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From: Borislav Petkov <bp@alien8.de>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
	linux-sgx@vger.kernel.org, akpm@linux-foundation.org,
	dave.hansen@intel.com, sean.j.christopherson@intel.com,
	nhorman@redhat.com, npmccallum@redhat.com, serge.ayoun@intel.com,
	shay.katz-zamir@intel.com, haitao.huang@intel.com,
	andriy.shevchenko@linux.intel.com, tglx@linutronix.de,
	kai.svahn@intel.com, josh@joshtriplett.org, luto@kernel.org,
	kai.huang@intel.com, rientjes@google.com, cedric.xing@intel.com
Subject: Re: [PATCH v22 09/24] x86/sgx: Add functions to allocate and free EPC pages
Date: Sat, 5 Oct 2019 18:44:08 +0200
Message-ID: <20191005164408.GB25699@zn.tnic> (raw)
In-Reply-To: <20190903142655.21943-10-jarkko.sakkinen@linux.intel.com>

On Tue, Sep 03, 2019 at 05:26:40PM +0300, Jarkko Sakkinen wrote:
> Add functions for grabbing EPC pages into use:
> 
> * sgx_alloc_page(): Iterate the EPC sections and return the first free
>   page, or ERR_PTR(-ENOMEM) when no free pages are available.
> * __sgx_free_page(): Return the page into uninitialized state and move
>   it back to the corresponding EPC section structure. Issues WARN()
>   when EREMOVE fails.
> * sgx_free_page(): Return the page into uninitialized state and move
>   it back to the corresponding EPC section structure. Returns
>   ENCLS[EREMOVE] error code back to the caller.
> 
> [1] Intel SDM: 40.3 INTEL® SGX SYSTEM LEAF FUNCTION REFERENCE
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
>  arch/x86/kernel/cpu/sgx/main.c | 90 ++++++++++++++++++++++++++++++++++
>  arch/x86/kernel/cpu/sgx/sgx.h  |  4 ++
>  2 files changed, 94 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index e2317f6e4374..6b4727df72ca 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -9,6 +9,7 @@
>  #include <linux/sched/signal.h>
>  #include <linux/slab.h>
>  #include "arch.h"
> +#include "encls.h"
>  #include "sgx.h"
>  
>  struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];
> @@ -16,6 +17,95 @@ EXPORT_SYMBOL_GPL(sgx_epc_sections);
>  
>  int sgx_nr_epc_sections;
>  
> +static struct sgx_epc_page *sgx_section_get_page(

That fits into 80 cols (oh well, 81) and even if not, a trailing opening
arg brace is ugly.

> +	struct sgx_epc_section *section)
> +{
> +	struct sgx_epc_page *page;
> +
> +	if (!section->free_cnt)
> +		return NULL;
> +
> +	page = list_first_entry(&section->page_list,
> +				struct sgx_epc_page, list);

That fits in 80-cols too. Why break it?

> +	list_del_init(&page->list);
> +	section->free_cnt--;
> +	return page;
> +}
> +
> +/**
> + * sgx_alloc_page - Allocate an EPC page
> + *
> + * Try to grab a page from the free EPC page list.
> + *
> + * Return:
> + *   a pointer to a &struct sgx_epc_page instance,
> + *   -errno on error
> + */
> +struct sgx_epc_page *sgx_alloc_page(void)
> +{
> +	struct sgx_epc_section *section;
> +	struct sgx_epc_page *page;
> +	int i;
> +
> +	for (i = 0; i < sgx_nr_epc_sections; i++) {
> +		section = &sgx_epc_sections[i];
> +		spin_lock(&section->lock);
> +		page = sgx_section_get_page(section);
> +		spin_unlock(&section->lock);
> +
> +		if (page)
> +			return page;
> +	}
> +
> +	return ERR_PTR(-ENOMEM);
> +}
> +EXPORT_SYMBOL_GPL(sgx_alloc_page);

That export gets removed later too. But you know already...

