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Subject[tip:x86/fpu] x86/fpu: Change math_error() to use unlazy_fpu(), kill (now) unused save_init_fpu()
Commit-ID:  08a744c6bfded3d5fa66f94263f81773226113d1
Gitweb: http://git.kernel.org/tip/08a744c6bfded3d5fa66f94263f81773226113d1
Author: Oleg Nesterov <oleg@redhat.com>
AuthorDate: Fri, 6 Feb 2015 15:02:00 -0500
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Thu, 19 Feb 2015 11:15:03 +0100

x86/fpu: Change math_error() to use unlazy_fpu(), kill (now) unused save_init_fpu()

math_error() calls save_init_fpu() after conditional_sti(), this means
that the caller can be preempted. If !use_eager_fpu() we can hit the
WARN_ON_ONCE(!__thread_has_fpu(tsk)) and/or save the wrong FPU state.

Change math_error() to use unlazy_fpu() and kill save_init_fpu().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1423252925-14451-4-git-send-email-riel@redhat.com
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/include/asm/fpu-internal.h | 18 ------------------
arch/x86/kernel/traps.c | 2 +-
2 files changed, 1 insertion(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index e97622f..02f2e08 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -518,24 +518,6 @@ static inline void __save_fpu(struct task_struct *tsk)
}

/*
- * These disable preemption on their own and are safe
- */
-static inline void save_init_fpu(struct task_struct *tsk)
-{
- WARN_ON_ONCE(!__thread_has_fpu(tsk));
-
- if (use_eager_fpu()) {
- __save_fpu(tsk);
- return;
- }
-
- preempt_disable();
- __save_init_fpu(tsk);
- __thread_fpu_end(tsk);
- preempt_enable();
-}
-
-/*
* i387 state interaction
*/
static inline unsigned short get_fpu_cwd(struct task_struct *tsk)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 88900e2..9d889f7 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -663,7 +663,7 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)
/*
* Save the info for the exception handler and clear the error.
*/
- save_init_fpu(task);
+ unlazy_fpu(task);
task->thread.trap_nr = trapnr;
task->thread.error_code = error_code;
info.si_signo = SIGFPE;

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