bpftool: Match programs by name

When working with frequently modified BPF programs, both the ID and the
tag may change.  bpftool currently doesn't provide a "stable" way to match
such programs.

This patch implements lookup by name for programs.  The show and dump
commands will return all programs with the given name, whereas other
commands will error out if several programs have the same name.
Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Link: https://lore.kernel.org/bpf/b5fc1a5dcfaeb5f16fc80295cdaa606dd2d91534.1576263640.git.paul.chaignon@gmail.com

tools/bpf/bpftool/Documentation/bpftool-map.rst

@@ -41,7 +41,7 @@ MAP COMMANDS
 |
 |	*MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
 |	*DATA* := { [**hex**] *BYTES* }
-|	*PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* }
+|	*PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* | **name** *PROG_NAME* }
 |	*VALUE* := { *DATA* | *MAP* | *PROG* }
 |	*UPDATE_FLAGS* := { **any** | **exist** | **noexist** }
 |	*TYPE* := { **hash** | **array** | **prog_array** | **perf_event_array** | **percpu_hash**

tools/bpf/bpftool/Documentation/bpftool-prog.rst

@@ -33,7 +33,7 @@ PROG COMMANDS
 |	**bpftool** **prog help**
 |
 |	*MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
-|	*PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* }
+|	*PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* | **name** *PROG_NAME* }
 |	*TYPE* := {
 |		**socket** | **kprobe** | **kretprobe** | **classifier** | **action** |
 |		**tracepoint** | **raw_tracepoint** | **xdp** | **perf_event** | **cgroup/skb** |
@@ -55,8 +55,8 @@ DESCRIPTION
 		  Show information about loaded programs.  If *PROG* is
 		  specified show information only about given programs,
 		  otherwise list all programs currently loaded on the system.
-		  In case of **tag**, *PROG* may match several programs which
-		  will all be shown.
+		  In case of **tag** or **name**, *PROG* may match several
+		  programs which will all be shown.
 
 		  Output will start with program ID followed by program type and
 		  zero or more named attributes (depending on kernel version).
@@ -75,9 +75,9 @@ DESCRIPTION
 		  output in human-readable format. In this case, **opcodes**
 		  controls if raw opcodes should be printed as well.
 
-		  In case of **tag**, *PROG* may match several programs which
-		  will all be dumped.  However, if **file** or **visual** is
-		  specified, *PROG* must match a single program.
+		  In case of **tag** or **name**, *PROG* may match several
+		  programs which will all be dumped.  However, if **file** or
+		  **visual** is specified, *PROG* must match a single program.
 
 		  If **file** is specified, the binary image will instead be
 		  written to *FILE*.

tools/bpf/bpftool/bash-completion/bpftool

@@ -71,6 +71,12 @@ _bpftool_get_prog_tags()
         command sed -n 's/.*"tag": "\(.*\)",$/\1/p' )" -- "$cur" ) )
 }
 
+_bpftool_get_prog_names()
+{
+    COMPREPLY+=( $( compgen -W "$( bpftool -jp prog 2>&1 | \
+        command sed -n 's/.*"name": "\(.*\)",$/\1/p' )" -- "$cur" ) )
+}
+
 _bpftool_get_btf_ids()
 {
     COMPREPLY+=( $( compgen -W "$( bpftool -jp btf 2>&1 | \
@@ -201,6 +207,10 @@ _bpftool()
             _bpftool_get_prog_tags
             return 0
             ;;
+        name)
+            _bpftool_get_prog_names
+            return 0
+            ;;
         dev)
             _sysfs_get_netdevs
             return 0
@@ -263,7 +273,7 @@ _bpftool()
                     ;;
             esac
 
