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>
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 608e72d..dd66d07 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 @@
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 @@
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 @@
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 @@
#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 @@
xstate_size = ebx;
+ prepare_fx_sw_frame();
+
setup_xstate_init();
printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%Lx, "
