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From: Borislav Petkov <bp@alien8.de>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: x86@kernel.org, linux-sgx@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Jethro Beekman <jethro@fortanix.com>,
	akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com,
	asapek@google.com, cedric.xing@intel.com,
	chenalexchen@google.com, conradparker@google.com,
	cyhanish@google.com, dave.hansen@intel.com,
	haitao.huang@intel.com, josh@joshtriplett.org,
	kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com,
	ludloff@google.com, luto@kernel.org, nhorman@redhat.com,
	npmccallum@redhat.com, puiterwijk@redhat.com,
	rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com
Subject: Re: [PATCH v33 15/21] x86/vdso: Add support for exception fixup in vDSO functions
Date: Mon, 29 Jun 2020 19:10:22 +0200
Message-ID: <20200629171022.GC32176@zn.tnic> (raw)
In-Reply-To: <20200617220844.57423-16-jarkko.sakkinen@linux.intel.com>

On Thu, Jun 18, 2020 at 01:08:37AM +0300, Jarkko Sakkinen wrote:
...
> intended benefit of massaging GCC's inlining algorithm is unlikely to
> realized in the vDSO any time soon, if ever.

That is a very good explanation and I would prefer if it would be in a
sgx-specific README or so instead of it getting lost in git...

> +bool fixup_vdso_exception(struct pt_regs *regs, int trapnr,
> +			  unsigned long error_code, unsigned long fault_addr)
> +{
> +	const struct vdso_image *image = current->mm->context.vdso_image;
> +	const struct vdso_exception_table_entry *extable;
> +	unsigned int nr_entries, i;
> +	unsigned long base;
> +
> +	/*
> +	 * Do not attempt to fixup #DB or #BP.  It's impossible to identify
> +	 * whether or not a #DB/#BP originated from within an SGX enclave and
> +	 * SGX enclaves are currently the only use case for vDSO fixup.
> +	 */

So this is all fine and dandy but nowhere do I see the code doing:

	if (am_I_an_sgx_enclave(tsk))
		fixup_vdso_exception()

because that vDSO exception fixup, albeit it looking kinda generic, is
SGX-only for now. So it should be designed to run only for SGX enclaves
for now.

Also, is there any particular reason for fixup_vdso_exception() to be in
arch/x86/entry/vdso/extable.c instead of in arch/x86/mm/extable.c?

I mean, it gets called by traps.c so it looks like normal kernel code to
me or am I missing some vdso magic?

And built only when CONFIG_INTEL_SGX is enabled.

And so on...

...

> diff --git a/arch/x86/entry/vdso/extable.h b/arch/x86/entry/vdso/extable.h
> new file mode 100644
> index 000000000000..aafdac396948
> --- /dev/null
> +++ b/arch/x86/entry/vdso/extable.h
> @@ -0,0 +1,29 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __VDSO_EXTABLE_H
> +#define __VDSO_EXTABLE_H
> +
> +/*
> + * Inject exception fixup for vDSO code.  Unlike normal exception fixup,
> + * vDSO uses a dedicated handler the addresses are relative to the overall
> + * exception table, not each individual entry.
> + */
> +#ifdef __ASSEMBLY__
> +#define _ASM_VDSO_EXTABLE_HANDLE(from, to)	\
> +	ASM_VDSO_EXTABLE_HANDLE from to
> +
> +.macro ASM_VDSO_EXTABLE_HANDLE from:req to:req
> +	.pushsection __ex_table, "a"
> +	.long (\from) - __ex_table
> +	.long (\to) - __ex_table
> +	.popsection
> +.endm
> +#else
> +#define _ASM_VDSO_EXTABLE_HANDLE(from, to)	\
> +	".pushsection __ex_table, \"a\"\n"      \
> +	".long (" #from ") - __ex_table\n"      \
> +	".long (" #to ") - __ex_table\n"        \
> +	".popsection\n"
> +#endif
> +
> +#endif /* __VDSO_EXTABLE_H */
> +

.git/rebase-apply/patch:122: new blank line at EOF.
+

Thx.

-- 
Regards/Gruss,
    Boris.

