libbb: make bb_common_bufsiz1 1 kbyte, add capability to use bss tail for it

The config item is FEATURE_USE_BSS_TAIL. When it is off (default):

function                                             old     new   delta
read_config                                          210     228     +18
doCommands                                          2279    2294     +15
ipneigh_list_or_flush                                763     772      +9
ipaddr_list_or_flush                                1256    1261      +5
display_process_list                                1301    1306      +5
conspy_main                                         1378    1383      +5
do_lzo_compress                                      352     355      +3
do_lzo_decompress                                    565     567      +2
push                                                  46      44      -2
inetd_main                                          2136    2134      -2
uevent_main                                          421     418      -3
addLines                                              97      92      -5
bb_common_bufsiz1                                   8193    1024   -7169
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 8/5 up/down: 62/-7181)        Total: -7119 bytes
   text	   data	    bss	    dec	    hex	filename
 829850	   4086	   9080	 843016	  cdd08	busybox_old
 829901	   4086	   1904	 835891	  cc133	busybox_unstripped

FEATURE_USE_BSS_TAIL=y:

read_config                                          210     228     +18
doCommands                                          2279    2294     +15
ipneigh_list_or_flush                                763     772      +9
ipaddr_list_or_flush                                1256    1261      +5
display_process_list                                1301    1306      +5
conspy_main                                         1378    1383      +5
do_lzo_compress                                      352     355      +3
do_lzo_decompress                                    565     567      +2
inetd_main                                          2136    2134      -2
bb_common_bufsiz1                                   8193       -   -8193
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 8/1 up/down: 62/-8195)        Total: -8133 bytes
   text	   data	    bss	    dec	    hex	filename
 829850	   4086	   9080	 843016	  cdd08	busybox_old
 829911	   4086	    880	 834877	  cbd3d	busybox_unstripped

FIXME: setup_common_bufsiz() calls are missing.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

4 files changed, 27 insertions, 24 deletions

diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index 496ab11a1..a526494d7 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -9,6 +9,7 @@
 #define UDHCP_COMMON_H 1
 
 #include "libbb.h"
+#include "common_bufsiz.h"
 #include <netinet/udp.h>
 #include <netinet/ip.h>
 
diff --git a/networking/udhcp/dhcpd.h b/networking/udhcp/dhcpd.h
index 183e7e24c..9dd5bef9e 100644
--- a/networking/udhcp/dhcpd.h
+++ b/networking/udhcp/dhcpd.h
@@ -57,7 +57,7 @@ struct server_config_t {
         struct static_lease *static_leases; /* List of ip/mac pairs to assign static leases */
 } FIX_ALIASING;
 
-#define server_config (*(struct server_config_t*)&bb_common_bufsiz1)
+#define server_config (*(struct server_config_t*)bb_common_bufsiz1)
 /* client_config sits in 2nd half of bb_common_bufsiz1 */
 
 #if ENABLE_FEATURE_UDHCP_PORT
diff --git a/networking/udhcp/dhcprelay.c b/networking/udhcp/dhcprelay.c
index f82ac05b4..1722a85de 100644
--- a/networking/udhcp/dhcprelay.c
+++ b/networking/udhcp/dhcprelay.c
@@ -33,7 +33,7 @@ struct xid_item {
         struct xid_item *next;
 } FIX_ALIASING;
 
-#define dhcprelay_xid_list (*(struct xid_item*)&bb_common_bufsiz1)
+#define dhcprelay_xid_list (*(struct xid_item*)bb_common_bufsiz1)
 
 static struct xid_item *xid_add(uint32_t xid, struct sockaddr_in *ip, int client)
 {
diff --git a/networking/udhcp/files.c b/networking/udhcp/files.c
index 7b57c6258..b22425352 100644
--- a/networking/udhcp/files.c
+++ b/networking/udhcp/files.c
@@ -57,33 +57,35 @@ static int FAST_FUNC read_staticlease(const char *const_line, void *arg)
 struct config_keyword {
         const char *keyword;
         int (*handler)(const char *line, void *var) FAST_FUNC;
-        void *var;
+        unsigned ofs;
         const char *def;
 };
 
