1 files changed, 316 insertions, 0 deletions

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
new file mode 100644
index 000000000000..07713d64debe
--- /dev/null
+++ b/arch/x86/kernel/xsave.c
@@ -0,0 +1,316 @@
+/*
+ * xsave/xrstor support.
+ *
+ * Author: Suresh Siddha <suresh.b.siddha@intel.com>
+ */
+#include <linux/bootmem.h>
+#include <linux/compat.h>
+#include <asm/i387.h>
+#ifdef CONFIG_IA32_EMULATION
+#include <asm/sigcontext32.h>
+#endif
+#include <asm/xcr.h>
+
+/*
+ * Supported feature mask by the CPU and the kernel.
+ */
+u64 pcntxt_mask;
+
+struct _fpx_sw_bytes fx_sw_reserved;
+#ifdef CONFIG_IA32_EMULATION
+struct _fpx_sw_bytes fx_sw_reserved_ia32;
+#endif
+
+/*
+ * Check for the presence of extended state information in the
+ * user fpstate pointer in the sigcontext.
+ */
+int check_for_xstate(struct i387_fxsave_struct __user *buf,
+                     void __user *fpstate,
+                     struct _fpx_sw_bytes *fx_sw_user)
+{
+        int min_xstate_size = sizeof(struct i387_fxsave_struct) +
+                              sizeof(struct xsave_hdr_struct);
+        unsigned int magic2;
+        int err;
+
+        err = __copy_from_user(fx_sw_user, &buf->sw_reserved[0],
+                               sizeof(struct _fpx_sw_bytes));
+
+        if (err)
+                return err;
+
+        /*
+         * First Magic check failed.
+         */
+        if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1)
+                return -1;
+
+        /*
+         * Check for error scenarios.
+         */
+        if (fx_sw_user->xstate_size < min_xstate_size ||
+            fx_sw_user->xstate_size > xstate_size ||
+            fx_sw_user->xstate_size > fx_sw_user->extended_size)
+                return -1;
+
+        err = __get_user(magic2, (__u32 *) (((void *)fpstate) +
+                                            fx_sw_user->extended_size -
+                                            FP_XSTATE_MAGIC2_SIZE));
+        /*
+         * Check for the presence of second magic word at the end of memory
+         * layout. This detects the case where the user just copied the legacy
+         * fpstate layout with out copying the extended state information
+         * in the memory layout.
+         */
+        if (err || magic2 != FP_XSTATE_MAGIC2)
+                return -1;
+
+        return 0;
+}
+
+#ifdef CONFIG_X86_64
+/*
+ * Signal frame handlers.
+ */
+
+int save_i387_xstate(void __user *buf)
+{
+        struct task_struct *tsk = current;
+        int err = 0;
+
+        if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size))
+                return -EACCES;
+
+        BUG_ON(sig_xstate_size < xstate_size);
+
+        if ((unsigned long)buf % 64)
+                printk("save_i387_xstate: bad fpstate %p\n", buf);
+
+        if (!used_math())
+                return 0;
+        clear_used_math(); /* trigger finit */
+        if (task_thread_info(tsk)->status & TS_USEDFPU) {
+                /*
+                 * Start with clearing the user buffer. This will present a
+                 * clean context for the bytes not touched by the fxsave/xsave.
+                 */
+                __clear_user(buf, sig_xstate_size);
+
+                if (task_thread_info(tsk)->status & TS_XSAVE)
+                        err = xsave_user(buf);
+                else
+                        err = fxsave_user(buf);
+
+                if (err)
+                        return err;
+                task_thread_info(tsk)->status &= ~TS_USEDFPU;
+                stts();
+        } else {
+                if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,
+                                   xstate_size))
+                        return -1;
+        }
+
+        if (task_thread_info(tsk)->status & TS_XSAVE) {
+                struct _fpstate __user *fx = buf;
+
+                err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
+                                     sizeof(struct _fpx_sw_bytes));
+
+                err |= __put_user(FP_XSTATE_MAGIC2,
+                                  (__u32 __user *) (buf + sig_xstate_size
+                                                    - FP_XSTATE_MAGIC2_SIZE));
+        }
+
+        return 1;
+}
+
+/*
+ * Restore the extended state if present. Otherwise, restore the FP/SSE
+ * state.
