dump: Print error codes if dumper failed in parasite section

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

include/parasite.h

@@ -42,6 +42,9 @@ typedef struct {
 	struct vma_entry	vma_entry;
 	unsigned long		nrpages_dumped;	/* how many pages are dumped */
 	unsigned long		fd;
+	long			ret;
+	long			sys_ret;
+	long			line;
 	unsigned long		open_mode;
 	unsigned long		open_flags;
 	char			open_path[64];

parasite-syscall.c

@@ -378,6 +378,45 @@ retry_signal:
 			pr_err("Can't get statistics (pid: %d)\n", ctl->pid);
 			goto err_restore;
 		}
+
+		/*
+		 * Check if error happened during dumping.
+		 */
+		if (ptrace_peek_area((long)ctl->pid,
+				     (void *)&parasite_dumppages.ret,
+				     (void *)(ctl->addr_args +
+					      offsetof(parasite_args_cmd_dumppages_t, ret)),
+				     sizeof(parasite_dumppages.ret))) {
+			pr_err("Can't get dumper ret code (pid: %d)\n", ctl->pid);
+			goto err_restore;
+		}
+		if (parasite_dumppages.ret) {
+			if (ptrace_peek_area((long)ctl->pid,
+					     (void *)&parasite_dumppages.sys_ret,
+					     (void *)(ctl->addr_args +
+						      offsetof(parasite_args_cmd_dumppages_t, sys_ret)),
+					     sizeof(parasite_dumppages.sys_ret))) {
+				pr_err("Can't get dumper sys_ret code (pid: %d)\n", ctl->pid);
+				goto err_restore;
+			}
+
+			if (ptrace_peek_area((long)ctl->pid,
+					     (void *)&parasite_dumppages.line,
+					     (void *)(ctl->addr_args +
+						      offsetof(parasite_args_cmd_dumppages_t, line)),
+					     sizeof(parasite_dumppages.line))) {
+				pr_err("Can't get dumper ret line (pid: %d)\n", ctl->pid);
+				goto err_restore;
+			}
+
+			pr_panic("Dumping pages failed with %li (%li) at %li\n",
+				 parasite_dumppages.ret,
+				 parasite_dumppages.sys_ret,
+				 parasite_dumppages.line);
+
+			goto err_restore;
+		}
+
 		pr_info("  (dumped: %16li pages)\n", parasite_dumppages.nrpages_dumped);
 		nrpages_dumped += parasite_dumppages.nrpages_dumped;
 	}

parasite.c

@@ -97,6 +97,8 @@ static int dump_pages(parasite_args_cmd_dumppages_t *args)
 		if ((long)args->fd < 0) {
 			sys_write_msg("sys_open failed\n");
 			ret = PARASITE_ERR_OPEN;
+			args->sys_ret = args->fd;
+			args->ret = ret, args->line = __LINE__;
 			goto err;
 		}
 	}
@@ -122,6 +124,8 @@ static int dump_pages(parasite_args_cmd_dumppages_t *args)
 		if ((long)map < 0) {
 			sys_write_msg("sys_mmap failed\n");
 			ret = PARASITE_ERR_MMAP;
+			args->sys_ret = (long)map;
+			args->ret = ret, args->line = __LINE__;
 			goto err;
 		}
 	}
@@ -135,11 +139,14 @@ static int dump_pages(parasite_args_cmd_dumppages_t *args)
 	if (!(args->vma_entry.prot & PROT_READ)) {
 		prot_old = (unsigned long)args->vma_entry.prot;
 		prot_new = prot_old | PROT_READ;
-		if (sys_mprotect((unsigned long)args->vma_entry.start,
+		ret = sys_mprotect((unsigned long)args->vma_entry.start,
 				   (unsigned long)vma_entry_len(&args->vma_entry),
-				 prot_new)) {
+				   prot_new);
+		if (ret) {
 			sys_write_msg("sys_mprotect failed\n");
 			ret = PARASITE_ERR_MPROTECT;
+			args->sys_ret = ret;
+			args->ret = ret, args->line = __LINE__;
 			goto err_free;
 		}
 	}
@@ -149,9 +156,12 @@ static int dump_pages(parasite_args_cmd_dumppages_t *args)
 	 * so stick for mincore as a basis.
 	 */
 
-	if (sys_mincore((unsigned long)args->vma_entry.start, length, map)) {
+	ret = sys_mincore((unsigned long)args->vma_entry.start, length, map);
+	if (ret) {
 		sys_write_msg("sys_mincore failed\n");
+		args->sys_ret = ret;
 		ret = PARASITE_ERR_MINCORE;
+		args->ret = ret, args->line = __LINE__;
 		goto err_free;
 	}
 
@@ -170,8 +180,10 @@ static int dump_pages(parasite_args_cmd_dumppages_t *args)
 			written += sys_write(args->fd, &vaddr, sizeof(vaddr));
 			written += sys_write(args->fd, (void *)vaddr, PAGE_SIZE);
 			if (written != sizeof(vaddr) + PAGE_SIZE) {
+				args->sys_ret = written; /* The caller are to decode value */
 				ret = PARASITE_ERR_WRITE;
 				sys_write_msg("sys_write on page failed\n");
+				args->ret = ret, args->line = __LINE__;
 				goto err_free;
 			}
 
@@ -183,15 +195,21 @@ static int dump_pages(parasite_args_cmd_dumppages_t *args)
 	 * Don't left pages readable if they were not.
 	 */
 	if (prot_old != prot_new) {
-		if (sys_mprotect((unsigned long)args->vma_entry.start,
+		ret = sys_mprotect((unsigned long)args->vma_entry.start,
 				   (unsigned long)vma_entry_len(&args->vma_entry),
-				 prot_old)) {
+				   prot_old);
+		if (ret) {
 			sys_write_msg("PANIC: Ouch! sys_mprotect failed on resore\n");
+			args->sys_ret = ret;
 			ret = PARASITE_ERR_MPROTECT;
+			args->ret = ret, args->line = __LINE__;
 			goto err_free;
 		}
 	}
 
+	/* on success ret = 0 */
+	args->ret = ret, args->line = __LINE__;
+
 err_free:
 	if (map_brk)
 		brk_free(nrpages);