Merge branch 'bpf-bpftool-cleanups'

Quentin Monnet says:

====================
This series contains several minor fixes for bpftool source and
documentation.

The first patches focus on documentation: addition of an option in the page
for "bpftool prog", clean up and update of the same page, and addition of
an example of prog array map manipulation in "bpftool map" page.

The last two fix warnings susceptible to appear when libbfd is not present
(patch 4), or with additional warning flags passed to the compiler (last
patch).
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

7 files changed, 124 insertions, 55 deletions

diff --git a/tools/bpf/bpftool/Documentation/bpftool-map.rst b/tools/bpf/bpftool/Documentation/bpftool-map.rst
index 5318dcb2085e..3221be1b9ccc 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-map.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-map.rst
@@ -170,6 +170,61 @@ The following three commands are equivalent:
 | **# bpftool map pin id 10 /sys/fs/bpf/map**
 | **# bpftool map del pinned /sys/fs/bpf/map key 13 00 07 00**
 
+Note that map update can also be used in order to change the program references
+hold by a program array map. This can be used, for example, to change the
+programs used for tail-call jumps at runtime, without having to reload the
+entry-point program. Below is an example for this use case: we load a program
+defining a prog array map, and with a main function that contains a tail call
+to other programs that can be used either to "process" packets or to "debug"
+processing. Note that the prog array map MUST be pinned into the BPF virtual
+file system for the map update to work successfully, as kernel flushes prog
+array maps when they have no more references from user space (and the update
+would be lost as soon as bpftool exits).
+
+|
+| **# bpftool prog loadall tail_calls.o /sys/fs/bpf/foo type xdp**
+| **# bpftool prog --bpffs**
+
+::
+
+  545: xdp  name main_func  tag 674b4b5597193dc3  gpl
+          loaded_at 2018-12-12T15:02:58+0000  uid 0
+          xlated 240B  jited 257B  memlock 4096B  map_ids 294
+          pinned /sys/fs/bpf/foo/xdp
+  546: xdp  name bpf_func_process  tag e369a529024751fc  gpl
+          loaded_at 2018-12-12T15:02:58+0000  uid 0
+          xlated 200B  jited 164B  memlock 4096B
+          pinned /sys/fs/bpf/foo/process
+  547: xdp  name bpf_func_debug  tag 0b597868bc7f0976  gpl
+          loaded_at 2018-12-12T15:02:58+0000  uid 0
+          xlated 200B  jited 164B  memlock 4096B
+          pinned /sys/fs/bpf/foo/debug
+
+**# bpftool map**
+
+::
+
+  294: prog_array  name jmp_table  flags 0x0
+          key 4B  value 4B  max_entries 1  memlock 4096B
+          owner_prog_type xdp  owner jited
+
+|
+| **# bpftool map pin id 294 /sys/fs/bpf/bar**
+| **# bpftool map dump pinned /sys/fs/bpf/bar**
+
+::
+
+  Found 0 elements
+
+|
+| **# bpftool map update pinned /sys/fs/bpf/bar key 0 0 0 0 value pinned /sys/fs/bpf/foo/debug**
+| **# bpftool map dump pinned /sys/fs/bpf/bar**
+
+::
+
+  key: 00 00 00 00  value: 22 02 00 00
+  Found 1 element
+
 SEE ALSO
 ========
         **bpf**\ (2),
diff --git a/tools/bpf/bpftool/Documentation/bpftool-prog.rst b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
index bb1aeb98b6da..53920ffc48dd 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-prog.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
@@ -158,83 +158,94 @@ OPTIONS
                   When showing BPF programs, show file names of pinned
                   programs.
 
