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From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: linux-kernel@vger.kernel.org
Cc: ravi.v.shankar@intel.com, chang.seok.bae@intel.com,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Tony Luck <tony.luck@intel.com>, Andi Kleen <ak@linux.intel.com>
Subject: [PATCH v8 07/17] x86/fsgsbase/64: Use FSGSBASE instructions on thread copy and ptrace
Date: Thu, 12 Sep 2019 13:06:48 -0700	[thread overview]
Message-ID: <1568318818-4091-8-git-send-email-chang.seok.bae@intel.com> (raw)
In-Reply-To: <1568318818-4091-1-git-send-email-chang.seok.bae@intel.com>

When FSGSBASE is enabled, copying threads and reading FS/GS base using
ptrace must read the actual values.

When copying a thread, use fsgs_save() and copy the saved values. For
ptrace, the bases must be read from memory regardless of the selector
if FSGSBASE is enabled.

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
---

Changes from v7:
* No code change
* Massaged changelog by Andy Lutomirski
---
 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 4c388817..7e582be 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -429,7 +429,8 @@ 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);
@@ -443,7 +444,8 @@ 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);
@@ -483,10 +485,11 @@ 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));
-- 
2.7.4


  parent reply	other threads:[~2019-09-12 20:08 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-12 20:06 [PATCH v8 00/17] Enable FSGSBASE instructions Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 01/17] x86/ptrace: Prevent ptrace from clearing the FS/GS selector Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 02/17] selftests/x86/fsgsbase: Test GS selector on ptracer-induced GS base write Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 03/17] x86/cpu: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 04/17] x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 05/17] x86/fsgsbase/64: Enable FSGSBASE instructions in helper functions Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 06/17] x86/fsgsbase/64: Use FSGSBASE in switch_to() if available Chang S. Bae
2019-09-12 20:06 ` Chang S. Bae [this message]
2019-09-12 20:06 ` [PATCH v8 08/17] x86/entry/64: Clean up paranoid exit Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 09/17] x86/entry/64: Switch CR3 before SWAPGS in paranoid entry Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 10/17] x86/entry/64: Introduce the FIND_PERCPU_BASE macro Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 11/17] x86/entry/64: Handle FSGSBASE enabled paranoid entry/exit Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 12/17] x86/entry/64: Document GSBASE handling in the paranoid path Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 13/17] x86/speculation/swapgs: Check FSGSBASE in enabling SWAPGS mitigation Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 14/17] selftests/x86/fsgsbase: Test ptracer-induced GS base write with FSGSBASE Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 15/17] x86/fsgsbase/64: Enable FSGSBASE on 64bit by default and add a chicken bit Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 16/17] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Chang S. Bae
2019-09-12 20:06 ` [PATCH v8 17/17] Documentation/x86/64: Add documentation for GS/FS addressing mode Chang S. Bae
2019-09-27 21:25   ` Randy Dunlap
2019-09-27 21:50     ` Bae, Chang Seok
2019-09-13  4:10 ` [PATCH v8 00/17] Enable FSGSBASE instructions Andy Lutomirski
2019-09-16  9:21   ` Thomas Gleixner
2019-09-18 21:02   ` Bae, Chang Seok

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