linux-kernel - Re: [PATCH v4 02/13] selftests/sgx: Produce static-pie executable for test enclave

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Message-ID: <ca765c3a-8457-81f0-614d-4165579bf034@cs.kuleuven.be>
Date:   Thu, 31 Aug 2023 10:49:24 +0200
From:   Jo Van Bulck <jo.vanbulck@...kuleuven.be>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v4 02/13] selftests/sgx: Produce static-pie executable for
 test enclave

On 29.08.23 12:55, Huang, Kai wrote:> Could you please add the linker 
error (as you mentioned in the v3) to the
> changelog to justify this code change?

Makes sense, done.

> And sigh.. I still don't quite understand why linker complains
> 
> 	lea	(encl_stack)(%rbx), %rax
> 
> because ....
> 
>>   	jmp encl_entry_core
>>   encl_dyn_entry:
>>   	# Entry point for dynamically created TCS page expected to follow
> 
> we have a
> 
> 	lea -1(%rbx), %rax
> 
> right here.
> 
> Can't the compiler/linker just treat it as an immediate just like -1?  :-(

I think the linker complains because with -static-pie -fPIE afaik all 
local symbols need to have RIP-relative addressing "encl_stack(%rip)".

Best,
Jo