Re: [PATCH v4 07/16] [gdbserver/aarch64] sme: Add support for SME

[Thiago Jung Bauermann <thiago.bauermann@linaro.org>]

Hello Luis,

After reviewing the SME2 patches, I spotted this suggestion that
I didn't notice when I reviewed v3. Sorry about that again.

Luis Machado <luis.machado@arm.com> writes:

> +/* Wrapper for aarch64_za_regs_copy_to_reg_buf, to help copying NT_ARM_ZA
> +   state from the thread (BUF) to the register cache.  */
> +
> +static void
> +aarch64_za_regs_copy_to_regcache (struct regcache *regcache,
> +				  ATTRIBUTE_UNUSED const void *buf)
> +{
> +  /* BUF is unused here since we collect the data straight from a ptrace
> +     request, therefore bypassing gdbserver's own call to ptrace.  */
> +  int tid = lwpid_of (current_thread);
> +
> +  gdb::optional<int> za_regnum
> +    = find_regno_no_throw (regcache->tdesc, "za");
> +  gdb::optional<int> svg_regnum
> +    = find_regno_no_throw (regcache->tdesc, "svg");
> +  gdb::optional<int> svcr_regnum
> +    = find_regno_no_throw (regcache->tdesc, "svcr");
> +
> +  gdb_assert (za_regnum.has_value ());
> +  gdb_assert (svg_regnum.has_value ());
> +  gdb_assert (svcr_regnum.has_value ());

By changing to find_regno() then this gdb_assert() becomes unnecessary.

> +
> +  /* Update the register cache.  aarch64_za_regs_copy_to_reg_buf handles
> +     fetching the NT_ARM_ZA state from thread TID.  */
> +  aarch64_za_regs_copy_to_reg_buf (tid, regcache, *za_regnum, *svg_regnum,
> +				   *svcr_regnum);
> +}
> +
> +/* Wrapper for aarch64_za_regs_copy_from_reg_buf, to help copying NT_ARM_ZA
> +   state from the register cache to the thread (BUF).  */
> +
> +static void
> +aarch64_za_regs_copy_from_regcache (struct regcache *regcache, void *buf)
> +{
> +  int tid = lwpid_of (current_thread);
> +
> +  gdb::optional<int> za_regnum
> +    = find_regno_no_throw (regcache->tdesc, "za");
> +  gdb::optional<int> svg_regnum
> +    = find_regno_no_throw (regcache->tdesc, "svg");
> +  gdb::optional<int> svcr_regnum
> +    = find_regno_no_throw (regcache->tdesc, "svcr");
> +
> +  gdb_assert (za_regnum.has_value ());
> +  gdb_assert (svg_regnum.has_value ());
> +  gdb_assert (svcr_regnum.has_value ());

Same comment about find_regno().

> +
> +  /* Update the thread NT_ARM_ZA state.  aarch64_za_regs_copy_from_reg_buf
> +     handles writing the ZA state back to thread TID.  */
> +  aarch64_za_regs_copy_from_reg_buf (tid, regcache, *za_regnum, *svg_regnum,
> +				     *svcr_regnum);
> +
> +  /* We need to return the expected data in BUF, so copy whatever the kernel
> +     already has to BUF.  */
> +
> +  /* Obtain a dump of ZA from ptrace.  */
> +  gdb::byte_vector za_state = aarch64_fetch_za_regset (tid);
> +  memcpy (buf, za_state.data (), za_state.size ());
> +}

-- 
Thiago