From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, tglx@linutronix.de, bp@alien8.de,
luto@kernel.org
Cc: hpa@zytor.com, dave.hansen@intel.com, tony.luck@intel.com,
ak@linux.intel.com, ravi.v.shankar@intel.com,
chang.seok.bae@intel.com, Sasha Levin <sashal@kernel.org>
Subject: [PATCH v11 13/18] x86/fsgsbase/64: Use FSGSBASE instructions on thread copy and ptrace
Date: Sat, 9 May 2020 13:36:50 -0400 [thread overview]
Message-ID: <20200509173655.13977-14-sashal@kernel.org> (raw)
In-Reply-To: <20200509173655.13977-1-sashal@kernel.org>
From: "Chang S. Bae" <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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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>
---
arch/x86/kernel/process.c | 10 ++++++----
arch/x86/kernel/process_64.c | 6 ++++--
2 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 9da70b279dad8..3ebb56cc2cfee 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -127,6 +127,7 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
struct inactive_task_frame *frame;
struct fork_frame *fork_frame;
struct pt_regs *childregs;
+ struct task_struct *me = current;
int ret = 0;
childregs = task_pt_regs(p);
@@ -140,10 +141,11 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
#ifdef CONFIG_X86_64
- savesegment(gs, p->thread.gsindex);
- p->thread.gsbase = p->thread.gsindex ? 0 : current->thread.gsbase;
- savesegment(fs, p->thread.fsindex);
- p->thread.fsbase = p->thread.fsindex ? 0 : current->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);
#else
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 4be88124d81ea..57cdbbb0381ac 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -346,7 +346,8 @@ 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);
@@ -360,7 +361,8 @@ 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);
--
2.20.1
next prev parent reply other threads:[~2020-05-09 17:37 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-09 17:36 [PATCH v11 00/18] Enable FSGSBASE instructions Sasha Levin
2020-05-09 17:36 ` [PATCH v11 01/18] x86/ptrace: Prevent ptrace from clearing the FS/GS selector Sasha Levin
2020-05-09 17:36 ` [PATCH v11 02/18] selftests/x86/fsgsbase: Test GS selector on ptracer-induced GS base write Sasha Levin
2020-05-09 17:36 ` [PATCH v11 03/18] x86/cpu: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Sasha Levin
2020-05-09 17:36 ` [PATCH v11 04/18] x86/entry/64: Clean up paranoid exit Sasha Levin
2020-05-09 17:36 ` [PATCH v11 05/18] x86/entry/64: Switch CR3 before SWAPGS in paranoid entry Sasha Levin
2020-05-09 17:36 ` [PATCH v11 06/18] x86/entry/64: Introduce the FIND_PERCPU_BASE macro Sasha Levin
2020-05-09 17:36 ` [PATCH v11 07/18] x86/entry/64: Handle FSGSBASE enabled paranoid entry/exit Sasha Levin
2020-05-09 17:36 ` [PATCH v11 08/18] x86/entry/64: Document GSBASE handling in the paranoid path Sasha Levin
2020-05-09 17:36 ` [PATCH v11 09/18] x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions Sasha Levin
2020-05-09 17:36 ` [PATCH v11 10/18] x86/fsgsbase/64: Enable FSGSBASE instructions in helper functions Sasha Levin
2020-05-09 17:36 ` [PATCH v11 11/18] x86/fsgsbase/64: Use FSGSBASE in switch_to() if available Sasha Levin
2020-05-09 17:36 ` [PATCH v11 12/18] x86/fsgsbase/64: move save_fsgs to header file Sasha Levin
2020-05-09 23:39 ` kbuild test robot
2020-05-09 17:36 ` Sasha Levin [this message]
2020-05-09 17:36 ` [PATCH v11 14/18] x86/speculation/swapgs: Check FSGSBASE in enabling SWAPGS mitigation Sasha Levin
2020-05-09 17:36 ` [PATCH v11 15/18] selftests/x86/fsgsbase: Test ptracer-induced GS base write with FSGSBASE Sasha Levin
2020-05-09 17:36 ` [PATCH v11 16/18] x86/fsgsbase/64: Enable FSGSBASE on 64bit by default and add a chicken bit Sasha Levin
2020-05-09 17:36 ` [PATCH v11 17/18] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Sasha Levin
2020-05-09 17:36 ` [PATCH v11 18/18] Documentation/x86/64: Add documentation for GS/FS addressing mode Sasha Levin
2020-05-10 1:40 ` [PATCH v11 00/18] Enable FSGSBASE instructions Dave Hansen
2020-05-10 14:16 ` Sasha Levin
2020-05-11 0:53 ` Andi Kleen
2020-05-11 4:47 ` Sasha Levin
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