> +
> +/**
> + * __sgx_free_page - Free an EPC page
> + * @page:	pointer a previously allocated EPC page
> + *
> + * EREMOVE an EPC page and insert it back to the list of free pages.
> + *
> + * Return:
> + *   0 on success
> + *   SGX error code if EREMOVE fails
> + */
> +int __sgx_free_page(struct sgx_epc_page *page)
> +{
> +	struct sgx_epc_section *section = sgx_epc_section(page);
> +	int ret;

Shouldn't you be grabbing the lock here already?

Or nothing can happen to that page from another thread after you
ENCLS[EREMOVE] it and before it is added to the ->page_list of the
section?

> +
> +	ret = __eremove(sgx_epc_addr(page));
> +	if (ret)
> +		return ret;
> +
> +	spin_lock(&section->lock);
> +	list_add_tail(&page->list, &section->page_list);
> +	section->free_cnt++;
> +	spin_unlock(&section->lock);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(__sgx_free_page);
> +
> +/**
> + * sgx_free_page - Free an EPC page and WARN on failure
> + * @page:	pointer to a previously allocated EPC page
> + *
> + * EREMOVE an EPC page and insert it back to the list of free pages, and WARN
> + * if EREMOVE fails.  For use when the call site cannot (or chooses not to)
> + * handle failure, i.e. the page is leaked on failure.
> + */
> +void sgx_free_page(struct sgx_epc_page *page)
> +{
> +	int ret;
> +
> +	ret = __sgx_free_page(page);
> +	WARN(ret > 0, "sgx: EREMOVE returned %d (0x%x)", ret, ret);

That will potentially flood dmesg. Why are we even accommodating such
callers? They either handle the error or they don't get to alloc EPC
pages. There's also __must_check with which you can enforce the error
code checking or we simply don't allow not handling failure. Fullstop.

Thx.

-- 
Regards/Gruss,
    Boris.

