uml: floating point signal delivery fixes

Handle floating point state in across signals correctly.  UML/i386 needs to
know whether the host does PTRACE_[GS]ETFPXREGS, so an arch_init_registers
hook is added, which on x86_64 does nothing.

UML doesn't save and restore floating point registers on kernel entry and
exit, so they need to be copied between the host process and the sigcontext.
save_fpx_registers and restore_fpx_registers are added for this purpose.
save_fp_registers and restore_fp_registers already exist.

There was a bunch of floating point state conversion code in
arch/um/sys-i386/ptrace.c which isn't needed there, but is needed in signal.c,
so it is moved over.

The i386 code now distinguishes between fp and fpx state and handles them
correctly.  The x86_64 code just needs to copy state as-is between the host
process and the stack.  There are also some fixes there to pass the correct
address of the floating point state around.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 39 insertions, 14 deletions

diff --git a/arch/um/sys-x86_64/signal.c b/arch/um/sys-x86_64/signal.c
index c98dd7f31396..a8e5fd7b2adb 100644
--- a/arch/um/sys-x86_64/signal.c
+++ b/arch/um/sys-x86_64/signal.c
@@ -42,8 +42,10 @@ void copy_sc(struct uml_pt_regs *regs, void *from)
 }
 
 static int copy_sc_from_user(struct pt_regs *regs,
-                             struct sigcontext __user *from)
+                             struct sigcontext __user *from,
+                             struct _fpstate __user *fpp)
 {
+        struct user_i387_struct fp;
         int err = 0;
 
 #define GETREG(regs, regno, sc, regname)                                \
@@ -69,10 +71,25 @@ static int copy_sc_from_user(struct pt_regs *regs,
         err |= GETREG(regs, RIP, from, rip);
         err |= GETREG(regs, EFLAGS, from, eflags);
         err |= GETREG(regs, CS, from, cs);
+        if (err)
+                return 1;
 
 #undef GETREG
 
-        return err;
+        err = copy_from_user(&fp, fpp, sizeof(struct user_i387_struct));
+        if (err)
+                return 1;
+
+        err = restore_fp_registers(userspace_pid[current_thread->cpu],
+                                   (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;
 }
 
 static int copy_sc_to_user(struct sigcontext __user *to,
@@ -80,6 +97,7 @@ static int copy_sc_to_user(struct sigcontext __user *to,
                            unsigned long mask, unsigned long sp)
 {
         struct faultinfo * fi = &current->thread.arch.faultinfo;
+        struct user_i387_struct fp;
         int err = 0;
 
         err |= __put_user(0, &to->gs);
@@ -120,6 +138,19 @@ static int copy_sc_to_user(struct sigcontext __user *to,
 #undef PUTREG
 
         err |= __put_user(mask, &to->oldmask);
+        if (err)
+                return 1;
+
+        err = save_fp_registers(userspace_pid[current_thread->cpu],
+                                (unsigned long *) &fp);
+        if (err < 0) {
+                printk(KERN_ERR "copy_sc_from_user - restore_fp_registers "
+                       "failed, errno = %d\n", -err);
+                return 1;
+        }
+
+        if (copy_to_user(to_fp, &fp, sizeof(struct user_i387_struct)))
+                return 1;
 
         return(err);
 }
@@ -129,6 +160,7 @@ struct rt_sigframe
         char __user *pretcode;
         struct ucontext uc;
         struct siginfo info;
+        struct _fpstate fpstate;
 };
 
 #define round_down(m, n) (((m) / (n)) * (n))
@@ -138,7 +170,6 @@ int setup_signal_stack_si(unsigned long stack_top, int sig,
                           siginfo_t *info, sigset_t *set)
 {
         struct rt_sigframe __user *frame;
-        struct _fpstate __user *fp = NULL;
         unsigned long save_sp = PT_REGS_RSP(regs);
         int err = 0;
         struct task_struct *me = current;
@@ -148,13 +179,6 @@ int setup_signal_stack_si(unsigned long stack_top, int sig,
         /* Subtract 128 for a red zone and 8 for proper alignment */
         frame = (struct rt_sigframe __user *) ((unsigned long) frame - 128 - 8);
 
-        if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate)))
-                goto out;
-
-#if 0 /* XXX */
-        if (save_i387(fp) < 0)
-                err |= -1;
-#endif
         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                 goto out;
 
@@ -181,9 +205,9 @@ int setup_signal_stack_si(unsigned long stack_top, int sig,
         err |= __put_user(sas_ss_flags(save_sp),
                           &frame->uc.uc_stack.ss_flags);
         err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
-        err |= copy_sc_to_user(&frame->uc.uc_mcontext, fp, regs, set->sig[0],
-                save_sp);
-        err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
+        err |= copy_sc_to_user(&frame->uc.uc_mcontext, &frame->fpstate, regs,
+                               set->sig[0], save_sp);
+        err |= __put_user(&frame->fpstate, &frame->uc.uc_mcontext.fpstate);
         if (sizeof(*set) == 16) {
                 __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
                 __put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]);
@@ -246,7 +270,8 @@ long sys_rt_sigreturn(struct pt_regs *regs)
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
-        if (copy_sc_from_user(&current->thread.regs, &uc->uc_mcontext))
+        if (copy_sc_from_user(&current->thread.regs, &uc->uc_mcontext,
+                              &frame->fpstate))
                 goto segfault;
 
         /* Avoid ERESTART handling */