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@@ -866,105 +866,17 @@ const void *get_xsave_field_ptr(int xsave_state)
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return get_xsave_addr(&fpu->state.xsave, xsave_state);
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}
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-
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-/*
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- * Set xfeatures (aka XSTATE_BV) bit for a feature that we want
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- * to take out of its "init state". This will ensure that an
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- * XRSTOR actually restores the state.
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- */
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-static void fpu__xfeature_set_non_init(struct xregs_state *xsave,
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- int xstate_feature_mask)
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-{
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- xsave->header.xfeatures |= xstate_feature_mask;
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-}
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-
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-/*
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- * This function is safe to call whether the FPU is in use or not.
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- *
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- * Note that this only works on the current task.
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- *
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- * Inputs:
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- * @xsave_state: state which is defined in xsave.h (e.g. XFEATURE_MASK_FP,
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- * XFEATURE_MASK_SSE, etc...)
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- * @xsave_state_ptr: a pointer to a copy of the state that you would
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- * like written in to the current task's FPU xsave state. This pointer
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- * must not be located in the current tasks's xsave area.
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- * Output:
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- * address of the state in the xsave area or NULL if the state
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- * is not present or is in its 'init state'.
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- */
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-static void fpu__xfeature_set_state(int xstate_feature_mask,
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- void *xstate_feature_src, size_t len)
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-{
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- struct xregs_state *xsave = ¤t->thread.fpu.state.xsave;
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- struct fpu *fpu = ¤t->thread.fpu;
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- void *dst;
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-
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- if (!boot_cpu_has(X86_FEATURE_XSAVE)) {
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- WARN_ONCE(1, "%s() attempted with no xsave support", __func__);
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- return;
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- }
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-
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- /*
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- * Tell the FPU code that we need the FPU state to be in
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- * 'fpu' (not in the registers), and that we need it to
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- * be stable while we write to it.
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- */
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- fpu__current_fpstate_write_begin();
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-
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- /*
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- * This method *WILL* *NOT* work for compact-format
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- * buffers. If the 'xstate_feature_mask' is unset in
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- * xcomp_bv then we may need to move other feature state
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- * "up" in the buffer.
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- */
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- if (xsave->header.xcomp_bv & xstate_feature_mask) {
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- WARN_ON_ONCE(1);
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- goto out;
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- }
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-
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- /* find the location in the xsave buffer of the desired state */
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- dst = __raw_xsave_addr(&fpu->state.xsave, xstate_feature_mask);
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-
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- /*
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- * Make sure that the pointer being passed in did not
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- * come from the xsave buffer itself.
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- */
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- WARN_ONCE(xstate_feature_src == dst, "set from xsave buffer itself");
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-
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- /* put the caller-provided data in the location */
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- memcpy(dst, xstate_feature_src, len);
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-
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- /*
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- * Mark the xfeature so that the CPU knows there is state
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- * in the buffer now.
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- */
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- fpu__xfeature_set_non_init(xsave, xstate_feature_mask);
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-out:
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- /*
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- * We are done writing to the 'fpu'. Reenable preeption
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- * and (possibly) move the fpstate back in to the fpregs.
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- */
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- fpu__current_fpstate_write_end();
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-}
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-
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#define NR_VALID_PKRU_BITS (CONFIG_NR_PROTECTION_KEYS * 2)
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#define PKRU_VALID_MASK (NR_VALID_PKRU_BITS - 1)
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/*
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- * This will go out and modify the XSAVE buffer so that PKRU is
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- * set to a particular state for access to 'pkey'.
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- *
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- * PKRU state does affect kernel access to user memory. We do
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- * not modfiy PKRU *itself* here, only the XSAVE state that will
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- * be restored in to PKRU when we return back to userspace.
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+ * This will go out and modify PKRU register to set the access
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+ * rights for @pkey to @init_val.
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*/
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int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
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unsigned long init_val)
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{
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- struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
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- struct pkru_state *old_pkru_state;
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- struct pkru_state new_pkru_state;
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+ u32 old_pkru;
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int pkey_shift = (pkey * PKRU_BITS_PER_PKEY);
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u32 new_pkru_bits = 0;
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@@ -974,6 +886,15 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
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*/
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if (!boot_cpu_has(X86_FEATURE_OSPKE))
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return -EINVAL;
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+ /*
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+ * For most XSAVE components, this would be an arduous task:
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+ * brining fpstate up to date with fpregs, updating fpstate,
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+ * then re-populating fpregs. But, for components that are
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+ * never lazily managed, we can just access the fpregs
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+ * directly. PKRU is never managed lazily, so we can just
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+ * manipulate it directly. Make sure it stays that way.
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+ */
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+ WARN_ON_ONCE(!use_eager_fpu());
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/* Set the bits we need in PKRU: */
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if (init_val & PKEY_DISABLE_ACCESS)
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@@ -984,37 +905,12 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
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/* Shift the bits in to the correct place in PKRU for pkey: */
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new_pkru_bits <<= pkey_shift;
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- /* Locate old copy of the state in the xsave buffer: */
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- old_pkru_state = get_xsave_addr(xsave, XFEATURE_MASK_PKRU);
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-
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- /*
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- * When state is not in the buffer, it is in the init
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- * state, set it manually. Otherwise, copy out the old
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- * state.
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- */
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- if (!old_pkru_state)
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- new_pkru_state.pkru = 0;
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- else
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- new_pkru_state.pkru = old_pkru_state->pkru;
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-
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- /* Mask off any old bits in place: */
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- new_pkru_state.pkru &= ~((PKRU_AD_BIT|PKRU_WD_BIT) << pkey_shift);
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-
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- /* Set the newly-requested bits: */
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- new_pkru_state.pkru |= new_pkru_bits;
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-
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- /*
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- * We could theoretically live without zeroing pkru.pad.
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- * The current XSAVE feature state definition says that
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- * only bytes 0->3 are used. But we do not want to
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- * chance leaking kernel stack out to userspace in case a
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- * memcpy() of the whole xsave buffer was done.
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- *
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- * They're in the same cacheline anyway.
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- */
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- new_pkru_state.pad = 0;
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+ /* Get old PKRU and mask off any old bits in place: */
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+ old_pkru = read_pkru();
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+ old_pkru &= ~((PKRU_AD_BIT|PKRU_WD_BIT) << pkey_shift);
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- fpu__xfeature_set_state(XFEATURE_MASK_PKRU, &new_pkru_state, sizeof(new_pkru_state));
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+ /* Write old part along with new part: */
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+ write_pkru(old_pkru | new_pkru_bits);
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return 0;
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}
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