From e6a2f4cc5a47d3022bdf5ca2cacbaa5a8c5baf7a Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Thu, 21 Apr 2016 16:26:30 +0200 Subject: 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 --- libbb/common_bufsiz.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 libbb/common_bufsiz.c (limited to 'libbb/common_bufsiz.c') diff --git a/libbb/common_bufsiz.c b/libbb/common_bufsiz.c new file mode 100644 index 000000000..c16c361c9 --- /dev/null +++ b/libbb/common_bufsiz.c @@ -0,0 +1,74 @@ +/* vi: set sw=4 ts=4: */ +/* + * Utility routines. + * + * Copyright (C) 2016 Denys Vlasenko + * + * Licensed under GPLv2, see file LICENSE in this source tree. + */ +//config:config FEATURE_USE_BSS_TAIL +//config: bool "Use the end of BSS page" +//config: default n +//config: help +//config: Attempt to reclaim a small unused part of BSS. +//config: +//config: Executables have the following parts: +//config: = read-only executable code and constants, also known as "text" +//config: = read-write data +//config: = non-initialized (zeroed on demand) data, also known as "bss" +//config: +//config: At link time, "text" is padded to a full page. At runtime, all "text" +//config: pages are mapped RO and executable. +//config: "Data" starts on the next page boundary, but is not padded +//config: to a full page at the end. "Bss" starts wherever "data" ends. +//config: At runtime, "data" pages are mapped RW and they are file-backed +//config: (this includes a small portion of "bss" which may live in the last +//config: partial page of "data"). +//config: Pages which are fully in "bss" are mapped to anonymous memory. +//config: +//config: "Bss" end is usually not page-aligned. There is an unused space +//config: in the last page. Linker marks its start with the "_end" symbol. +//config: +//config: This option will attempt to use that space for bb_common_bufsiz1[] +//config: array. If it fits after _end, it will be used, and COMMON_BUFSIZE +//config: will be enlarged from its guaranteed minimum size of 1 kbyte. +//config: This may require recompilation a second time, since value of _end +//config: is known only after final link. +//config: +//config: If you are getting a build error like this: +//config: appletlib.c:(.text.main+0xd): undefined reference to '_end' +//config: disable this option. + +//kbuild:lib-y += common_bufsiz.o + +#include "libbb.h" +#include "common_bufsiz.h" + +#if !ENABLE_FEATURE_USE_BSS_TAIL + +/* We use it for "global" data via *(struct global*)bb_common_bufsiz1. + * Since gcc insists on aligning struct global's members, it would be a pity + * (and an alignment fault on some CPUs) to mess it up. */ +char bb_common_bufsiz1[COMMON_BUFSIZE] ALIGNED(sizeof(long long)); + +#else + +# ifndef setup_common_bufsiz +/* + * It is not a "((void)0)" macro. It means we have to provide this function. + */ +char* bb_common_bufsiz1; +char* setup_common_bufsiz(void) +{ + if (!bb_common_bufsiz1) + bb_common_bufsiz1 = xzalloc(COMMON_BUFSIZE); + return bb_common_bufsiz1; +} +# else +# ifndef bb_common_bufsiz1 + /* bb_common_bufsiz1[] is not aliased to _end[] */ +char bb_common_bufsiz1[COMMON_BUFSIZE] ALIGNED(sizeof(long long)); +# endif +# endif + +#endif -- cgit v1.2.3