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

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;
 }