Commit-ID: f60a83df4593c5e03e746ded66d8b436c4ad6e41 Gitweb: https://git.kernel.org/tip/f60a83df4593c5e03e746ded66d8b436c4ad6e41 Author: Chang S. Bae <chang.seok....@intel.com> AuthorDate: Wed, 8 May 2019 03:02:23 -0700 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Sat, 22 Jun 2019 11:38:53 +0200
x86/process/64: Use FSGSBASE instructions on thread copy and ptrace When FSGSBASE is enabled, copying threads and reading fsbase and gsbase using ptrace must read the actual values. When copying a thread, use save_fsgs() and copy the saved values. For ptrace, the bases must be read from memory regardless of the selector if FSGSBASE is enabled. [ tglx: Invoke __rdgsbase_inactive() with interrupts disabled ] [ luto: Massage changelog ] Suggested-by: Andy Lutomirski <l...@kernel.org> Signed-off-by: Chang S. Bae <chang.seok....@intel.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: "H . Peter Anvin" <h...@zytor.com> Cc: Andi Kleen <a...@linux.intel.com> Cc: Ravi Shankar <ravi.v.shan...@intel.com> Cc: H. Peter Anvin <h...@zytor.com> Link: https://lkml.kernel.org/r/1557309753-24073-9-git-send-email-chang.seok....@intel.com --- arch/x86/kernel/process_64.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 59013f480b86..8f239091c15d 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -245,13 +245,17 @@ static __always_inline void save_fsgs(struct task_struct *task) savesegment(fs, task->thread.fsindex); savesegment(gs, task->thread.gsindex); if (static_cpu_has(X86_FEATURE_FSGSBASE)) { + unsigned long flags; + /* * If FSGSBASE is enabled, we can't make any useful guesses * about the base, and user code expects us to save the current * value. Fortunately, reading the base directly is efficient. */ task->thread.fsbase = rdfsbase(); + local_irq_save(flags); task->thread.gsbase = __rdgsbase_inactive(); + local_irq_restore(flags); } else { save_base_legacy(task, task->thread.fsindex, FS); save_base_legacy(task, task->thread.gsindex, GS); @@ -433,7 +437,8 @@ 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); @@ -447,7 +452,8 @@ 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); @@ -487,10 +493,11 @@ 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));