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

  reply index

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-17 22:08 [PATCH v33 00/21] Intel SGX foundations Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 01/21] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits Jarkko Sakkinen
2020-06-22 17:37   ` Borislav Petkov
2020-06-25  1:25     ` Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 02/21] x86/cpufeatures: x86/msr: Add Intel SGX Launch Control " Jarkko Sakkinen
2020-06-24 13:04   ` Borislav Petkov
2020-06-24 14:34     ` Sean Christopherson
2020-06-25  1:28       ` Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 03/21] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
2020-06-25  8:59   ` Borislav Petkov
2020-06-25 15:34     ` Sean Christopherson
2020-06-25 16:49       ` Borislav Petkov
2020-06-25 20:52     ` Jarkko Sakkinen
2020-06-25 21:11       ` Borislav Petkov
2020-06-26 13:34         ` Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 04/21] x86/sgx: Add SGX microarchitectural data structures Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 05/21] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 06/21] x86/cpu/intel: Detect SGX support Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 07/21] x86/cpu/intel: Add nosgx kernel parameter Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 08/21] x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections Jarkko Sakkinen
2020-06-25 10:14   ` Borislav Petkov
2020-06-25 20:11     ` Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 09/21] x86/sgx: Add __sgx_alloc_epc_page() and sgx_free_epc_page() Jarkko Sakkinen
2020-06-25 17:06   ` Borislav Petkov
2020-06-25 20:55     ` Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 10/21] mm: Introduce vm_ops->may_mprotect() Jarkko Sakkinen
2020-06-25 17:14   ` Borislav Petkov
2020-06-25 17:30     ` Matthew Wilcox
2020-06-25 18:06       ` Sean Christopherson
2020-06-25 22:40         ` Jarkko Sakkinen
2020-06-25 22:26     ` Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 11/21] x86/sgx: Linux Enclave Driver Jarkko Sakkinen
2020-06-25 17:23   ` Borislav Petkov
2020-06-25 18:34     ` Sean Christopherson
2020-06-25 18:45       ` Borislav Petkov
2020-06-26 14:19       ` Jarkko Sakkinen
2020-06-25 20:21     ` Jarkko Sakkinen
2020-06-25 20:25       ` Borislav Petkov
2020-06-26 13:40         ` Jarkko Sakkinen
2020-06-25 18:53   ` Borislav Petkov
2020-06-26 14:17     ` Jarkko Sakkinen
2020-06-26  9:14   ` Borislav Petkov
2020-06-26 14:16     ` Sean Christopherson
2020-06-26 14:20       ` Borislav Petkov
2020-07-03  3:09     ` Jarkko Sakkinen
2020-06-26 15:34   ` Borislav Petkov
2020-06-27 17:43   ` Borislav Petkov
2020-06-29 15:27     ` Sean Christopherson
2020-06-29 15:37       ` Borislav Petkov
2020-07-02  3:59   ` Sean Christopherson
2020-06-17 22:08 ` [PATCH v33 12/21] x86/sgx: Allow a limited use of ATTRIBUTE.PROVISIONKEY for attestation Jarkko Sakkinen
2020-06-29 16:02   ` Borislav Petkov
2020-06-29 22:04     ` Sean Christopherson
2020-06-30  8:49       ` Borislav Petkov
2020-06-30 14:20         ` Sean Christopherson
2020-06-30 17:13           ` Andy Lutomirski
2020-07-02 20:47         ` Dr. Greg
2020-07-03  2:43         ` Jarkko Sakkinen
2020-07-03  2:38       ` Jarkko Sakkinen
2020-07-03  2:32     ` Jarkko Sakkinen
2020-07-03  2:55       ` Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 13/21] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 14/21] x86/sgx: ptrace() support for the SGX driver Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 15/21] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2020-06-29 17:10   ` Borislav Petkov [this message]
2020-06-30  6:00     ` Sean Christopherson
2020-06-30  8:41       ` Borislav Petkov
2020-06-30 14:55         ` Sean Christopherson
2020-06-30 16:48         ` Andy Lutomirski
2020-06-30 17:23           ` Sean Christopherson
2020-07-02 12:52           ` Thomas Gleixner
2020-06-17 22:08 ` [PATCH v33 16/21] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 17/21] x86/traps: Attempt to fixup exceptions in vDSO before signaling Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 18/21] x86/vdso: Implement a vDSO for Intel SGX enclave call Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 19/21] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 20/21] docs: x86/sgx: Document SGX micro architecture and kernel internals Jarkko Sakkinen
2020-06-17 22:08 ` [PATCH v33 21/21] x86/sgx: Update MAINTAINERS Jarkko Sakkinen

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