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Message-ID: <882e400f-913b-4ed5-9611-ef87cd8b58b2@zytor.com>
Date: Sun, 28 Jan 2024 11:33:20 -0800
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Subject: Re: [PATCH 1/2] x86/fred: Fix build with clang
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To: "Li, Xin3" <xin3.li@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>, "bp@alien8.de" <bp@alien8.de>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "x86@kernel.org" <x86@kernel.org>, "luto@kernel.org" <luto@kernel.org>,
        "Shankar, Ravi V" <ravi.v.shankar@intel.com>,
        "andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>
References: <20240127093728.1323-1-xin3.li@intel.com>
 <20240127093728.1323-2-xin3.li@intel.com>
 <49BA730F-E9A0-44AA-AB62-D2F40C5C11DD@zytor.com>
 <SA1PR11MB6734916F2BB7E296A6FEE52EA8782@SA1PR11MB6734.namprd11.prod.outlook.com>
From: "H. Peter Anvin" <hpa@zytor.com>
In-Reply-To: <SA1PR11MB6734916F2BB7E296A6FEE52EA8782@SA1PR11MB6734.namprd11.prod.outlook.com>
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On 1/27/24 11:46, Li, Xin3 wrote:
>>> diff --git a/arch/x86/entry/entry_64_fred.S
>>> b/arch/x86/entry/entry_64_fred.S index eedf98de7538..5427e0da190d
>>> 100644
>>> --- a/arch/x86/entry/entry_64_fred.S
>>> +++ b/arch/x86/entry/entry_64_fred.S
>>> @@ -43,13 +43,12 @@ SYM_INNER_LABEL(asm_fred_exit_user,
>> SYM_L_GLOBAL)
>>> 	_ASM_EXTABLE_TYPE(1b, asm_fred_entrypoint_user, EX_TYPE_ERETU)
>>> SYM_CODE_END(asm_fred_entrypoint_user)
>>>
>>> -.fill asm_fred_entrypoint_kernel - ., 1, 0xcc
>>> -
>>> /*
>>>   * The new RIP value that FRED event delivery establishes is
>>>   * (IA32_FRED_CONFIG & ~FFFH) + 256 for events that occur in
>>>   * ring 0, i.e., asm_fred_entrypoint_user + 256.
>>>   */
>>> +	.fill asm_fred_entrypoint_user + 256 - ., 1, 0xcc
>>> 	.org asm_fred_entrypoint_user + 256
>>> SYM_CODE_START_NOALIGN(asm_fred_entrypoint_kernel)
>>> 	FRED_ENTER
>>
>> .fill and .org here are redundant; in fact, there two directives mean exactly the
>> same thing except that .org implicitly subtracts the current offset.
> 
> Ah, right, .fill already does the job!
> 
> I will remove .org.
> 

Incidentally, was there a problem with .org ..., 0xcc?

Not a criticism, I just want to know to better understand current 
binutils limitations.

	-hpa