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, 203 insertions, 20 deletions

diff --git a/arch/um/sys-i386/signal.c b/arch/um/sys-i386/signal.c
index 1eb21a023e33..0147227ce18d 100644
--- a/arch/um/sys-i386/signal.c
+++ b/arch/um/sys-i386/signal.c
@@ -32,25 +32,186 @@ void copy_sc(struct uml_pt_regs *regs, void *from)
         REGS_SS(regs->gp) = sc->ss;
 }
 
+/*
+ * FPU tag word conversions.
+ */
+
+static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
+{
+        unsigned int tmp; /* to avoid 16 bit prefixes in the code */
+
+        /* Transform each pair of bits into 01 (valid) or 00 (empty) */
+        tmp = ~twd;
+        tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
+        /* and move the valid bits to the lower byte. */
+        tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
+        tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
+        tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
+        return tmp;
+}
+
+static inline unsigned long twd_fxsr_to_i387(struct user_fxsr_struct *fxsave)
+{
+        struct _fpxreg *st = NULL;
+        unsigned long twd = (unsigned long) fxsave->twd;
+        unsigned long tag;
+        unsigned long ret = 0xffff0000;
+        int i;
+
+#define FPREG_ADDR(f, n)        ((char *)&(f)->st_space + (n) * 16);
+
+        for (i = 0; i < 8; i++) {
+                if (twd & 0x1) {
+                        st = (struct _fpxreg *) FPREG_ADDR(fxsave, i);
+
+                        switch (st->exponent & 0x7fff) {
+                        case 0x7fff:
+                                tag = 2;                /* Special */
+                                break;
+                        case 0x0000:
+                                if ( !st->significand[0] &&
+                                     !st->significand[1] &&
+                                     !st->significand[2] &&
+                                     !st->significand[3] ) {
+                                        tag = 1;        /* Zero */
+                                } else {
+                                        tag = 2;        /* Special */
+                                }
+                                break;
+                        default:
+                                if (st->significand[3] & 0x8000) {
+                                        tag = 0;        /* Valid */
+                                } else {
+                                        tag = 2;        /* Special */
+                                }
+                                break;
+                        }
+                } else {
+                        tag = 3;                        /* Empty */
+                }
+                ret |= (tag << (2 * i));
+                twd = twd >> 1;
+        }
+        return ret;
+}
+
+static int convert_fxsr_to_user(struct _fpstate __user *buf,
+                                struct user_fxsr_struct *fxsave)
+{
+        unsigned long env[7];
+        struct _fpreg __user *to;
+        struct _fpxreg *from;
+        int i;
+
+        env[0] = (unsigned long)fxsave->cwd | 0xffff0000ul;
+        env[1] = (unsigned long)fxsave->swd | 0xffff0000ul;
+        env[2] = twd_fxsr_to_i387(fxsave);
+        env[3] = fxsave->fip;
+        env[4] = fxsave->fcs | ((unsigned long)fxsave->fop << 16);
+        env[5] = fxsave->foo;
+        env[6] = fxsave->fos;
+
+        if (__copy_to_user(buf, env, 7 * sizeof(unsigned long)))
+                return 1;
+
+        to = &buf->_st[0];
+        from = (struct _fpxreg *) &fxsave->st_space[0];
+        for (i = 0; i < 8; i++, to++, from++) {
+                unsigned long __user *t = (unsigned long __user *)to;
+                unsigned long *f = (unsigned long *)from;
+
+                if (__put_user(*f, t) ||
+                                __put_user(*(f + 1), t + 1) ||
+                                __put_user(from->exponent, &to->exponent))
+                        return 1;
+        }
+        return 0;
+}
+
+static int convert_fxsr_from_user(struct user_fxsr_struct *fxsave,
+                                  struct _fpstate __user *buf)
+{
+        unsigned long env[7];
+        struct _fpxreg *to;
+        struct _fpreg __user *from;
+        int i;
+
+        if (copy_from_user( env, buf, 7 * sizeof(long)))
+                return 1;
+
+        fxsave->cwd = (unsigned short)(env[0] & 0xffff);
+        fxsave->swd = (unsigned short)(env[1] & 0xffff);
+        fxsave->twd = twd_i387_to_fxsr((unsigned short)(env[2] & 0xffff));
+        fxsave->fip = env[3];
+        fxsave->fop = (unsigned short)((env[4] & 0xffff0000ul) >> 16);
+        fxsave->fcs = (env[4] & 0xffff);
+        fxsave->foo = env[5];
+        fxsave->fos = env[6];
+
+        to = (struct _fpxreg *) &fxsave->st_space[0];
+        from = &buf->_st[0];
+        for (i = 0; i < 8; i++, to++, from++) {
+                unsigned long *t = (unsigned long *)to;
+                unsigned long __user *f = (unsigned long __user *)from;
+
+                if (__get_user(*t, f) ||
+                    __get_user(*(t + 1), f + 1) ||
+                    __get_user(to->exponent, &from->exponent))
+                        return 1;
+        }
+        return 0;
+}
+
+extern int have_fpx_regs;
+
 static int copy_sc_from_user(struct pt_regs *regs,
                              struct sigcontext __user *from)
 {
-        struct sigcontext sc;
-        unsigned long fpregs[HOST_FP_SIZE];
+        struct sigcontext sc;
         int err;
 
