Linux-Sgx Archive on lore.kernel.org
 help / color / Atom feed
From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: linux-kernel@vger.kernel.org, x86@kernel.org, linux-sgx@vger.kernel.org
Cc: akpm@linux-foundation.org, dave.hansen@intel.com,
	sean.j.christopherson@intel.com, nhorman@redhat.com,
	npmccallum@redhat.com, haitao.huang@intel.com,
	andriy.shevchenko@linux.intel.com, tglx@linutronix.de,
	kai.svahn@intel.com, bp@alien8.de, josh@joshtriplett.org,
	luto@kernel.org, kai.huang@intel.com, rientjes@google.com,
	cedric.xing@intel.com, puiterwijk@redhat.com,
	Andy Lutomirski <luto@amacapital.net>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Subject: [PATCH v25 18/21] x86/traps: Attempt to fixup exceptions in vDSO before signaling
Date: Tue,  4 Feb 2020 08:05:42 +0200
Message-ID: <20200204060545.31729-19-jarkko.sakkinen@linux.intel.com> (raw)
In-Reply-To: <20200204060545.31729-1-jarkko.sakkinen@linux.intel.com>

From: Sean Christopherson <sean.j.christopherson@intel.com>

vDSO functions can now leverage an exception fixup mechanism similar to
kernel exception fixup.  For vDSO exception fixup, the initial user is
Intel's Software Guard Extensions (SGX), which will wrap the low-level
transitions to/from the enclave, i.e. EENTER and ERESUME instructions,
in a vDSO function and leverage fixup to intercept exceptions that would
otherwise generate a signal.  This allows the vDSO wrapper to return the
fault information directly to its caller, obviating the need for SGX
applications and libraries to juggle signal handlers.

Attempt to fixup vDSO exceptions immediately prior to populating and
sending signal information.  Except for the delivery mechanism, an
exception in a vDSO function should be treated like any other exception
in userspace, e.g. any fault that is successfully handled by the kernel
should not be directly visible to userspace.

Although it's debatable whether or not all exceptions are of interest to
enclaves, defer to the vDSO fixup to decide whether to do fixup or
generate a signal.  Future users of vDSO fixup, if there ever are any,
will undoubtedly have different requirements than SGX enclaves, e.g. the
fixup vs. signal logic can be made function specific if/when necessary.

Suggested-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 arch/x86/kernel/traps.c | 14 ++++++++++++++
 arch/x86/mm/fault.c     |  8 ++++++++
 2 files changed, 22 insertions(+)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 6ef00eb6fbb9..a814b1aea94d 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -56,6 +56,7 @@
 #include <asm/umip.h>
 #include <asm/insn.h>
 #include <asm/insn-eval.h>
+#include <asm/vdso.h>
 
 #ifdef CONFIG_X86_64
 #include <asm/x86_init.h>
@@ -205,6 +206,9 @@ do_trap_no_signal(struct task_struct *tsk, int trapnr, const char *str,
 		tsk->thread.error_code = error_code;
 		tsk->thread.trap_nr = trapnr;
 		die(str, regs, error_code);
+	} else {
+		if (fixup_vdso_exception(regs, trapnr, error_code, 0))
+			return 0;
 	}
 
 	/*
@@ -518,6 +522,9 @@ dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code)
 		tsk->thread.error_code = error_code;
 		tsk->thread.trap_nr = X86_TRAP_GP;
 
+		if (fixup_vdso_exception(regs, X86_TRAP_GP, error_code, 0))
+			return;
+
 		show_signal(tsk, SIGSEGV, "", desc, regs, error_code);
 		force_sig(SIGSEGV);
 
@@ -762,6 +769,10 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
 							SIGTRAP) == NOTIFY_STOP)
 		goto exit;
 
+	if (user_mode(regs) &&
+	    fixup_vdso_exception(regs, X86_TRAP_DB, error_code, 0))
+		goto exit;
+
 	/*
 	 * Let others (NMI) know that the debug stack is in use
 	 * as we may switch to the interrupt stack.
@@ -842,6 +853,9 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)
 	if (!si_code)
 		return;
 
