MIPS: genvdso: Remove GOT checks

Our genvdso tool performs some rather paranoid checking that the VDSO
library isn't attempting to make use of a GOT by constraining the number
of entries that the GOT is allowed to contain to the minimum 2 entries
that are always generated by binutils.

Unfortunately lld prior to revision 334390 generates a third entry,
which is unused & thus harmless but falls foul of genvdso's checks &
causes the build to fail.

Since we already check that the VDSO contains no relocations it seems
reasonable to presume that it also doesn't contain use of a GOT, which
would involve relocations. Thus rather than attempting to work around
this issue by allowing 3 GOT entries when using lld, simply remove the
GOT checks which seem overly paranoid.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/20152/
Cc: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org

diff --git a/arch/mips/vdso/genvdso.h b/arch/mips/vdso/genvdso.h
index 9433472..611b06f 100644 (file)
--- a/arch/mips/vdso/genvdso.h
+++ b/arch/mips/vdso/genvdso.h
@@ -15,8 +15,6 @@ static inline bool FUNC(patch_vdso)(const char *path, void *vdso)
        ELF(Shdr) *shdr;
        char *shstrtab, *name;
        uint16_t sh_count, sh_entsize, i;
-       unsigned int local_gotno, symtabno, gotsym;
-       ELF(Dyn) *dyn = NULL;
 
        shdrs = vdso + FUNC(swap_uint)(ehdr->e_shoff);
        sh_count = swap_uint16(ehdr->e_shnum);
@@ -41,9 +39,6 @@ static inline bool FUNC(patch_vdso)(const char *path, void *vdso)
                                "%s: '%s' contains relocation sections\n",
                                program_name, path);
                        return false;
-               case SHT_DYNAMIC:
-                       dyn = vdso + FUNC(swap_uint)(shdr->sh_offset);
-                       break;
                }
 
                /* Check for existing sections. */
@@ -61,52 +56,6 @@ static inline bool FUNC(patch_vdso)(const char *path, void *vdso)
                }
        }
 
-       /*
-        * Ensure the GOT has no entries other than the standard 2, for the same
-        * reason we check that there's no relocation sections above.
-        * The standard two entries are:
-        * - Lazy resolver
-        * - Module pointer
-        */
-       if (dyn) {
-               local_gotno = symtabno = gotsym = 0;
-
-               while (FUNC(swap_uint)(dyn->d_tag) != DT_NULL) {
-                       switch (FUNC(swap_uint)(dyn->d_tag)) {
-                       /*
-                        * This member holds the number of local GOT entries.
-                        */
-                       case DT_MIPS_LOCAL_GOTNO:
-                               local_gotno = FUNC(swap_uint)(dyn->d_un.d_val);
-                               break;
-                       /*
-                        * This member holds the number of entries in the
-                        * .dynsym section.
-                        */
-                       case DT_MIPS_SYMTABNO:
-                               symtabno = FUNC(swap_uint)(dyn->d_un.d_val);
-                               break;
-                       /*
-                        * This member holds the index of the first dynamic
-                        * symbol table entry that corresponds to an entry in
-                        * the GOT.
-                        */
-                       case DT_MIPS_GOTSYM:
-                               gotsym = FUNC(swap_uint)(dyn->d_un.d_val);
-                               break;
-                       }
-
-                       dyn++;
-               }
-
-               if (local_gotno > 2 || symtabno - gotsym) {
-                       fprintf(stderr,
-                               "%s: '%s' contains unexpected GOT entries\n",
-                               program_name, path);
-                       return false;
-               }
-       }
-
        return true;
 }