         err = copy_from_user(&sc, from, sizeof(sc));
-        err |= copy_from_user(fpregs, sc.fpstate, sizeof(fpregs));
         if (err)
                 return err;
 
         copy_sc(&regs->regs, &sc);
-
-        err = restore_fp_registers(userspace_pid[0], fpregs);
-        if (err < 0) {
-                printk(KERN_ERR "copy_sc_from_user_skas - PTRACE_SETFPREGS "
-                       "failed, errno = %d\n", -err);
-                return err;
+        if (have_fpx_regs) {
+                struct user_fxsr_struct fpx;
+
+                err = copy_from_user(&fpx, &sc.fpstate->_fxsr_env[0],
+                                     sizeof(struct user_fxsr_struct));
+                if (err)
+                        return 1;
+
+                err = convert_fxsr_from_user(&fpx, sc.fpstate);
+                if (err)
+                        return 1;
+
+                err = restore_fpx_registers(userspace_pid[current_thread->cpu],
+                                            (unsigned long *) &fpx);
+                if (err < 0) {
+                        printk(KERN_ERR "copy_sc_from_user - "
+                               "restore_fpx_registers failed, errno = %d\n",
+                               -err);
+                        return 1;
+                }
+        }
+        else {
+                struct user_i387_struct fp;
+
+                err = copy_from_user(&fp, sc.fpstate,
+                                     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;
@@ -61,7 +222,6 @@ static int copy_sc_to_user(struct sigcontext __user *to,
                            unsigned long sp)
 {
         struct sigcontext sc;
-        unsigned long fpregs[HOST_FP_SIZE];
         struct faultinfo * fi = &current->thread.arch.faultinfo;
         int err;
 
@@ -86,20 +246,43 @@ static int copy_sc_to_user(struct sigcontext __user *to,
         sc.err = fi->error_code;
         sc.trapno = fi->trap_no;
 
-        err = save_fp_registers(userspace_pid[0], fpregs);
-        if (err < 0) {
-                printk(KERN_ERR "copy_sc_to_user_skas - PTRACE_GETFPREGS "
-                       "failed, errno = %d\n", err);
-                return 1;
-        }
         to_fp = (to_fp ? to_fp : (struct _fpstate __user *) (to + 1));
         sc.fpstate = to_fp;
 
-        if (err)
-                return err;
+        if (have_fpx_regs) {
+                struct user_fxsr_struct fpx;
+
+                err = save_fpx_registers(userspace_pid[current_thread->cpu],
+                                         (unsigned long *) &fpx);
+                if (err < 0){
+                        printk(KERN_ERR "copy_sc_to_user - save_fpx_registers "
+                               "failed, errno = %d\n", err);
+                        return 1;
+                }
+
+                err = convert_fxsr_to_user(to_fp, &fpx);
+                if (err)
+                        return 1;
+
+                err |= __put_user(fpx.swd, &to_fp->status);
+                err |= __put_user(X86_FXSR_MAGIC, &to_fp->magic);
+                if (err)
+                        return 1;
+
+                if (copy_to_user(&to_fp->_fxsr_env[0], &fpx,
+                                 sizeof(struct user_fxsr_struct)))
+                        return 1;
+        }
+        else {
+                struct user_i387_struct fp;
+
+                err = save_fp_registers(userspace_pid[current_thread->cpu],
+                                        (unsigned long *) &fp);
+                if (copy_to_user(to_fp, &fp, sizeof(struct user_i387_struct)))
+                        return 1;
+        }
 
-        return copy_to_user(to, &sc, sizeof(sc)) ||
-               copy_to_user(to_fp, fpregs, sizeof(fpregs));
+        return copy_to_user(to, &sc, sizeof(sc));
 }
 
 static int copy_ucontext_to_user(struct ucontext __user *uc,