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>

1 files changed, 114 insertions, 0 deletions

diff --git a/scripts/generate_BUFSIZ.sh b/scripts/generate_BUFSIZ.sh
new file mode 100755
index 000000000..afe9eee1e
--- /dev/null
+++ b/scripts/generate_BUFSIZ.sh
@@ -0,0 +1,114 @@
+#!/bin/sh
+# Called from top-level directory a-la
+#
+# scripts/generate_BUFSIZ.sh include/common_bufsiz.h
+
+. ./.config || exit 1
+
+debug=false
+
+common_bufsiz_h=$1
+
+test x"$NM" = x"" && NM="${CONFIG_CROSS_COMPILER_PREFIX}nm"
+test x"$CC" = x"" && CC="${CONFIG_CROSS_COMPILER_PREFIX}gcc"
+
+regenerate() {
+	cat >"$1.$$"
+	test -f "$1" && diff "$1.$$" "$1" >/dev/null && rm "$1.$$" && return
+	mv "$1.$$" "$1"
+}
+
+generate_std_and_exit() {
+	$debug && echo "Default: bb_common_bufsiz1[] in bss"
+	{
+	echo "enum { COMMON_BUFSIZE = 1024 };"
+	echo "extern char bb_common_bufsiz1[];"
+	echo "#define setup_common_bufsiz() ((void)0)"
+	} | regenerate "$common_bufsiz_h"
+	exit 0
+}
+
+# User does not want any funky stuff?
+test x"$CONFIG_FEATURE_USE_BSS_TAIL" = x"y" || generate_std_and_exit
+
+test -f busybox_unstripped || {
+	# We did not try anything yet
+	$debug && echo "Will try to fit bb_common_bufsiz1[] into _end[]"
+	{
+	echo "enum { COMMON_BUFSIZE = 1024 };"
+	echo "extern char _end[]; /* linker-provided label */"
+	echo "#define bb_common_bufsiz1 _end"
+	echo "#define setup_common_bufsiz() ((void)0)"
+	} | regenerate "$common_bufsiz_h"
+	echo 1024 >"$common_bufsiz_h.BUFSIZE"
+	exit 0
+}
+
+# Get _end address
+END=`$NM busybox_unstripped | grep ' . _end$'| cut -d' ' -f1`
+test x"$END" = x"" && generate_std_and_exit
+$debug && echo "END:0x$END $((0x$END))"
+END=$((0x$END))
+
+# Get PAGE_SIZE
+echo "\
+#include <sys/user.h>
+#if defined(PAGE_SIZE) && PAGE_SIZE > 0
+char page_size[PAGE_SIZE];
+#else
+char page_size[1];
+#endif
+" >page_size_$$.c
+$CC -c "page_size_$$.c" || generate_std_and_exit
+PAGE_SIZE=`$NM --size-sort "page_size_$$.o" | cut -d' ' -f1`
+rm "page_size_$$.c" "page_size_$$.o"
+test x"$PAGE_SIZE" = x"" && generate_std_and_exit
+$debug && echo "PAGE_SIZE:0x$PAGE_SIZE $((0x$PAGE_SIZE))"
+PAGE_SIZE=$((0x$PAGE_SIZE))
+test $PAGE_SIZE -lt 1024 && generate_std_and_exit
+
+# How much space between _end[] and next page?
+PAGE_MASK=$((PAGE_SIZE-1))
+REM=$(( (-END) & PAGE_MASK ))
+$debug && echo "REM:$REM"
+
+if test $REM -lt 1024; then
+	# _end[] has no enough space for bb_common_bufsiz1[],
+	# users will need to malloc it.
+	{
+	echo "enum { COMMON_BUFSIZE = 1024 };"
+	echo "extern char *bb_common_bufsiz1;"
+	echo "void setup_common_bufsiz(void);"
+	} | regenerate "$common_bufsiz_h"
+	# Check that we aren't left with a buggy binary:
+	if test -f "$common_bufsiz_h.BUFSIZE"; then
+		rm "$common_bufsiz_h.BUFSIZE"
+		echo "Warning! Space in _end[] is too small ($REM bytes)!"
+		echo "Rerun make to build a binary which doesn't use it!"
+		exit 1
+	fi
+        exit 0
+fi
+
+# _end[] has REM bytes for bb_common_bufsiz1[]
+OLD=1024
+test -f "$common_bufsiz_h.BUFSIZE" && OLD=`cat "$common_bufsiz_h.BUFSIZE"`
+$debug && echo "OLD:$OLD"
+{
+echo "enum { COMMON_BUFSIZE = $REM };"
+echo "extern char _end[]; /* linker-provided label */"
+echo "#define bb_common_bufsiz1 _end"
+echo "#define setup_common_bufsiz() ((void)0)"
+} | regenerate "$common_bufsiz_h"
+echo $REM >"$common_bufsiz_h.BUFSIZE"
+
+# Check that code did not grow too much and thus _end[] did not shink:
+if test $OLD -gt $REM; then
+	echo "Warning! Space in _end[] has decreased from $OLD to $REM bytes!"
+	echo "Rerun make!"
+	exit 1
+fi
+
+if test $OLD != $REM; then
+	echo "Space in _end[] is $REM bytes. Rerun make to use larger COMMON_BUFSIZE."
+fi