x86/fpu: Remove fpu->initialized usage in copy_fpstate_to_sigframe()
With lazy-FPU support the (now named variable) ->initialized was set to true if the CPU's FPU registers were holding a valid state of the FPU registers for the active process. If it was set to false then the FPU state was saved in fpu->state and the FPU was deactivated. With lazy-FPU gone, ->initialized is always true for user threads and kernel threads never call this function so ->initialized is always true in copy_fpstate_to_sigframe(). The using_compacted_format() check is also a leftover from the lazy-FPU time. In the ->initialized == false case copy_to_user() would copy the compacted buffer while userland would expect the non-compacted format instead. So in order to save the FPU state in the non-compacted form it issues XSAVE to save the *current* FPU state. If the FPU is not enabled, the attempt raises the FPU trap, the trap restores the FPU contents and re-enables the FPU and XSAVE is invoked again and succeeds. *This* does not longer work since commit bef8b6da9522 ("x86/fpu: Handle #NM without FPU emulation as an error") Remove the check for ->initialized because it is always true and remove the false condition. Update the comment to reflect that the state is always live. [ bp: Massage. ] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Dave Hansen <dave.hansen@intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: kvm ML <kvm@vger.kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Rik van Riel <riel@surriel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190403164156.19645-6-bigeasy@linutronix.de
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@ -144,9 +144,8 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
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* buf == buf_fx for 64-bit frames and 32-bit fsave frame.
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* buf != buf_fx for 32-bit frames with fxstate.
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*
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* If the fpu, extended register state is live, save the state directly
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* to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise,
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* copy the thread's fpu state to the user frame starting at 'buf_fx'.
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* Save the state directly to the user frame pointed by the aligned pointer
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* 'buf_fx'.
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*
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* If this is a 32-bit frame with fxstate, put a fsave header before
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* the aligned state at 'buf_fx'.
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@ -157,7 +156,6 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
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int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
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{
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struct fpu *fpu = ¤t->thread.fpu;
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struct xregs_state *xsave = &fpu->state.xsave;
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struct task_struct *tsk = current;
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int ia32_fxstate = (buf != buf_fx);
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@ -172,29 +170,12 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
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sizeof(struct user_i387_ia32_struct), NULL,
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(struct _fpstate_32 __user *) buf) ? -1 : 1;
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if (fpu->initialized || using_compacted_format()) {
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/* Save the live register state to the user directly. */
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if (copy_fpregs_to_sigframe(buf_fx))
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return -1;
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/* Update the thread's fxstate to save the fsave header. */
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if (ia32_fxstate)
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copy_fxregs_to_kernel(fpu);
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} else {
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/*
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* It is a *bug* if kernel uses compacted-format for xsave
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* area and we copy it out directly to a signal frame. It
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* should have been handled above by saving the registers
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* directly.
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*/
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if (boot_cpu_has(X86_FEATURE_XSAVES)) {
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WARN_ONCE(1, "x86/fpu: saving compacted-format xsave area to a signal frame!\n");
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return -1;
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}
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fpstate_sanitize_xstate(fpu);
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if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size))
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return -1;
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}
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/* Save the live registers state to the user frame directly. */
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if (copy_fpregs_to_sigframe(buf_fx))
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return -1;
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/* Update the thread's fxstate to save the fsave header. */
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if (ia32_fxstate)
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copy_fxregs_to_kernel(fpu);
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/* Save the fsave header for the 32-bit frames. */
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if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
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