Received-SPF: pass (google.com: domain of linux-kernel+bounces-140747-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Received-SPF: Pass (protection.outlook.com: domain of amd.com designates
 165.204.84.17 as permitted sender) receiver=protection.outlook.com;
 client-ip=165.204.84.17; helo=SATLEXMB03.amd.com; pr=C
Message-ID: <74465ac2-0060-4047-97d7-acadcdff4cd4@amd.com>
Date: Thu, 11 Apr 2024 11:26:11 -0400
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH 2/5] x86/pvh: Make PVH entrypoint PIC for x86-64
To: Brian Gerst <brgerst@gmail.com>
CC: Juergen Gross <jgross@suse.com>, Boris Ostrovsky
	<boris.ostrovsky@oracle.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo
 Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Dave Hansen
	<dave.hansen@linux.intel.com>, <x86@kernel.org>, "H. Peter Anvin"
	<hpa@zytor.com>, Stefano Stabellini <sstabellini@kernel.org>, Oleksandr
 Tyshchenko <oleksandr_tyshchenko@epam.com>, Paolo Bonzini
	<pbonzini@redhat.com>, <xen-devel@lists.xenproject.org>,
	<linux-kernel@vger.kernel.org>
References: <20240410194850.39994-1-jason.andryuk@amd.com>
 <20240410194850.39994-3-jason.andryuk@amd.com>
 <CAMzpN2h6S69bOLXCUhmkVJErvoKxq-wPmfoaqR7eGHYLgirn+Q@mail.gmail.com>
Content-Language: en-US
From: Jason Andryuk <jason.andryuk@amd.com>
In-Reply-To: <CAMzpN2h6S69bOLXCUhmkVJErvoKxq-wPmfoaqR7eGHYLgirn+Q@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 8bit
Received-SPF: None (SATLEXMB03.amd.com: jason.andryuk@amd.com does not
 designate permitted sender hosts)
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Apr 2024 15:26:15.2440
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 5bcd1676-4bda-40f5-8697-08dc5a3bba2b
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB03.amd.com]
X-MS-Exchange-CrossTenant-AuthSource:
	BL02EPF00021F68.namprd02.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL3PR12MB6401

On 2024-04-10 17:00, Brian Gerst wrote:
> On Wed, Apr 10, 2024 at 3:50 PM Jason Andryuk <jason.andryuk@amd.com> wrote:

>>          /* 64-bit entry point. */
>>          .code64
>>   1:
>> +       UNWIND_HINT_END_OF_STACK
>> +
>>          /* Set base address in stack canary descriptor. */
>>          mov $MSR_GS_BASE,%ecx
>> -       mov $_pa(canary), %eax
>> +       leal rva(canary)(%ebp), %eax
> 
> Since this is in 64-bit mode, RIP-relative addressing can be used.
> 
>>          xor %edx, %edx
>>          wrmsr
>>
>>          call xen_prepare_pvh
>>
>>          /* startup_64 expects boot_params in %rsi. */
>> -       mov $_pa(pvh_bootparams), %rsi
>> -       mov $_pa(startup_64), %rax
>> +       lea rva(pvh_bootparams)(%ebp), %rsi
>> +       lea rva(startup_64)(%ebp), %rax
> 
> RIP-relative here too.

Yes, thanks for catching that.  With the RIP-relative conversion, there 
is now:
vmlinux.o: warning: objtool: pvh_start_xen+0x10d: relocation to !ENDBR: 
startup_64+0x0

I guess RIP-relative made it visible.  That can be quieted by adding 
ANNOTATE_NOENDBR to startup_64.

Thanks,
Jason