+        -m, --mapcompat
+                  Allow loading maps with unknown map definitions.
+
 EXAMPLES
 ========
 **# bpftool prog show**
+
 ::
 
-  10: xdp  name some_prog  tag 005a3d2123620c8b  gpl
-        loaded_at Sep 29/20:11  uid 0
-        xlated 528B  jited 370B  memlock 4096B  map_ids 10
+    10: xdp  name some_prog  tag 005a3d2123620c8b  gpl
+            loaded_at 2017-09-29T20:11:00+0000  uid 0
+            xlated 528B  jited 370B  memlock 4096B  map_ids 10
 
 **# bpftool --json --pretty prog show**
 
 ::
 
-    {
-        "programs": [{
-                "id": 10,
-                "type": "xdp",
-                "tag": "005a3d2123620c8b",
-                "gpl_compatible": true,
-                "loaded_at": "Sep 29/20:11",
-                "uid": 0,
-                "bytes_xlated": 528,
-                "jited": true,
-                "bytes_jited": 370,
-                "bytes_memlock": 4096,
-                "map_ids": [10
-                ]
-            }
-        ]
-    }
+    [{
+            "id": 10,
+            "type": "xdp",
+            "tag": "005a3d2123620c8b",
+            "gpl_compatible": true,
+            "loaded_at": 1506715860,
+            "uid": 0,
+            "bytes_xlated": 528,
+            "jited": true,
+            "bytes_jited": 370,
+            "bytes_memlock": 4096,
+            "map_ids": [10
+            ]
+        }
+    ]
 
 |
 | **# bpftool prog dump xlated id 10 file /tmp/t**
 | **# ls -l /tmp/t**
-|   -rw------- 1 root root 560 Jul 22 01:42 /tmp/t
 
-**# bpftool prog dum jited tag 005a3d2123620c8b**
+::
+
+    -rw------- 1 root root 560 Jul 22 01:42 /tmp/t
+
+**# bpftool prog dump jited tag 005a3d2123620c8b**
 
 ::
 
-    push   %rbp
-    mov    %rsp,%rbp
-    sub    $0x228,%rsp
-    sub    $0x28,%rbp
-    mov    %rbx,0x0(%rbp)
+    0:   push   %rbp
+    1:   mov    %rsp,%rbp
+    2:   sub    $0x228,%rsp
+    3:   sub    $0x28,%rbp
+    4:   mov    %rbx,0x0(%rbp)
 
 |
 | **# mount -t bpf none /sys/fs/bpf/**
 | **# bpftool prog pin id 10 /sys/fs/bpf/prog**
 | **# bpftool prog load ./my_prog.o /sys/fs/bpf/prog2**
 | **# ls -l /sys/fs/bpf/**
-|   -rw------- 1 root root 0 Jul 22 01:43 prog
-|   -rw------- 1 root root 0 Jul 22 01:44 prog2
 
-**# bpftool prog dum jited pinned /sys/fs/bpf/prog opcodes**
+::
+
+    -rw------- 1 root root 0 Jul 22 01:43 prog
+    -rw------- 1 root root 0 Jul 22 01:44 prog2
+
+**# bpftool prog dump jited pinned /sys/fs/bpf/prog opcodes**
 
 ::
 
-    push   %rbp
-    55
-    mov    %rsp,%rbp
-    48 89 e5
-    sub    $0x228,%rsp
-    48 81 ec 28 02 00 00
-    sub    $0x28,%rbp
-    48 83 ed 28
-    mov    %rbx,0x0(%rbp)
-    48 89 5d 00
+   0:   push   %rbp
+        55
+   1:   mov    %rsp,%rbp
+        48 89 e5
+   4:   sub    $0x228,%rsp
+        48 81 ec 28 02 00 00
+   b:   sub    $0x28,%rbp
+        48 83 ed 28
+   f:   mov    %rbx,0x0(%rbp)
+        48 89 5d 00
 
 |
 | **# bpftool prog load xdp1_kern.o /sys/fs/bpf/xdp1 type xdp map name rxcnt id 7**
 | **# bpftool prog show pinned /sys/fs/bpf/xdp1**
-|   9: xdp  name xdp_prog1  tag 539ec6ce11b52f98  gpl
-|       loaded_at 2018-06-25T16:17:31-0700  uid 0
-|       xlated 488B  jited 336B  memlock 4096B  map_ids 7
-| **# rm /sys/fs/bpf/xdp1**
-|
+
+::
+
+    9: xdp  name xdp_prog1  tag 539ec6ce11b52f98  gpl
+            loaded_at 2018-06-25T16:17:31-0700  uid 0
+            xlated 488B  jited 336B  memlock 4096B  map_ids 7
+
+**# rm /sys/fs/bpf/xdp1**
 
