Messages in this thread Patch in this message | | | From | "Chang S. Bae" <> | Subject | [PATCH 12/15] x86/fsgsbase/64: When copying a thread, use FSGSBASE if enabled | Date | Mon, 19 Mar 2018 10:49:24 -0700 |
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When FSGSBASE enabled, copy real FS/GS base values instead of approximation.
Factor out to save_fsgs() does not yield the exact same behavior, because save_base_legacy() does not copy FS/GS base when 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: 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 7249a54..5aae132 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -491,10 +491,16 @@ 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 = rd_shadow_gsbase(); + } 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)); -- 2.7.4
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