dump: Reseve space and construc sigframes for parasites

We're about to implement functionality to allow parasite to
return to dumpee via sigreturn in case crtools suddenly detached
from it. Thus, we need a space for sigframe in shared area.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/parasite-syscall.h

@@ -16,6 +16,8 @@ struct parasite_thread_ctl
 	bool			use_sig_blocked;
 
 	void			*rstack;
+	struct rt_sigframe	*sigframe;
+	struct rt_sigframe	*rsigframe;				/* address in a parasite */
 };
 
 /* parasite control block */

include/parasite.h

@@ -75,6 +75,8 @@ struct parasite_init_args {
 	int			nr_threads;
 
 	k_rtsigset_t		sig_blocked;
+
+	struct rt_sigframe	*sigframe;
 };
 
 struct parasite_log_args {

parasite-syscall.c

@@ -25,14 +25,16 @@
 #include "net.h"
 #include "mem.h"
 #include "vdso.h"
+#include "restorer.h"
 
 #include <string.h>
 #include <stdlib.h>
 
 #include "asm/parasite-syscall.h"
 #include "asm/dump.h"
+#include "asm/restorer.h"
 
-#define parasite_size		(round_up(sizeof(parasite_blob), sizeof(long)))
+#define parasite_size		(round_up(sizeof(parasite_blob), PAGE_SIZE))
 
 static int can_run_syscall(unsigned long ip, unsigned long start, unsigned long end)
 {
@@ -387,6 +389,7 @@ static int parasite_init(struct parasite_ctl *ctl, pid_t pid, int nr_threads)
 	args->h_addr_len = gen_parasite_saddr(&args->h_addr, getpid());
 	args->p_addr_len = gen_parasite_saddr(&args->p_addr, pid);
 	args->nr_threads = nr_threads;
+	args->sigframe = ctl->threads[0].rsigframe;
 	args->id = 0;
 
 	if (sock == -1) {
@@ -1068,7 +1071,7 @@ static unsigned long parasite_args_size(struct vm_area_list *vmas, struct parasi
 		size = max(size, (unsigned long)drain_fds_size(dfds));
 	size = max(size, (unsigned long)dump_pages_args_size(vmas));
 
-	return size;
+	return round_up(size, PAGE_SIZE);
 }
 
 struct parasite_ctl *parasite_infect_seized(pid_t pid, struct pstree_item *item,
@@ -1096,6 +1099,7 @@ struct parasite_ctl *parasite_infect_seized(pid_t pid, struct pstree_item *item,
 
 	ctl->args_size = parasite_args_size(vma_area_list, dfds);
 	ret = parasite_map_exchange(ctl, parasite_size + ctl->args_size +
+					 item->nr_threads * RESTORE_STACK_SIGFRAME +
 					 item->nr_threads * PARASITE_STACK_SIZE);
 	if (ret)
 		goto err_restore;
@@ -1112,8 +1116,11 @@ struct parasite_ctl *parasite_infect_seized(pid_t pid, struct pstree_item *item,
 	for (i = 0; i < item->nr_threads; i++) {
 		struct parasite_thread_ctl *thread = &ctl->threads[i];
 
-		thread->rstack = ctl->remote_map + p;
-		p += PARASITE_STACK_SIZE;
+		thread->rstack		= ctl->remote_map + p;
+		thread->rsigframe	= ctl->remote_map + p + PARASITE_STACK_SIZE;
+		thread->sigframe	= ctl->local_map  + p + PARASITE_STACK_SIZE;
+
+		p += PARASITE_STACK_SIZE + RESTORE_STACK_SIGFRAME;
 	}
 
 	ret = parasite_init(ctl, pid, item->nr_threads);
@@ -1152,6 +1159,9 @@ struct parasite_ctl *parasite_infect_seized(pid_t pid, struct pstree_item *item,
 				&thread->sig_blocked, sizeof(k_rtsigset_t));
 			item->core[i]->thread_core->has_blk_sigset = true;
 		}
+
+		if (construct_sigframe(thread->sigframe, thread->rsigframe, item->core[i]))
+			goto err_restore;
 	}
 
 	return ctl;

pie/parasite.c

@@ -26,6 +26,8 @@ static struct tid_state_s {
 
 	bool		use_sig_blocked;
 	k_rtsigset_t	sig_blocked;
+
+	struct rt_sigframe *sigframe;
 } *tid_state;
 
 static unsigned int nr_tid_state;
@@ -213,6 +215,7 @@ static int init_thread(struct parasite_init_args *args)
 	args->sig_blocked = tid_state[next_tid_state].sig_blocked;
 
 	tid_state[next_tid_state].id = next_tid_state;
+	tid_state[next_tid_state].sigframe = args->sigframe;
 
 	futex_set(&tid_state[next_tid_state].cmd, PARASITE_CMD_IDLE);