The following commit has been merged into the x86/fsgsbase branch of tip: Commit-ID: 005f141e5d5e05d3986539567d0bc5aa2f4dc640 Gitweb: https://git.kernel.org/tip/005f141e5d5e05d3986539567d0bc5aa2f4dc640 Author: Chang S. Bae <chang.seok.bae@xxxxxxxxx> AuthorDate: Thu, 28 May 2020 16:13:53 -04:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Thu, 18 Jun 2020 15:47:02 +02:00 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 <luto@xxxxxxxxxx> Signed-off-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/1557309753-24073-9-git-send-email-chang.seok.bae@xxxxxxxxx Link: https://lkml.kernel.org/r/20200528201402.1708239-8-sashal@xxxxxxxxxx --- 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 f362ce0..216c88d 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -140,10 +140,12 @@ 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; + current_save_fsgs(); + p->thread.fsindex = current->thread.fsindex; + p->thread.fsbase = current->thread.fsbase; + p->thread.gsindex = current->thread.gsindex; + p->thread.gsbase = current->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 8ccc587..d618969 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -426,7 +426,8 @@ 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); @@ -440,7 +441,8 @@ 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);
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