+	if (fixup_vdso_exception(regs, trapnr, error_code, 0))
+		return;
+
 	force_sig_fault(SIGFPE, si_code,
 			(void __user *)uprobe_get_trap_addr(regs));
 }
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 6b662d272af6..42965b47b52f 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -30,6 +30,7 @@
 #include <asm/desc.h>			/* store_idt(), ...		*/
 #include <asm/cpu_entry_area.h>		/* exception stack		*/
 #include <asm/pgtable_areas.h>		/* VMALLOC_START, ...		*/
+#include <asm/vdso.h>			/* fixup_vdso_exception()	*/
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/exceptions.h>
@@ -902,6 +903,10 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 
 		sanitize_error_code(address, &error_code);
 
+		if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code,
+		    address))
+			return;
+
 		if (likely(show_unhandled_signals))
 			show_signal_msg(regs, error_code, address, tsk);
 
@@ -1019,6 +1024,9 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 
 	sanitize_error_code(address, &error_code);
 
+	if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
+		return;
+
 	set_signal_archinfo(address, error_code);
 
 #ifdef CONFIG_MEMORY_FAILURE
-- 
2.20.1


  parent reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-04  6:05 [PATCH v25 00/21] Intel SGX foundations Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 01/21] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 02/21] x86/cpufeatures: x86/msr: Intel SGX Launch Control " Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 03/21] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 04/21] x86/sgx: Add SGX microarchitectural data structures Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 05/21] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 06/21] x86/cpu/intel: Detect SGX supprt Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 07/21] x86/sgx: Enumerate and track EPC sections Jarkko Sakkinen
2020-02-05 19:57   ` Sean Christopherson
2020-02-05 23:11     ` Jarkko Sakkinen
2020-02-06 15:34       ` Jarkko Sakkinen
2020-02-06 15:35     ` Jarkko Sakkinen
2020-02-06 15:55       ` Sean Christopherson
2020-02-04  6:05 ` [PATCH v25 08/21] x86/sgx: Add functions to allocate and free EPC pages Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 09/21] mm: Introduce vm_ops->may_mprotect() Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 10/21] x86/sgx: Linux Enclave Driver Jarkko Sakkinen
2020-02-04  6:18   ` Jarkko Sakkinen
2020-02-05 15:58   ` Haitao Huang
2020-02-07 17:03   ` Haitao Huang
2020-02-04  6:05 ` [PATCH v25 11/21] selftests/x86: Recurse into subdirectories Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 12/21] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 13/21] x86/sgx: Add provisioning Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 14/21] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 15/21] x86/sgx: ptrace() support for the SGX driver Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 16/21] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 17/21] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2020-02-04  6:05 ` Jarkko Sakkinen [this message]
2020-02-04  6:05 ` [PATCH v25 19/21] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 20/21] selftests/x86: Add vDSO selftest for SGX Jarkko Sakkinen
2020-02-04  6:05 ` [PATCH v25 21/21] docs: x86/sgx: Document SGX micro architecture and kernel internals Jarkko Sakkinen
2020-02-05 17:54   ` Randy Dunlap
2020-02-05 23:07     ` Jarkko Sakkinen
2020-02-05 23:10       ` Randy Dunlap
2020-02-06 14:50         ` Jarkko Sakkinen
2020-02-04 15:11 ` [PATCH v25 00/21] Intel SGX foundations Sean Christopherson
2020-02-05 21:59   ` Jarkko Sakkinen
2020-02-05 23:09     ` Jarkko Sakkinen
2020-02-05 16:01 ` Haitao Huang
2020-02-05 22:01   ` Jarkko Sakkinen

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200204060545.31729-19-jarkko.sakkinen@linux.intel.com \
    --to=jarkko.sakkinen@linux.intel.com \
    --cc=akpm@linux-foundation.org \
    --cc=andriy.shevchenko@linux.intel.com \
    --cc=bp@alien8.de \
    --cc=cedric.xing@intel.com \
    --cc=dave.hansen@intel.com \
    --cc=haitao.huang@intel.com \
    --cc=josh@joshtriplett.org \
    --cc=kai.huang@intel.com \
    --cc=kai.svahn@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-sgx@vger.kernel.org \
    --cc=luto@amacapital.net \
    --cc=luto@kernel.org \
    --cc=nhorman@redhat.com \
    --cc=npmccallum@redhat.com \
    --cc=puiterwijk@redhat.com \
    --cc=rientjes@google.com \
    --cc=sean.j.christopherson@intel.com \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Sgx Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-sgx/0 linux-sgx/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-sgx linux-sgx/ https://lore.kernel.org/linux-sgx \
		linux-sgx@vger.kernel.org
	public-inbox-index linux-sgx

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-sgx


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git