x86, xsave: save/restore the extended state context in sigframe

On cpu's supporting xsave/xrstor, fpstate pointer in the sigcontext, will
include the extended state information along with fpstate information. Presence
of extended state information is indicated by the presence
of FP_XSTATE_MAGIC1 at fpstate.sw_reserved.magic1 and FP_XSTATE_MAGIC2
at fpstate + (fpstate.sw_reserved.extended_size - FP_XSTATE_MAGIC2_SIZE).

Extended feature bit mask that is saved in the memory layout is represented
by the fpstate.sw_reserved.xstate_bv

For RT signal frames, UC_FP_XSTATE in the uc_flags also indicate the
presence of extended state information in the sigcontext's fpstate
pointer.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

8 files changed, 264 insertions, 22 deletions

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index c596eabbe98b..f25a10124005 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -544,7 +544,10 @@ int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                 goto give_sigsegv;
 
         /* Create the ucontext.  */
-        err |= __put_user(0, &frame->uc.uc_flags);
+        if (cpu_has_xsave)
+                err |= __put_user(UC_FP_XSTATE, &frame->uc.uc_flags);
+        else
+                err |= __put_user(0, &frame->uc.uc_flags);
         err |= __put_user(0, &frame->uc.uc_link);
         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
         err |= __put_user(sas_ss_flags(regs->sp),
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 7daf3a011dd9..cbb9dc474a21 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -26,6 +26,7 @@
 # define _fpstate_ia32          _fpstate
 # define _xstate_ia32           _xstate
 # define sig_xstate_ia32_size   sig_xstate_size
+# define fx_sw_reserved_ia32    fx_sw_reserved
 # define user_i387_ia32_struct  user_i387_struct
 # define user32_fxsr_struct     user_fxsr_struct
 #endif
@@ -447,12 +448,30 @@ static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
         if (err)
                 return -1;
 
-        if (__copy_to_user(&buf->_fxsr_env[0], fx,
-                           sizeof(struct i387_fxsave_struct)))
+        if (__copy_to_user(&buf->_fxsr_env[0], fx, xstate_size))
                 return -1;
         return 1;
 }
 
+static int save_i387_xsave(void __user *buf)
+{
+        struct _fpstate_ia32 __user *fx = buf;
+        int err = 0;
+
+        if (save_i387_fxsave(fx) < 0)
+                return -1;
+
+        err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved_ia32,
+                             sizeof(struct _fpx_sw_bytes));
+        err |= __put_user(FP_XSTATE_MAGIC2,
+                          (__u32 __user *) (buf + sig_xstate_ia32_size
+                                            - FP_XSTATE_MAGIC2_SIZE));
+        if (err)
+                return -1;
+
+        return 1;
+}
+
 int save_i387_xstate_ia32(void __user *buf)
 {
         struct _fpstate_ia32 __user *fp = (struct _fpstate_ia32 __user *) buf;
@@ -477,6 +496,8 @@ int save_i387_xstate_ia32(void __user *buf)
 
         unlazy_fpu(tsk);
 
+        if (cpu_has_xsave)
+                return save_i387_xsave(fp);
         if (cpu_has_fxsr)
                 return save_i387_fxsave(fp);
         else
@@ -491,14 +512,15 @@ static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
                                 sizeof(struct i387_fsave_struct));
 }
 
-static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
+static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf,
+                               unsigned int size)
 {
         struct task_struct *tsk = current;
         struct user_i387_ia32_struct env;
         int err;
 
         err = __copy_from_user(&tsk->thread.xstate->fxsave, &buf->_fxsr_env[0],
-                               sizeof(struct i387_fxsave_struct));
+                               size);
         /* mxcsr reserved bits must be masked to zero for security reasons */
         tsk->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
         if (err || __copy_from_user(&env, buf, sizeof(env)))
@@ -508,6 +530,51 @@ static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
         return 0;
 }
 
