x86/fpu: Split an fpstate_alloc_init() function out of init_fpu()

Most init_fpu() users don't want the register-saving aspect of the
function, they are calling it for 'current' and when FPU registers
are not allocated and initialized yet.

Split out a simplified API that does just that (and add debug-checks
for these conditions): fpstate_alloc_init().

Use it where appropriate.

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index d4419da9b2109248e5c4082a91fd41ea57cc5904..1a896b4533c42fcc7b687f466017df18e0bdaa72 100644 (file)
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -18,7 +18,10 @@
 struct pt_regs;
 struct user_i387_struct;
 
+extern int fpstate_alloc_init(struct task_struct *curr);
+
 extern int init_fpu(struct task_struct *child);
+
 extern void fpu_finit(struct fpu *fpu);
 extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
 extern void math_state_restore(void);

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 29251f5668b1c84f3712b78de222cd464829281d..56b6e726fb60cec9fbb4228f98d6ad7058e26583 100644 (file)
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -246,6 +246,37 @@ void fpu_finit(struct fpu *fpu)
 }
 EXPORT_SYMBOL_GPL(fpu_finit);
 
+/*
+ * Allocate the backing store for the current task's FPU registers
+ * and initialize the registers themselves as well.
+ *
+ * Can fail.
+ */
+int fpstate_alloc_init(struct task_struct *curr)
+{
+       int ret;
+
+       if (WARN_ON_ONCE(curr != current))
+               return -EINVAL;
+       if (WARN_ON_ONCE(curr->flags & PF_USED_MATH))
+               return -EINVAL;
+
+       /*
+        * Memory allocation at the first usage of the FPU and other state.
+        */
+       ret = fpu_alloc(&curr->thread.fpu);
+       if (ret)
+               return ret;
+
+       fpu_finit(&curr->thread.fpu);
+
+       /* Safe to do for the current task: */
+       curr->flags |= PF_USED_MATH;
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(fpstate_alloc_init);
+
 /*
  * The _current_ task is using the FPU for the first time
  * so initialize it and set the mxcsr to its default

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 6e338e3b1dc04cc69ab41c012fe5671cc25321cd..abdb81d074236fd3546e6836f01421ae03f7f54b 100644 (file)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -159,7 +159,7 @@ void flush_thread(void)
        } else {
                if (!tsk_used_math(tsk)) {
                        /* kthread execs. TODO: cleanup this horror. */
-                       if (WARN_ON(init_fpu(tsk)))
+               if (WARN_ON(fpstate_alloc_init(tsk)))
                                force_sig(SIGKILL, tsk);
                        user_fpu_begin();
                }

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 12f29f9907cdd03f2941cc05c847d6b50233bbd4..cf9c9627be1909ce41ae68a168708364da32bb66 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -846,7 +846,7 @@ void math_state_restore(void)
                /*
                 * does a slab alloc which can sleep
                 */
-               if (init_fpu(tsk)) {
+               if (fpstate_alloc_init(tsk)) {
                        /*
                         * ran out of memory!
                         */

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 87a815b85f3e5c1b9ee6db83224ad954eef1df75..a977cdd0382556d70f1427ef9bb7b02ef9f57677 100644 (file)
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -349,7 +349,7 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
        if (!access_ok(VERIFY_READ, buf, size))
                return -EACCES;
 
-       if (!used_math() && init_fpu(tsk))
+       if (!used_math() && fpstate_alloc_init(tsk))
                return -1;
 
        if (!static_cpu_has(X86_FEATURE_FPU))

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c73efcd03e294a2e5bc2ef276dc7fa4a6e9d837f..bfc396632ee84c87597e6db498e4b82795dba279 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6600,7 +6600,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
        int r;
        sigset_t sigsaved;
 
-       if (!tsk_used_math(current) && init_fpu(current))
+       if (!tsk_used_math(current) && fpstate_alloc_init(current))
                return -ENOMEM;
 
        if (vcpu->sigset_active)

diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c
index 9b868124128d79699d6325dc579908bc575c3f4a..c9ff09a0238516a37d1f9e0847bdef88afd3bde7 100644 (file)
--- a/arch/x86/math-emu/fpu_entry.c
+++ b/arch/x86/math-emu/fpu_entry.c
@@ -149,7 +149,7 @@ void math_emulate(struct math_emu_info *info)
        struct desc_struct code_descriptor;
 
        if (!used_math()) {
-               if (init_fpu(current)) {
+               if (fpstate_alloc_init(current)) {
                        do_group_exit(SIGKILL);
                        return;
                }