linux-kernel - Re: [PATCH v17 04/26] x86/cpufeatures: Introduce X86_FEATURE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <7def977d-ce6b-e9b4-ea4a-467a9d652147@intel.com>
Date:   Mon, 11 Jan 2021 12:25:07 -0800
From:   "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>
Subject: Re: [PATCH v17 04/26] x86/cpufeatures: Introduce X86_FEATURE_CET and
 setup functions

On 1/11/2021 9:56 AM, Borislav Petkov wrote:
> On Tue, Dec 29, 2020 at 01:30:31PM -0800, Yu-cheng Yu wrote:
>> @@ -895,6 +903,12 @@ static void init_speculation_control(struct cpuinfo_x86 *c)
>>   	}
>>   }
>>   
>> +static void init_cet_features(struct cpuinfo_x86 *c)
>> +{
>> +	if (cpu_has(c, X86_FEATURE_SHSTK) || cpu_has(c, X86_FEATURE_IBT))
>> +		set_cpu_cap(c, X86_FEATURE_CET);
>> +}
> 
> No need for that function - just add this two-liner to bsp_init_intel()
> and not in get_cpu_cap().
> 

I will move these to bsp_init_intel(), and change to:

if (cpu_has(c, X86_FEATURE_SHSTK) || cpu_has(c, X86_FEATURE_IBT))
	setup_force_cpu_cap(X86_FEATURE_CET);

>> +static void adjust_combined_cpu_features(void)
>> +{
>> +#ifdef CONFIG_X86_CET_USER
>> +	if (test_bit(X86_FEATURE_SHSTK, (unsigned long *)cpu_caps_cleared) &&
>> +	    test_bit(X86_FEATURE_IBT, (unsigned long *)cpu_caps_cleared))
>> +		setup_clear_cpu_cap(X86_FEATURE_CET);
>> +#endif
> 
> There's no need for this function...
> 
>> +}
>> +
>>   /*
>>    * We parse cpu parameters early because fpu__init_system() is executed
>>    * before parse_early_param().
>> @@ -1252,9 +1276,19 @@ static void __init cpu_parse_early_param(void)
>>   	if (cmdline_find_option_bool(boot_command_line, "noxsaves"))
>>   		setup_clear_cpu_cap(X86_FEATURE_XSAVES);
>>   
>> +	/*
>> +	 * CET states are XSAVES states and options must be parsed early.
>> +	 */
>> +#ifdef CONFIG_X86_CET_USER
>> +	if (cmdline_find_option_bool(boot_command_line, "no_user_shstk"))
>> +		setup_clear_cpu_cap(X86_FEATURE_SHSTK);
> 
> ... when you can do
> 
> 	setup_clear_cpu_cap(X86_FEATURE_CET);
> 
> here and...
> 
>> +	if (cmdline_find_option_bool(boot_command_line, "no_user_ibt"))
>> +		setup_clear_cpu_cap(X86_FEATURE_IBT);
> 
> ... here.
>

Two problems here.  X86_FEATURE_CET indicates either CET features is 
enabled, not both.  Also, "clearcpuid" can has CET features.  However, 
since X86_FEATURE_CET is now set in bsp_init_intel() (after 
cpu_parse_early_params()), I think, adjust_combined_cpu_features() can 
be removed.  I will test it.

--
Thanks,
Yu-cheng