Messages in this thread Patch in this message | | | From | Sasha Levin <> | Subject | [PATCH v10 13/18] x86/fsgsbase/64: Use FSGSBASE instructions on thread copy and ptrace | Date | Thu, 23 Apr 2020 19:22:02 -0400 |
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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> 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> Signed-off-by: Sasha Levin <sashal@kernel.org> --- 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
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