libvmm: constify vm_get_name()

Allows callers of vm_get_name() to retrieve the vm name without having
to allocate a buffer.

While in the vicinity, do minor cleanup in vm_snapshot_basic_metadata().

Reviewed by:	jhb
Differential Revision:	https://reviews.freebsd.org/D34290

(cherry picked from commit 3efc45f34e13c63cb37a77a67fea39937004b75a)

3 files changed, 8 insertions, 31 deletions

diff --git a/lib/libvmmapi/vmmapi.c b/lib/libvmmapi/vmmapi.c
index f6d83dd0e08f..4fc9c4dc69e9 100644
--- a/lib/libvmmapi/vmmapi.c
+++ b/lib/libvmmapi/vmmapi.c
@@ -498,14 +498,11 @@ vm_rev_map_gpa(struct vmctx *ctx, void *addr)
 	return ((vm_paddr_t)-1);
 }
 
-/* TODO: maximum size for vmname */
-int
-vm_get_name(struct vmctx *ctx, char *buf, size_t max_len)
+const char *
+vm_get_name(struct vmctx *ctx)
 {
 
-	if (strlcpy(buf, ctx->name, max_len) >= max_len)
-		return (EINVAL);
-	return (0);
+	return (ctx->name);
 }
 
 size_t
diff --git a/lib/libvmmapi/vmmapi.h b/lib/libvmmapi/vmmapi.h
index 586392a0ff29..c8454150f0b1 100644
--- a/lib/libvmmapi/vmmapi.h
+++ b/lib/libvmmapi/vmmapi.h
@@ -135,7 +135,7 @@ uint32_t vm_get_lowmem_limit(struct vmctx *ctx);
 void	vm_set_lowmem_limit(struct vmctx *ctx, uint32_t limit);
 void	vm_set_memflags(struct vmctx *ctx, int flags);
 int	vm_get_memflags(struct vmctx *ctx);
-int	vm_get_name(struct vmctx *ctx, char *buffer, size_t max_len);
+const char *vm_get_name(struct vmctx *ctx);
 size_t	vm_get_lowmem_size(struct vmctx *ctx);
 size_t	vm_get_highmem_size(struct vmctx *ctx);
 int	vm_set_desc(struct vmctx *ctx, int vcpu, int reg,
diff --git a/usr.sbin/bhyve/snapshot.c b/usr.sbin/bhyve/snapshot.c
index aae8353b89db..4bd2ea273171 100644
--- a/usr.sbin/bhyve/snapshot.c
+++ b/usr.sbin/bhyve/snapshot.c
@@ -1123,28 +1123,15 @@ err_vm_snapshot_kern_data:
 static int
 vm_snapshot_basic_metadata(struct vmctx *ctx, xo_handle_t *xop, size_t memsz)
 {
-	int error;
-	int memflags;
-	char vmname_buf[MAX_VMNAME];
-
-	memset(vmname_buf, 0, MAX_VMNAME);
-	error = vm_get_name(ctx, vmname_buf, MAX_VMNAME - 1);
-	if (error != 0) {
-		perror("Failed to get VM name");
-		goto err;
-	}
-
-	memflags = vm_get_memflags(ctx);
 
 	xo_open_container_h(xop, JSON_BASIC_METADATA_KEY);
 	xo_emit_h(xop, "{:" JSON_NCPUS_KEY "/%ld}\n", guest_ncpus);
-	xo_emit_h(xop, "{:" JSON_VMNAME_KEY "/%s}\n", vmname_buf);
+	xo_emit_h(xop, "{:" JSON_VMNAME_KEY "/%s}\n", vm_get_name(ctx));
 	xo_emit_h(xop, "{:" JSON_MEMSIZE_KEY "/%lu}\n", memsz);
-	xo_emit_h(xop, "{:" JSON_MEMFLAGS_KEY "/%d}\n", memflags);
+	xo_emit_h(xop, "{:" JSON_MEMFLAGS_KEY "/%d}\n", vm_get_memflags(ctx));
 	xo_close_container_h(xop, JSON_BASIC_METADATA_KEY);
 
-err:
-	return (error);
+	return (0);
 }
 
 static int
@@ -1518,7 +1505,6 @@ init_checkpoint_thread(struct vmctx *ctx)
 	struct sockaddr_un addr;
 	int socket_fd;
 	pthread_t checkpoint_pthread;
-	char vmname_buf[MAX_VMNAME];
 	int err;
 
 	memset(&addr, 0, sizeof(addr));
@@ -1532,14 +1518,8 @@ init_checkpoint_thread(struct vmctx *ctx)
 
 	addr.sun_family = AF_UNIX;
 
-	err = vm_get_name(ctx, vmname_buf, MAX_VMNAME - 1);
-	if (err != 0) {
-		perror("Failed to get VM name");
-		goto fail;
-	}
-
 	snprintf(addr.sun_path, sizeof(addr.sun_path), "%s%s",
-		 BHYVE_RUN_DIR, vmname_buf);
+		 BHYVE_RUN_DIR, vm_get_name(ctx));
 	addr.sun_len = SUN_LEN(&addr);
 	unlink(addr.sun_path);