From: Alexander Popov <alex.popov@linux.com>
To: Dave Hansen <dave.hansen@linux.intel.com>,
kernel-hardening@lists.openwall.com,
Kees Cook <keescook@chromium.org>,
PaX Team <pageexec@freemail.hu>,
Brad Spengler <spender@grsecurity.net>,
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"H . Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
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x86@kernel.org, linux-kernel@vger.kernel.org
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 09:58:32 +0300 [thread overview]
Message-ID: <16a56461-6501-7eb9-e1a4-761c9eff9386@linux.com> (raw)
In-Reply-To: <77fab6ea-0bbf-d68b-a38e-3e22d1ae6093@linux.intel.com>
On 29.03.2018 01:55, Dave Hansen wrote:
> On 03/28/2018 12:57 PM, Alexander Popov wrote:
>> +.macro ERASE_KSTACK
>> +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
>> + PUSH_AND_CLEAR_REGS
>> + call erase_kstack
>> + POP_REGS
>> +#endif
>> +.endm
>
> Thanks again for the hard work to trim down the complexity of the
> assembly.
Hello Dave, thanks!
> 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.
Best regards,
Alexander
next prev parent reply other threads:[~2018-03-29 6:58 UTC|newest]
Thread overview: 14+ 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 [this message]
2018-03-29 13:51 ` Dave Hansen
[not found] ` <CAFUG7Cd7cSqSHCrqxKUFwBBQLuix0Mi5-=V6pq_U7KtFh20Kqg@mail.gmail.com>
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
2018-03-28 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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