x86: fix broken math-emu with lazy allocation of fpu area

Fix the math emulation that got broken with the recent lazy allocation of FPU
area. init_fpu() need to be added for the math-emulation path aswell
for the FPU area allocation.

math emulation enabled kernel booted fine with this, in the presence
of "no387 nofxsr" boot param.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: hpa@zytor.com
Cc: mingo@elte.hu
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 37 insertions, 20 deletions

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index e03cc952f233..eb9ddd8efb82 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -56,6 +56,11 @@ void __cpuinit mxcsr_feature_mask_init(void)
 
 void __init init_thread_xstate(void)
 {
+        if (!HAVE_HWFP) {
+                xstate_size = sizeof(struct i387_soft_struct);
+                return;
+        }
+
         if (cpu_has_fxsr)
                 xstate_size = sizeof(struct i387_fxsave_struct);
 #ifdef CONFIG_X86_32
@@ -94,7 +99,7 @@ void __cpuinit fpu_init(void)
 int init_fpu(struct task_struct *tsk)
 {
         if (tsk_used_math(tsk)) {
-                if (tsk == current)
+                if (HAVE_HWFP && tsk == current)
                         unlazy_fpu(tsk);
                 return 0;
         }
@@ -109,6 +114,15 @@ int init_fpu(struct task_struct *tsk)
                         return -ENOMEM;
         }
 
+#ifdef CONFIG_X86_32
+        if (!HAVE_HWFP) {
+                memset(tsk->thread.xstate, 0, xstate_size);
+                finit();
+                set_stopped_child_used_math(tsk);
+                return 0;
+        }
+#endif
+
         if (cpu_has_fxsr) {
                 struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
 
@@ -330,13 +344,13 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset,
         struct user_i387_ia32_struct env;
         int ret;
 
-        if (!HAVE_HWFP)
-                return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
-
         ret = init_fpu(target);
         if (ret)
                 return ret;
 
+        if (!HAVE_HWFP)
+                return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
+
         if (!cpu_has_fxsr) {
                 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
                                            &target->thread.xstate->fsave, 0,
@@ -360,15 +374,15 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
         struct user_i387_ia32_struct env;
         int ret;
 
-        if (!HAVE_HWFP)
-                return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
-
         ret = init_fpu(target);
         if (ret)
                 return ret;
 
         set_stopped_child_used_math(target);
 
+        if (!HAVE_HWFP)
+                return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
+
         if (!cpu_has_fxsr) {
                 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
                                           &target->thread.xstate->fsave, 0, -1);
@@ -474,18 +488,18 @@ static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
 int restore_i387_ia32(struct _fpstate_ia32 __user *buf)
 {
         int err;
+        struct task_struct *tsk = current;
 
-        if (HAVE_HWFP) {
-                struct task_struct *tsk = current;
-
+        if (HAVE_HWFP)
                 clear_fpu(tsk);
 
-                if (!used_math()) {
-                        err = init_fpu(tsk);
-                        if (err)
-                                return err;
-                }
+        if (!used_math()) {
+                err = init_fpu(tsk);
+                if (err)
+                        return err;
+        }
 
+        if (HAVE_HWFP) {
                 if (cpu_has_fxsr)
                         err = restore_i387_fxsave(buf);
                 else
diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c
index 6e38d877ea77..c7b06feb139b 100644
--- a/arch/x86/math-emu/fpu_entry.c
+++ b/arch/x86/math-emu/fpu_entry.c
@@ -30,6 +30,7 @@
 #include <asm/uaccess.h>
 #include <asm/desc.h>
 #include <asm/user.h>
+#include <asm/i387.h>
 
 #include "fpu_system.h"
 #include "fpu_emu.h"
@@ -146,6 +147,13 @@ asmlinkage void math_emulate(long arg)
         unsigned long code_limit = 0;   /* Initialized to stop compiler warnings */
         struct desc_struct code_descriptor;
 
+        if (!used_math()) {
+                if (init_fpu(current)) {
+                        do_group_exit(SIGKILL);
+                        return;
+                }
+        }
+
 #ifdef RE_ENTRANT_CHECKING
         if (emulating) {
                 printk("ERROR: wm-FPU-emu is not RE-ENTRANT!\n");
@@ -153,11 +161,6 @@ asmlinkage void math_emulate(long arg)
         RE_ENTRANT_CHECK_ON;
 #endif /* RE_ENTRANT_CHECKING */
 
-        if (!used_math()) {
-                finit();
-                set_used_math();
-        }
-
         SETUP_DATA_AREA(arg);
 
         FPU_ORIG_EIP = FPU_EIP;