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 <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Dave Hansen <[email protected]> --- 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 1d975cadc256..71cc8abe208c 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -510,10 +510,16 @@ 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_inactive_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)); -- 2.19.1
