From 97185c95f7ab7f752473c34672dab0925758094b Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 3 Apr 2015 12:02:02 +0200 Subject: [PATCH] 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 Cc: Andy Lutomirski Cc: Dave Hansen Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/x86/include/asm/i387.h | 3 +++ arch/x86/kernel/i387.c | 31 +++++++++++++++++++++++++++++++ arch/x86/kernel/process.c | 2 +- arch/x86/kernel/traps.c | 2 +- arch/x86/kernel/xsave.c | 2 +- arch/x86/kvm/x86.c | 2 +- arch/x86/math-emu/fpu_entry.c | 2 +- 7 files changed, 39 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h index d4419da9b210..1a896b4533c4 100644 --- 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 29251f5668b1..56b6e726fb60 100644 --- 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 6e338e3b1dc0..abdb81d07423 100644 --- 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 12f29f9907cd..cf9c9627be19 100644 --- 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 87a815b85f3e..a977cdd03825 100644 --- 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 c73efcd03e29..bfc396632ee8 100644 --- 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 9b868124128d..c9ff09a02385 100644 --- 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; } -- 2.20.1