From 451133cefa839104aa127d230436fb609dbef37f Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Tue, 9 Jun 2015 23:06:29 -0400 Subject: [PATCH] gas: section name substitution sequence This patch adds the ability to automatically construct a section name based on the prior section. When gas is invoked with --sectname-subst, the occurrence of %S in a section name will be substituted by the name of the current section. For example: .macro exception_code .pushsection %S.exception [exception code here] .popsection .endm .text [code] exception_code [...] .section .init [init code] exception_code [...] The first and second exception_code invocations create the .text.exception and the .init.exception sections respectively. This is useful e.g. to discriminate between anciliary sections that are tied to .init code and can be discarded at run time when initialization is over vs anciliary sections tied to .text sections that need to stay resident. * as.c (show_usage): Document --sectname-subst. (parse_args): Add --sectname-subst. * as.h (flag_sectname_subst): New. * config/obj-elf.c (obj_elf_section_name): Add %S substitution. * doc/as.texinfo: Document it. --- gas/ChangeLog | 8 ++++++++ gas/as.c | 8 ++++++++ gas/as.h | 3 +++ gas/config/obj-elf.c | 21 +++++++++++++++++++++ gas/doc/as.texinfo | 42 +++++++++++++++++++++++++++++++++++++++++- 5 files changed, 81 insertions(+), 1 deletion(-) diff --git a/gas/ChangeLog b/gas/ChangeLog index c0be3f557d..7acc12a756 100644 --- a/gas/ChangeLog +++ b/gas/ChangeLog @@ -1,3 +1,11 @@ +2015-06-17 Nicolas Pitre + + * as.c (show_usage): Document --sectname-subst. + (parse_args): Add --sectname-subst. + * as.h (flag_sectname_subst): New. + * config/obj-elf.c (obj_elf_section_name): Add %S substitution. + * doc/as.texinfo: Document it. + 2015-06-15 Renlin Li * config/tc-aarch64.c (reloc_table): New relocation modifier. diff --git a/gas/as.c b/gas/as.c index 2a8923f6fa..fecfcd2143 100644 --- a/gas/as.c +++ b/gas/as.c @@ -284,6 +284,8 @@ Options:\n\ fprintf (stream, _("\ --size-check=[error|warning]\n\ ELF .size directive check (default --size-check=error)\n")); + fprintf (stream, _("\ + --sectname-subst enable section name substitution sequences\n")); #endif fprintf (stream, _("\ -f skip whitespace and comment preprocessing\n")); @@ -447,6 +449,7 @@ parse_args (int * pargc, char *** pargv) OPTION_EXECSTACK, OPTION_NOEXECSTACK, OPTION_SIZE_CHECK, + OPTION_SECTNAME_SUBST, OPTION_ALTERNATE, OPTION_AL, OPTION_HASH_TABLE_SIZE, @@ -481,6 +484,7 @@ parse_args (int * pargc, char *** pargv) ,{"execstack", no_argument, NULL, OPTION_EXECSTACK} ,{"noexecstack", no_argument, NULL, OPTION_NOEXECSTACK} ,{"size-check", required_argument, NULL, OPTION_SIZE_CHECK} + ,{"sectname-subst", no_argument, NULL, OPTION_SECTNAME_SUBST} #endif ,{"fatal-warnings", no_argument, NULL, OPTION_WARN_FATAL} ,{"gdwarf-2", no_argument, NULL, OPTION_GDWARF2} @@ -848,6 +852,10 @@ This program has absolutely no warranty.\n")); else as_fatal (_("Invalid --size-check= option: `%s'"), optarg); break; + + case OPTION_SECTNAME_SUBST: + flag_sectname_subst = 1; + break; #endif case 'Z': flag_always_generate_output = 1; diff --git a/gas/as.h b/gas/as.h index 6de319e839..635b2c570b 100644 --- a/gas/as.h +++ b/gas/as.h @@ -589,6 +589,9 @@ COMMON enum size_check_warning } flag_size_check; + +/* If section name substitution sequences should be honored */ +COMMON int flag_sectname_subst; #endif #ifndef DOLLAR_AMBIGU diff --git a/gas/config/obj-elf.c b/gas/config/obj-elf.c index 4d7a8a7301..78dc6d9df1 100644 --- a/gas/config/obj-elf.c +++ b/gas/config/obj-elf.c @@ -917,6 +917,27 @@ obj_elf_section_name (void) name = (char *) xmalloc (end - input_line_pointer + 1); memcpy (name, input_line_pointer, end - input_line_pointer); name[end - input_line_pointer] = '\0'; + + while (flag_sectname_subst) + { + char *subst = strchr (name, '%'); + if (subst && subst[1] == 'S') + { + int oldlen = strlen (name); + int substlen = strlen (now_seg->name); + int newlen = oldlen - 2 + substlen; + char *newname = (char *) xmalloc (newlen + 1); + int headlen = subst - name; + memcpy (newname, name, headlen); + strcpy (newname + headlen, now_seg->name); + strcat (newname + headlen, subst + 2); + xfree (name); + name = newname; + } + else + break; + } + #ifdef tc_canonicalize_section_name name = tc_canonicalize_section_name (name); #endif diff --git a/gas/doc/as.texinfo b/gas/doc/as.texinfo index 5710e1c853..6694b23700 100644 --- a/gas/doc/as.texinfo +++ b/gas/doc/as.texinfo @@ -238,7 +238,7 @@ gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}. @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}] [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}] - [@b{--size-check=[error|warning]}] + [@b{--sectname-subst}] [@b{--size-check=[error|warning]}] [@b{--target-help}] [@var{target-options}] [@b{--}|@var{files} @dots{}] @c @@ -766,6 +766,14 @@ This option reduces GAS's memory requirements, at the expense of making the assembly processes slower. Currently this switch is a synonym for @samp{--hash-size=4051}, but in the future it may have other effects as well. +@ifset ELF +@item --sectname-subst +Honor substitution sequences in section names. +@ifclear man +@xref{Section Name Substitutions,,@code{.section @var{name}}}. +@end ifclear +@end ifset + @item --statistics Print the maximum space (in bytes) and total time (in seconds) used by assembly. @@ -6259,6 +6267,38 @@ For ELF targets, the @code{.section} directive is used like this: .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]] @end smallexample +@anchor{Section Name Substitutions} +@kindex --sectname-subst +@cindex section name substitution +If the @samp{--sectname-subst} command-line option is provided, the @var{name} +argument may contain a substitution sequence. Only @code{%S} is supported +at the moment, and substitutes the current section name. For example: + +@smallexample +.macro exception_code +.section %S.exception +[exception code here] +.previous +.endm + +.text +[code] +exception_code +[...] + +.section .init +[init code] +exception_code +[...] +@end smallexample + +The two @code{exception_code} invocations above would create the +@code{.text.exception} and @code{.init.exception} sections respectively. +This is useful e.g. to discriminate between anciliary sections that are +tied to setup code to be discarded after use from anciliary sections that +need to stay resident without having to define multiple @code{exception_code} +macros just for that purpose. + The optional @var{flags} argument is a quoted string which may contain any combination of the following characters: @table @code