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Subject[PATCH 1/1] x86, xsave: fix non-lazy allocation of the xsave area
Date
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@amd.com>
---
arch/x86/include/asm/i387.h | 6 ------
arch/x86/kernel/process.c | 7 +++++++
fs/exec.c | 9 +++++++++
3 files changed, 16 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/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..c5b5c1e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1022,10 +1022,19 @@ void set_task_comm(struct task_struct *tsk, char *buf)
perf_event_comm(tsk);
}

+int __attribute__((weak)) arch_prealloc_fpu(struct task_struct *tsk)
+{
+ return 0;
+}
+
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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