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Message-ID: <20221003140109.jgn3per7vbthifn5@box.shutemov.name>
Date: Mon, 3 Oct 2022 17:01:09 +0300
From: "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>
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>,
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Balbir Singh <bsingharora@...il.com>,
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Cyrill Gorcunov <gorcunov@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
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Florian Weimer <fweimer@...hat.com>,
"H . J . Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
Jonathan Corbet <corbet@....net>,
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Randy Dunlap <rdunlap@...radead.org>,
"Ravi V . Shankar" <ravi.v.shankar@...el.com>,
Weijiang Yang <weijiang.yang@...el.com>,
joao.moreira@...el.com, John Allen <john.allen@....com>,
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Yu-cheng Yu <yu-cheng.yu@...el.com>,
Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH v2 07/39] x86/cet: Add user control-protection fault
handler
On Thu, Sep 29, 2022 at 03:29:04PM -0700, Rick Edgecombe wrote:
> +#else
> +static void do_user_control_protection_fault(struct pt_regs *regs,
> + unsigned long error_code)
> +{
> + WARN_ONCE(1, "User-mode control protection fault with shadow support disabled\n");
Why is this a warning, but runtime check for !X86_FEATURE_IBT and
!X86_FEATURE_SHSTK below is fatal?
> +}
> +#endif
> +
> +#ifdef CONFIG_X86_KERNEL_IBT
> +
> +static __ro_after_init bool ibt_fatal = true;
> +
> +extern void ibt_selftest_ip(void); /* code label defined in asm below */
>
> +static void do_kernel_control_protection_fault(struct pt_regs *regs)
> +{
> if (unlikely(regs->ip == (unsigned long)&ibt_selftest_ip)) {
> regs->ax = 0;
> return;
> @@ -283,9 +335,29 @@ static int __init ibt_setup(char *str)
> }
>
> __setup("ibt=", ibt_setup);
> -
> +#else
> +static void do_kernel_control_protection_fault(struct pt_regs *regs)
> +{
> + WARN_ONCE(1, "Kernel-mode control protection fault with IBT disabled\n");
Ditto.
> +}
> #endif /* CONFIG_X86_KERNEL_IBT */
>
> +#if defined(CONFIG_X86_KERNEL_IBT) || defined(CONFIG_X86_SHADOW_STACK)
> +DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)
> +{
> + if (!cpu_feature_enabled(X86_FEATURE_IBT) &&
> + !cpu_feature_enabled(X86_FEATURE_SHSTK)) {
> + pr_err("Unexpected #CP\n");
> + BUG();
> + }
> +
> + if (user_mode(regs))
> + do_user_control_protection_fault(regs, error_code);
> + else
> + do_kernel_control_protection_fault(regs);
> +}
> +#endif /* defined(CONFIG_X86_KERNEL_IBT) || defined(CONFIG_X86_SHADOW_STACK) */
> +
> #ifdef CONFIG_X86_F00F_BUG
> void handle_invalid_op(struct pt_regs *regs)
> #else
--
Kiryl Shutsemau / Kirill A. Shutemov
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