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build system: make CONFIG_FEATURE_USE_BSS_TAIL less funky

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CONFIG_FEATURE_USE_BSS_TAIL code was aliasing bb_common_bufsiz1 to _end.
This is unreliable: _end may be not sufficiently aligned.

Change code to simply enlarge COMMON_BUFSIZE when we detect that _end
has significant amount of space to the end of page.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2016-06-29 15:00:52 +02:00
parent 8f4faa1e3d
commit 5b8c89d1f2
1 changed files with 28 additions and 72 deletions
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92
scripts/generate_BUFSIZ.sh
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@ -36,11 +36,10 @@ generate_std_and_exit() {
}
generate_big_and_exit() {
$debug && echo "Configuring: bb_common_bufsiz1[] in _end[], COMMON_BUFSIZE = $1"
$debug && echo "Configuring: bb_common_bufsiz1[] in bss, COMMON_BUFSIZE = $1"
{
echo "enum { COMMON_BUFSIZE = $1 };"
echo "extern char _end[]; /* linker-provided label */"
echo "#define bb_common_bufsiz1 _end"
echo "extern char bb_common_bufsiz1[];"
echo "#define setup_common_bufsiz() ((void)0)"
} | regenerate "$common_bufsiz_h"
echo "$2" >"$common_bufsiz_h.method"
@ -51,20 +50,10 @@ generate_1k_and_exit() {
generate_big_and_exit 1024 "1k"
}
generate_malloc_and_exit() {
$debug && echo "Configuring: bb_common_bufsiz1[] is malloced"
{
echo "enum { COMMON_BUFSIZE = 1024 };"
echo "extern char *const bb_common_bufsiz1;"
echo "void setup_common_bufsiz(void);"
} | regenerate "$common_bufsiz_h"
echo "malloc" >"$common_bufsiz_h.method"
$exitcmd
}
round_down_COMMON_BUFSIZE() {
COMMON_BUFSIZE=$(( ($1-32) & 0xfffffe0 ))
COMMON_BUFSIZE=1024
test "$1" -le 32 && return
COMMON_BUFSIZE=$(( ($1-32) & 0x0ffffff0 ))
COMMON_BUFSIZE=$(( COMMON_BUFSIZE < 1024 ? 1024 : COMMON_BUFSIZE ))
}
@ -104,77 +93,44 @@ if $postcompile; then
test x"$PAGE_SIZE" = x"" && exit 1
$debug && echo "PAGE_SIZE:0x$PAGE_SIZE $((0x$PAGE_SIZE))"
PAGE_SIZE=$((0x$PAGE_SIZE))
test $PAGE_SIZE -lt 512 && exit 1
test $PAGE_SIZE -lt 1024 && exit 1
# How much space between _end[] and next page?
PAGE_MASK=$((PAGE_SIZE-1))
TAIL_SIZE=$(( (-END) & PAGE_MASK ))
$debug && echo "TAIL_SIZE:$TAIL_SIZE bytes"
if test x"$method" = x"1k" || test x"$method" = x"big"; then
if test $TAIL_SIZE -lt 1024; then
# _end[] has no enough space for bb_common_bufsiz1[]
echo "Warning! Space in _end[] is too small ($TAIL_SIZE bytes)!"
echo "Rerun make to build a binary which doesn't use it!"
rm -- "$common_bufsiz_h.1k.OK" 2>/dev/null
{ md5sum <.config | cut -d' ' -f1; stat -c "%Y" .config; } >"$common_bufsiz_h.1k.FAIL"
rm busybox_unstripped busybox 2>/dev/null
# Note: here we can do either a "malloc" or "std" build.
# "malloc" gives a bit bigger code:
# text bss filename
# 804355 5385 busybox.std
# 804618 4361 busybox.malloc
# but may have a smaller .bss (not guaranteed!). Use "pmap -x" to verify.
exitcmd="exit 1"
generate_malloc_and_exit
else
PREV_SIZE=1024
test x"$method" = x"big" && PREV_SIZE=`cat -- "$common_bufsiz_h.1k.OK"`
round_down_COMMON_BUFSIZE $PREV_SIZE
PREV_BUFSIZE=$COMMON_BUFSIZE
rm -- "$common_bufsiz_h.1k.FAIL" 2>/dev/null
echo $TAIL_SIZE >"$common_bufsiz_h.1k.OK"
round_down_COMMON_BUFSIZE $TAIL_SIZE
if test x"$method" = x"1k"; then
{
echo $TAIL_SIZE
md5sum <.config | cut -d' ' -f1
stat -c "%Y" .config
} >"$common_bufsiz_h.1k.OK"
round_down_COMMON_BUFSIZE $((1024 + TAIL_SIZE))
# emit message only if COMMON_BUFSIZE is indeed larger
test $COMMON_BUFSIZE -gt $PREV_BUFSIZE \
test $COMMON_BUFSIZE -gt 1024 \
&& echo "Rerun make to use larger COMMON_BUFSIZE ($COMMON_BUFSIZE)"
#TODO: test $PREV_BUFSIZE -lt $TAIL_SIZE && PANIC!!!
#Code size with COMMON_BUFSIZE > 1024 may be bigger than code with COMMON_BUFSIZE = 1024!
#(currently we just hope "-32 and round down to 32" saves us)
test $COMMON_BUFSIZE = 1024 && generate_1k_and_exit
generate_big_and_exit $COMMON_BUFSIZE "big"
fi
fi
fi
# Based on past success/fail of 1k build, decide next build type
if test -f "$common_bufsiz_h.1k.OK"; then
# Previous build succeeded fitting 1k into _end[].
# Try bigger COMMON_BUFSIZE if possible.
TAIL_SIZE=`cat -- "$common_bufsiz_h.1k.OK"`
round_down_COMMON_BUFSIZE $TAIL_SIZE
# previous 1k build succeeded
oldcfg=`tail -n2 -- "$common_bufsiz_h.1k.OK"`
curcfg=`md5sum <.config | cut -d' ' -f1; stat -c "%Y" .config`
# config did not change
if test x"$oldcfg" = x"$curcfg"; then
# Try bigger COMMON_BUFSIZE if possible
TAIL_SIZE=`head -n1 -- "$common_bufsiz_h.1k.OK"`
round_down_COMMON_BUFSIZE $((1024 + TAIL_SIZE))
test $COMMON_BUFSIZE = 1024 && generate_1k_and_exit
generate_big_and_exit $COMMON_BUFSIZE "big"
fi
if test -f "$common_bufsiz_h.1k.FAIL"; then
# Previous build FAILED to fit 1k into _end[].
# Was it with same .config?
oldcfg=`cat -- "$common_bufsiz_h.1k.FAIL"`
curcfg=`md5sum <.config | cut -d' ' -f1; stat -c "%Y" .config`
# If yes, then build a "malloced" version
if test x"$oldcfg" = x"$curcfg"; then
echo "Will not try 1k build, it failed before. Touch .config to override"
# Note: here we can do either a "malloc" or "std" build.
generate_malloc_and_exit
fi
# else: try 1k version
echo "New .config, will try 1k build"
rm -- "$common_bufsiz_h.1k.FAIL"
generate_1k_and_exit
# config did change
rm -rf -- "$common_bufsiz_h.1k.OK"
fi
# There was no 1k build yet. Try it.