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From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, Andy Lutomirski <luto@kernel.org>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Andi Kleen <ak@linux.intel.com>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>,
	"Chang S . Bae" <chang.seok.bae@intel.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: [RESEND PATCH v6 06/12] x86/fsgsbase/64: When copying a thread, use the FSGSBASE instructions if available
Date: Fri, 15 Mar 2019 13:06:39 -0700
Message-ID: <1552680405-5265-7-git-send-email-chang.seok.bae@intel.com> (raw)
In-Reply-To: <1552680405-5265-1-git-send-email-chang.seok.bae@intel.com>

Copy real FS/GSBASE values instead of approximation when FSGSBASE is
enabled.

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
---
 arch/x86/kernel/process_64.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index d3abe4748d8b..c4de0907d909 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -422,7 +422,8 @@ unsigned long x86_fsbase_read_task(struct task_struct *task)
 
 	if (task == current)
 		fsbase = x86_fsbase_read_cpu();
-	else if (task->thread.fsindex == 0)
+	else if (static_cpu_has(X86_FEATURE_FSGSBASE) ||
+		 (task->thread.fsindex == 0))
 		fsbase = task->thread.fsbase;
 	else
 		fsbase = x86_fsgsbase_read_task(task, task->thread.fsindex);
@@ -436,7 +437,8 @@ unsigned long x86_gsbase_read_task(struct task_struct *task)
 
 	if (task == current)
 		gsbase = x86_gsbase_read_cpu_inactive();
-	else if (task->thread.gsindex == 0)
+	else if (static_cpu_has(X86_FEATURE_FSGSBASE) ||
+		 (task->thread.gsindex == 0))
 		gsbase = task->thread.gsbase;
 	else
 		gsbase = x86_fsgsbase_read_task(task, task->thread.gsindex);
@@ -475,10 +477,11 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 	p->thread.sp = (unsigned long) fork_frame;
 	p->thread.io_bitmap_ptr = NULL;
 
-	savesegment(gs, p->thread.gsindex);
-	p->thread.gsbase = p->thread.gsindex ? 0 : me->thread.gsbase;
-	savesegment(fs, p->thread.fsindex);
-	p->thread.fsbase = p->thread.fsindex ? 0 : me->thread.fsbase;
+	save_fsgs(me);
+	p->thread.fsindex = me->thread.fsindex;
+	p->thread.fsbase = me->thread.fsbase;
+	p->thread.gsindex = me->thread.gsindex;
+	p->thread.gsbase = me->thread.gsbase;
 	savesegment(es, p->thread.es);
 	savesegment(ds, p->thread.ds);
 	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
-- 
2.19.1


  parent reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-15 20:06 [RESEND PATCH v6 00/12] x86: Enable FSGSBASE instructions Chang S. Bae
2019-03-15 20:06 ` [RESEND PATCH v6 01/12] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
2019-03-15 20:06 ` [RESEND PATCH v6 02/12] kbuild: Raise the minimum required binutils version to 2.21 Chang S. Bae
2019-03-15 20:06 ` [RESEND PATCH v6 03/12] x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions Chang S. Bae
2019-03-15 20:06 ` [RESEND PATCH v6 04/12] x86/fsgsbase/64: Enable FSGSBASE instructions in the helper functions Chang S. Bae
2019-03-25 11:38   ` Thomas Gleixner
2019-03-25 12:46     ` Thomas Gleixner
2019-03-25 13:05       ` Thomas Gleixner
2019-03-26  0:38     ` Andi Kleen
2019-03-26 15:01       ` New feature/ABI review process [was Re: [RESEND PATCH v6 04/12] x86/fsgsbase/64:..] Thomas Gleixner
2019-03-26 22:56         ` Andi Kleen
2019-03-27 21:15           ` Thomas Gleixner
2019-03-15 20:06 ` [RESEND PATCH v6 05/12] x86/fsgsbase/64: Preserve FS/GS state in __switch_to() if FSGSBASE is on Chang S. Bae
2019-03-15 20:06 ` Chang S. Bae [this message]
2019-03-15 20:06 ` [RESEND PATCH v6 07/12] x86/fsgsbase/64: Introduce the FIND_PERCPU_BASE macro Chang S. Bae
2019-03-25  9:02   ` Thomas Gleixner
2019-05-01 13:52     ` Bae, Chang Seok
2019-03-15 20:06 ` [RESEND PATCH v6 08/12] x86/fsgsbase/64: Use the per-CPU base as GSBASE at the paranoid_entry Chang S. Bae
2019-03-25  9:44   ` Thomas Gleixner
2019-04-05  8:35     ` Thomas Gleixner
2019-04-05 13:50       ` Andy Lutomirski
2019-05-01 13:52         ` Bae, Chang Seok
2019-05-01 17:40           ` Andy Lutomirski
2019-05-01 18:01             ` Bae, Chang Seok
     [not found]               ` <7029A32B-958E-4C1E-8B5F-D49BA68E4755@intel.com>
2019-05-01 20:25                 ` Andy Lutomirski
2019-05-01 21:04                   ` Bae, Chang Seok
2019-05-02  0:29                     ` Andy Lutomirski
2019-05-06 22:56     ` Bae, Chang Seok
2019-03-15 20:06 ` [RESEND PATCH v6 09/12] selftests/x86/fsgsbase: Test WRGSBASE Chang S. Bae
2019-03-15 20:06 ` [RESEND PATCH v6 10/12] x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit Chang S. Bae
2019-03-15 20:06 ` [RESEND PATCH v6 11/12] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Chang S. Bae
2019-03-15 20:06 ` [RESEND PATCH v6 12/12] x86/fsgsbase/64: Add documentation for FSGSBASE Chang S. Bae
2019-03-30 16:15   ` Randy Dunlap
2019-03-26  0:43 ` [RESEND PATCH v6 00/12] x86: Enable FSGSBASE instructions Andy Lutomirski

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