linux-kernel - Re: [PATCH v22 07/24] x86/sgx: Add wrappers for ENCLS leaf functions

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Date:   Tue, 8 Oct 2019 09:18:45 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org, akpm@...ux-foundation.org,
        dave.hansen@...el.com, nhorman@...hat.com, npmccallum@...hat.com,
        serge.ayoun@...el.com, shay.katz-zamir@...el.com,
        haitao.huang@...el.com, andriy.shevchenko@...ux.intel.com,
        tglx@...utronix.de, kai.svahn@...el.com, josh@...htriplett.org,
        luto@...nel.org, kai.huang@...el.com, rientjes@...gle.com,
        cedric.xing@...el.com
Subject: Re: [PATCH v22 07/24] x86/sgx: Add wrappers for ENCLS leaf functions

On Mon, Oct 07, 2019 at 09:04:05PM -0700, Sean Christopherson wrote:
> > BIT(30)
> 
> This is intentionally open coded so that it can be stringified in asm.

It stringifies just fine with the BIT() macro too:

# 187 "arch/x86/kernel/cpu/sgx/encls.h" 1
        1: .byte 0x0f, 0x01, 0xcf;
        2:
.section .fixup,"ax"
3: orl $((((1UL))) << (30)),%eax
   jmp 2b
.previous

and the resulting object:

Disassembly of section .fixup:

0000000000000000 <.fixup>:
   0:   0d 00 00 00 40          or     $0x40000000,%eax
   5:   e9 00 00 00 00          jmpq   a <__addressable_sgx_free_page107+0x2>

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette