[PATCH] strip: Properly handle LLVM IR bitcode
H.J. Lu
hjl.tools@gmail.com
Thu Jul 24 13:51:01 GMT 2025
On Wed, Jul 23, 2025 at 8:58 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> commit 717a38e9a02109fcbcb18bb2ec3aa251e2ad0a0d
> Author: H.J. Lu <hjl.tools@gmail.com>
> Date: Sun May 4 05:12:46 2025 +0800
>
> strip: Add GCC LTO IR support
>
> added "-R .gnu.lto_.*" to strip to remove the GCC LTO sections. When
> "-R .gnu.lto_.*" is used, the plugin target is ignored so that the LTO
> sections are stripped as the regular sections. It works for the non-fat
> GCC LTO IR since the GCC LTO IR is stored in the regular sections. When
> the plugin target is ignored, the GCC LTO IR can be recognized as the
> normal object files. But it doesn't work for the non-fat LLVM IR which
> is stored in a standalone file.
>
> 1. Add bfd_check_format_matches_lto and bfd_check_format_lto to take an
> argument, lto_sections_removed, to indicate if LTO sections should be
> ignored.
> 2. Update strip to always enable the plugin target so that the plugin
> target is enabled when checking for bfd_archive.
> 3. Update strip to ignore the plugin target for bfd_object when all LTO
> sections should be removed. If the object is unknown, copy it as an
> unknown file without any messages.
> 4. Treat the "-R .llvm.lto" strip option as removing all LTO sections.
>
> bfd/
>
> PR binutils/33198
> * format.c (bfd_check_format_lto): New function.
> (bfd_check_format): Call bfd_check_format_matches_lto.
> (bfd_check_format_matches): Renamed to ...
> (bfd_check_format_matches_lto): This. Add an argument,
> lto_sections_removed, to indicate if LTO sections should be
> removed and don't match the plugin target if lto_sections_removed
> is true.
> (bfd_check_format_matches): Call bfd_check_format_matches_lto.
> * bfd-in2.h: Regenerated.
>
> binutils/
>
> PR binutils/33198
> * objcopy.c (copy_archive): Call bfd_check_format_lto, instead
> of bfd_check_format, and pass lto_sections_removed. Remove the
> non-fatal message on unknown element since it will be copied as
> an unknown file.
> (copy_file): Don't check lto_sections_removed when enabling LTO
> plugin in strip.
> (copy_file): Ignore plugin target first if all LTO sections should
> be removed. Try with plugin target next if ignoring plugin target
> fails to match the format.
> (strip_main): Also set lto_sections_removed for -R .llvm.lto.
> * testsuite/binutils-all/x86-64/pr33198.c: New file.
> * testsuite/binutils-all/x86-64/x86-64.exp (run_pr33198_test):
> New.
> Run binutils/33198 tests.
> * testsuite/lib/binutils-common.exp (llvm_plug_opt): New.
> (CLANG_FOR_TARGET): New. Set to "clang" for native build if
> "clang -v" reports "clang version".
>
> Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Hi,
Nick asked me to check it into master branch and backport it to 2.45
branch.
> ---
> bfd/bfd-in2.h | 7 +
> bfd/format.c | 84 ++++++++--
> binutils/objcopy.c | 40 +++--
> .../testsuite/binutils-all/x86-64/pr33198.c | 4 +
> .../testsuite/binutils-all/x86-64/x86-64.exp | 158 ++++++++++++++++++
> binutils/testsuite/lib/binutils-common.exp | 27 +++
> 6 files changed, 299 insertions(+), 21 deletions(-)
> create mode 100644 binutils/testsuite/binutils-all/x86-64/pr33198.c
>
> diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
> index b013ef954da..2ff3e930bfa 100644
> --- a/bfd/bfd-in2.h
> +++ b/bfd/bfd-in2.h
> @@ -2903,8 +2903,15 @@ bool generic_core_file_matches_executable_p
> (bfd *core_bfd, bfd *exec_bfd);
>
> /* Extracted from format.c. */
> +bool bfd_check_format_lto (bfd *abfd, bfd_format format,
> + bool lto_sections_removed);
> +
> bool bfd_check_format (bfd *abfd, bfd_format format);
>
> +bool bfd_check_format_matches_lto
> + (bfd *abfd, bfd_format format, char ***matching,
> + bool lto_sections_removed);
> +
> bool bfd_check_format_matches
> (bfd *abfd, bfd_format format, char ***matching);
>
> diff --git a/bfd/format.c b/bfd/format.c
> index a909b70fe81..f3a0774af08 100644
> --- a/bfd/format.c
> +++ b/bfd/format.c
> @@ -56,16 +56,19 @@ extern const size_t _bfd_target_vector_entries;
>
> /*
> FUNCTION
> - bfd_check_format
> + bfd_check_format_lto
>
> SYNOPSIS
> - bool bfd_check_format (bfd *abfd, bfd_format format);
> + bool bfd_check_format_lto (bfd *abfd, bfd_format format,
> + bool lto_sections_removed);
>
> DESCRIPTION
> Verify if the file attached to the BFD @var{abfd} is compatible
> with the format @var{format} (i.e., one of <<bfd_object>>,
> <<bfd_archive>> or <<bfd_core>>).
