[gcc r10-10687] libiberty: Fix up debug.temp.o creation if *.o has 64K+ sections [PR104617]

[gcc r10-10687] libiberty: Fix up debug.temp.o creation if *.o has 64K+ sections [PR104617]

[Jakub Jelinek]

https://gcc.gnu.org/g:60d1efc075ac297e208d4dcfc5a5c2a02b9a208b

commit r10-10687-g60d1efc075ac297e208d4dcfc5a5c2a02b9a208b
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Feb 22 11:32:08 2022 +0100

    libiberty: Fix up debug.temp.o creation if *.o has 64K+ sections [PR104617]
    
    On
     #define A(n) int foo1##n(void) { return 1##n; }
     #define B(n) A(n##0) A(n##1) A(n##2) A(n##3) A(n##4) A(n##5) A(n##6) A(n##7) A(n##8) A(n##9)
     #define C(n) B(n##0) B(n##1) B(n##2) B(n##3) B(n##4) B(n##5) B(n##6) B(n##7) B(n##8) B(n##9)
     #define D(n) C(n##0) C(n##1) C(n##2) C(n##3) C(n##4) C(n##5) C(n##6) C(n##7) C(n##8) C(n##9)
     #define E(n) D(n##0) D(n##1) D(n##2) D(n##3) D(n##4) D(n##5) D(n##6) D(n##7) D(n##8) D(n##9)
     E(0) E(1) E(2) D(30) D(31) C(320) C(321) C(322) C(323) C(324) C(325)
     B(3260) B(3261) B(3262) B(3263) A(32640) A(32641) A(32642)
    testcase with
    ./xgcc -B ./ -c -g -fpic -ffat-lto-objects -flto  -O0 -o foo1.o foo1.c -ffunction-sections
    ./xgcc -B ./ -shared -g -fpic -flto -O0 -o foo1.so foo1.o
    /tmp/ccTW8mBm.debug.temp.o: file not recognized: file format not recognized
    (testcase too slow to be included into testsuite).
    The problem is clearly reported by readelf:
    readelf: foo1.o.debug.temp.o: Warning: Section 2 has an out of range sh_link value of 65321
    readelf: foo1.o.debug.temp.o: Warning: Section 5 has an out of range sh_link value of 65321
    readelf: foo1.o.debug.temp.o: Warning: Section 10 has an out of range sh_link value of 65323
    readelf: foo1.o.debug.temp.o: Warning: [ 2]: Link field (65321) should index a symtab section.
    readelf: foo1.o.debug.temp.o: Warning: [ 5]: Link field (65321) should index a symtab section.
    readelf: foo1.o.debug.temp.o: Warning: [10]: Link field (65323) should index a string section.
    because simple_object_elf_copy_lto_debug_sections doesn't adjust sh_info and
    sh_link fields in ElfNN_Shdr if they are in between SHN_{LO,HI}RESERVE
    inclusive.  Not adjusting those is incorrect though, SHN_{LO,HI}RESERVE
    range is only relevant to the 16-bit fields, mainly st_shndx in ElfNN_Sym
    where if one needs >= SHN_LORESERVE section number, SHN_XINDEX should be
    used instead and .symtab_shndx section should contain the real section
    index, and in ElfNN_Ehdr e_shnum and e_shstrndx fields, where if >=
    SHN_LORESERVE value is needed it should put those into
    Shdr[0].sh_{size,link}.  But, sh_{link,info} are 32-bit fields which can
    contain any section index.
    
    Note, as simple-object-elf.c mentions, binutils from 2.12 to 2.18 (so before
    2011) used to mishandle the > 63.75K sections case and assumed there is a
    hole in between the sections, but what
    simple_object_elf_copy_lto_debug_sections does wouldn't help in that case
    for the debug temp object creation, we'd need to detect the case also in
    that routine and take it into account in the remapping etc.  I think
    it is not worth it given that it is over 10 years, if somebody needs
    63.75K or more sections, better use more recent binutils.
    
    2022-02-22  Jakub Jelinek  <jakub@redhat.com>
    
            PR lto/104617
            * simple-object-elf.c (simple_object_elf_match): Fix up URL
            in comment.
            (simple_object_elf_copy_lto_debug_sections): Remap sh_info and
            sh_link even if they are in the SHN_LORESERVE .. SHN_HIRESERVE
            range (inclusive).
    
    (cherry picked from commit 2f59f067610f22c3f2ec9b1516e24b85836676ed)

Diff:
---
 libiberty/simple-object-elf.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/libiberty/simple-object-elf.c b/libiberty/simple-object-elf.c
index 37e73348cb7..18b9abe2d63 100644
--- a/libiberty/simple-object-elf.c
+++ b/libiberty/simple-object-elf.c
@@ -528,7 +528,7 @@ simple_object_elf_match (unsigned char header[SIMPLE_OBJECT_MATCH_HEADER_LEN],
 	     not handle objects with more than SHN_LORESERVE sections
 	     correctly.  All large section indexes were offset by
 	     0x100.  There is more information at
-	     http://sourceware.org/bugzilla/show_bug.cgi?id-5900 .
+	     https://sourceware.org/PR5900 .
 	     Fortunately these object files are easy to detect, as the
 	     GNU binutils always put the section header string table
 	     near the end of the list of sections.  Thus if the
@@ -1559,17 +1559,13 @@ simple_object_elf_copy_lto_debug_sections (simple_object_read *sobj,
 	  {
 	    sh_info = ELF_FETCH_FIELD (type_functions, ei_class, Shdr,
 				       shdr, sh_info, Elf_Word);
-	    if (sh_info < SHN_LORESERVE
-		|| sh_info > SHN_HIRESERVE)
-	      sh_info = sh_map[sh_info];
+	    sh_info = sh_map[sh_info];
 	    ELF_SET_FIELD (type_functions, ei_class, Shdr,
 			   shdr, sh_info, Elf_Word, sh_info);
 	  }
 	sh_link = ELF_FETCH_FIELD (type_functions, ei_class, Shdr,
 				   shdr, sh_link, Elf_Word);
-	if (sh_link < SHN_LORESERVE
-	    || sh_link > SHN_HIRESERVE)
-	  sh_link = sh_map[sh_link];
+	sh_link = sh_map[sh_link];
 	ELF_SET_FIELD (type_functions, ei_class, Shdr,
 		       shdr, sh_link, Elf_Word, sh_link);
       }