From 0fb4ed6d648a69799cdbf6b19fd36c6125c5fc41 Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Thu, 23 Feb 2023 12:53:40 +0100 Subject: [PATCH] gas: Add --compress-debug-sections=force Gas has an option --compress-debug-sections that allows it to generate compressed debug sections. That does not guarantee that the debug sections are in fact compressed: ... $ gcc hello.c -Wa,-gdwarf-5 -c -Wa,--compress-debug-sections=zstd $ readelf -S -W hello.o | grep " .debug" [ 9] .debug_line PROGBITS 0000a8 000053 00 0 0 1 [11] .debug_line_str PROGBITS 0000fb 000025 01 MS 0 0 1 [12] .debug_info PROGBITS 000120 000039 00 0 0 1 [14] .debug_abbrev PROGBITS 000159 000028 00 0 0 1 [15] .debug_aranges PROGBITS 000190 000030 00 0 0 16 [17] .debug_str PROGBITS 0001c0 000039 01 MS 0 0 1 ... Sensibly so, they're only compressed if that provides a size benefit. However, for the purpose of testing components consuming dwarf we may want the sections to be compressed regardless. Add a new suboption --compress-debug-sections=force that ignores the size heuristic, such that we have instead: ... $ gcc hello.c -Wa,-gdwarf-5 -c -Xassembler \ --compress-debug-sections=zstd,force $ readelf -S -W hello.o | grep " .debug" [ 9] .debug_line PROGBITS 0000a8 000064 00 C 0 0 8 [11] .debug_line_str PROGBITS 000110 000046 01 MSC 0 0 8 [12] .debug_info PROGBITS 000158 000046 00 C 0 0 8 [14] .debug_abbrev PROGBITS 0001a0 000049 00 C 0 0 8 [15] .debug_aranges PROGBITS 0001f0 000034 00 C 0 0 8 [17] .debug_str PROGBITS 000228 00005a 01 MSC 0 0 8 ... Advertised as: ... $ as --help ... --compress-debug-sections[={none||force|force,}] where is {zlib|zlib-gnu|zlib-gabi|zstd} compress DWARF debug sections Default: zstd ... Tested on x86_64-linux. --- gas/as.c | 106 +++++++++++++++++++++++++++++++++++++++--------- gas/as.h | 10 +++++ gas/doc/as.texi | 10 ++++- gas/write.c | 5 ++- 4 files changed, 108 insertions(+), 23 deletions(-) diff --git a/gas/as.c b/gas/as.c index 598bfd56cf5..acbccfb5dce 100644 --- a/gas/as.c +++ b/gas/as.c @@ -230,6 +230,8 @@ enum compressed_debug_section_type flag_compress_debug = DEFAULT_COMPRESSED_DEBUG_ALGORITHM; #endif +enum compress_debug_action compress_debug_action = cda_default; + static void show_usage (FILE * stream) { @@ -252,7 +254,8 @@ Options:\n\ fprintf (stream, _("\ --alternate initially turn on alternate macro syntax\n")); fprintf (stream, _("\ - --compress-debug-sections[={none|zlib|zlib-gnu|zlib-gabi|zstd}]\n\ + --compress-debug-sections[={none||force|force,}]\n\ + where is {zlib|zlib-gnu|zlib-gabi|zstd}\n\ compress DWARF debug sections\n")), fprintf (stream, _("\ Default: %s\n"), @@ -418,6 +421,84 @@ Options:\n\ fprintf (stream, _("Report bugs to %s\n"), REPORT_BUGS_TO); } +static void +parse_compress_debug_optarg_1 (const char *optarg) +{ + gas_assert (optarg != NULL); + + if (strcmp (optarg, "force") == 0) + { + compress_debug_action = cda_force; + return; + } + + enum compressed_debug_section_type tmp + = bfd_get_compression_algorithm (optarg); + +#ifndef HAVE_ZSTD + if (tmp == COMPRESS_DEBUG_ZSTD) + as_fatal (_ ("--compress-debug-sections=zstd: gas is not " + "built with zstd support")); +#endif + + if (tmp == COMPRESS_UNKNOWN) + as_fatal (_("Invalid --compress-debug-sections option: `%s'"), + optarg); + + if (tmp == COMPRESS_DEBUG_NONE) + { + compress_debug_action = cda_none; + return; + } + + compress_debug_action = cda_yes; + flag_compress_debug = tmp; +} + +static void +parse_compress_debug_optarg (const char *optarg) +{ +#if !defined OBJ_ELF && !defined OBJ_MAYBE_ELF + as_fatal (_("--compress-debug-sections=%s is unsupported"), + optarg); +#endif + + /* Tokenize subopts pass to parse_compress_debug_optarg_1. */ + char sep = ','; + while (true) + { + const char *idx = optarg; + while (*idx != '\0' && *idx != sep) + idx++; + + size_t len = idx - optarg; + if (len == 0) + { + /* Generate error. */ + parse_compress_debug_optarg_1 (""); + break; + } + + char *tmp = xstrndup (optarg, len); + parse_compress_debug_optarg_1 (tmp); + free (tmp); + + if (*idx == '\0') + break; + + /* Step over separator and continue tokenizing. */ + gas_assert (*idx == sep); + optarg = idx + 1; + } +} + +static void +finalize_parse_compress_debug_optarg (void) +{ + if (compress_debug_action == cda_none) + flag_compress_debug = COMPRESS_DEBUG_NONE; +} + /* Since it is easy to do here we interpret the special arg "-" to mean "use stdin" and we set that argv[] pointing to "". After we have munged argv[], the only things left are source file @@ -747,28 +828,13 @@ This program has absolutely no warranty.