From: Jarkko Sakkinen <jarkko@kernel.org>
To: Reinette Chatre <reinette.chatre@intel.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Shuah Khan <shuah@kernel.org>,
"open list:INTEL SGX" <linux-sgx@vger.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/2] selftests/sgx: Use rip relative addressing for encl_stack
Date: Wed, 30 Mar 2022 17:54:14 +0300 [thread overview]
Message-ID: <YkRvFkEO8Ic1VdQ8@iki.fi> (raw)
In-Reply-To: <7b7732ec-c7ff-cf92-510f-64c83ed985cd@intel.com>
On Mon, Mar 28, 2022 at 02:49:04PM -0700, Reinette Chatre wrote:
> Hi Jarkko,
>
> On 3/22/2022 12:43 AM, Jarkko Sakkinen wrote:
> > Simplify the test_encl_bootstrap.S flow by using rip-relative addressing.
> > Compiler does the right thing here, and this removes dependency on where
> > TCS entries need to be located in the binary, i.e. allows the binary layout
> > changed freely in the future.
> >
> > Cc: Reinette Chatre <reinette.chatre@intel.com>
> > Cc: Dave Hansen <dave.hansen@linux.intel.com>
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> > tools/testing/selftests/sgx/test_encl_bootstrap.S | 6 +-----
> > 1 file changed, 1 insertion(+), 5 deletions(-)
> >
> > diff --git a/tools/testing/selftests/sgx/test_encl_bootstrap.S b/tools/testing/selftests/sgx/test_encl_bootstrap.S
> > index 82fb0dfcbd23..1c1b5c6c4ffe 100644
> > --- a/tools/testing/selftests/sgx/test_encl_bootstrap.S
> > +++ b/tools/testing/selftests/sgx/test_encl_bootstrap.S
> > @@ -40,11 +40,7 @@
> > .text
> >
> > encl_entry:
> > - # RBX contains the base address for TCS, which is the first address
> > - # inside the enclave for TCS #1 and one page into the enclave for
> > - # TCS #2. By adding the value of encl_stack to it, we get
> > - # the absolute address for the stack.
> > - lea (encl_stack)(%rbx), %rax
> > + lea (encl_stack)(%rip), %rax
> > xchg %rsp, %rax
> > push %rax
> >
>
> The goal of the above snippet is to set RSP to ensure that each thread has its own stack.
>
> Since EENTER computes RIP as EnclaveBase + TCS.OENTRY, by using offset from RIP this
> would result in all TCS with OENTRY of encl_entry to use the same stack, no?
>
> Could you please consider the following as an alternative:
> https://lore.kernel.org/lkml/65c137c875bd4da675eaba35316ff43d7cfd52f8.1644274683.git.reinette.chatre@intel.com/
>
> The idea in that patch is that a new TCS would always need to be accompanied by a
> dedicated stack so, at least for testing purposes, the TCS and stack can be dynamically
> allocated together with the TCS page following its stack. This seems much simpler
> to me and also makes the following patch unnecessary.
There's no better alternative than use rip. Compiler will fix it up.
So, no, I won't consider that. This a dead obvious change.
BR, Jarkko
next prev parent reply other threads:[~2022-03-30 14:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-22 7:43 [PATCH v2 1/2] selftests/sgx: Use rip relative addressing for encl_stack Jarkko Sakkinen
2022-03-22 7:43 ` [PATCH v2 2/2] selftests/sgx: Make TCS table relocatable Jarkko Sakkinen
2022-03-28 21:49 ` [PATCH v2 1/2] selftests/sgx: Use rip relative addressing for encl_stack Reinette Chatre
2022-03-30 14:54 ` Jarkko Sakkinen [this message]
2022-03-30 14:56 ` Jarkko Sakkinen
2022-03-30 17:40 ` Reinette Chatre
[not found] ` <f68d472877b7136c32d8770603a3de38de59c322.camel@kernel.org>
2022-03-30 19:22 ` Jarkko Sakkinen
2022-03-30 20:05 ` Reinette Chatre
2022-03-30 20:40 ` Jarkko Sakkinen
2022-03-30 21:29 ` Reinette Chatre
2022-03-30 22:30 ` Jarkko Sakkinen
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