While debugging an application with GDB the following might happen:

(gdb) return
Make xxx return now? (y or n) y
Could not fetch register "fflags"; remote failure reply 'E14'

This is because riscv_gdb_get_fpu calls riscv_csrrw_debug with a wrong csr
number (8). It should use the csr_register_map in order to reach the
riscv_cpu_get_fflags callback.

Signed-off-by: KONRAD Frederic <frederic.konrad@adacore.com>
---
 target/riscv/gdbstub.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/target/riscv/gdbstub.c b/target/riscv/gdbstub.c
index 27be932..ded140e 100644
--- a/target/riscv/gdbstub.c
+++ b/target/riscv/gdbstub.c
@@ -313,7 +313,8 @@ static int riscv_gdb_get_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
          * register 33, so we recalculate the map index.
          * This also works for CSR_FRM and CSR_FCSR.
          */
-        result = riscv_csrrw_debug(env, n - 33 +  8, &val, 0, 0);
+        result = riscv_csrrw_debug(env, n - 33 + csr_register_map[8], &val,
+                                   0, 0);
         if (result == 0) {
             return gdb_get_regl(mem_buf, val);
         }
@@ -335,7 +336,8 @@ static int riscv_gdb_set_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
          * register 33, so we recalculate the map index.
          * This also works for CSR_FRM and CSR_FCSR.
          */
-        result = riscv_csrrw_debug(env, n - 33 + 8, NULL, val, -1);
+        result = riscv_csrrw_debug(env, n - 33 + csr_register_map[8], NULL,
+                                   val, -1);
         if (result == 0) {
             return sizeof(target_ulong);
         }
-- 
1.8.3.1

On Tue, 10 Sep 2019 01:15:41 PDT (-0700), frederic.konrad@adacore.com wrote:
> While debugging an application with GDB the following might happen:
>
> (gdb) return
> Make xxx return now? (y or n) y
> Could not fetch register "fflags"; remote failure reply 'E14'
>
> This is because riscv_gdb_get_fpu calls riscv_csrrw_debug with a wrong csr
> number (8). It should use the csr_register_map in order to reach the
> riscv_cpu_get_fflags callback.
>
> Signed-off-by: KONRAD Frederic <frederic.konrad@adacore.com>
> ---
>  target/riscv/gdbstub.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/target/riscv/gdbstub.c b/target/riscv/gdbstub.c
> index 27be932..ded140e 100644
> --- a/target/riscv/gdbstub.c
> +++ b/target/riscv/gdbstub.c
> @@ -313,7 +313,8 @@ static int riscv_gdb_get_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
>           * register 33, so we recalculate the map index.
>           * This also works for CSR_FRM and CSR_FCSR.
>           */
> -        result = riscv_csrrw_debug(env, n - 33 +  8, &val, 0, 0);
> +        result = riscv_csrrw_debug(env, n - 33 + csr_register_map[8], &val,
> +                                   0, 0);
>          if (result == 0) {
>              return gdb_get_regl(mem_buf, val);
>          }
> @@ -335,7 +336,8 @@ static int riscv_gdb_set_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
>           * register 33, so we recalculate the map index.
>           * This also works for CSR_FRM and CSR_FCSR.
>           */
> -        result = riscv_csrrw_debug(env, n - 33 + 8, NULL, val, -1);
> +        result = riscv_csrrw_debug(env, n - 33 + csr_register_map[8], NULL,
> +                                   val, -1);
>          if (result == 0) {
>              return sizeof(target_ulong);
>          }

Reviewed-by: Palmer Dabbelt <palmer@sifive.com>

I just tagged a fixed version of my PR, but I'll include this in the next one.

On Tue, Sep 10, 2019 at 1:16 AM KONRAD Frederic
<frederic.konrad@adacore.com> wrote:
>
> While debugging an application with GDB the following might happen:
>
> (gdb) return
> Make xxx return now? (y or n) y
> Could not fetch register "fflags"; remote failure reply 'E14'
>
> This is because riscv_gdb_get_fpu calls riscv_csrrw_debug with a wrong csr
> number (8). It should use the csr_register_map in order to reach the
> riscv_cpu_get_fflags callback.
>
> Signed-off-by: KONRAD Frederic <frederic.konrad@adacore.com>

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

Alistair

> ---
>  target/riscv/gdbstub.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/target/riscv/gdbstub.c b/target/riscv/gdbstub.c
> index 27be932..ded140e 100644
> --- a/target/riscv/gdbstub.c
> +++ b/target/riscv/gdbstub.c
> @@ -313,7 +313,8 @@ static int riscv_gdb_get_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
>           * register 33, so we recalculate the map index.
>           * This also works for CSR_FRM and CSR_FCSR.
>           */
> -        result = riscv_csrrw_debug(env, n - 33 +  8, &val, 0, 0);
> +        result = riscv_csrrw_debug(env, n - 33 + csr_register_map[8], &val,
> +                                   0, 0);
>          if (result == 0) {
>              return gdb_get_regl(mem_buf, val);
>          }
> @@ -335,7 +336,8 @@ static int riscv_gdb_set_fpu(CPURISCVState *env, uint8_t *mem_buf, int n)
>           * register 33, so we recalculate the map index.
>           * This also works for CSR_FRM and CSR_FCSR.
>           */
> -        result = riscv_csrrw_debug(env, n - 33 + 8, NULL, val, -1);
> +        result = riscv_csrrw_debug(env, n - 33 + csr_register_map[8], NULL,
> +                                   val, -1);
>          if (result == 0) {
>              return sizeof(target_ulong);
>          }
> --
> 1.8.3.1
>
>