-            local PROG_TYPE='id pinned tag'
+            local PROG_TYPE='id pinned tag name'
             local MAP_TYPE='id pinned'
             case $command in
                 show|list)
@@ -559,7 +569,7 @@ _bpftool()
                                     return 0
                                     ;;
                                 prog_array)
-                                    local PROG_TYPE='id pinned tag'
+                                    local PROG_TYPE='id pinned tag name'
                                     COMPREPLY+=( $( compgen -W "$PROG_TYPE" \
                                         -- "$cur" ) )
                                     return 0
@@ -644,7 +654,7 @@ _bpftool()
             esac
             ;;
         btf)
-            local PROG_TYPE='id pinned tag'
+            local PROG_TYPE='id pinned tag name'
             local MAP_TYPE='id pinned'
             case $command in
                 dump)
@@ -735,7 +745,7 @@ _bpftool()
                         connect6 sendmsg4 sendmsg6 recvmsg4 recvmsg6 sysctl \
                         getsockopt setsockopt'
                     local ATTACH_FLAGS='multi override'
-                    local PROG_TYPE='id pinned tag'
+                    local PROG_TYPE='id pinned tag name'
                     case $prev in
                         $command)
                             _filedir
@@ -760,7 +770,7 @@ _bpftool()
                             elif [[ "$command" == "attach" ]]; then
                                 # We have an attach type on the command line,
                                 # but it is not the previous word, or
-                                # "id|pinned|tag" (we already checked for
+                                # "id|pinned|tag|name" (we already checked for
                                 # that). This should only leave the case when
                                 # we need attach flags for "attach" commamnd.
                                 _bpftool_one_of_list "$ATTACH_FLAGS"
@@ -786,7 +796,7 @@ _bpftool()
             esac
             ;;
         net)
-            local PROG_TYPE='id pinned tag'
+            local PROG_TYPE='id pinned tag name'
             local ATTACH_TYPES='xdp xdpgeneric xdpdrv xdpoffload'
             case $command in
                 show|list)

tools/bpf/bpftool/main.h

@@ -42,7 +42,7 @@
 #define BPF_TAG_FMT	"%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx"
 
 #define HELP_SPEC_PROGRAM						\
-	"PROG := { id PROG_ID | pinned FILE | tag PROG_TAG }"
+	"PROG := { id PROG_ID | pinned FILE | tag PROG_TAG | name PROG_NAME }"
 #define HELP_SPEC_OPTIONS						\
 	"OPTIONS := { {-j|--json} [{-p|--pretty}] | {-f|--bpffs} |\n"	\
 	"\t            {-m|--mapcompat} | {-n|--nomount} }"

tools/bpf/bpftool/prog.c

@@ -82,7 +82,7 @@ static void print_boot_time(__u64 nsecs, char *buf, unsigned int size)
 		strftime(buf, size, "%FT%T%z", &load_tm);
 }
 
-static int prog_fd_by_tag(unsigned char *tag, int **fds)
+static int prog_fd_by_nametag(void *nametag, int **fds, bool tag)
 {
 	unsigned int id = 0;
 	int fd, nb_fds = 0;
@@ -116,7 +116,8 @@ static int prog_fd_by_tag(unsigned char *tag, int **fds)
 			goto err_close_fd;
 		}
 
-		if (memcmp(tag, info.tag, BPF_TAG_SIZE)) {
+		if ((tag && memcmp(nametag, info.tag, BPF_TAG_SIZE)) ||
+		    (!tag && strncmp(nametag, info.name, BPF_OBJ_NAME_LEN))) {
 			close(fd);
 			continue;
 		}
@@ -174,7 +175,20 @@ static int prog_parse_fds(int *argc, char ***argv, int **fds)
 		}
 		NEXT_ARGP();
 
-		return prog_fd_by_tag(tag, fds);
+		return prog_fd_by_nametag(tag, fds, true);
+	} else if (is_prefix(**argv, "name")) {
+		char *name;
+
+		NEXT_ARGP();
+
+		name = **argv;
+		if (strlen(name) > BPF_OBJ_NAME_LEN - 1) {
+			p_err("can't parse name");
+			return -1;
+		}
+		NEXT_ARGP();
+
+		return prog_fd_by_nametag(name, fds, false);
 	} else if (is_prefix(**argv, "pinned")) {
 		char *path;
 
@@ -189,7 +203,7 @@ static int prog_parse_fds(int *argc, char ***argv, int **fds)
 		return 1;
 	}
 
-	p_err("expected 'id', 'tag' or 'pinned', got: '%s'?", **argv);
+	p_err("expected 'id', 'tag', 'name' or 'pinned', got: '%s'?", **argv);
 	return -1;
 }