 SEE ALSO
 ========
diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
index 99e4027dde75..24582e8a96fb 100644
--- a/tools/bpf/bpftool/common.c
+++ b/tools/bpf/bpftool/common.c
@@ -28,7 +28,7 @@
 #define BPF_FS_MAGIC            0xcafe4a11
 #endif
 
-void p_err(const char *fmt, ...)
+void __printf(1, 2) p_err(const char *fmt, ...)
 {
         va_list ap;
 
@@ -46,7 +46,7 @@ void p_err(const char *fmt, ...)
         va_end(ap);
 }
 
-void p_info(const char *fmt, ...)
+void __printf(1, 2) p_info(const char *fmt, ...)
 {
         va_list ap;
 
diff --git a/tools/bpf/bpftool/json_writer.c b/tools/bpf/bpftool/json_writer.c
index a07d17918725..bff7ee026680 100644
--- a/tools/bpf/bpftool/json_writer.c
+++ b/tools/bpf/bpftool/json_writer.c
@@ -20,6 +20,7 @@
 #include <malloc.h>
 #include <inttypes.h>
 #include <stdint.h>
+#include <linux/compiler.h>
 
 #include "json_writer.h"
 
@@ -157,7 +158,8 @@ void jsonw_name(json_writer_t *self, const char *name)
                 putc(' ', self->out);
 }
 
-void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
+void __printf(2, 0)
+jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
 {
         jsonw_eor(self);
         putc('"', self->out);
@@ -165,7 +167,7 @@ void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)
         putc('"', self->out);
 }
 
-void jsonw_printf(json_writer_t *self, const char *fmt, ...)
+void __printf(2, 3) jsonw_printf(json_writer_t *self, const char *fmt, ...)
 {
         va_list ap;
 
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index d2beb88f0e2e..9487345b04a7 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -147,8 +147,8 @@ int prog_parse_fd(int *argc, char ***argv);
 int map_parse_fd(int *argc, char ***argv);
 int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len);
 
-#ifdef HAVE_LIBBFD_SUPPORT
 struct bpf_prog_linfo;
+#ifdef HAVE_LIBBFD_SUPPORT
 void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
                        const char *arch, const char *disassembler_options,
                        const struct btf *btf,
diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index ee51279be9c7..2d1bb7d6ff51 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -32,7 +32,7 @@ static const char * const attach_type_strings[] = {
         [__MAX_BPF_ATTACH_TYPE] = NULL,
 };
 
-enum bpf_attach_type parse_attach_type(const char *str)
+static enum bpf_attach_type parse_attach_type(const char *str)
 {
         enum bpf_attach_type type;
 
@@ -798,7 +798,7 @@ struct map_replace {
         char *name;
 };
 
-int map_replace_compar(const void *p1, const void *p2)
+static int map_replace_compar(const void *p1, const void *p2)
 {
         const struct map_replace *a = p1, *b = p2;
 
diff --git a/tools/bpf/bpftool/xlated_dumper.c b/tools/bpf/bpftool/xlated_dumper.c
index 640ffe86a655..7073dbe1ff27 100644
--- a/tools/bpf/bpftool/xlated_dumper.c
+++ b/tools/bpf/bpftool/xlated_dumper.c
@@ -81,7 +81,7 @@ struct kernel_sym *kernel_syms_search(struct dump_data *dd,
                        sizeof(*dd->sym_mapping), kernel_syms_cmp) : NULL;
 }
 
-static void print_insn(void *private_data, const char *fmt, ...)
+static void __printf(2, 3) print_insn(void *private_data, const char *fmt, ...)
 {
         va_list args;
 
@@ -90,7 +90,7 @@ static void print_insn(void *private_data, const char *fmt, ...)
         va_end(args);
 }
 
-static void
+static void __printf(2, 3)
 print_insn_for_graph(void *private_data, const char *fmt, ...)
 {
         char buf[64], *p;
@@ -121,7 +121,8 @@ print_insn_for_graph(void *private_data, const char *fmt, ...)
         printf("%s", buf);
 }
 
-static void print_insn_json(void *private_data, const char *fmt, ...)
+static void __printf(2, 3)
+print_insn_json(void *private_data, const char *fmt, ...)
 {
         unsigned int l = strlen(fmt);
         char chomped_fmt[l];