[hjl@gnu-cfl-2 pr93492]$ cat x.i void _start (void) { } [hjl@gnu-cfl-2 pr93492]$ gcc -c -fpatchable-function-entry=1 x.i [hjl@gnu-cfl-2 pr93492]$ readelf -SW x.o | grep __patch [ 4] __patchable_function_entries PROGBITS 0000000000000000 000048 000008 00 WA 0 0 1 [ 5] .rela__patchable_function_entries RELA 0000000000000000 000200 000018 18 I 11 4 8 [hjl@gnu-cfl-2 pr93492]$ ld x.o [hjl@gnu-cfl-2 pr93492]$ readelf -SW a.out | grep __patch [ 4] __patchable_function_entries PROGBITS 0000000000404000 003000 000008 00 WA 0 0 1 [hjl@gnu-cfl-2 pr93492]$ ld --gc-sections x.o [hjl@gnu-cfl-2 pr93492]$ readelf -SW a.out | grep __patch [hjl@gnu-cfl-2 pr93492]$
A patch is posted at https://sourceware.org/ml/binutils/2020-02/msg00009.html
An updated patch is at https://sourceware.org/ml/binutils/2020-02/msg00010.html
The master branch has been updated by H.J. Lu <hjl@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b7d072167715829eed0622616f6ae0182900de3e commit b7d072167715829eed0622616f6ae0182900de3e Author: H.J. Lu <hjl.tools@gmail.com> Date: Thu Feb 6 18:04:58 2020 -0800 ELF: Support the section flag 'o' in .section directive As shown in https://sourceware.org/bugzilla/show_bug.cgi?id=25490 --gc-sections will silently remove __patchable_function_entries section and generate corrupt result. This patch adds the section flag 'o' to .section directive: .section __patchable_function_entries,"awo",@progbits,foo .section __patchable_function_entries,"awoG",@progbits,foo,foo,comdat .section __patchable_function_entries,"awo",@progbits,bar,unique,4 .section __patchable_function_entries,"awoG",@progbits,foo,foo,comdat,unique,1 which specifies the symbol name which the section references. Assmebler will set its elf_linked_to_section to a local section where the symbol is defined. Linker is updated to call mark_hook if gc_mark of any of its linked-to sections is set after all sections, except for backend specific ones, have been garbage collected. bfd/ PR gas/25381 * bfd-in2.h: Regenerated. * elflink.c (_bfd_elf_gc_mark_extra_sections): Call mark_hook on section if gc_mark of any of its linked-to sections is set and don't set gc_mark again. * section.c (asection): Add linked_to_symbol_name to map_head union. gas/ PR gas/25381 * config/obj-elf.c (get_section): Also check linked_to_symbol_name. (obj_elf_change_section): Also set map_head.linked_to_symbol_name. (obj_elf_parse_section_letters): Handle the 'o' flag. (build_group_lists): Renamed to ... (build_additional_section_info): This. Set elf_linked_to_section from map_head.linked_to_symbol_name. (elf_adjust_symtab): Updated. * config/obj-elf.h (elf_section_match): Add linked_to_symbol_name. * doc/as.texi: Document the 'o' flag. * testsuite/gas/elf/elf.exp: Run PR gas/25381 tests. * testsuite/gas/elf/section18.d: New file. * testsuite/gas/elf/section18.s: Likewise. * testsuite/gas/elf/section19.d: Likewise. * testsuite/gas/elf/section19.s: Likewise. * testsuite/gas/elf/section20.d: Likewise. * testsuite/gas/elf/section20.s: Likewise. * testsuite/gas/elf/section21.d: Likewise. * testsuite/gas/elf/section21.l: Likewise. * testsuite/gas/elf/section21.s: Likewise. ld/ PR ld/24526 PR ld/25021 PR ld/25490 * testsuite/ld-elf/elf.exp: Run PR ld/25490 tests. * testsuite/ld-elf/pr24526.d: New file. * testsuite/ld-elf/pr24526.s: Likewise. * testsuite/ld-elf/pr25021.d: Likewise. * testsuite/ld-elf/pr25021.s: Likewise. * testsuite/ld-elf/pr25490-2-16.rd: Likewise. * testsuite/ld-elf/pr25490-2-32.rd: Likewise. * testsuite/ld-elf/pr25490-2-64.rd: Likewise. * testsuite/ld-elf/pr25490-2.s: Likewise. * testsuite/ld-elf/pr25490-3-16.rd: Likewise. * testsuite/ld-elf/pr25490-3-32.rd: Likewise. * testsuite/ld-elf/pr25490-3-64.rd: Likewise. * testsuite/ld-elf/pr25490-3.s: Likewise. * testsuite/ld-elf/pr25490-4-16.rd: Likewise. * testsuite/ld-elf/pr25490-4-32.rd: Likewise. * testsuite/ld-elf/pr25490-4-64.rd: Likewise. * testsuite/ld-elf/pr25490-4.s: Likewise. * testsuite/ld-elf/pr25490-5-16.rd: Likewise. * testsuite/ld-elf/pr25490-5-32.rd: Likewise. * testsuite/ld-elf/pr25490-5-64.rd: Likewise. * testsuite/ld-elf/pr25490-5.s: Likewise. * testsuite/ld-elf/pr25490-6-16.rd: Likewise. * testsuite/ld-elf/pr25490-6-32.rd: Likewise. * testsuite/ld-elf/pr25490-6-64.rd: Likewise. * testsuite/ld-elf/pr25490-6.s: Likewise.
The master branch has been updated by H.J. Lu <hjl@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=5242a0a000ad7d3f2fa1cd0023f692d53261b302 commit 5242a0a000ad7d3f2fa1cd0023f692d53261b302 Author: H.J. Lu <hjl.tools@gmail.com> Date: Thu Feb 6 19:37:54 2020 -0800 ld: Issue an error for GC on __patchable_function_entries section __patchable_function_entries section is generated by a compiler with -fpatchable-function-entry=XX. The assembly code looks like this: --- .text .globl _start .type _start, %function _start: .section __patchable_function_entries,"aw",%progbits .dc.a .LPFE1 .text .LPFE1: .byte 0 --- But --gc-sections will silently remove __patchable_function_entries section and generate corrupt result. This patch disallows garbage collection on __patchable_function_entries section without linked-to section. bfd/ PR ld/25490 * elflink.c (_bfd_elf_gc_mark_extra_sections): Issue an error for garbage collection on __patchable_function_entries section without linked-to section. ld/ PR ld/25490 * testsuite/ld-elf/pr25490-1.d: New file. * testsuite/ld-elf/pr25490-1.s: Likewise.
Fixed for 2.35.