+static int restore_i387_xsave(void __user *buf)
+{
+        struct _fpx_sw_bytes fx_sw_user;
+        struct _fpstate_ia32 __user *fx_user =
+                        ((struct _fpstate_ia32 __user *) buf);
+        struct i387_fxsave_struct __user *fx =
+                (struct i387_fxsave_struct __user *) &fx_user->_fxsr_env[0];
+        struct xsave_hdr_struct *xsave_hdr =
+                                &current->thread.xstate->xsave.xsave_hdr;
+        unsigned int lmask, hmask;
+        int err;
+
+        if (check_for_xstate(fx, buf, &fx_sw_user))
+                goto fx_only;
+
+        lmask = fx_sw_user.xstate_bv;
+        hmask = fx_sw_user.xstate_bv >> 32;
+
+        err = restore_i387_fxsave(buf, fx_sw_user.xstate_size);
+
+        xsave_hdr->xstate_bv &=  (pcntxt_lmask | (((u64) pcntxt_hmask) << 32));
+        /*
+         * These bits must be zero.
+         */
+        xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
+
+        /*
+         * Init the state that is not present in the memory layout
+         * and enabled by the OS.
+         */
+        lmask = ~(pcntxt_lmask & ~lmask);
+        hmask = ~(pcntxt_hmask & ~hmask);
+        xsave_hdr->xstate_bv &=  (lmask | (((u64) hmask) << 32));
+
+        return err;
+fx_only:
+        /*
+         * Couldn't find the extended state information in the memory
+         * layout. Restore the FP/SSE and init the other extended state
+         * enabled by the OS.
+         */
+        xsave_hdr->xstate_bv = XSTATE_FPSSE;
+        return restore_i387_fxsave(buf, sizeof(struct i387_fxsave_struct));
+}
+
 int restore_i387_xstate_ia32(void __user *buf)
 {
         int err;
@@ -535,8 +602,11 @@ int restore_i387_xstate_ia32(void __user *buf)
         }
 
         if (HAVE_HWFP) {
-                if (cpu_has_fxsr)
-                        err = restore_i387_fxsave(fp);
+                if (cpu_has_xsave)
+                        err = restore_i387_xsave(buf);
+                else if (cpu_has_fxsr)
+                        err = restore_i387_fxsave(fp, sizeof(struct
+                                                           i387_fxsave_struct));
                 else
                         err = restore_i387_fsave(fp);
         } else {
diff --git a/arch/x86/kernel/signal_32.c b/arch/x86/kernel/signal_32.c
index 690cc616ac07..0f98d69fbdb0 100644
--- a/arch/x86/kernel/signal_32.c
+++ b/arch/x86/kernel/signal_32.c
@@ -441,7 +441,10 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                 goto give_sigsegv;
 
         /* Create the ucontext.  */
-        err |= __put_user(0, &frame->uc.uc_flags);
+        if (cpu_has_xsave)
+                err |= __put_user(UC_FP_XSTATE, &frame->uc.uc_flags);
+        else
+                err |= __put_user(0, &frame->uc.uc_flags);
         err |= __put_user(0, &frame->uc.uc_link);
         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
         err |= __put_user(sas_ss_flags(regs->sp),
diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index ddf6123a55c8..2621b98f5bf6 100644
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -192,7 +192,7 @@ get_stack(struct k_sigaction *ka, struct pt_regs *regs, unsigned long size)
                         sp = current->sas_ss_sp + current->sas_ss_size;
         }
 
-        return (void __user *)round_down(sp - size, 16);
+        return (void __user *)round_down(sp - size, 64);
 }
 
 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
@@ -226,7 +226,10 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
         }
                 
         /* Create the ucontext.  */
-        err |= __put_user(0, &frame->uc.uc_flags);
+        if (cpu_has_xsave)
+                err |= __put_user(UC_FP_XSTATE, &frame->uc.uc_flags);
+        else
+                err |= __put_user(0, &frame->uc.uc_flags);
         err |= __put_user(0, &frame->uc.uc_link);
         err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
         err |= __put_user(sas_ss_flags(regs->sp),
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 608e72d7ca64..dd66d0714c18 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -6,12 +6,68 @@
 #include <linux/bootmem.h>
 #include <linux/compat.h>
 #include <asm/i387.h>
+#ifdef CONFIG_IA32_EMULATION
+#include <asm/sigcontext32.h>
+#endif
 
 /*
  * Supported feature mask by the CPU and the kernel.
  */
 unsigned int pcntxt_hmask, pcntxt_lmask;
 
+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.
@@ -28,15 +84,18 @@ int save_i387_xstate(void __user *buf)
         BUILD_BUG_ON(sizeof(struct user_i387_struct) !=
                         sizeof(tsk->thread.xstate->fxsave));
 
