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>

diff --git a/arch/x86/um/signal.c b/arch/x86/um/signal.c
index 14fcd01..dac23ee 100644 (file)
--- 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;
        }