From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Florian Weimer <fweimer@redhat.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
"Shanbhogue, Vedvyas" <vedvyas.shanbhogue@intel.com>,
"H.J. Lu via Libc-alpha" <libc-alpha@sourceware.org>,
Joseph Myers <joseph@codesourcery.com>
Subject: Re: [RFC] <sys/tagged-address.h>: An API for tagged address
Date: Mon, 22 Feb 2021 08:27:24 +0000 [thread overview]
Message-ID: <20210222082723.GH12795@arm.com> (raw)
In-Reply-To: <CAMe9rOrUm89Rnp2cPLe1h8Bav3pKnhxGk-OcUnNBR1+9Wac0xQ@mail.gmail.com>
The 02/18/2021 14:32, H.J. Lu wrote:
>
> We are working to enable LAM in glibc and GCC (HWASAN).
>
> 0. LAM is disabled when the process starts.
> 1. Define GNU property markers for LAM compatibility.
> 2. Update ld.so to support LAM.
> 3. Make libc.so LAM compatible (memmove).
if pointers to the same object always have the same tag,
then memmove should work without changes i think.
if such pointers can have different tags then all pointer
comparisions are problematic, not just memmove.
> 4. Provide an API to enable LAM.
>
> We noticed a few issues:
>
> 1. HWASAN should use the glibc API to enable tagged address
> since glibc must track the tagged address mask.
how does that mask work?
is it possible to set it to different values or just on/off?
> 2. set_tagged_address_mask shouldn't be allowed after
> pthread_create is called.
such api breaks software composability.
i don't have a good solution (other than libc doing an early
decision on its own).
> 3. After set_tagged_address_mask is called, can it be called
> again to change tagged address mask.
after tagged pointers escape it is unlikely that changing
settings works.
next prev parent reply other threads:[~2021-02-22 8:28 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-11 17:37 H.J. Lu
2021-02-11 20:28 ` Joseph Myers
2021-02-11 21:39 ` H.J. Lu
2021-02-12 9:43 ` Florian Weimer
2021-02-12 13:06 ` H.J. Lu
2021-02-17 18:43 ` H.J. Lu
2021-02-17 21:58 ` H.J. Lu
2021-02-18 13:24 ` Szabolcs Nagy
2021-02-18 13:28 ` Florian Weimer
2021-02-18 13:50 ` Szabolcs Nagy
2021-02-18 22:32 ` H.J. Lu
2021-02-22 8:27 ` Szabolcs Nagy [this message]
2021-02-22 13:57 ` H.J. Lu
2021-02-18 13:17 ` Szabolcs Nagy
2021-02-18 13:21 ` Florian Weimer
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