[PATCH 1/2] x86, xsave: fix non-lazy allocation of the xsave area

[Hans Rosenfeld]

A single static xsave area just for init is not enough, since there are
more user processes that are directly executed by kernel threads. Add a
call to a new arch-specific function to flush_old_exec(), which will in
turn call fpu_alloc() to allocate a xsave area if necessary.

Signed-off-by: Hans Rosenfeld <hans.rosenfeld@xxxxxxx>
---
 arch/x86/include/asm/i387.h        |    6 ------
 arch/x86/include/asm/thread_info.h |    2 ++
 arch/x86/kernel/process.c          |    7 +++++++
 fs/exec.c                          |    8 ++++++++
 4 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index 989c0ac..0448f45 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -329,15 +329,9 @@ static inline void fpu_copy(struct fpu *dst, struct fpu *src)
 }
 
 extern void fpu_finit(struct fpu *fpu);
-static union thread_xstate __init_xstate, *init_xstate = &__init_xstate;
 
 static inline void fpu_clear(struct fpu *fpu)
 {
-	if (!fpu_allocated(fpu)) {
-		BUG_ON(init_xstate == NULL);
-		fpu->state = init_xstate;
-		init_xstate = NULL;
-	}
 	memset(fpu->state, 0, xstate_size);
 	fpu_finit(fpu);
 	set_used_math();
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 0e691c6..07c8cfe 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -265,6 +265,8 @@ static inline void set_restore_sigmask(void)
 extern void arch_task_cache_init(void);
 extern void free_thread_info(struct thread_info *ti);
 extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
+extern int arch_prealloc_fpu(struct task_struct *tsk);
+#define arch_prealloc_fpu arch_prealloc_fpu
 #define arch_task_cache_init arch_task_cache_init
 #endif
 #endif /* _ASM_X86_THREAD_INFO_H */
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 0382f98..3edfbf2 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -26,6 +26,13 @@
 struct kmem_cache *task_xstate_cachep;
 EXPORT_SYMBOL_GPL(task_xstate_cachep);
 
+int arch_prealloc_fpu(struct task_struct *tsk)
+{
+	if (!fpu_allocated(&tsk->thread.fpu))
+		return fpu_alloc(&tsk->thread.fpu);
+	return 0;
+}
+
 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 {
 	int ret;
diff --git a/fs/exec.c b/fs/exec.c
index 5e62d26..932b9ad 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1022,10 +1022,18 @@ void set_task_comm(struct task_struct *tsk, char *buf)
 	perf_event_comm(tsk);
 }
 
+#if !defined(arch_prealloc_fpu)
+#define arch_prealloc_fpu(tsk) (0)
+#endif
+
 int flush_old_exec(struct linux_binprm * bprm)
 {
 	int retval;
 
+	retval = arch_prealloc_fpu(current);
+	if (retval)
+		goto out;
+
 	/*
 	 * Make sure we have a private signal table and that
 	 * we are unassociated from the previous thread group.
-- 
1.5.6.5


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