1 files changed, 152 insertions, 18 deletions

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index a4ae302f03aa..9c253bd65e24 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -16,11 +16,88 @@
  */
 u64 pcntxt_mask;
 
+/*
+ * Represents init state for the supported extended state.
+ */
+static struct xsave_struct *init_xstate_buf;
+
 struct _fpx_sw_bytes fx_sw_reserved;
 #ifdef CONFIG_IA32_EMULATION
 struct _fpx_sw_bytes fx_sw_reserved_ia32;
 #endif
 
+static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;
+
+/*
+ * If a processor implementation discern that a processor state component is
+ * in its initialized state it may modify the corresponding bit in the
+ * xsave_hdr.xstate_bv as '0', with out modifying the corresponding memory
+ * layout in the case of xsaveopt. While presenting the xstate information to
+ * the user, we always ensure that the memory layout of a feature will be in
+ * the init state if the corresponding header bit is zero. This is to ensure
+ * that the user doesn't see some stale state in the memory layout during
+ * signal handling, debugging etc.
+ */
+void __sanitize_i387_state(struct task_struct *tsk)
+{
+        u64 xstate_bv;
+        int feature_bit = 0x2;
+        struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave;
+
+        if (!fx)
+                return;
+
+        BUG_ON(task_thread_info(tsk)->status & TS_USEDFPU);
+
+        xstate_bv = tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv;
+
+        /*
+         * None of the feature bits are in init state. So nothing else
+         * to do for us, as the memory layout is upto date.
+         */
+        if ((xstate_bv & pcntxt_mask) == pcntxt_mask)
+                return;
+
+        /*
+         * FP is in init state
+         */
+        if (!(xstate_bv & XSTATE_FP)) {
+                fx->cwd = 0x37f;
+                fx->swd = 0;
+                fx->twd = 0;
+                fx->fop = 0;
+                fx->rip = 0;
+                fx->rdp = 0;
+                memset(&fx->st_space[0], 0, 128);
+        }
+
+        /*
+         * SSE is in init state
+         */
+        if (!(xstate_bv & XSTATE_SSE))
+                memset(&fx->xmm_space[0], 0, 256);
+
+        xstate_bv = (pcntxt_mask & ~xstate_bv) >> 2;
+
+        /*
+         * Update all the other memory layouts for which the corresponding
+         * header bit is in the init state.
+         */
+        while (xstate_bv) {
+                if (xstate_bv & 0x1) {
+                        int offset = xstate_offsets[feature_bit];
+                        int size = xstate_sizes[feature_bit];
+
+                        memcpy(((void *) fx) + offset,
+                               ((void *) init_xstate_buf) + offset,
+                               size);
+                }
+
+                xstate_bv >>= 1;
+                feature_bit++;
+        }
+}
+
 /*
  * Check for the presence of extended state information in the
  * user fpstate pointer in the sigcontext.
@@ -102,6 +179,7 @@ int save_i387_xstate(void __user *buf)
                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
                 stts();
         } else {
+                sanitize_i387_state(tsk);
                 if (__copy_to_user(buf, &tsk->thread.fpu.state->fxsave,
                                    xstate_size))
                         return -1;
@@ -267,11 +345,6 @@ static void prepare_fx_sw_frame(void)
 #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
@@ -279,37 +352,77 @@ unsigned int sig_xstate_size = sizeof(struct _fpstate);
 /*
  * Enable the extended processor state save/restore feature
  */
-void __cpuinit xsave_init(void)
+static inline void xstate_enable(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);
 }
 
 /*
+ * Record the offsets and sizes of different state managed by the xsave
+ * memory layout.
+ */
+static void __init setup_xstate_features(void)
+{
+        int eax, ebx, ecx, edx, leaf = 0x2;
+
+        xstate_features = fls64(pcntxt_mask);
+        xstate_offsets = alloc_bootmem(xstate_features * sizeof(int));
+        xstate_sizes = alloc_bootmem(xstate_features * sizeof(int));
+
+        do {
+                cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx);
+
+                if (eax == 0)
+                        break;
+
+                xstate_offsets[leaf] = ebx;
+                xstate_sizes[leaf] = eax;
+
+                leaf++;
+        } while (1);
+}
+
+/*
  * setup the xstate image representing the init state
  */
 static void __init setup_xstate_init(void)
 {
+        setup_xstate_features();
+
+        /*
+         * Setup init_xstate_buf to represent the init state of
+         * all the features managed by the xsave
+         */
         init_xstate_buf = alloc_bootmem(xstate_size);
         init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
+
+        clts();
+        /*
+         * Init all the features state with header_bv being 0x0
+         */
+        xrstor_state(init_xstate_buf, -1);
+        /*
+         * Dump the init state again. This is to identify the init state
+         * of any feature which is not represented by all zero's.
+         */
+        xsave_state(init_xstate_buf, -1);
+        stts();
 }
 
 /*
  * Enable and initialize the xsave feature.
  */
-void __ref xsave_cntxt_init(void)
+static void __init xstate_enable_boot_cpu(void)
 {
         unsigned int eax, ebx, ecx, edx;
 
-        cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
+        if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
+                WARN(1, KERN_ERR "XSTATE_CPUID missing\n");
+                return;
+        }
+
+        cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
         pcntxt_mask = eax + ((u64)edx << 32);
 
         if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
@@ -322,12 +435,13 @@ void __ref xsave_cntxt_init(void)
          * Support only the state known to OS.
          */
         pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
-        xsave_init();
+
+        xstate_enable();
 
         /*
          * Recompute the context size for enabled features
          */
-        cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
+        cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
         xstate_size = ebx;
 
         update_regset_xstate_info(xstate_size, pcntxt_mask);
@@ -339,3 +453,23 @@ void __ref xsave_cntxt_init(void)
                "cntxt size 0x%x\n",
                pcntxt_mask, xstate_size);
 }
+
+/*
+ * For the very first instance, this calls xstate_enable_boot_cpu();
+ * for all subsequent instances, this calls xstate_enable().
+ *
+ * This is somewhat obfuscated due to the lack of powerful enough
+ * overrides for the section checks.
+ */
+void __cpuinit xsave_init(void)
+{
+        static __refdata void (*next_func)(void) = xstate_enable_boot_cpu;
+        void (*this_func)(void);
+
+        if (!cpu_has_xsave)
+                return;
+
+        this_func = next_func;
+        next_func = xstate_enable;
+        this_func();
+}