+ */
+int restore_user_xstate(void __user *buf)
+{
+        struct _fpx_sw_bytes fx_sw_user;
+        u64 mask;
+        int err;
+
+        if (((unsigned long)buf % 64) ||
+             check_for_xstate(buf, buf, &fx_sw_user))
+                goto fx_only;
+
+        mask = fx_sw_user.xstate_bv;
+
+        /*
+         * restore the state passed by the user.
+         */
+        err = xrestore_user(buf, mask);
+        if (err)
+                return err;
+
+        /*
+         * init the state skipped by the user.
+         */
+        mask = pcntxt_mask & ~mask;
+
+        xrstor_state(init_xstate_buf, mask);
+
+        return 0;
+
+fx_only:
+        /*
+         * couldn't find the extended state information in the
+         * memory layout. Restore just the FP/SSE and init all
+         * the other extended state.
+         */
+        xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
+        return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
+}
+
+/*
+ * This restores directly out of user space. Exceptions are handled.
+ */
+int restore_i387_xstate(void __user *buf)
+{
+        struct task_struct *tsk = current;
+        int err = 0;
+
+        if (!buf) {
+                if (used_math())
+                        goto clear;
+                return 0;
+        } else
+                if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
+                        return -EACCES;
+
+        if (!used_math()) {
+                err = init_fpu(tsk);
+                if (err)
+                        return err;
+        }
+
+        if (!(task_thread_info(current)->status & TS_USEDFPU)) {
+                clts();
+                task_thread_info(current)->status |= TS_USEDFPU;
+        }
+        if (task_thread_info(tsk)->status & TS_XSAVE)
+                err = restore_user_xstate(buf);
+        else
+                err = fxrstor_checking((__force struct i387_fxsave_struct *)
+                                       buf);
+        if (unlikely(err)) {
+                /*
+                 * Encountered an error while doing the restore from the
+                 * user buffer, clear the fpu state.
+                 */
+clear:
+                clear_fpu(tsk);
+                clear_used_math();
+        }
+        return err;
+}
+#endif
+
+/*
+ * Prepare the SW reserved portion of the fxsave memory layout, indicating
+ * the presence of the extended state information in the memory layout
+ * pointed by the fpstate pointer in the sigcontext.
+ * This will be saved when ever the FP and extended state context is
+ * saved on the user stack during the signal handler delivery to the user.
+ */
+void prepare_fx_sw_frame(void)
+{
+        int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
+                             FP_XSTATE_MAGIC2_SIZE;
+
+        sig_xstate_size = sizeof(struct _fpstate) + size_extended;
+
+#ifdef CONFIG_IA32_EMULATION
+        sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
+#endif
+
+        memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));
+
+        fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
+        fx_sw_reserved.extended_size = sig_xstate_size;
+        fx_sw_reserved.xstate_bv = pcntxt_mask;
+        fx_sw_reserved.xstate_size = xstate_size;
+#ifdef CONFIG_IA32_EMULATION
+        memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
+               sizeof(struct _fpx_sw_bytes));
+        fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
+#endif
+}
+
+/*
+ * Represents init state for the supported extended state.
+ */
+struct xsave_struct *init_xstate_buf;
+
+#ifdef CONFIG_X86_64
+unsigned int sig_xstate_size = sizeof(struct _fpstate);
+#endif
+
+/*
+ * Enable the extended processor state save/restore feature
+ */
+void __cpuinit xsave_init(void)
+{
+        if (!cpu_has_xsave)
+                return;
+
+        set_in_cr4(X86_CR4_OSXSAVE);
+
+        /*
+         * Enable all the features that the HW is capable of
+         * and the Linux kernel is aware of.
+         */
+        xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
+}
+
+/*
+ * setup the xstate image representing the init state
+ */
+void setup_xstate_init(void)
+{
+        init_xstate_buf = alloc_bootmem(xstate_size);
+        init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
+}
+
+/*
+ * Enable and initialize the xsave feature.
+ */
+void __init xsave_cntxt_init(void)
+{
+        unsigned int eax, ebx, ecx, edx;
+
+        cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
+        pcntxt_mask = eax + ((u64)edx << 32);
+
+        if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
+                printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n",
+                       pcntxt_mask);
+                BUG();
+        }
+
+        /*
+         * for now OS knows only about FP/SSE
+         */
+        pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
+        xsave_init();
+
+        /*
+         * Recompute the context size for enabled features
+         */
+        cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
+        xstate_size = ebx;
+
+        prepare_fx_sw_frame();
+
+        setup_xstate_init();
+
+        printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
+               "cntxt size 0x%x\n",
+               pcntxt_mask, xstate_size);
+}