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Re: [PATCH v5 13/31] linux-user: Explicitly untag memory management sysc
From: |
Peter Maydell |
Subject: |
Re: [PATCH v5 13/31] linux-user: Explicitly untag memory management syscalls |
Date: |
Mon, 8 Feb 2021 16:33:32 +0000 |
On Mon, 8 Feb 2021 at 14:10, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Wed, 3 Feb 2021 at 19:00, Richard Henderson
> <richard.henderson@linaro.org> wrote:
> >
> > We define target_mmap et al as untagged, so that they can be
> > used from the binary loaders. Explicitly call cpu_untagged_addr
> > for munmap, mprotect, mremap syscall entry points.
> >
> > Add a few comments for the syscalls that are exempted by the
> > kernel's tagged-address-abi.rst.
> >
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> > linux-user/syscall.c | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> > index 748893904e..4451f8e4f0 100644
> > --- a/linux-user/syscall.c
> > +++ b/linux-user/syscall.c
> > @@ -889,6 +889,8 @@ abi_long do_brk(abi_ulong new_brk)
> > abi_long mapped_addr;
> > abi_ulong new_alloc_size;
> >
> > + /* brk pointers are always untagged */
> > +
> > DEBUGF_BRK("do_brk(" TARGET_ABI_FMT_lx ") -> ", new_brk);
> >
> > if (!new_brk) {
>
> It's not clear to me from
> https://www.kernel.org/doc/Documentation/arm64/tagged-address-abi.rst
> whether brk() pointers are "always untagged", or only "always untagged
> when at stage 1 of relaxation"... Unlike shmat and shmdt pointers,
> they aren't listed in the section 3 "must be untagged regardless
> of the ABI relaxation" part of the doc. I've asked the kernel folks
> for clarification.
>
> Same applies to mmap() and mremap() new_address.
I got back the clarification: these should have been added to
the section 3 "always untagged" list (and they'll update the
kernel docs). So this patch is correct.
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
thanks
-- PMM
- [PATCH v5 00/31] target-arm: Implement ARMv8.5-MemTag, user mode, Richard Henderson, 2021/02/03
- [PATCH v5 01/31] tcg: Introduce target-specific page data for user-only, Richard Henderson, 2021/02/03
- [PATCH v5 05/31] exec: Improve types for guest_addr_valid, Richard Henderson, 2021/02/03
- [PATCH v5 06/31] linux-user: Check for overflow in access_ok, Richard Henderson, 2021/02/03
- [PATCH v5 02/31] linux-user: Introduce PAGE_ANON, Richard Henderson, 2021/02/03
- [PATCH v5 07/31] linux-user: Tidy VERIFY_READ/VERIFY_WRITE, Richard Henderson, 2021/02/03
- [PATCH v5 08/31] bsd-user: Tidy VERIFY_READ/VERIFY_WRITE, Richard Henderson, 2021/02/03
- [PATCH v5 10/31] linux-user: Fix guest_addr_valid vs reserved_va, Richard Henderson, 2021/02/03
- [PATCH v5 13/31] linux-user: Explicitly untag memory management syscalls, Richard Henderson, 2021/02/03
- [PATCH v5 03/31] exec: Use uintptr_t for guest_base, Richard Henderson, 2021/02/03
- [PATCH v5 12/31] exec: Use cpu_untagged_addr in g2h; split out g2h_untagged, Richard Henderson, 2021/02/03
- [PATCH v5 11/31] exec: Introduce cpu_untagged_addr, Richard Henderson, 2021/02/03
- [PATCH v5 19/31] linux-user: Handle tags in lock_user/unlock_user, Richard Henderson, 2021/02/03