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Diffstat (limited to 'arch/x86/kernel/process_64.c')
-rw-r--r--arch/x86/kernel/process_64.c99
1 files changed, 55 insertions, 44 deletions
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index bbfbf017065c..ddd4fa718c43 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -339,24 +339,6 @@ static unsigned long x86_fsgsbase_read_task(struct task_struct *task,
return base;
}
-void x86_fsbase_write_cpu(unsigned long fsbase)
-{
- /*
- * Set the selector to 0 as a notion, that the segment base is
- * overwritten, which will be checked for skipping the segment load
- * during context switch.
- */
- loadseg(FS, 0);
- wrmsrl(MSR_FS_BASE, fsbase);
-}
-
-void x86_gsbase_write_cpu_inactive(unsigned long gsbase)
-{
- /* Set the selector to 0 for the same reason as %fs above. */
- loadseg(GS, 0);
- wrmsrl(MSR_KERNEL_GS_BASE, gsbase);
-}
-
unsigned long x86_fsbase_read_task(struct task_struct *task)
{
unsigned long fsbase;
@@ -385,38 +367,18 @@ unsigned long x86_gsbase_read_task(struct task_struct *task)
return gsbase;
}
-int x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase)
+void x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase)
{
- /*
- * Not strictly needed for %fs, but do it for symmetry
- * with %gs
- */
- if (unlikely(fsbase >= TASK_SIZE_MAX))
- return -EPERM;
+ WARN_ON_ONCE(task == current);
- preempt_disable();
task->thread.fsbase = fsbase;
- if (task == current)
- x86_fsbase_write_cpu(fsbase);
- task->thread.fsindex = 0;
- preempt_enable();
-
- return 0;
}
-int x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase)
+void x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase)
{
- if (unlikely(gsbase >= TASK_SIZE_MAX))
- return -EPERM;
+ WARN_ON_ONCE(task == current);
- preempt_disable();
task->thread.gsbase = gsbase;
- if (task == current)
- x86_gsbase_write_cpu_inactive(gsbase);
- task->thread.gsindex = 0;
- preempt_enable();
-
- return 0;
}
int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
@@ -754,11 +716,60 @@ long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2)
switch (option) {
case ARCH_SET_GS: {
- ret = x86_gsbase_write_task(task, arg2);
+ if (unlikely(arg2 >= TASK_SIZE_MAX))
+ return -EPERM;
+
+ preempt_disable();
+ /*
+ * ARCH_SET_GS has always overwritten the index
+ * and the base. Zero is the most sensible value
+ * to put in the index, and is the only value that
+ * makes any sense if FSGSBASE is unavailable.
+ */
+ if (task == current) {
+ loadseg(GS, 0);
+ x86_gsbase_write_cpu_inactive(arg2);
+
+ /*
+ * On non-FSGSBASE systems, save_base_legacy() expects
+ * that we also fill in thread.gsbase.
+ */
+ task->thread.gsbase = arg2;
+
+ } else {
+ task->thread.gsindex = 0;
+ x86_gsbase_write_task(task, arg2);
+ }
+ preempt_enable();
break;
}
case ARCH_SET_FS: {
- ret = x86_fsbase_write_task(task, arg2);
+ /*
+ * Not strictly needed for %fs, but do it for symmetry
+ * with %gs
+ */
+ if (unlikely(arg2 >= TASK_SIZE_MAX))
+ return -EPERM;
+
+ preempt_disable();
+ /*
+ * Set the selector to 0 for the same reason
+ * as %gs above.
+ */
+ if (task == current) {
+ loadseg(FS, 0);
+ x86_fsbase_write_cpu(arg2);
+
+ /*
+ * On non-FSGSBASE systems, save_base_legacy() expects
+ * that we also fill in thread.fsbase.
+ */
+ task->thread.fsbase = arg2;
+ } else {
+ task->thread.fsindex = 0;
+ x86_fsbase_write_task(task, arg2);
+ }
+ preempt_enable();
break;
}
case ARCH_GET_FS: {