Re: [Qemu-riscv] [Qemu-devel] [PULL 17/29] target/riscv: Convert quadrant 1 of RVXC insns to decodetree

[Palmer Dabbelt]

On Fri, Mar 15, 2019 at 4:19 AM Palmer Dabbelt <address@hidden> wrote:

On Fri, 15 Mar 2019 02:06:07 PDT (-0700), Bastian Koppelmann wrote:
> Hi Alistair
>
> On 3/14/19 9:28 PM, Alistair Francis wrote:
>> On Wed, Mar 13, 2019 at 7:53 AM Palmer Dabbelt <address@hidden> wrote:
>>> From: Bastian Koppelmann <address@hidden>
>>>
>>> Reviewed-by: Richard Henderson <address@hidden>
>>> Signed-off-by: Bastian Koppelmann <address@hidden>
>>> Signed-off-by: Peer Adelt <address@hidden>
>> This commit is the first bad commit in breaking 32-bit boot.
>>
>> It looks like the jal doesn't jump to the correct address:
>>
>> ----------------
>> IN:
>> 0x80000022:  00050433          add             s0,a0,zero
>> 0x80000026:  000584b3          add             s1,a1,zero
>> 0x8000002a:  2c79              jal             ra,670          # 0x800002c8
>>
>> ----------------
>> IN:
>> 0x800002c8:  00000533          add             a0,zero,zero
>> 0x800002cc:  8082              ret
>
>
> Oops! Can you point me to the binary to reproduce this?

I think I've traced it down to something simple: in my hello world binary I see

    20401a8c:       2a45                    jal     20401c3c <atexit>

in the objdump, and I see

    IN: _start
    0x20401a8c:  2a45              jal             ra,432          # 0x20401c3c

but then QEMU jumps to 0x20401a9d.  I have a feeling it's something wrong with
gen_jal() that disappeared during the cleanups that we dropped in order to fix
the build issues.

I'm running

    ./riscv32-softmmu/qemu-system-riscv32 -machine sifive_e -kernel ~/work/sifive/freedom-e-sdk/software/hello/hello -nographic -d in_asm,out_asm,exec,cpu -singlestep |& tee out.log

on the "hifive1" branch of github.com/palmer-dabbelt/qemu, which just has a
PRCI fixup that I forgot about and haven't sent upstream yet (I'll do that
after this issue).  The binary should be at

    http://www.dabbelt.com/~palmer/hello.elf

and the debug log at

    http://www.dabbelt.com/~palmer/out.log

You can build the binary from github.com/sifive/freedom-e-sdk via

   make software PROGRAM=hello TARGET=sifive-hifive1

using the riscv64-unknown-elf-gcc-20181127-x86_64-linux-ubuntu14 toolchain
binaries from our website (newer ones should work, but probably won't produce
exactly the same output).

I'll poke around after grabbing some dinner...

OK, I'm pretty sure this is it:

c_jal_addiw       001 .  .....  ..... 01 @ci #Note: parse rd and/or imm manually

static bool trans_c_jal_addiw(DisasContext *ctx, arg_c_jal_addiw *a)

{

#ifdef TARGET_RISCV32

    /* C.JAL */

    arg_jal arg = { .rd = 1, .imm = a->imm };

    return trans_jal(ctx, &arg);

#else

    /* C.ADDIW */

    arg_addiw arg = { .rd = a->rd, .rs1 = a->rd, .imm = a->imm };

    return trans_addiw(ctx, &arg);

#endif

}

It parses RD manually, but not IMM :)  I'm actually going to eat now...