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>

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index e03cc952f233db9a2d77a1592798a96cf68a0674..eb9ddd8efb828175e7be0efcc0616257c67c5943 100644 (file)
--- 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 6e38d877ea7725fb8d94d2c91a0ee7daab2585d1..c7b06feb139b9af7077a3c3ff8d15c4534a29368 100644 (file)
--- 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;

diff --git a/include/asm-x86/i387.h b/include/asm-x86/i387.h
index 6b722d315936705605850bdd43141064bae9f71f..37672f79dcc8f3c879e7899f31868d7d06c2e0ae 100644 (file)
--- a/include/asm-x86/i387.h
+++ b/include/asm-x86/i387.h
@@ -193,6 +193,8 @@ static inline int restore_i387(struct _fpstate __user *buf)
 
 #else  /* CONFIG_X86_32 */
 
+extern void finit(void);
+
 static inline void tolerant_fwait(void)
 {
        asm volatile("fnclex ; fwait");