[Devel] [PATCH 22/38] C/R: i386 xstate

[Alexey Dobriyan]

The only check is if xstate length doesn't match.
This is insufficient, but posted anyway, because glibc manages
to do FP calculations and create xstate which would prevent
checkpointing.

Signed-off-by: Alexey Dobriyan <adobriyan at gmail.com>
---
 include/linux/kstate-image.h  |    3 ++
 kernel/kstate/kstate-x86_32.c |   44 ++++++++++++++++++++++++++++++++++++----
 2 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/include/linux/kstate-image.h b/include/linux/kstate-image.h
index 6f11b4d..3c93432 100644
--- a/include/linux/kstate-image.h
+++ b/include/linux/kstate-image.h
@@ -105,6 +105,9 @@ struct kstate_image_task_struct_i386 {
 	__u32		dr7;
 
 	__u64		tls_array[3];
+
+	__u32		len_xstate;
+	/* __u8	xstate[len_xstate]; */
 } __packed;
 
 struct kstate_image_mm_struct {
diff --git a/kernel/kstate/kstate-x86_32.c b/kernel/kstate/kstate-x86_32.c
index c738e16..d5c162b 100644
--- a/kernel/kstate/kstate-x86_32.c
+++ b/kernel/kstate/kstate-x86_32.c
@@ -1,5 +1,6 @@
 /* Copyright (C) 2000-2009 Parallels Holdings, Ltd. */
 #include <linux/sched.h>
+#include <asm/i387.h>
 
 #include <linux/kstate.h>
 #include <linux/kstate-image.h>
@@ -74,12 +75,16 @@ static int check_tls(struct desc_struct *desc)
 int kstate_arch_check_image_task_struct(struct kstate_image_task_struct *tsk_i)
 {
 	struct kstate_image_task_struct_i386 *i = (void *)(tsk_i + 1);
+	unsigned int len_xstate;
 	int rv;
 
 	if (tsk_i->tsk_arch != KSTATE_ARCH_I386)
 		return -EINVAL;
 	if (tsk_i->hdr.obj_len < sizeof(*tsk_i) + sizeof(*i))
 		return -EINVAL;
+	len_xstate = i->len_xstate;
+	if (tsk_i->hdr.obj_len - sizeof(*tsk_i) - sizeof(*i) < len_xstate)
+		return -EINVAL;
 
 	rv = check_eflags(i->eflags);
 	if (rv < 0)
@@ -126,22 +131,28 @@ int kstate_arch_check_image_task_struct(struct kstate_image_task_struct *tsk_i)
 			return rv;
 	}
 
+	if (len_xstate > 0 && len_xstate != xstate_size) {
+		WARN(1, "xstate size mismatch %u:%u\n", len_xstate, xstate_size);
+		return -EINVAL;
+	}
+
 	return 0;
 }
 
 unsigned int kstate_arch_len_task_struct(struct task_struct *tsk)
 {
-	return sizeof(struct kstate_image_task_struct_i386);
+	unsigned int len;
+
+	len = sizeof(struct kstate_image_task_struct_i386);
+	if (tsk->thread.xstate)
+		len += xstate_size;
+	return len;
 }
 
 int kstate_arch_check_task_struct(struct task_struct *tsk)
 {
 	struct restart_block *rb;
 
-	if (tsk->thread.xstate) {
-		WARN_ON(1);
-		return -EINVAL;
-	}
 	rb = &task_thread_info(tsk)->restart_block;
 	if (rb->fn != current_thread_info()->restart_block.fn) {
 		WARN(1, "rb->fn = %pF\n", rb->fn);
@@ -237,13 +248,30 @@ int kstate_arch_dump_task_struct(struct kstate_context *ctx, struct task_struct
 	BUILD_BUG_ON(sizeof(tsk->thread.tls_array) != 3 * 8);
 	memcpy(i->tls_array, tsk->thread.tls_array, sizeof(i->tls_array));
 
+	i->len_xstate = 0;
+	if (tsk->thread.xstate) {
+		i->len_xstate = xstate_size;
+		memcpy(i + 1, tsk->thread.xstate, xstate_size);
+	}
+
 	return 0;
 }
 
+static int restore_xstate(struct task_struct *tsk, void *xstate, unsigned int len)
+{
+	int rv;
+
+	rv = init_fpu(tsk);
+	if (rv == 0)
+		memcpy(tsk->thread.xstate, xstate, len);
+	return rv;
+}
+
 asmlinkage void ret_from_fork(void);
 static int restore_task_struct_i386(struct task_struct *tsk, struct kstate_image_task_struct_i386 *i)
 {
 	struct pt_regs *regs = task_pt_regs(tsk);
+	int rv;
 
 	tsk->thread.sp = (unsigned long)regs;
 	tsk->thread.sp0 = (unsigned long)(regs + 1);
@@ -281,6 +309,12 @@ static int restore_task_struct_i386(struct task_struct *tsk, struct kstate_image
 
 	memcpy(tsk->thread.tls_array, i->tls_array, 3 * 8);
 
+	if (i->len_xstate) {
+		rv = restore_xstate(tsk, i + 1, i->len_xstate);
+		if (rv < 0)
+			return rv;
+	}
+
 	return 0;
 }
 
-- 
1.5.6.5

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