lto: fix LTO debug sections copying.

readelf -S prints:

There are 81999 section headers, starting at offset 0x1f488060:

Section Headers:
  [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            0000000000000000 000000 01404f 00     81998   0  0
  [ 1] .group            GROUP           0000000000000000 000040 000008 04     81995 105027  4
...
  [81995] .symtab           SYMTAB          0000000000000000 d5d9298 2db310 18     81997 105026  8
  [81996] .symtab_shndx     SYMTAB SECTION INDICES 0000000000000000 d8b45a8 079dd8 04     81995   0  4
  [81997] .strtab           STRTAB          0000000000000000 d92e380 80460c 00      0   0  1
...

Looking at the documentation:
Table 7–15 ELF sh_link and sh_info Interpretation

sh_type - sh_link
SHT_SYMTAB - The section header index of the associated string table.
SHT_SYMTAB_SHNDX - The section header index of the associated symbol table.

As seen, sh_link of a SHT_SYMTAB always points to a .strtab and readelf
confirms that.

So we need to use reverse mapping taken from
  [81996] .symtab_shndx     SYMTAB SECTION INDICES 0000000000000000 d8b45a8 079dd8 04     81995   0  4

where sh_link points to 81995.

libiberty/ChangeLog:

	PR lto/97290
	* simple-object-elf.c (simple_object_elf_copy_lto_debug_sections):
	Use sh_link of a .symtab_shndx section.

diff --git a/libiberty/simple-object-elf.c b/libiberty/simple-object-elf.c
index 7c9d492f6a42d32f921f65f7dac20139b4283d31..37e73348cb72c7e59792dc19c02cf51937b2ec4c 100644 (file)
--- a/libiberty/simple-object-elf.c
+++ b/libiberty/simple-object-elf.c
@@ -1191,7 +1191,7 @@ simple_object_elf_copy_lto_debug_sections (simple_object_read *sobj,
          unsigned int sh_link;
          sh_link = ELF_FETCH_FIELD (type_functions, ei_class, Shdr,
                                     shdr, sh_link, Elf_Word);
-         symtab_indices_shndx[sh_link - 1] = i;
+         symtab_indices_shndx[sh_link - 1] = i - 1;
          /* Always discard the extended index sections, after
             copying it will not be needed.  This way we don't need to
             update it and deal with the ordering constraints of
@@ -1372,19 +1372,22 @@ simple_object_elf_copy_lto_debug_sections (simple_object_read *sobj,
        {
          unsigned entsize = ELF_FETCH_FIELD (type_functions, ei_class, Shdr,
                                              shdr, sh_entsize, Elf_Addr);
-         unsigned strtab = ELF_FETCH_FIELD (type_functions, ei_class, Shdr,
-                                            shdr, sh_link, Elf_Word);
          size_t prevailing_name_idx = 0;
          unsigned char *ent;
          unsigned *shndx_table = NULL;
          /* Read the section index table if present.  */
          if (symtab_indices_shndx[i - 1] != 0)
            {
-             unsigned char *sidxhdr = shdrs + (strtab - 1) * shdr_size;
+             unsigned char *sidxhdr = shdrs + symtab_indices_shndx[i - 1] * shdr_size;
              off_t sidxoff = ELF_FETCH_FIELD (type_functions, ei_class, Shdr,
                                               sidxhdr, sh_offset, Elf_Addr);
              size_t sidxsz = ELF_FETCH_FIELD (type_functions, ei_class, Shdr,
                                               sidxhdr, sh_size, Elf_Addr);
+             unsigned int shndx_type
+               = ELF_FETCH_FIELD (type_functions, ei_class, Shdr,
+                                  sidxhdr, sh_type, Elf_Word);
+             if (shndx_type != SHT_SYMTAB_SHNDX)
+               return "Wrong section type of a SYMTAB SECTION INDICES section";
              shndx_table = (unsigned *)XNEWVEC (char, sidxsz);
              simple_object_internal_read (sobj->descriptor,
                                           sobj->offset + sidxoff,