\n")); case OPTION_COMPRESS_DEBUG: if (optarg) - { -#if defined OBJ_ELF || defined OBJ_MAYBE_ELF - flag_compress_debug = bfd_get_compression_algorithm (optarg); -#ifndef HAVE_ZSTD - if (flag_compress_debug == COMPRESS_DEBUG_ZSTD) - as_fatal (_ ("--compress-debug-sections=zstd: gas is not " - "built with zstd support")); -#endif - if (flag_compress_debug == COMPRESS_UNKNOWN) - as_fatal (_("Invalid --compress-debug-sections option: `%s'"), - optarg); -#else - as_fatal (_("--compress-debug-sections=%s is unsupported"), - optarg); -#endif - } + parse_compress_debug_optarg (optarg); else - flag_compress_debug = COMPRESS_DEBUG_GABI_ZLIB; + parse_compress_debug_optarg ("zlib-gabi"); break; case OPTION_NOCOMPRESS_DEBUG: - flag_compress_debug = COMPRESS_DEBUG_NONE; + parse_compress_debug_optarg ("none"); break; case OPTION_DEBUG_PREFIX_MAP: @@ -1136,6 +1202,8 @@ This program has absolutely no warranty.\n")); *pargc = new_argc; *pargv = new_argv; + finalize_parse_compress_debug_optarg (); + #ifdef md_after_parse_args md_after_parse_args (); #endif diff --git a/gas/as.h b/gas/as.h index 4c5fa9ecf7d..bc0fe7f5cd9 100644 --- a/gas/as.h +++ b/gas/as.h @@ -331,6 +331,16 @@ COMMON int flag_traditional_format; /* Type of compressed debug sections we should generate. */ COMMON enum compressed_debug_section_type flag_compress_debug; +/* Whether we should compress debug sections. */ +enum compress_debug_action +{ + cda_default, + cda_none, + cda_force, + cda_yes, +}; +COMMON enum compress_debug_action compress_debug_action; + /* TRUE if .note.GNU-stack section with SEC_CODE should be created */ COMMON int flag_execstack; diff --git a/gas/doc/as.texi b/gas/doc/as.texi index bbdfa4bfdca..f0140c09779 100644 --- a/gas/doc/as.texi +++ b/gas/doc/as.texi @@ -718,7 +718,8 @@ Begin in alternate macro mode. Compress DWARF debug sections using zlib with SHF_COMPRESSED from the ELF ABI. The resulting object file may not be compatible with older linkers and object file utilities. Note if compression would make a -given section @emph{larger} then it is not compressed. +given section @emph{larger} then it is not compressed, unless +@option{--compress-debug-section=force} is used. @ifset ELF @cindex @samp{--compress-debug-sections=} option @@ -727,6 +728,7 @@ given section @emph{larger} then it is not compressed. @itemx --compress-debug-sections=zlib-gnu @itemx --compress-debug-sections=zlib-gabi @itemx --compress-debug-sections=zstd +@itemx --compress-debug-sections=force These options control how DWARF debug sections are compressed. @option{--compress-debug-sections=none} is equivalent to @option{--nocompress-debug-sections}. @@ -738,7 +740,11 @@ using the obsoleted zlib-gnu format. The debug sections are renamed to begin with @samp{.zdebug}. @option{--compress-debug-sections=zstd} compresses DWARF debug sections using zstd. Note - if compression would actually make a section -@emph{larger}, then it is not compressed nor renamed. +@emph{larger}, then it is not compressed nor renamed, unless +@option{--compress-debug-section=force} is used. +@option{--compress-debug-sections=force} compresses DWARF debug sections, +even if this does not reduce size. It can be used in conjunction with a format +selection, for instance @option{--compress-debug-section=zstd,force}. @end ifset diff --git a/gas/write.c b/gas/write.c index 8273b7a42f1..1fa3b54a03b 100644 --- a/gas/write.c +++ b/gas/write.c @@ -1463,9 +1463,10 @@ compress_debug (bfd *abfd, asection *sec, void *xxx ATTRIBUTE_UNUSED) segment_info_type *seginfo = seg_info (sec); bfd_size_type uncompressed_size = sec->size; flagword flags = bfd_section_flags (sec); + bool force_compress_debug = compress_debug_action == cda_force; if (seginfo == NULL - || uncompressed_size < 32 + || (!force_compress_debug && uncompressed_size < 32) || (flags & SEC_HAS_CONTENTS) == 0) return; @@ -1582,7 +1583,7 @@ compress_debug (bfd *abfd, asection *sec, void *xxx ATTRIBUTE_UNUSED) /* PR binutils/18087: If compression didn't make the section smaller, just keep it uncompressed. */ - if (compressed_size >= uncompressed_size) + if (!force_compress_debug && compressed_size >= uncompressed_size) return; /* Replace the uncompressed frag list with the compressed frag list. */ -- 2.35.3