+#define OFS(field) offsetof(struct server_config_t, field)
+
 static const struct config_keyword keywords[] = {
         /* keyword        handler           variable address               default */
-        {"start"        , udhcp_str2nip   , &server_config.start_ip     , "192.168.0.20"},
-        {"end"          , udhcp_str2nip   , &server_config.end_ip       , "192.168.0.254"},
-        {"interface"    , read_str        , &server_config.interface    , "eth0"},
+        {"start"        , udhcp_str2nip   , OFS(start_ip     ), "192.168.0.20"},
+        {"end"          , udhcp_str2nip   , OFS(end_ip       ), "192.168.0.254"},
+        {"interface"    , read_str        , OFS(interface    ), "eth0"},
         /* Avoid "max_leases value not sane" warning by setting default
          * to default_end_ip - default_start_ip + 1: */
-        {"max_leases"   , read_u32        , &server_config.max_leases   , "235"},
-        {"auto_time"    , read_u32        , &server_config.auto_time    , "7200"},
-        {"decline_time" , read_u32        , &server_config.decline_time , "3600"},
-        {"conflict_time", read_u32        , &server_config.conflict_time, "3600"},
-        {"offer_time"   , read_u32        , &server_config.offer_time   , "60"},
-        {"min_lease"    , read_u32        , &server_config.min_lease_sec, "60"},
-        {"lease_file"   , read_str        , &server_config.lease_file   , LEASES_FILE},
-        {"pidfile"      , read_str        , &server_config.pidfile      , "/var/run/udhcpd.pid"},
-        {"siaddr"       , udhcp_str2nip   , &server_config.siaddr_nip   , "0.0.0.0"},
+        {"max_leases"   , read_u32        , OFS(max_leases   ), "235"},
+        {"auto_time"    , read_u32        , OFS(auto_time    ), "7200"},
+        {"decline_time" , read_u32        , OFS(decline_time ), "3600"},
+        {"conflict_time", read_u32        , OFS(conflict_time), "3600"},
+        {"offer_time"   , read_u32        , OFS(offer_time   ), "60"},
+        {"min_lease"    , read_u32        , OFS(min_lease_sec), "60"},
+        {"lease_file"   , read_str        , OFS(lease_file   ), LEASES_FILE},
+        {"pidfile"      , read_str        , OFS(pidfile      ), "/var/run/udhcpd.pid"},
+        {"siaddr"       , udhcp_str2nip   , OFS(siaddr_nip   ), "0.0.0.0"},
         /* keywords with no defaults must be last! */
-        {"option"       , udhcp_str2optset, &server_config.options      , ""},
-        {"opt"          , udhcp_str2optset, &server_config.options      , ""},
-        {"notify_file"  , read_str        , &server_config.notify_file  , NULL},
-        {"sname"        , read_str        , &server_config.sname        , NULL},
-        {"boot_file"    , read_str        , &server_config.boot_file    , NULL},
-        {"static_lease" , read_staticlease, &server_config.static_leases, ""},
+        {"option"       , udhcp_str2optset, OFS(options      ), ""},
+        {"opt"          , udhcp_str2optset, OFS(options      ), ""},
+        {"notify_file"  , read_str        , OFS(notify_file  ), NULL},
+        {"sname"        , read_str        , OFS(sname        ), NULL},
+        {"boot_file"    , read_str        , OFS(boot_file    ), NULL},
+        {"static_lease" , read_staticlease, OFS(static_leases), ""},
 };
 enum { KWS_WITH_DEFAULTS = ARRAY_SIZE(keywords) - 6 };
 
@@ -95,17 +97,17 @@ void FAST_FUNC read_config(const char *file)
         char *token[2];
 
         for (i = 0; i < KWS_WITH_DEFAULTS; i++)
-                keywords[i].handler(keywords[i].def, keywords[i].var);
+                keywords[i].handler(keywords[i].def, (char*)&server_config + keywords[i].ofs);
 
         parser = config_open(file);
         while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) {
                 for (k = keywords, i = 0; i < ARRAY_SIZE(keywords); k++, i++) {
                         if (strcasecmp(token[0], k->keyword) == 0) {
-                                if (!k->handler(token[1], k->var)) {
+                                if (!k->handler(token[1], (char*)&server_config + k->ofs)) {
                                         bb_error_msg("can't parse line %u in %s",
                                                         parser->lineno, file);
                                         /* reset back to the default value */
-                                        k->handler(k->def, k->var);
+                                        k->handler(k->def, (char*)&server_config + k->ofs);
                                 }
                                 break;
                         }