Re: [PATCH for-9.1 v3 2/2] trans_privileged.c.inc: set (m|s)tval on ebreak breakpoint

[Alistair Francis]

On Wed, Apr 17, 2024 at 9:05 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> Privileged spec section 4.1.9 mentions:
>
> "When a trap is taken into S-mode, stval is written with
> exception-specific information to assist software in handling the trap.
> (...)
>
> If stval is written with a nonzero value when a breakpoint,
> address-misaligned, access-fault, or page-fault exception occurs on an
> instruction fetch, load, or store, then stval will contain the faulting
> virtual address."
>
> A similar text is found for mtval in section 3.1.16.
>
> Setting mtval/stval in this scenario is optional, but some softwares read
> these regs when handling ebreaks.
>
> Write 'badaddr' in all ebreak breakpoints to write the appropriate
> 'tval' during riscv_do_cpu_interrrupt().
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/insn_trans/trans_privileged.c.inc | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/target/riscv/insn_trans/trans_privileged.c.inc 
> b/target/riscv/insn_trans/trans_privileged.c.inc
> index 620ab54eb0..bc5263a4e0 100644
> --- a/target/riscv/insn_trans/trans_privileged.c.inc
> +++ b/target/riscv/insn_trans/trans_privileged.c.inc
> @@ -62,6 +62,8 @@ static bool trans_ebreak(DisasContext *ctx, arg_ebreak *a)
>      if (pre == 0x01f01013 && ebreak == 0x00100073 && post == 0x40705013) {
>          generate_exception(ctx, RISCV_EXCP_SEMIHOST);
>      } else {
> +        tcg_gen_st_tl(tcg_constant_tl(ebreak_addr), tcg_env,
> +                      offsetof(CPURISCVState, badaddr));
>          generate_exception(ctx, RISCV_EXCP_BREAKPOINT);
>      }
>      return true;
> --
> 2.44.0
>
>