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

  reply index

Thread overview: 102+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-03 14:26 [PATCH v22 00/24] Intel SGX foundations Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 01/24] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits Jarkko Sakkinen
2019-09-24 15:28   ` Borislav Petkov
2019-09-24 16:11     ` Sean Christopherson
2019-09-24 16:25       ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 02/24] x86/cpufeatures: x86/msr: Intel SGX Launch Control " Jarkko Sakkinen
2019-09-24 15:52   ` Borislav Petkov
2019-09-24 20:22     ` Sean Christopherson
2019-09-25  8:51       ` Borislav Petkov
2019-09-25 17:18         ` Sean Christopherson
2019-09-25 18:31           ` Borislav Petkov
2019-09-25 19:08             ` Sean Christopherson
2019-09-27 16:11           ` Jarkko Sakkinen
2019-09-25 14:09     ` Jarkko Sakkinen
2019-09-25 14:10       ` Jarkko Sakkinen
2019-09-25 14:38         ` Jarkko Sakkinen
2019-09-25 15:19       ` Borislav Petkov
2019-09-25 16:49         ` Sean Christopherson
2019-09-25 17:28           ` Borislav Petkov
2019-09-25 18:18             ` Sean Christopherson
2019-09-03 14:26 ` [PATCH v22 03/24] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
2019-09-24 16:04   ` Borislav Petkov
2019-09-25 14:16     ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 04/24] x86/cpu/intel: Detect SGX supprt Jarkko Sakkinen
2019-09-24 16:13   ` Borislav Petkov
2019-09-24 17:43     ` Sean Christopherson
2019-09-24 18:21       ` Borislav Petkov
2019-09-25 14:46         ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 05/24] x86/sgx: Add ENCLS architectural error codes Jarkko Sakkinen
2019-09-27 10:20   ` Borislav Petkov
2019-09-27 16:08     ` Jarkko Sakkinen
2019-09-27 17:20       ` Sean Christopherson
2019-10-01 20:23         ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 06/24] x86/sgx: Add SGX microarchitectural data structures Jarkko Sakkinen
2019-09-27 16:27   ` Borislav Petkov
2019-10-01 19:10     ` Jarkko Sakkinen
2019-10-01 20:39     ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 07/24] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2019-10-04  9:45   ` Borislav Petkov
2019-10-04 18:56     ` Jarkko Sakkinen
2019-10-08  4:04     ` Sean Christopherson
2019-10-08  7:18       ` Borislav Petkov
2019-10-08 13:35         ` Sean Christopherson
2019-10-08 14:56           ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 08/24] x86/sgx: Enumerate and track EPC sections Jarkko Sakkinen
2019-10-05  9:26   ` Borislav Petkov
2019-10-07 11:58     ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 09/24] x86/sgx: Add functions to allocate and free EPC pages Jarkko Sakkinen
2019-10-05 16:44   ` Borislav Petkov [this message]
2019-10-07 14:50     ` Sean Christopherson
2019-10-08  9:09       ` Borislav Petkov
2019-10-08 13:31         ` Sean Christopherson
2019-10-07 17:55     ` Jarkko Sakkinen
2019-10-07 18:09       ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 10/24] x86/sgx: Add sgx_einit() for wrapping ENCLS[EINIT] Jarkko Sakkinen
2019-10-08 17:30   ` Borislav Petkov
2019-10-08 17:45     ` Sean Christopherson
2019-10-08 17:46       ` Sean Christopherson
2019-10-08 17:53         ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 11/24] mm: Introduce vm_ops->may_mprotect() Jarkko Sakkinen
2019-10-08 17:41   ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 12/24] x86/sgx: Linux Enclave Driver Jarkko Sakkinen
2019-10-08 17:59   ` Borislav Petkov
2019-10-08 18:17     ` Sean Christopherson
2019-10-08 19:19       ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 13/24] x86/sgx: Add provisioning Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 14/24] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 15/24] x86/sgx: ptrace() support for the SGX driver Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 16/24] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2019-10-02 23:18   ` Jarkko Sakkinen
2019-10-02 23:45     ` Jarkko Sakkinen
2019-10-04  0:03     ` Sean Christopherson
2019-10-04 18:49       ` Jarkko Sakkinen
2019-10-04  0:15     ` Sean Christopherson
2019-10-04 18:52       ` Jarkko Sakkinen
2019-10-05 15:54         ` Sean Christopherson
2019-10-07  7:57           ` Jarkko Sakkinen
2019-10-07  8:10             ` Jarkko Sakkinen
2019-10-07 12:04               ` Jarkko Sakkinen
2019-10-08  4:54                 ` Sean Christopherson
2019-10-05 18:39         ` Sean Christopherson
2019-10-07  8:01           ` Jarkko Sakkinen
2019-10-06 23:38         ` Jarkko Sakkinen
2019-10-06 23:40           ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 17/24] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 18/24] x86/traps: Attempt to fixup exceptions in vDSO before signaling Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 19/24] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 20/24] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 21/24] selftests/x86: Recurse into subdirectories Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 22/24] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 23/24] docs: x86/sgx: Document microarchitecture Jarkko Sakkinen
2019-09-27 18:15   ` Randy Dunlap
2019-09-03 14:26 ` [PATCH v22 24/24] docs: x86/sgx: Document kernel internals Jarkko Sakkinen
2019-09-27 17:07   ` Randy Dunlap
2019-10-01 19:34     ` Jarkko Sakkinen
2019-09-13 20:38 ` [PATCH v22 00/24] Intel SGX foundations Dave Hansen
2019-09-14 13:41   ` Jarkko Sakkinen
2019-09-14 15:32     ` Dave Hansen
2019-09-16  5:23       ` Jarkko Sakkinen
2019-09-24 17:20         ` Andy Lutomirski
2019-09-25 14:32           ` Jarkko Sakkinen
2019-10-02 23:42             ` Jarkko Sakkinen

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