diff options
Diffstat (limited to 'libbb')
| -rw-r--r-- | libbb/common_bufsiz.c | 74 | ||||
| -rw-r--r-- | libbb/messages.c | 5 |
2 files changed, 74 insertions, 5 deletions
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 diff --git a/libbb/messages.c b/libbb/messages.c index 23e440bcd..cb0836de8 100644 --- a/libbb/messages.c +++ b/libbb/messages.c @@ -59,8 +59,3 @@ const char bb_path_wtmp_file[] ALIGN1 = # error unknown path to wtmp file # endif #endif - -/* 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)); |