>
> + If LTO_SECTION_REMOVED is true, ignore plugin target.
> +
> If the BFD has been set to a specific target before the
> call, only the named target and format combination is
> checked. If the target has not been set, or has been set to
> @@ -99,10 +102,31 @@ DESCRIPTION
> itself.
> */
>
> +bool
> +bfd_check_format_lto (bfd *abfd, bfd_format format,
> + bool lto_sections_removed)
> +{
> + return bfd_check_format_matches_lto (abfd, format, NULL,
> + lto_sections_removed);
> +}
> +
> +
> +/*
> +FUNCTION
> + bfd_check_format
> +
> +SYNOPSIS
> + bool bfd_check_format (bfd *abfd, bfd_format format);
> +
> +DESCRIPTION
> + Similar to bfd_check_format_plugin, except plugin target isn't
> + ignored.
> +*/
> +
> bool
> bfd_check_format (bfd *abfd, bfd_format format)
> {
> - return bfd_check_format_matches (abfd, format, NULL);
> + return bfd_check_format_matches_lto (abfd, format, NULL, false);
> }
>
> struct bfd_preserve
> @@ -407,11 +431,12 @@ bfd_set_lto_type (bfd *abfd ATTRIBUTE_UNUSED)
>
> /*
> FUNCTION
> - bfd_check_format_matches
> + bfd_check_format_matches_lto
>
> SYNOPSIS
> - bool bfd_check_format_matches
> - (bfd *abfd, bfd_format format, char ***matching);
> + bool bfd_check_format_matches_lto
> + (bfd *abfd, bfd_format format, char ***matching,
> + bool lto_sections_removed);
>
> DESCRIPTION
> Like <<bfd_check_format>>, except when it returns FALSE with
> @@ -423,10 +448,14 @@ DESCRIPTION
>
> When done with the list that @var{matching} points to, the caller
> should free it.
> +
> + If LTO_SECTION_REMOVED is true, ignore plugin target.
> */
>
> bool
> -bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
> +bfd_check_format_matches_lto (bfd *abfd, bfd_format format,
> + char ***matching,
> + bool lto_sections_removed ATTRIBUTE_UNUSED)
> {
> extern const bfd_target binary_vec;
> const bfd_target * const *target;
> @@ -495,8 +524,13 @@ bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
> if (!bfd_preserve_save (abfd, &preserve, NULL))
> goto err_ret;
>
> - /* If the target type was explicitly specified, just check that target. */
> - if (!abfd->target_defaulted)
> + /* If the target type was explicitly specified, just check that target.
