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x86/process/64: Use FSGSBASE instructions on thread copy and ptrace

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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@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1557309753-24073-9-git-send-email-chang.seok.bae@intel.com
Link: https://lkml.kernel.org/r/20200528201402.1708239-8-sashal@kernel.org
This commit is contained in:
Chang S. Bae 2020-05-28 16:13:53 -04:00 committed by Thomas Gleixner
parent 673903495c
commit 005f141e5d
2 changed files with 10 additions and 6 deletions
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10
arch/x86/kernel/process.c
View file

@ -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

6
arch/x86/kernel/process_64.c
View file

@ -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);