Unverified Commit 4467f7ad authored by Paul Burton's avatar Paul Burton
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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: default avatarPaul 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
parent 7dc084d6

arch/mips/vdso/genvdso.h

+0 −51
Original line number Diff line number Diff line
@@ -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;

}

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