Messages in this thread Patch in this message | | | From | "Chang S. Bae" <> | Subject | [PATCH v5 07/13] x86/fsgsbase/64: When copying a thread, use the FSGSBASE instructions if available | Date | Fri, 1 Feb 2019 12:53:13 -0800 |
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Copy real FS/GSBASE values instead of approximation when FSGSBASE is enabled.
Factoring out to save_fsgs() does not result in the same behavior because save_base_legacy() does not copy FS/GSBASE when the index is zero.
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Andi Kleen <ak@linux.intel.com> --- arch/x86/kernel/process_64.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index d8ade9530fdb..648e43b58c69 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -477,10 +477,16 @@ 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; + savesegment(gs, p->thread.gsindex); + if (static_cpu_has(X86_FEATURE_FSGSBASE)) { + p->thread.fsbase = rdfsbase(); + p->thread.gsbase = __rdgsbase_inactive(); + } else { + /* save_base_legacy() does not set base when index is zero. */ + p->thread.fsbase = p->thread.fsindex ? 0 : me->thread.fsbase; + p->thread.gsbase = p->thread.gsindex ? 0 : me->thread.gsbase; + } savesegment(es, p->thread.es); savesegment(ds, p->thread.ds); memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); -- 2.19.1
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