[PATCH 008/208] x86/fpu: Rename init_fpu() to fpu__unlazy_stopped() and add debugging check

Ingo Molnar
2015-05-05T17:07:31Z

This function name is a misnomer now that we've split out all the
other users from it. Rename it accordingly: it's used to save
the FPU state of (ptrace-)stopped child tasks.

Add debugging check to double check this intended usage: that this
function is only called for non-current, stopped child tasks.

Reviewed-by: Borislav 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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/i387.c | 31 +++++++++++++++++--------------
1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 95079026c386..909d10d2fb70 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -283,27 +283,30 @@ EXPORT_SYMBOL_GPL(fpstate_alloc_init);
* value at reset if we support XMM instructions and then
* remember the current task has used the FPU.
*/
-static int init_fpu(struct task_struct *tsk)
+static int fpu__unlazy_stopped(struct task_struct *child)
{
int ret;

- if (tsk_used_math(tsk)) {
- if (cpu_has_fpu && tsk == current)
- fpu__save(tsk);
- task_disable_lazy_fpu_restore(tsk);
+ if (WARN_ON_ONCE(child == current))
+ return -EINVAL;
+
+ if (tsk_used_math(child)) {
+ if (cpu_has_fpu && child == current)
+ fpu__save(child);
+ task_disable_lazy_fpu_restore(child);
return 0;
}

/*
* Memory allocation at the first usage of the FPU and other state.
*/
- ret = fpu_alloc(&tsk->thread.fpu);
+ ret = fpu_alloc(&child->thread.fpu);
if (ret)
return ret;

- fpu_finit(&tsk->thread.fpu);
+ fpu_finit(&child->thread.fpu);

- set_stopped_child_used_math(tsk);
+ set_stopped_child_used_math(child);
return 0;
}

@@ -331,7 +334,7 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
if (!cpu_has_fxsr)
return -ENODEV;

- ret = init_fpu(target);
+ ret = fpu__unlazy_stopped(target);
if (ret)
return ret;

@@ -350,7 +353,7 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
if (!cpu_has_fxsr)
return -ENODEV;

- ret = init_fpu(target);
+ ret = fpu__unlazy_stopped(target);
if (ret)
return ret;

@@ -384,7 +387,7 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
if (!cpu_has_xsave)
return -ENODEV;

- ret = init_fpu(target);
+ ret = fpu__unlazy_stopped(target);
if (ret)
return ret;

@@ -414,7 +417,7 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
if (!cpu_has_xsave)
return -ENODEV;

- ret = init_fpu(target);
+ ret = fpu__unlazy_stopped(target);
if (ret)
return ret;

@@ -577,7 +580,7 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset,
struct user_i387_ia32_struct env;
int ret;

- ret = init_fpu(target);
+ ret = fpu__unlazy_stopped(target);
if (ret)
return ret;

@@ -608,7 +611,7 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
struct user_i387_ia32_struct env;
int ret;

- ret = init_fpu(target);
+ ret = fpu__unlazy_stopped(target);
if (ret)
return ret;

--
2.1.0