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Commit 97185c95 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

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: default avatarBorislav 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: default avatarIngo Molnar <mingo@kernel.org>
parent 68ad8b9f

arch/x86/include/asm/i387.h

+3 −0
Original line number Diff line number Diff line
@@ -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);

arch/x86/kernel/i387.c

+31 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/process.c

+1 −1
Original line number Diff line number Diff line
@@ -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();

		}

arch/x86/kernel/traps.c

+1 −1
Original line number Diff line number Diff line
@@ -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!

			 */

arch/x86/kernel/xsave.c

+1 −1
Original line number Diff line number Diff line
@@ -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))