dump: Add dumping of alternative signal stack

[alekskartashov@: use encode_pointer]
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Alexander Kartashov <alekskartashov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/parasite.h

@@ -10,6 +10,7 @@
 
 #include <sys/un.h>
 #include <time.h>
+#include <signal.h>
 
 #include "image.h"
 #include "util-net.h"
@@ -71,6 +72,7 @@ struct parasite_init_args {
 	k_rtsigset_t		sig_blocked;
 
 	struct rt_sigframe	*sigframe;
+	stack_t			sas;
 };
 
 struct parasite_log_args {
@@ -163,6 +165,7 @@ struct parasite_dump_thread {
 	pid_t			tid;
 	k_rtsigset_t		blocked;
 	u32			tls;
+	stack_t			sas;
 };
 
 #define PARASITE_MAX_FDS	(PAGE_SIZE / sizeof(int))

parasite-syscall.c

@@ -370,7 +370,14 @@ static int parasite_set_logfd(struct parasite_ctl *ctl, pid_t pid)
 	return 0;
 }
 
-static int parasite_init(struct parasite_ctl *ctl, pid_t pid, int nr_threads)
+static void copy_sas(ThreadSasEntry *dst, stack_t *src)
+{
+	dst->ss_sp = encode_pointer(src->ss_sp);
+	dst->ss_size = (u64)src->ss_size;
+	dst->ss_flags = src->ss_flags;
+}
+
+static int parasite_init(struct parasite_ctl *ctl, pid_t pid, struct pstree_item *item)
 {
 	static int ssock = -1;
 
@@ -421,6 +428,9 @@ static int parasite_init(struct parasite_ctl *ctl, pid_t pid, int nr_threads)
 	ctl->sig_blocked = args->sig_blocked;
 	ctl->use_sig_blocked = true;
 
+	BUG_ON(!item->core[0]->thread_core->sas);
+	copy_sas(item->core[0]->thread_core->sas, &args->sas);
+
 	sock = accept(ssock, NULL, 0);
 	if (sock < 0) {
 		pr_perror("Can't accept connection to the transport socket");
@@ -516,6 +526,9 @@ int parasite_dump_thread_seized(struct parasite_ctl *ctl, int id,
 		memcpy(&core->thread_core->blk_sigset,
 			&args->blocked, sizeof(k_rtsigset_t));
 		core->thread_core->has_blk_sigset = true;
+
+		BUG_ON(!core->thread_core->sas);
+		copy_sas(core->thread_core->sas, &args->sas);
 	}
 
 	CORE_THREAD_ARCH_INFO(core)->clear_tid_addr = encode_pointer(args->tid_addr);
@@ -1069,7 +1082,7 @@ struct parasite_ctl *parasite_infect_seized(pid_t pid, struct pstree_item *item,
 		p += PARASITE_STACK_SIZE;
 	}
 
-	ret = parasite_init(ctl, pid, item->nr_threads);
+	ret = parasite_init(ctl, pid, item);
 	if (ret) {
 		pr_err("%d: Can't create a transport socket\n", pid);
 		goto err_restore;

pie/parasite.c

@@ -230,6 +230,9 @@ static int init_thread(struct parasite_dump_thread *args)
 	args->tid = tid;
 	args->tls = arch_get_tls();
 
+	ret = sys_sigaltstack(NULL, &args->sas);
+	if (ret)
+		goto err;
 
 	return ret;
 err:
@@ -258,6 +261,10 @@ static int init(struct parasite_init_args *args)
 	if (ret)
 		return -1;
 
+	ret = sys_sigaltstack(NULL, &args->sas);
+	if (ret)
+		goto err;
+
 	tsock = sys_socket(PF_UNIX, SOCK_STREAM, 0);
 	if (tsock < 0) {
 		ret = tsock;