tss->io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
}
+/*
+ * This function selects if the context switch from prev to next
+ * has to tweak the TSC disable bit in the cr4.
+ */
+static inline void disable_tsc(struct task_struct *prev_p,
+ struct task_struct *next_p)
+{
+ struct thread_info *prev, *next;
+
+ /*
+ * gcc should eliminate the ->thread_info dereference if
+ * has_secure_computing returns 0 at compile time (SECCOMP=n).
+ */
+ prev = prev_p->thread_info;
+ next = next_p->thread_info;
+
+ if (has_secure_computing(prev) || has_secure_computing(next)) {
+ /* slow path here */
+ if (has_secure_computing(prev) &&
+ !has_secure_computing(next)) {
+ write_cr4(read_cr4() & ~X86_CR4_TSD);
+ } else if (!has_secure_computing(prev) &&
+ has_secure_computing(next))
+ write_cr4(read_cr4() | X86_CR4_TSD);
+ }
+}
+
/*
* switch_to(x,yn) should switch tasks from x to y.
*
/*
* Restore %fs and %gs if needed.
+ *
+ * Glibc normally makes %fs be zero, and %gs is one of
+ * the TLS segments.
*/
- if (unlikely(prev->fs | prev->gs | next->fs | next->gs)) {
+ if (unlikely(prev->fs | next->fs))
loadsegment(fs, next->fs);
+
+ if (prev->gs | next->gs)
loadsegment(gs, next->gs);
- }
/*
* Now maybe reload the debug registers
*/
if (unlikely(next->debugreg[7])) {
- set_debugreg(current->thread.debugreg[0], 0);
- set_debugreg(current->thread.debugreg[1], 1);
- set_debugreg(current->thread.debugreg[2], 2);
- set_debugreg(current->thread.debugreg[3], 3);
+ set_debugreg(next->debugreg[0], 0);
+ set_debugreg(next->debugreg[1], 1);
+ set_debugreg(next->debugreg[2], 2);
+ set_debugreg(next->debugreg[3], 3);
/* no 4 and 5 */
- set_debugreg(current->thread.debugreg[6], 6);
- set_debugreg(current->thread.debugreg[7], 7);
+ set_debugreg(next->debugreg[6], 6);
+ set_debugreg(next->debugreg[7], 7);
}
if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr))
handle_io_bitmap(next, tss);
+ disable_tsc(prev_p, next_p);
+
return prev_p;
}
if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
return -EINVAL;
+ memset(&info, 0, sizeof(info));
+
desc = current->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
info.entry_number = idx;