affects symbol lookup.  So, we have to mask (and zero-extend) the
address on RV32 to get correct address 0xffffff00.

Also, the background provided by Peter gives us a context: highest address space
may be important for some systems/programs.  So, not only fixing PR29342, I
decided to make the address -1 (originally reserved as a non-printing address)
printable by separating (a) the address to print and (b) whether the address
should be printed.  This isn't zero-overhead but close to.

This patchset:

1.  fits an address into a 32-bit value on RV32 (resolves PR29342)
2.  makes the highest address printable
    (0xffffffff can be printed as a real symbol)
3.  clarifies the meaning of the `wide' argument
    (`is_addiw' fits the context).

It also has new testcases and a testcase modification (it seems lla32.d is
affected by this patchset but not harmful so that modifying the testcase
lla32.d seemed better).

Thanks,
Tsukasa




Tsukasa OI (3):
  RISC-V: Print highest address on disassembler
  RISC-V: Fix RV32 disassembler address computation
  RISC-V: Add address printer tests on disassembler

 gas/testsuite/gas/riscv/dis-addr-1-32.d | 29 ++++++++++
 gas/testsuite/gas/riscv/dis-addr-1-64.d | 33 ++++++++++++
 gas/testsuite/gas/riscv/dis-addr-1.s    | 70 +++++++++++++++++++++++++
 gas/testsuite/gas/riscv/lla32.d         |  2 +-
 opcodes/riscv-dis.c                     | 34 +++++++-----
 5 files changed, 154 insertions(+), 14 deletions(-)
 create mode 100644 gas/testsuite/gas/riscv/dis-addr-1-32.d
 create mode 100644 gas/testsuite/gas/riscv/dis-addr-1-64.d
 create mode 100644 gas/testsuite/gas/riscv/dis-addr-1.s


base-commit: b245c595aaa59812f8f3a0e8b70ea5f52e045627
-- 
2.34.1