Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 asm updates from Ingo Molnar:
 "The main changes in this cycle were:

   - MSR access API fixes and enhancements (Andy Lutomirski)

   - early exception handling improvements (Andy Lutomirski)

   - user-space FS/GS prctl usage fixes and improvements (Andy
     Lutomirski)

   - Remove the cpu_has_*() APIs and replace them with equivalents
     (Borislav Petkov)

   - task switch micro-optimization (Brian Gerst)

   - 32-bit entry code simplification (Denys Vlasenko)

   - enhance PAT handling in enumated CPUs (Toshi Kani)

  ... and lots of other cleanups/fixlets"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  x86/arch_prctl/64: Restore accidentally removed put_cpu() in ARCH_SET_GS
  x86/entry/32: Remove asmlinkage_protect()
  x86/entry/32: Remove GET_THREAD_INFO() from entry code
  x86/entry, sched/x86: Don't save/restore EFLAGS on task switch
  x86/asm/entry/32: Simplify pushes of zeroed pt_regs->REGs
  selftests/x86/ldt_gdt: Test set_thread_area() deletion of an active segment
  x86/tls: Synchronize segment registers in set_thread_area()
  x86/asm/64: Rename thread_struct's fs and gs to fsbase and gsbase
  x86/arch_prctl/64: Remove FSBASE/GSBASE < 4G optimization
  x86/segments/64: When load_gs_index fails, clear the base
  x86/segments/64: When loadsegment(fs, ...) fails, clear the base
  x86/asm: Make asm/alternative.h safe from assembly
  x86/asm: Stop depending on ptrace.h in alternative.h
  x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()
  x86/asm: Make sure verify_cpu() has a good stack
  x86/extable: Add a comment about early exception handlers
  x86/msr: Set the return value to zero when native_rdmsr_safe() fails
  x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y
  x86/paravirt: Add paravirt_{read,write}_msr()
  x86/msr: Carry on after a non-"safe" MSR access fails
  ...

1 files changed, 42 insertions, 0 deletions

diff --git a/arch/x86/kernel/tls.c b/arch/x86/kernel/tls.c
index 7fc5e843f247..9692a5e9fdab 100644
--- a/arch/x86/kernel/tls.c
+++ b/arch/x86/kernel/tls.c
@@ -114,6 +114,7 @@ int do_set_thread_area(struct task_struct *p, int idx,
 		       int can_allocate)
 {
 	struct user_desc info;
+	unsigned short __maybe_unused sel, modified_sel;
 
 	if (copy_from_user(&info, u_info, sizeof(info)))
 		return -EFAULT;
@@ -141,6 +142,47 @@ int do_set_thread_area(struct task_struct *p, int idx,
 
 	set_tls_desc(p, idx, &info, 1);
 
+	/*
+	 * If DS, ES, FS, or GS points to the modified segment, forcibly
+	 * refresh it.  Only needed on x86_64 because x86_32 reloads them
+	 * on return to user mode.
+	 */
+	modified_sel = (idx << 3) | 3;
+
+	if (p == current) {
+#ifdef CONFIG_X86_64
+		savesegment(ds, sel);
+		if (sel == modified_sel)
+			loadsegment(ds, sel);
+
+		savesegment(es, sel);
+		if (sel == modified_sel)
+			loadsegment(es, sel);
+
+		savesegment(fs, sel);
+		if (sel == modified_sel)
+			loadsegment(fs, sel);
+
+		savesegment(gs, sel);
+		if (sel == modified_sel)
+			load_gs_index(sel);
+#endif
+
+#ifdef CONFIG_X86_32_LAZY_GS
+		savesegment(gs, sel);
+		if (sel == modified_sel)
+			loadsegment(gs, sel);
+#endif
+	} else {
+#ifdef CONFIG_X86_64
+		if (p->thread.fsindex == modified_sel)
+			p->thread.fsbase = info.base_addr;
+
+		if (p->thread.gsindex == modified_sel)
+			p->thread.gsbase = info.base_addr;
+#endif
+	}
+
 	return 0;
 }