Re: [PATCH v6 06/11] target/arm: Factor out code for setting MTE TCF0 field

["Alex Bennée" <alex.bennee@linaro.org>]

Gustavo Romero <gustavo.romero@linaro.org> writes:

> Hi Alex,
>
> On 6/28/24 9:14 AM, Alex Bennée wrote:
>> Gustavo Romero <gustavo.romero@linaro.org> writes:
>> 
>>> Factor out the code used for setting the MTE TCF0 field from the prctl
>>> code into a convenient function. Other subsystems, like gdbstub, need to
>>> set this field as well, so keep it as a separate function to avoid
>>> duplication and ensure consistency in how this field is set across the
>>> board.
>>>
>>> Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
>>> ---
>>>   linux-user/aarch64/meson.build       |  2 ++
>>>   linux-user/aarch64/mte_user_helper.c | 34 ++++++++++++++++++++++++++++
>>>   linux-user/aarch64/mte_user_helper.h | 25 ++++++++++++++++++++
>>>   linux-user/aarch64/target_prctl.h    | 22 ++----------------
>>>   4 files changed, 63 insertions(+), 20 deletions(-)
>>>   create mode 100644 linux-user/aarch64/mte_user_helper.c
>>>   create mode 100644 linux-user/aarch64/mte_user_helper.h
>>>
>>> diff --git a/linux-user/aarch64/meson.build b/linux-user/aarch64/meson.build
>>> index 248c578d15..f75bb3cd75 100644
>>> --- a/linux-user/aarch64/meson.build
>>> +++ b/linux-user/aarch64/meson.build
>>> @@ -9,3 +9,5 @@ vdso_le_inc = gen_vdso.process('vdso-le.so',
>>>                                  extra_args: ['-r', '__kernel_rt_sigreturn'])
>>>     linux_user_ss.add(when: 'TARGET_AARCH64', if_true:
>>> [vdso_be_inc, vdso_le_inc])
>>> +
>>> +linux_user_ss.add(when: 'TARGET_AARCH64', if_true: [files('mte_user_helper.c')])
>>> diff --git a/linux-user/aarch64/mte_user_helper.c b/linux-user/aarch64/mte_user_helper.c
>>> new file mode 100644
>>> index 0000000000..8be6deaf03
>>> --- /dev/null
>>> +++ b/linux-user/aarch64/mte_user_helper.c
>>> @@ -0,0 +1,34 @@
>>> +/*
>>> + * ARM MemTag convenience functions.
>>> + *
>>> + * This code is licensed under the GNU GPL v2 or later.
>>> + *
>>> + * SPDX-License-Identifier: LGPL-2.1-or-later
>>> + */
>>> +
>>> +#include <sys/prctl.h>
>> Aside from missing the osdep Phillipe pointed out including prctl.h
>> here
>> is very suspect as its a system header. I assume if we need
>> PR_MTE_TCF_SYNC we should hoist the definition that linux-user uses into
>> a common header.
> Other .c files include <sys/prctl.h> for other PR_ definitions. For example,
> syscall.c and elfload.c. Is this really a problem?

If your building on an arch that doesn't natively have MTE but you'll
run an aarch64 linux-user guest.

> I see that would be a
> problem when trying to build, for instance, aarch64-linux-user target on a
> BSD host, but we don't support it. Building *-linux-user target is only
> supported on Linux host, no?

True, but multiple libcs. Anyway I've fixed up and posted the maintainer
tree.

>
>
> Cheers,
> Gustavo

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro