x86/signal/64: Re-add support for SS in the 64-bit signal context

[deliverable/linux.git] / arch / x86 / kernel / signal.c

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 52f82c7ef57d4f1eaf782bc56d3993a467c0a38e..548ddf7d6fd2085676328ffcde6375ce3e88b477 100644 (file)
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -90,7 +90,9 @@ static void force_valid_ss(struct pt_regs *regs)
 }
 #endif
 
-int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
+static int restore_sigcontext(struct pt_regs *regs,
+                             struct sigcontext __user *sc,
+                             unsigned long uc_flags)
 {
        unsigned long buf_val;
        void __user *buf;
@@ -123,15 +125,18 @@ int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
                COPY(r15);
 #endif /* CONFIG_X86_64 */
 
-#ifdef CONFIG_X86_32
                COPY_SEG_CPL3(cs);
                COPY_SEG_CPL3(ss);
-#else /* !CONFIG_X86_32 */
-               /* Kernel saves and restores only the CS segment register on signals,
-                * which is the bare minimum needed to allow mixed 32/64-bit code.
-                * App's signal handler can save/restore other segments if needed. */
-               COPY_SEG_CPL3(cs);
-#endif /* CONFIG_X86_32 */
+
+#ifdef CONFIG_X86_64
+               /*
+                * Fix up SS if needed for the benefit of old DOSEMU and
+                * CRIU.
+                */
+               if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) &&
+                            user_64bit_mode(regs)))
+                       force_valid_ss(regs);
+#endif
 
                get_user_ex(tmpflags, &sc->flags);
                regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
@@ -194,6 +199,7 @@ int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
                put_user_ex(regs->cs, &sc->cs);
                put_user_ex(0, &sc->gs);
                put_user_ex(0, &sc->fs);
+               put_user_ex(regs->ss, &sc->ss);
 #endif /* CONFIG_X86_32 */
 
                put_user_ex(fpstate, &sc->fpstate);
@@ -432,6 +438,21 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
        return 0;
 }
 #else /* !CONFIG_X86_32 */
+static unsigned long frame_uc_flags(struct pt_regs *regs)
+{
+       unsigned long flags;
+
+       if (cpu_has_xsave)
+               flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
+       else
+               flags = UC_SIGCONTEXT_SS;
+
+       if (likely(user_64bit_mode(regs)))
+               flags |= UC_STRICT_RESTORE_SS;
+
+       return flags;
+}
+
 static int __setup_rt_frame(int sig, struct ksignal *ksig,
                            sigset_t *set, struct pt_regs *regs)
 {
@@ -451,10 +472,7 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
 
        put_user_try {
                /* Create the ucontext.  */
-               if (cpu_has_xsave)
-                       put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
-               else
-                       put_user_ex(0, &frame->uc.uc_flags);
+               put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
                put_user_ex(0, &frame->uc.uc_link);
                save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 
@@ -536,10 +554,7 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
 
        put_user_try {
                /* Create the ucontext.  */
-               if (cpu_has_xsave)
-                       put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
-               else
-                       put_user_ex(0, &frame->uc.uc_flags);
+               put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
                put_user_ex(0, &frame->uc.uc_link);
                compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
                put_user_ex(0, &frame->uc.uc__pad0);
@@ -601,7 +616,11 @@ asmlinkage unsigned long sys_sigreturn(void)
 
        set_current_blocked(&set);
 
-       if (restore_sigcontext(regs, &frame->sc))
+       /*
+        * x86_32 has no uc_flags bits relevant to restore_sigcontext.
+        * Save a few cycles by skipping the __get_user.
+        */
+       if (restore_sigcontext(regs, &frame->sc, 0))
                goto badframe;
        return regs->ax;
 
@@ -617,16 +636,19 @@ asmlinkage long sys_rt_sigreturn(void)
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe __user *frame;
        sigset_t set;
+       unsigned long uc_flags;
 
        frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
        if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
                goto badframe;
        if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
                goto badframe;
+       if (__get_user(uc_flags, &frame->uc.uc_flags))
+               goto badframe;
 
        set_current_blocked(&set);
 
-       if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
+       if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
                goto badframe;
 
        if (restore_altstack(&frame->uc.uc_stack))
@@ -813,6 +835,7 @@ asmlinkage long sys32_x32_rt_sigreturn(void)
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe_x32 __user *frame;
        sigset_t set;
+       unsigned long uc_flags;
 
        frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
 
@@ -820,10 +843,12 @@ asmlinkage long sys32_x32_rt_sigreturn(void)
                goto badframe;
        if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
                goto badframe;
+       if (__get_user(uc_flags, &frame->uc.uc_flags))
+               goto badframe;
 
        set_current_blocked(&set);
 
-       if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
+       if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
                goto badframe;
 
        if (compat_restore_altstack(&frame->uc.uc_stack))