lkml.org 
[lkml]   [2019]   [Feb]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v5 07/13] x86/fsgsbase/64: When copying a thread, use the FSGSBASE instructions if available
Date
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
\
 
 \ /
  Last update: 2019-02-01 21:55    [W:0.167 / U:0.508 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site