> + If LTO_SECTION_REMOVED is true, don't match the plugin target. */
> + if (!abfd->target_defaulted
> +#if BFD_SUPPORTS_PLUGINS
> + && (!lto_sections_removed || !bfd_plugin_target_p (abfd->xvec))
> +#endif
> + )
> {
> if (bfd_seek (abfd, 0, SEEK_SET) != 0) /* rewind! */
> goto err_ret;
> @@ -540,10 +574,12 @@ bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
> searching. Don't match the plugin target if we have another
> alternative since we want to properly set the input format
> before allowing a plugin to claim the file. Also, don't
> - check the default target twice. */
> + check the default target twice. If LTO_SECTION_REMOVED is
> + true, don't match the plugin target. */
> if (*target == &binary_vec
> #if BFD_SUPPORTS_PLUGINS
> - || (match_count != 0 && bfd_plugin_target_p (*target))
> + || ((lto_sections_removed || match_count != 0)
> + && bfd_plugin_target_p (*target))
> #endif
> || (!abfd->target_defaulted && *target == save_targ))
> continue;
> @@ -795,6 +831,32 @@ bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
> return false;
> }
>
> +/*
> +FUNCTION
> + bfd_check_format_matches
> +
> +SYNOPSIS
> + bool bfd_check_format_matches
> + (bfd *abfd, bfd_format format, char ***matching);
> +
> +DESCRIPTION
> + Like <<bfd_check_format>>, except when it returns FALSE with
> + <<bfd_errno>> set to <<bfd_error_file_ambiguously_recognized>>. In that
> + case, if @var{matching} is not NULL, it will be filled in with
> + a NULL-terminated list of the names of the formats that matched,
> + allocated with <<malloc>>.
> + Then the user may choose a format and try again.
> +
> + When done with the list that @var{matching} points to, the caller
> + should free it.
> +*/
> +
> +bool
> +bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
> +{
> + return bfd_check_format_matches_lto (abfd, format, matching, false);
> +}
> +
> /*
> FUNCTION
> bfd_set_format
> diff --git a/binutils/objcopy.c b/binutils/objcopy.c
> index 2ca04e84d47..905ce917708 100644
> --- a/binutils/objcopy.c
> +++ b/binutils/objcopy.c
> @@ -3741,10 +3741,13 @@ copy_archive (bfd *ibfd, bfd *obfd, const char *output_target,
> l->obfd = NULL;
> list = l;
>
> +#if BFD_SUPPORTS_PLUGINS
> + /* Ignore plugin target if all LTO sections should be removed. */
> + ok_object = bfd_check_format_lto (this_element, bfd_object,
> + lto_sections_removed);
> +#else
> ok_object = bfd_check_format (this_element, bfd_object);
> - if (!ok_object)
> - bfd_nonfatal_message (NULL, this_element, NULL,
> - _("Unable to recognise the format of file"));
> +#endif
>
> /* PR binutils/3110: Cope with archives
> containing multiple target types. */
> @@ -3880,9 +3883,8 @@ copy_file (const char *input_filename, const char *output_filename, int ofd,
> }
>
> #if BFD_SUPPORTS_PLUGINS
> - /* Enable LTO plugin in strip unless all LTO sections should be
> - removed. */
> - if (is_strip && !target && !lto_sections_removed)
> + /* Enable LTO plugin in strip. */
> + if (is_strip && !target)
> target = "plugin";
> #endif
>
> @@ -3980,7 +3982,21 @@ copy_file (const char *input_filename, const char *output_filename, int ofd,
> input_arch))
> status = 1;
> }
> - else if (bfd_check_format_matches (ibfd, bfd_object, &obj_matching))
> + else if (
> +#if BFD_SUPPORTS_PLUGINS
> + /* Ignore plugin target first if all LTO sections should be
> + removed. Try with plugin target next if ignoring plugin
> + target fails to match the format. */
