[CRIU] [PATCHv1 26/26] x86-32: restore TLS

[Dmitry Safonov]

Put dumped TLS descriptors back to GDT.
Do it only if it was present.

Cc: Cyrill Gorcunov <gorcunov at openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov at virtuozzo.com>
---
 criu/arch/x86/include/asm/restore.h  | 23 +++++++++++++-
 criu/arch/x86/include/asm/restorer.h |  5 +--
 criu/arch/x86/restorer.c             | 61 ++++++++++++++++++++++++++++++++++++
 criu/pie/Makefile                    |  1 +
 4 files changed, 85 insertions(+), 5 deletions(-)

diff --git a/criu/arch/x86/include/asm/restore.h b/criu/arch/x86/include/asm/restore.h
index c00553dff24a..c5aa7cdebf03 100644
--- a/criu/arch/x86/include/asm/restore.h
+++ b/criu/arch/x86/include/asm/restore.h
@@ -28,7 +28,28 @@
 	;
 #endif /* CONFIG_X86_64 */
 
-#define core_get_tls(pcore, ptls)
+static inline void core_get_tls(CoreEntry *pcore, tls_t *ptls)
+{
+	ThreadInfoX86 *ti = pcore->thread_info;
+	int i;
+
+	for (i = 0; i < GDT_ENTRY_TLS_NUM; i++) {
+		user_desc_t *to = &ptls->desc[i];
+		UserDescT *from = ti->tls[i];
+
+#define COPY_TLS(field) to->field = from->field
+		COPY_TLS(entry_number);
+		COPY_TLS(base_addr);
+		COPY_TLS(limit);
+		COPY_TLS(seg_32bit);
+		to->contents = ((u32)from->contents_h << 1) | from->contents_l;
+		COPY_TLS(read_exec_only);
+		COPY_TLS(limit_in_pages);
+		COPY_TLS(seg_not_present);
+		COPY_TLS(useable);
+#undef COPY_TLS
+	}
+}
 
 
 int restore_fpu(struct rt_sigframe *sigframe, CoreEntry *core);
diff --git a/criu/arch/x86/include/asm/restorer.h b/criu/arch/x86/include/asm/restorer.h
index f4ba22180a39..f5065d118ddb 100644
--- a/criu/arch/x86/include/asm/restorer.h
+++ b/criu/arch/x86/include/asm/restorer.h
@@ -334,10 +334,7 @@ int restore_nonsigframe_gpregs(UserX86RegsEntry *r);
 int sigreturn_prep_fpu_frame(struct rt_sigframe *sigframe,
 		struct rt_sigframe *rsigframe);
 
-static inline void restore_tls(tls_t *ptls)
-{
-	(void)ptls;
-}
+void restore_tls(tls_t *ptls);
 
 int ptrace_set_breakpoint(pid_t pid, void *addr);
 int ptrace_flush_breakpoints(pid_t pid);
diff --git a/criu/arch/x86/restorer.c b/criu/arch/x86/restorer.c
index 364b156be91e..db7254f26672 100644
--- a/criu/arch/x86/restorer.c
+++ b/criu/arch/x86/restorer.c
@@ -31,3 +31,64 @@ int restore_nonsigframe_gpregs(UserX86RegsEntry *r)
 #endif
 	return 0;
 }
+
+extern unsigned long call32_from_64(void *stack, void (*function)(void));
+
+asm (	".pushsection .text					\n"
+	"restore_set_thread_area:				\n"
+	".code32						\n"
+	"mov %edx, %ebx						\n"
+	"movl $"__stringify(__NR32_set_thread_area)",%eax	\n"
+	"int $0x80						\n"
+	"ret							\n"
+	".code64");
+extern void restore_set_thread_area(void);
+
+static void __restore_tls(tls_t *ptls)
+{
+	char *stack32 = (void*)sys_mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE,
+				MAP_32BIT | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	int i;
+
+	if (stack32 == MAP_FAILED) {
+		pr_err("Failed to allocate stack for 32-bit TLS restore\n");
+		return;
+	}
+
+	for (i = 0; i < GDT_ENTRY_TLS_NUM; i++) {
+		user_desc_t *desc = &ptls->desc[i];
+		int ret;
+
+		if (desc->seg_not_present)
+			continue;
+
+		memcpy(stack32, desc, sizeof(user_desc_t));
+
+		/* user_desc parameter for set_thread_area syscall */
+		asm volatile ("\t movl %%edx,%%edx\n" : :"d"(stack32));
+		call32_from_64(stack32 + PAGE_SIZE, restore_set_thread_area);
+		asm volatile ("\t movl %%eax,%0\n" : "=r"(ret));
+		if (ret)
+			pr_err("Failed to restore TLS descriptor %d in GDT ret %d\n",
+					desc->entry_number, ret);
+	}
+
+	sys_munmap(stack32, PAGE_SIZE);
+}
+
+void restore_tls(tls_t *ptls)
+{
+	int i;
+
+	for (i = 0; i < GDT_ENTRY_TLS_NUM; i++) {
+		user_desc_t *desc = &ptls->desc[i];
+
+		if (!desc->seg_not_present)
+			goto need_restore;
+	}
+
+	return;
+
+need_restore:
+	__restore_tls(ptls);
+}
diff --git a/criu/pie/Makefile b/criu/pie/Makefile
index 4adec495fe74..fee5d3c6f911 100644
--- a/criu/pie/Makefile
+++ b/criu/pie/Makefile
@@ -14,6 +14,7 @@ restorer-obj-y		+= ./$(ARCH_DIR)/restorer.o
 
 ifeq ($(ARCH),x86)
         restorer-obj-e		+= ./$(ARCH_DIR)/syscalls-64.built-in.o
+        restorer-obj-y		+= ./$(ARCH_DIR)/call32.o
 
         native-obj-y		+= ./$(ARCH_DIR)/parasite-head-64.o
         native-obj-e		+= ./$(ARCH_DIR)/syscalls-64.built-in.o
-- 
2.8.3