httpd: code shrink via "split-globals" trick

function                                             old     new   delta
httpd_main                                           957     968     +11
log_and_exit                                          25      26      +1
send_headers                                         712     708      -4
handle_incoming_and_exit                            2292    2285      -7
sigalrm_handler                                      102      93      -9
parse_conf                                          1332    1323      -9
send_cgi_and_exit                                    803     790     -13
cgi_io_loop_and_exit                                 656     635     -21
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/6 up/down: 12/-63)            Total: -51 bytes

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

2 files changed, 18 insertions, 3 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 8d252d455..17c9bc785 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -457,6 +457,11 @@ void *xmmap_anon(size_t size) FAST_FUNC;
 //sparc64,alpha,openrisc: fixed 8k pages
 #endif
 
+#if defined(__x86_64__) || defined(i386)
+/* 0x7f would be better, but it causes alignment problems */
+# define ARCH_GLOBAL_PTR_OFF 0x80
+#endif
+
 #if defined BB_ARCH_FIXED_PAGESIZE
 # define IF_VARIABLE_ARCH_PAGESIZE(...) /*nothing*/
 # define bb_getpagesize()     BB_ARCH_FIXED_PAGESIZE
@@ -2423,6 +2428,16 @@ void XZALLOC_CONST_PTR(const void *pptr, size_t size) FAST_FUNC;
         } \
 } while (0)
 
+#if defined(ARCH_GLOBAL_PTR_OFF)
+# define SET_OFFSET_PTR_TO_GLOBALS(x) \
+        ASSIGN_CONST_PTR(&ptr_to_globals, (char*)(x) + ARCH_GLOBAL_PTR_OFF)
+# define OFFSET_PTR_TO_GLOBALS \
+        ((struct globals*)((char*)ptr_to_globals - ARCH_GLOBAL_PTR_OFF))
+#else
+# define SET_OFFSET_PTR_TO_GLOBALS(x) SET_PTR_TO_GLOBALS(x)
+# define OFFSET_PTR_TO_GLOBALS ptr_to_globals
+#endif
+
 
 /* You can change LIBBB_DEFAULT_LOGIN_SHELL, but don't use it,
  * use bb_default_login_shell and following defines.
diff --git a/networking/httpd.c b/networking/httpd.c
index ce557c1bf..176eb244b 100644
--- a/networking/httpd.c
+++ b/networking/httpd.c
@@ -484,7 +484,6 @@ static const struct {
 };
 
 struct globals {
-        int verbose;            /* must be int (used by getopt32) */
         smallint flg_deny_all;
 #if ENABLE_FEATURE_HTTPD_GZIP
         /* client can handle gzip / we are going to send gzip */
@@ -494,6 +493,7 @@ struct globals {
 #if ENABLE_FEATURE_HTTPD_CGI
         smallint cgi_output;
 #endif
+        int verbose;            /* must be int (used by getopt32) */
         time_t last_mod;
 #if ENABLE_FEATURE_HTTPD_ETAG
         char *if_none_match;
@@ -555,7 +555,7 @@ struct globals {
 #endif
         char iobuf[IOBUF_SIZE] ALIGN8;
 };
-#define G (*ptr_to_globals)
+#define G (*OFFSET_PTR_TO_GLOBALS)
 #define verbose           (G.verbose          )
 #define flg_deny_all      (G.flg_deny_all     )
 #if ENABLE_FEATURE_HTTPD_GZIP
@@ -598,7 +598,7 @@ enum {
 #define iobuf             (G.iobuf            )
 #define INIT_G() do { \
         setup_common_bufsiz(); \
-        SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
+        SET_OFFSET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
         IF_FEATURE_HTTPD_BASIC_AUTH(g_realm = "Web Server Authentication";) \
         IF_FEATURE_HTTPD_RANGES(range_start = -1;) \
         bind_addr_or_port = STR(CONFIG_FEATURE_HTTPD_PORT_DEFAULT); \