um: fix FPU state preservation around signal handlers

This patch makes UML saves/restores FPU state from/to the fpstate in
pt_regs when setting up or returning from a signal stack, rather than
calling ptrace directly. This ensures that FPU state is correctly
preserved around signal handlers in a multi-threaded scenario.

Signed-off-by: Eli Cooper <elicooper@gmx.com>

1 files changed, 3 insertions, 15 deletions

diff --git a/arch/x86/um/signal.c b/arch/x86/um/signal.c
index 14fcd01ed992..dac23ee4e5a1 100644
--- a/arch/x86/um/signal.c
+++ b/arch/x86/um/signal.c
@@ -225,20 +225,10 @@ static int copy_sc_from_user(struct pt_regs *regs,
         } else
 #endif
         {
-                struct user_i387_struct fp;
-
-                err = copy_from_user(&fp, (void *)sc.fpstate,
+                err = copy_from_user(regs->regs.fp, (void *)sc.fpstate,
                                      sizeof(struct user_i387_struct));
                 if (err)
                         return 1;
-
-                err = restore_fp_registers(pid, (unsigned long *) &fp);
-                if (err < 0) {
-                        printk(KERN_ERR "copy_sc_from_user - "
-                               "restore_fp_registers failed, errno = %d\n",
-                               -err);
-                        return 1;
-                }
         }
         return 0;
 }
@@ -325,10 +315,8 @@ static int copy_sc_to_user(struct sigcontext __user *to,
         } else
 #endif
         {
-                struct user_i387_struct fp;
-
-                err = save_fp_registers(pid, (unsigned long *) &fp);
-                if (copy_to_user(to_fp, &fp, sizeof(struct user_i387_struct)))
+                if (copy_to_user(to_fp, regs->regs.fp,
+                                 sizeof(struct user_i387_struct)))
                         return 1;
         }