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-rw-r--r--arch/x86/kernel/xsave.c345
1 files changed, 345 insertions, 0 deletions
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
new file mode 100644
index 000000000000..9abac8a9d823
--- /dev/null
+++ b/arch/x86/kernel/xsave.c
@@ -0,0 +1,345 @@
+/*
+ * 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.
+ */
+ err = __clear_user(buf, sig_xstate_size);
+ if (err)
+ return err;
+
+ 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;
+ struct _xstate __user *x = buf;
+ u64 xstate_bv;
+
+ 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));
+
+ /*
+ * Read the xstate_bv which we copied (directly from the cpu or
+ * from the state in task struct) to the user buffers and
+ * set the FP/SSE bits.
+ */
+ err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);
+
+ /*
+ * For legacy compatible, we always set FP/SSE bits in the bit
+ * vector while saving the state to the user context. This will
+ * enable us capturing any changes(during sigreturn) to
+ * the FP/SSE bits by the legacy applications which don't touch
+ * xstate_bv in the xsave header.
+ *
+ * xsave aware apps can change the xstate_bv in the xsave
+ * header as well as change any contents in the memory layout.
+ * xrestore as part of sigreturn will capture all the changes.
+ */
+ xstate_bv |= XSTATE_FPSSE;
+
+ err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);
+
+ if (err)
+ return err;
+ }
+
+ 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
+ */
+static void __init 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);
+}
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