-        if ((unsigned long)buf % 16)
+        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) {
-                err = save_i387_checking((struct i387_fxsave_struct __user *)
-                                         buf);
+                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;
@@ -46,23 +105,77 @@ int save_i387_xstate(void __user *buf)
                                    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;
+        unsigned int lmask, hmask;
+        int err;
+
+        if (((unsigned long)buf % 64) ||
+             check_for_xstate(buf, buf, &fx_sw_user))
+                goto fx_only;
+
+        lmask = fx_sw_user.xstate_bv;
+        hmask = fx_sw_user.xstate_bv >> 32;
+
+        /*
+         * restore the state passed by the user.
+         */
+        err = xrestore_user(buf, lmask, hmask);
+        if (err)
+                return err;
+
+        /*
+         * init the state skipped by the user.
+         */
+        lmask = pcntxt_lmask & ~lmask;
+        hmask = pcntxt_hmask & ~hmask;
+
+        xrstor_state(init_xstate_buf, lmask, hmask);
+
+        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_lmask & ~XSTATE_FPSSE,
+                     pcntxt_hmask);
+        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;
+        int err = 0;
 
         if (!buf) {
-                if (used_math()) {
-                        clear_fpu(tsk);
-                        clear_used_math();
-                }
-
+                if (used_math())
+                        goto clear;
                 return 0;
         } else
                 if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
@@ -78,12 +191,17 @@ int restore_i387_xstate(void __user *buf)
                 clts();
                 task_thread_info(current)->status |= TS_USEDFPU;
         }
-        err = fxrstor_checking((__force struct i387_fxsave_struct *)buf);
+        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();
         }
@@ -92,6 +210,38 @@ int restore_i387_xstate(void __user *buf)
 #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_lmask |
+                                         (((u64) (pcntxt_hmask)) << 32);
+        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;
@@ -162,6 +312,8 @@ void __init xsave_cntxt_init(void)
 
         xstate_size = ebx;
 
+        prepare_fx_sw_frame();
+
         setup_xstate_init();
 
         printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%Lx, "
diff --git a/include/asm-x86/i387.h b/include/asm-x86/i387.h
index dc3745e8040a..d3dda7161954 100644
--- a/include/asm-x86/i387.h
+++ b/include/asm-x86/i387.h
@@ -31,8 +31,10 @@ extern user_regset_active_fn fpregs_active, xfpregs_active;
 extern user_regset_get_fn fpregs_get, xfpregs_get, fpregs_soft_get;
 extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set;
 
+extern struct _fpx_sw_bytes fx_sw_reserved;
 #ifdef CONFIG_IA32_EMULATION
 extern unsigned int sig_xstate_ia32_size;
+extern struct _fpx_sw_bytes fx_sw_reserved_ia32;
 struct _fpstate_ia32;
 struct _xstate_ia32;
 extern int save_i387_xstate_ia32(void __user *buf);
@@ -104,7 +106,7 @@ static inline void clear_fpu_state(struct task_struct *tsk)
                           X86_FEATURE_FXSAVE_LEAK);
 }
 
-static inline int save_i387_checking(struct i387_fxsave_struct __user *fx)
+static inline int fxsave_user(struct i387_fxsave_struct __user *fx)
 {
         int err;
 
diff --git a/include/asm-x86/ucontext.h b/include/asm-x86/ucontext.h
index 9948dd328084..89eaa5456a7e 100644
--- a/include/asm-x86/ucontext.h
+++ b/include/asm-x86/ucontext.h
@@ -1,6 +1,12 @@
 #ifndef ASM_X86__UCONTEXT_H
 #define ASM_X86__UCONTEXT_H
 
+#define UC_FP_XSTATE    0x1     /* indicates the presence of extended state
+                                 * information in the memory layout pointed
+                                 * by the fpstate pointer in the ucontext's
+                                 * sigcontext struct (uc_mcontext).
+                                 */
+
 struct ucontext {
         unsigned long     uc_flags;
         struct ucontext  *uc_link;
diff --git a/include/asm-x86/xsave.h b/include/asm-x86/xsave.h
index b716511aede2..b7f64b9fcd94 100644
--- a/include/asm-x86/xsave.h
+++ b/include/asm-x86/xsave.h
@@ -29,6 +29,9 @@ extern struct xsave_struct *init_xstate_buf;
 extern void xsave_cntxt_init(void);
 extern void xsave_init(void);
 extern int init_fpu(struct task_struct *child);
+extern int check_for_xstate(struct i387_fxsave_struct __user *buf,
+                            void __user *fpstate,
+                            struct _fpx_sw_bytes *sw);
 
 static inline int xrstor_checking(struct xsave_struct *fx)
 {
@@ -48,7 +51,7 @@ static inline int xrstor_checking(struct xsave_struct *fx)
         return err;
 }
 
-static inline int xsave_check(struct xsave_struct __user *buf)
+static inline int xsave_user(struct xsave_struct __user *buf)
 {
         int err;
         __asm__ __volatile__("1: .byte " REX_PREFIX "0x0f,0xae,0x27\n"