> + bfd_check_format_matches_lto (ibfd, bfd_object, &obj_matching,
> + lto_sections_removed)
> + || (lto_sections_removed
> + && bfd_check_format_matches_lto (ibfd, bfd_object,
> + &obj_matching, false))
> +#else
> + bfd_check_format_matches_lto (ibfd, bfd_object, &obj_matching,
> + false)
> +#endif
> + )
> {
> bfd *obfd;
> do_copy:
> @@ -5036,9 +5052,13 @@ strip_main (int argc, char *argv[])
> #if BFD_SUPPORTS_PLUGINS
> /* Check if all GCC LTO sections should be removed, assuming all LTO
> sections will be removed with -R .gnu.lto_.*. * Remove .gnu.lto_.*
> - sections will also remove .gnu.debuglto_. sections. */
> - lto_sections_removed = !!find_section_list (".gnu.lto_.*", false,
> - SECTION_CONTEXT_REMOVE);
> + sections will also remove .gnu.debuglto_. sections. LLVM IR
> + bitcode is stored in .llvm.lto section which will be removed with
> + -R .llvm.lto. */
> + lto_sections_removed = (!!find_section_list (".gnu.lto_.*", false,
> + SECTION_CONTEXT_REMOVE)
> + || !!find_section_list (".llvm.lto", false,
> + SECTION_CONTEXT_REMOVE));
> #endif
>
> i = optind;
> diff --git a/binutils/testsuite/binutils-all/x86-64/pr33198.c b/binutils/testsuite/binutils-all/x86-64/pr33198.c
> new file mode 100644
> index 00000000000..cd0130cacdf
> --- /dev/null
> +++ b/binutils/testsuite/binutils-all/x86-64/pr33198.c
> @@ -0,0 +1,4 @@
> +void
> +foo (void)
> +{
> +}
> diff --git a/binutils/testsuite/binutils-all/x86-64/x86-64.exp b/binutils/testsuite/binutils-all/x86-64/x86-64.exp
> index 05c73047b60..ab1aa50a9a1 100644
> --- a/binutils/testsuite/binutils-all/x86-64/x86-64.exp
> +++ b/binutils/testsuite/binutils-all/x86-64/x86-64.exp
> @@ -96,3 +96,161 @@ if {[catch "system \"bzip2 -dc $t > $tempfile\""] != 0} {
> }
> }
> }
> +
> +proc run_pr33198_test { fat strip_flags } {
> + global srcdir
> + global subdir
> + global llvm_plug_opt
> + global AR
> + global CLANG_FOR_TARGET
> + global NM
> + global READELF
> + global STRIP
> +
> + set test pr33198
> + set testname "${test}${fat} with $strip_flags"
> +
> + if { [istarget "x86_64-*-linux*-gnux32"] \
> + || ![info exists CLANG_FOR_TARGET]
> + || [string match "" $llvm_plug_opt] } then {
> + untested $testname
> + return
> + }
> +
> + set src $srcdir/$subdir/${test}.c
> + set obj tmpdir/${test}${fat}.o
> + set archive tmpdir/${test}${fat}.a
> + set CLANG_CFLAGS "-c -O2 -flto"
> + if { "$fat" == "-fat" } {
> + append CLANG_CFLAGS " -ffat-lto-objects"
> + }
> +
> + append strip_flags " --strip-unneeded $llvm_plug_opt"
> +
> + set cmd "$CLANG_FOR_TARGET $CLANG_CFLAGS -o $obj $src"
> + send_log "$cmd\n"
> + verbose "$cmd" 1
> + catch "exec $cmd" got
> + if ![string match "" $got] then {
> + send_log "$got\n"
> + verbose "$got" 1
> + fail "$testname ($obj)"
> + return
> + }
> +
> + set cmd "$NM $llvm_plug_opt $obj\n"
> + send_log "$cmd\n"
> + verbose "$cmd" 1
> + catch "exec $cmd" got
> + if ![regexp "0+ T foo" $got] then {
> + send_log "$got\n"
> + verbose "$got" 1
> + fail "$testname ($obj)"
> + return
> + }
> +
> + pass "$testname ($obj)"
> +
> + set cmd "$STRIP $strip_flags $obj -o ${obj}.strip"
> + send_log "$cmd\n"
> + verbose "$cmd" 1
> + catch "exec $cmd" got
> + if ![string match "" $got] then {
> + send_log "$got\n"
> + verbose "$got" 1
> + fail "$testname (strip $obj)"
> + return
> + }
> +
> + set cmd "$NM $llvm_plug_opt ${obj}.strip"
> + send_log "$cmd\n"
> + verbose "$cmd" 1
