diff options
| author | Ingo Molnar <mingo@kernel.org> | 2015-05-27 12:22:29 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-05-27 12:40:18 +0200 |
| commit | 47f01e8cc23f3d041f6b9fb97627369eaf75ba7f (patch) | |
| tree | 803963c8168a75b69146432cdd31263def99aa7f /arch/x86/kernel/fpu/regset.c | |
| parent | 8c05f05edb7795ecd1fa95d5d44bc5b22fd85287 (diff) | |
x86/fpu: Fix FPU register read access to the current task
Bobby Powers reported the following FPU warning during ELF coredumping:
WARNING: CPU: 0 PID: 27452 at arch/x86/kernel/fpu/core.c:324 fpu__activate_stopped+0x8a/0xa0()
This warning unearthed an invalid assumption about fpu__activate_stopped()
that I added in:
67e97fc2ec57 ("x86/fpu: Rename init_fpu() to fpu__unlazy_stopped() and add debugging check")
the old init_fpu() function had an (intentional but obscure) side effect:
when FPU registers are accessed for the current task, for reading, then
it synchronized live in-register FPU state with the fpstate by saving it.
So fix this bug by saving the FPU if we are the current task. We'll
still warn in fpu__save() if this is called for not yet stopped
child tasks, so the debugging check is still preserved.
Also rename the function to fpu__activate_fpstate(), because it's not
exclusively used for stopped tasks, but for the current task as well.
( Note that this bug calls for a cleaner separation of access-for-read
and access-for-modification FPU methods, but we'll do that in separate
patches. )
Reported-by: Bobby Powers <bobbypowers@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
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: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/fpu/regset.c')
| -rw-r--r-- | arch/x86/kernel/fpu/regset.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index 297b3da8e4c4..a1f97d9d6a45 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -33,7 +33,7 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset, if (!cpu_has_fxsr) return -ENODEV; - fpu__activate_stopped(fpu); + fpu__activate_fpstate(fpu); fpstate_sanitize_xstate(fpu); return user_regset_copyout(&pos, &count, &kbuf, &ubuf, @@ -50,7 +50,7 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset, if (!cpu_has_fxsr) return -ENODEV; - fpu__activate_stopped(fpu); + fpu__activate_fpstate(fpu); fpstate_sanitize_xstate(fpu); ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, @@ -82,7 +82,7 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset, if (!cpu_has_xsave) return -ENODEV; - fpu__activate_stopped(fpu); + fpu__activate_fpstate(fpu); xsave = &fpu->state.xsave; @@ -111,7 +111,7 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset, if (!cpu_has_xsave) return -ENODEV; - fpu__activate_stopped(fpu); + fpu__activate_fpstate(fpu); xsave = &fpu->state.xsave; @@ -273,7 +273,7 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset, struct fpu *fpu = &target->thread.fpu; struct user_i387_ia32_struct env; - fpu__activate_stopped(fpu); + fpu__activate_fpstate(fpu); if (!static_cpu_has(X86_FEATURE_FPU)) return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf); @@ -303,7 +303,7 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset, struct user_i387_ia32_struct env; int ret; - fpu__activate_stopped(fpu); + fpu__activate_fpstate(fpu); fpstate_sanitize_xstate(fpu); if (!static_cpu_has(X86_FEATURE_FPU)) |