kdat: add compat_sigreturn feature

Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/arch/aarch64/include/asm/restorer.h

@@ -52,6 +52,7 @@
 			: "sp", "x0", "memory")
 
 
+#define kdat_compat_sigreturn_test()			0
 
 int restore_gpregs(struct rt_sigframe *f, UserAarch64RegsEntry *r);
 int restore_nonsigframe_gpregs(UserAarch64RegsEntry *r);

criu/arch/arm/include/asm/restorer.h

@@ -53,7 +53,7 @@
 		     : "memory")
 
 
-
+#define kdat_compat_sigreturn_test()			0
 
 int restore_gpregs(struct rt_sigframe *f, UserArmRegsEntry *r);
 int restore_nonsigframe_gpregs(UserArmRegsEntry *r);

criu/arch/ppc64/include/asm/restorer.h

@@ -47,6 +47,7 @@
 		  "r"(&thread_args[i])		/* %6 */		\
 		: "memory","0","3","4","5","6","7","14","15")
 
+#define kdat_compat_sigreturn_test()			0
 
 int restore_gpregs(struct rt_sigframe *f, UserPpc64RegsEntry *r);
 int restore_nonsigframe_gpregs(UserPpc64RegsEntry *r);

criu/arch/x86/crtools.c

@@ -3,6 +3,8 @@
 #include <elf.h>
 #include <sys/user.h>
 #include <sys/mman.h>
+#include <sys/syscall.h>
+#include <sys/auxv.h>
 
 #include "types.h"
 #include "asm/processor-flags.h"
@@ -20,6 +22,7 @@
 #include "cpu.h"
 #include "errno.h"
 #include "syscall-codes.h"
+#include "kerndat.h"
 
 #include "protobuf.h"
 #include "images/core.pb-c.h"
@@ -67,6 +70,31 @@ void parasite_setup_regs(unsigned long new_ip, void *stack, user_regs_struct_t *
 			~(X86_EFLAGS_TF | X86_EFLAGS_DF | X86_EFLAGS_IF));
 }
 
+#ifdef CONFIG_X86_64
+/* Remaps 64-bit vDSO on the same addr, where it already is */
+int kdat_compat_sigreturn_test(void)
+{
+	unsigned long auxval;
+	int ret;
+
+	errno = 0;
+	auxval = getauxval(AT_SYSINFO_EHDR);
+	if (!auxval || errno == ENOENT) {
+		pr_err("Failed to get auxval, err: %lu\n", auxval);
+		return 0;
+	}
+	/*
+	 * Mapping vDSO on very low unaligned address (1).
+	 * We will get ENOMEM or EPERM if ARCH_MAP_VDSO_* exist,
+	 * and ENOSYS if patches aren't in kernel.
+	 */
+	ret = syscall(SYS_arch_prctl, ARCH_MAP_VDSO_32, 1);
+	if (ret == -1 && errno == ENOSYS)
+		return 0;
+	return 1;
+}
+#endif /* CONFIG_X86_64 */
+
 int ptrace_get_regs(pid_t pid, user_regs_struct_t *regs);
 int arch_task_compatible(pid_t pid)
 {
@@ -103,9 +131,13 @@ static bool ldt_task_selectors(pid_t pid)
 bool arch_can_dump_task(struct parasite_ctl *ctl)
 {
 	pid_t pid = ctl->rpid;
+	int ret;
 
-	/* FIXME: remove it */
-	if (arch_task_compatible(pid)) {
+	ret = arch_task_compatible(pid);
+	if (ret < 0)
+		return false;
+
+	if (ret && !kdat.has_compat_sigreturn) {
 		pr_err("Can't dump task %d running in 32-bit mode\n", pid);
 		return false;
 	}

criu/arch/x86/include/asm/restorer.h

@@ -54,6 +54,12 @@
 		     :						\
 		     : "r"(ret)					\
 		     : "memory")
+
+#ifndef ARCH_MAP_VDSO_32
+# define ARCH_MAP_VDSO_32		0x2002
+#endif
+
+extern int kdat_compat_sigreturn_test(void);
 #else /* CONFIG_X86_64 */
 #define RUN_CLONE_RESTORE_FN(ret, clone_flags, new_sp, parent_tid,      \
 			     thread_args, clone_restore_fn)             \
@@ -72,6 +78,8 @@
 		     :						\
 		     : "r"(ret)					\
 		     : "memory")
+
+#define kdat_compat_sigreturn_test()			0
 #endif /* CONFIG_X86_64 */
 
 static inline void

criu/include/kerndat.h

@@ -34,6 +34,7 @@ struct kerndat_s {
 	unsigned long task_size;
 	bool ipv6;
 	bool has_loginuid;
+	bool has_compat_sigreturn;
 	enum pagemap_func pmap;
 	unsigned int has_xtlocks;
 	unsigned long mmap_min_addr;

criu/kerndat.c

@@ -557,6 +557,16 @@ err:
 	return exit_code;
 }
 
+static int kerndat_compat_restore(void)
+{
+	int ret = kdat_compat_sigreturn_test();
+
+	if (ret < 0) /* failure */
+		return ret;
+	kdat.has_compat_sigreturn = !!ret;
+	return 0;
+}
+
 int kerndat_init(void)
 {
 	int ret;
@@ -582,6 +592,8 @@ int kerndat_init(void)
 		ret = kerndat_iptables_has_xtlocks();
 	if (!ret)
 		ret = kerndat_tcp_repair();
+	if (!ret)
+		ret = kerndat_compat_restore();
 
 	kerndat_lsm();
 	kerndat_mmap_min_addr();
@@ -614,6 +626,8 @@ int kerndat_init_rst(void)
 		ret = kerndat_iptables_has_xtlocks();
 	if (!ret)
 		ret = kerndat_tcp_repair();
+	if (!ret)
+		ret = kerndat_compat_restore();
 
 	kerndat_lsm();
 	kerndat_mmap_min_addr();
@@ -626,6 +640,8 @@ int kerndat_init_cr_exec(void)
 	int ret;
 
 	ret = get_task_size();
+	if (!ret)
+		ret = kerndat_compat_restore();
 
 	return ret;
 }