> + catch "exec $cmd" got
> + if ![regexp "0+ T foo" $got] then {
> + send_log "$got\n"
> + verbose "$got" 1
> + fail "$testname (strip $obj)"
> + return
> + }
> +
> + if { "$fat" == "-fat" } {
> + set cmd "$READELF -SW ${obj}.strip"
> + send_log "$cmd\n"
> + verbose "$cmd" 1
> + catch "exec $cmd" got
> + if [regexp "\.llvm\.lto *LLVM_LTO *" $got] then {
> + send_log "$got\n"
> + verbose "$got" 1
> + fail "$testname (strip $obj)"
> + return
> + }
> + }
> +
> + pass "$testname (strip $obj)"
> +
> + set cmd "$AR $llvm_plug_opt -s -r -c $archive $obj"
> + send_log "$cmd\n"
> + verbose "$cmd" 1
> + catch "exec $cmd" got
> + if ![string match "" $got] then {
> + send_log "$got\n"
> + verbose "$got" 1
> + fail "$testname ($archive)"
> + return
> + }
> +
> + set cmd "$NM $llvm_plug_opt $archive\n"
> + send_log "$cmd\n"
> + verbose "$cmd" 1
> + catch "exec $cmd" got
> + if ![regexp "0+ T foo" $got] then {
> + send_log "$got\n"
> + verbose "$got" 1
> + fail "$testname ($archive)"
> + return
> + }
> +
> + pass "$testname ($archive)"
> +
> + set cmd "$STRIP $strip_flags $archive -o ${archive}.strip"
> + send_log "$cmd\n"
> + verbose "$cmd" 1
> + catch "exec $cmd" got
> + if ![string match "" $got] then {
> + send_log "$got\n"
> + verbose "$got" 1
> + fail "$testname (strip $archive)"
> + return
> + }
> +
> + set cmd "$NM $llvm_plug_opt ${archive}.strip"
> + send_log "$cmd\n"
> + verbose "$cmd" 1
> + catch "exec $cmd" got
> + if ![regexp "0+ T foo" $got] then {
> + send_log "$got\n"
> + verbose "$got" 1
> + fail "$testname (strip $archive)"
> + return
> + }
> +
> + if { "$fat" == "-fat" } {
> + set cmd "$READELF -SW ${archive}.strip"
> + send_log "$cmd\n"
> + verbose "$cmd" 1
> + catch "exec $cmd" got
> + if [regexp "\.llvm\.lto *LLVM_LTO *" $got] then {
> + send_log "$got\n"
> + verbose "$got" 1
> + fail "$testname (strip $archive)"
> + return
> + }
> + }
> +
> + pass "$testname (strip $archive)"
> +}
> +
> +run_pr33198_test "" "-R .gnu.lto_* -R .gnu.debuglto_* -R .llvm.lto -N __gnu_lto_v1"
> +run_pr33198_test "-fat" "-R .gnu.lto_* -R .gnu.debuglto_* -R .llvm.lto -N __gnu_lto_v1"
> +run_pr33198_test "" "-R .llvm.lto"
> +run_pr33198_test "-fat" "-R .llvm.lto"
> diff --git a/binutils/testsuite/lib/binutils-common.exp b/binutils/testsuite/lib/binutils-common.exp
> index b73b5558c27..7297f6d29d3 100644
> --- a/binutils/testsuite/lib/binutils-common.exp
> +++ b/binutils/testsuite/lib/binutils-common.exp
> @@ -1811,3 +1811,30 @@ proc get_standard_section_names {} {
> }
> return
> }
> +
> +set llvm_plug_opt ""
> +if { [isnative] } then {
> + if ![info exists CLANG_FOR_TARGET] then {
> + catch "exec clang -v" got
> + if [regexp "clang version" $got] then {
> + set CLANG_FOR_TARGET clang
> + }
> + }
> + if [info exists CLANG_FOR_TARGET] then {
> + set llvm_plug_so [string trim [exec $CLANG_FOR_TARGET -print-file-name=LLVMgold.so]]
> + if { $llvm_plug_so ne "LLVMgold.so" } then {
> + set llvm_plug_opt "--plugin $llvm_plug_so"
> + }
> +
> + if { $llvm_plug_opt eq "" } then {
> + # If it is still blank, try llvm-config --libdir. Clang
> + # searches CLANG_INSTALL_LIBDIR_BASENAME which corresponds
> + # to this.
> + catch "exec llvm-config --libdir" got
> + if {[file isdirectory $got] \
> + && [file isfile $got/LLVMgold.so]} then {
> + set llvm_plug_opt "--plugin $got/LLVMgold.so"
> + }
> + }
> + }
> +}
> --
> 2.50.1
>
--
H.J.
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