From: Dave Hansen <dave.hansen@linux.intel.com>
To: alex.popov@linux.com, kernel-hardening@lists.openwall.com,
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Subject: Re: [PATCH RFC v10 2/6] x86/entry: Add STACKLEAK erasing the kernel stack at the end of syscalls
Date: Thu, 29 Mar 2018 06:51:23 -0700 [thread overview]
Message-ID: <ad614e86-7e39-e9b7-4a8f-3ea1f5a7b61d@linux.intel.com> (raw)
In-Reply-To: <16a56461-6501-7eb9-e1a4-761c9eff9386@linux.com>
On 03/28/2018 11:58 PM, Alexander Popov wrote:
>> I noticed the 64-bit version saves/restores registers while
>> the 32-bit version doesn't. What's the reasoning there?
> When erase_kstack() is called from the trampoline stack, it must save and
> restore any modified registers, since all registers except RDI are live
> (prepared for the userspace).
>
> When erase_kstack() is called from the thread stack, it can clobber registers
> according the function call convention without any harm.
Oh, and since there's no 32-bit trampoline stack, we don't need it on
32-bit?
If end up reposting this set again, could you add a few comments about
this around the ERASE_KSTACK macro definitions, or perhaps the call
sites? You might even want to call them ERASE_KSTACK_CLOBBER (for
32-bit) and ERASE_KSTACK_NOCLOBBER (for 64-bit) to make this more clear.
next prev parent reply other threads:[~2018-03-29 13:51 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-28 19:57 [PATCH RFC v10 0/6] Introduce the STACKLEAK feature and a test for it Alexander Popov
2018-03-28 19:57 ` [PATCH RFC v10 1/6] gcc-plugins: Clean up the cgraph_create_edge* macros Alexander Popov
2018-03-28 19:57 ` [PATCH RFC v10 2/6] x86/entry: Add STACKLEAK erasing the kernel stack at the end of syscalls Alexander Popov
2018-03-28 22:55 ` Dave Hansen
2018-03-29 6:58 ` Alexander Popov
2018-03-29 13:51 ` Dave Hansen [this message]
[not found] ` <CAFUG7Cd7cSqSHCrqxKUFwBBQLuix0Mi5-=V6pq_U7KtFh20Kqg@mail.gmail.com>
2018-03-29 20:56 ` Alexander Popov
2018-03-29 20:56 ` Alexander Popov
2018-03-29 21:00 ` Dave Hansen
[not found] ` <alpine.DEB.2.10.1803291137150.27913@vshiva-Udesk>
2018-03-29 21:34 ` Alexander Popov
2018-03-29 21:34 ` Alexander Popov
2018-03-28 19:57 ` [PATCH RFC v10 3/6] gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack Alexander Popov
2018-03-28 19:57 ` [PATCH RFC v10 4/6] lkdtm: Add a test for STACKLEAK Alexander Popov
2018-03-28 19:57 ` [PATCH RFC v10 5/6] fs/proc: Show STACKLEAK metrics in the /proc file system Alexander Popov
2018-03-28 19:57 ` [PATCH RFC v10 6/6] doc: self-protection: Add information about STACKLEAK feature Alexander Popov
2018-03-28 20:13 ` [PATCH RFC v10 0/6] Introduce the STACKLEAK feature and a test for it Kees Cook
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